Grid

• 1: Selenium Grid快速起步
• 2: 什么时候应该使用Grid
• 3: 服务网格的组件
• 4: 配置组件
• 4.1: 配置帮助
• 4.2: CLI 选项
• 4.3: Toml配置选项
• 5: Grid架构
• 6: 高级功能
• 6.1: 可观测性
• 6.2: GraphQL查询支持
• 6.3: Grid端点
• 6.4: Customizing a Node
• 6.5: External datastore

1 - Selenium Grid快速起步

快速开始

1. 先决条件
   • 需要安装 Java 11 或更高版本
   • 需要安装浏览器
   • 需要安装浏览器驱动程序
     • Selenium Manager will configure the drivers automatically if you add --selenium-manager true.
     • 需要已经安装并配置了 PATH 环境变量
   • 从最新的发布版本下载 Selenium Server jar 文件
2. 启动 Grid
   • java -jar selenium-server-<version>.jar standalone
3. 将您的 WebDriver 测试指向 http://localhost:4444
4. (可选) 通过在浏览器中打开 http://localhost:4444 检查正在运行的测试和可用的功能

*想知道如何将您的测试指向 http://localhost:4444吗? 请查看 RemoteWebDriver section。

要了解更多不同的配置选项，请查看以下各小节。

Grid 角色

Grid由六个不同的组件组成，这使您可以以不同的方式部署它。

根据您的需求，您可以单独启动每个组件（分布式），将它们分组为Hub和Node，或者全部在单个机器上运行（独立）。

单机部署（Standalone）

Standalone 可以将所有 Grid 组件 无缝地整合成一个单独的实体。在 Standalone 模式下运行 Grid，只需一个命令即可获得一个完整的 Grid，并在一个进程中运行。Standalone 只能在一台机器上运行。

Standalone 模式也是最容易启动 Selenium Grid 的模式。默认情况下，服务器将在 http://localhost:4444 上监听 RemoteWebDriver 请求，并且服务器将从系统 PATH 中检测可以使用的驱动程序。

java -jar selenium-server-<version>.jar standalone

成功启动 Standalone 模式的 Grid 后，将你的 WebDriver 测试指向 http://localhost:4444。

Standalone 的常见用途包括：

• 本地使用 RemoteWebDriver 开发或调试测试
• 推送代码之前运行快速测试套件
• 在 CI/CD 工具（GitHub Actions、Jenkins 等）中设置简单的 Grid

Hub and Node

Hub和Node是最常用的角色，因为它允许：

• 将不同的机器组合成一个单一的Grid
  • 例如拥有不同操作系统和/或浏览器版本的机器
• 在不同的环境中运行WebDriver测试有一个单一的入口点
• 在不破坏Grid的情况下增加或减少容量。

Hub

一个Hub由以下组件组成： 路由器（Router）、分发器（Distributor）、会话映射（Session Map）、新会话队列（New Session Queue）和事件总线（Event Bus）。

java -jar selenium-server-<version>.jar hub

默认情况下，服务器将在 http://localhost:4444 上监听RemoteWebDriver请求。

Node

在启动时，Node将从系统的PATH中检测可用的驱动程序。

以下命令假设Node正在运行的机器与Hub在同一台机器上。

java -jar selenium-server-<version>.jar node

同一台机器上的多个Node

Node 1

java -jar selenium-server-<version>.jar node --port 5555

Node 2

java -jar selenium-server-<version>.jar node --port 6666

不同机器上的Node和Hub

Hub和Nodes通过HTTP和事件总线（事件总线位于Hub内部）进行通信。

Node通过事件总线向Hub发送消息以开始注册过程。当Hub收到消息时，通过HTTP与Node联系以确认其存在。

要成功将Node注册到Hub，重要的是要在Hub机器上公开事件总线端口（默认为4442和4443）。这也适用于Node端口。有了这个，Hub和Node都能够通信。

如果Hub使用默认端口，则可以使用 --hub 注册Node。

java -jar selenium-server-<version>.jar node --hub http://<hub-ip>:4444

当Hub未使用默认端口时，需要使用--publish-events和--subscribe-events。

例如，如果Hub使用端口8886、8887和8888。

java -jar selenium-server-<version>.jar hub --publish-events tcp://<hub-ip>:8886 --subscribe-events tcp://<hub-ip>:8887 --port 8888

Node需要使用这些端口才能成功注册。

java -jar selenium-server-<version>.jar node --publish-events tcp://<hub-ip>:8886 --subscribe-events tcp://<hub-ip>:8887

分部署部署（Distributed）

在使用分布式Grid时，每个组件都需要单独启动，并且理想情况下应该在不同的机器上。

1. 事件总线（Event Bus）: 使不同网格组件之间的内部通信成为可能。

默认端口为：4442、4443和5557。

java -jar selenium-server-<version>.jar event-bus --publish-events tcp://<event-bus-ip>:4442 --subscribe-events tcp://<event-bus-ip>:4443 --port 5557

2. 新会话队列（New Session Queue）: 将新的会话请求添加到一个队列中，Distributor将查询该队列。

默认端口为5559。

java -jar selenium-server-<version>.jar sessionqueue --port 5559

3. 会话映射（Session Map）: 将会话ID映射到运行该会话的节点。

默认会话映射端口为5556。会话映射与事件总线进行交互。

java -jar selenium-server-<version>.jar sessions --publish-events tcp://<event-bus-ip>:4442 --subscribe-events tcp://<event-bus-ip>:4443 --port 5556

4. 分配器（Distributor）: 查询新 会话队列（New Session Queue） 以获取新会话请求，并在能力匹配时将其分配给 Node。 Nodes 注册到 Distributor 的方式与在 Hub/Node 网格中注册到 Hub 相同。

默认分配器端口为5553。分配器 与 新会话队列、会话映射、事件总线 和 Node(s) 进行交互。

java -jar selenium-server-<version>.jar distributor --publish-events tcp://<event-bus-ip>:4442 --subscribe-events tcp://<event-bus-ip>:4443 --sessions http://<sessions-ip>:5556 --sessionqueue http://<new-session-queue-ip>:5559 --port 5553 --bind-bus false

5. 路由器（Router）: 将新会话请求重定向到队列，并将正在运行的会话请求重定向到运行该会话的Node。

默认路由器端口为4444。路由器 与 新会话队列、会话映射和分配器 进行交互。

java -jar selenium-server-<version>.jar router --sessions http://<sessions-ip>:5556 --distributor http://<distributor-ip>:5553 --sessionqueue http://<new-session-queue-ip>:5559 --port 4444

6. Node(s)

默认 Node 端口是 5555.

java -jar selenium-server-<version>.jar node --publish-events tcp://<event-bus-ip>:4442 --subscribe-events tcp://<event-bus-ip>:4443

测试中的 Metadata

向测试中添加 Metadata 并通过GraphQL进行消费，或通过 Selenium Grid UI 可视化其部分内容（例如se:name）。

可以通过在 capability 前加上 se: 来添加元数据。以下是一个Java的快速示例。

ChromeOptions chromeOptions = new ChromeOptions();
chromeOptions.setCapability("browserVersion", "100");
chromeOptions.setCapability("platformName", "Windows");
// Showing a test name instead of the session id in the Grid UI
chromeOptions.setCapability("se:name", "My simple test"); 
// Other type of metadata can be seen in the Grid UI by clicking on the 
// session info or via GraphQL
chromeOptions.setCapability("se:sampleMetadata", "Sample metadata value"); 
WebDriver driver = new RemoteWebDriver(new URL("http://gridUrl:4444"), chromeOptions);
driver.get("http://www.google.com");
driver.quit();

查询 Selenium Grid 相关状态

启动 Grid 后，主要有两种方式查询其状态，通过 Grid UI 或通过 API 调用。

可以通过打开您喜欢的浏览器并前往http://localhost:4444。

API 调用可以通过 http://localhost:4444/status 端点或使用 GraphQL

使用 Java 11 中的 HTTP Client

Selenium v4.5

默认情况下，Grid 将使用 AsyncHttpClient。 AsyncHttpClient 是一个建立在 Netty 之上的开源库。 它允许异步执行 HTTP 请求和响应。 此外，它还提供 WebSocket 支持。 因此它很合适。

然而，AsyncHttpClient 从 2021 年 6 月开始就没有主动维护了。恰逢 Java 11+ 提供了内置的 HTTP 和 WebSocket 客户端。

目前，Selenium 计划将支持的最低版本升级到 Java 11。然而，这需要大量的工作。为了确保用户体验不受影响，将其与主要发布版本和相应的公告对齐是至关重要的。

要使用 Java 11 客户端，您需要下载 selenium-http-jdk-client jar文件并使用 --ext 参数使其在 Grid jar 的类路径中可用。

jar文件可以直接从 repo1.maven.org 下载，然后使用以下方式启动Grid：

java -Dwebdriver.http.factory=jdk-http-client -jar selenium-server-<version>.jar --ext selenium-http-jdk-client-<version>.jar standalone

下载 selenium-http-jdk-client jar 文件的替代方法是使用 Coursier。

java -Dwebdriver.http.factory=jdk-http-client -jar selenium-server-<version>.jar --ext $(coursier fetch -p org.seleniumhq.selenium:selenium-http-jdk-client:<version>) standalone

如果您使用的是集线器/节点模式或分布式模式，则需要为每个组件设置 -Dwebdriver.http.factory=jdk-http-client 和 --ext 参数。

Grid 的规模

选择 Grid 角色取决于需要支持什么操作系统和浏览器、需要执行多少个并行会话、可用机器的数量以及这些机器的配置（CPU、RAM）。

并发创建会话依赖于 分配器 的可用处理器。 例如，如果一台机器有 4 个 CPU，则 分配器 最多只能同时创建 4 个会话。

默认情况下，Node 支持的最大并发会话数受可用 CPU 数量的限制。 例如，如果 Node 机器有 8 个 CPU，它最多可以运行 8 个并发浏览器会话（Safari 除外，它始终是一个）。 此外，预计每个浏览器会话应使用大约 1GB 的 RAM。

通常，建议 Nodes 尽可能小。 与其让机器有 32 个 CPU 和 32GB RAM 来运行 32 个并发浏览器会话，不如有 32 个小的 Node，以便更好地隔离进程。 有了这个，如果一个 Node 发生故障，它将以孤立的方式进行。 Docker 是实现这种方法的好工具。

请注意，默认值（每个浏览器 1 个 CPU/1GB RAM）是建议值，它们不适用于您的上下文。 建议将它们用作参考，但持续测量性能将有助于确定您的环境的理想值。

Grid 大小与支持的并发会话数量和 Node 数量有关，没有“一刀切”的说法。 下面提到的尺寸是粗略的估计，不同环境之间可能会有所不同。 例如，当 Hub 具有足够的资源时，具有 120 个 Nodes 的 Hub/Node 可能运行良好。 以下值并非一成不变，欢迎提供反馈！

小规模

Standalone 或 Hub/Node 不超过5个 Nodes.

中等规模

Hub/Node 介于6到60个 Nodes 之间。

大规模

Hub/Node 介于60到100个 Nodes 之间， Distributed 超过100个 Nodes。

请注意

必须使用适当的防火墙权限保护Selenium Grid免受外部访问。

以下一种或多种情况可能会导致你的 Grid 处于一个不安全的状态：

• 您提供对您的 Grid 基础设施的开放访问
• 您允许第三方访问内部网络应用程序和文件
• 您允许第三方运行自定义二进制文件

请参阅 Detectify 上的这篇博文，它提供了一个很好的公开暴露的 Grid 如何被滥用的概述：不要让你的 Grid 暴露在外

延伸阅读

• Components：了解 Grid 的内部组件如何相互关联。
• Configuration: 自定义您的 Grid 设置。
• Architecture: 理解 Grid 中的关键概念。
• Advanced Features: 通过Grid的特性探索更多的可能性。

2 - 什么时候应该使用Grid

什么情况下可以使用 Selenium Grid ？

• 想要在不同的浏览器类型、浏览器版本和操作系统上并行运行测试时
• 想要缩短执行测试案例所需的时间

Selenium Grid 可以并行地在多台计算机（称为节点）上运行测试案例。对于大型和长时间运行的测试案例，这可以节省几分钟、几小时甚至几天的时间。

这有效的缩短了测试结果的反馈时间，使得在测试的应用程序发生变化时能够更快地得到测试结果。

Grid 可以并行地运行测试，支持多种不同的浏览器类型，并且可以同时运行多个相同浏览器的实例。

举个例子，假设一个拥有六个节点的Grid。第一台计算机拥有Firefox的最新版本，第二台拥有Firefox的上一个版本，第三台运行最新版Chrome，而其余三台机器是Mac Mini，允许在最新版本的Safari上并行运行三个测试。

执行时间可以用一个简单的公式来表示：

测试次数 × 平均测试时间 / 节点数 = 总执行时间

   15      *       45s        /        1        =      11m 15s   // Without Grid
   15      *       45s        /        5        =      2m 15s    // Grid with 5 Nodes
   15      *       45s        /        15       =      45s       // Grid with 15 Nodes
  100      *       120s       /        15       =      13m 20s   // Would take over 3 hours without Grid

在测试案例执行时，Grid 会按照测试配置将测试分配到相应的浏览器上运行。

即使对于比较复杂的 Selenium 测试案例，这样的配置也可以极大地加快执行时间。

Selenium Grid 是 Selenium 项目中的重要组成部分，由同一团队的核心Selenium开发人员并行维护。由于意识到测试执行速度的重要性，Grid 自设计之初就成为 Selenium 项目的关键部分。

3 - 服务网格的组件

Selenium Grid 4 是对以前版本的彻底重写。除了对性能和标准合规性进行全面改进外，还分解了 Grid 的不同功能以反映更现代的计算和软件开发时代。 Selenium Grid 4 专为容器化和云分布式可扩展性而构建，是现代时代的全新解决方案。

路由器（Router）

路由器 是 Grid 的入口点，接收所有外部请求，并将它们转发给正确的组件。

如果路由器收到新的会话请求，它将被转发到新会话队列。

如果请求属于一个已经存在的session，路由器会查询Session Map得到session运行所在的Node ID，然后将请求直接转发给Node。

路由器通过将请求发送到能够更好地处理它们的组件来平衡网格中的负载，而不会使过程中不需要的任何组件过载。

分发器（Distributor）

分发器有两个主要职责：

注册并跟踪所有Node及其功能

Node通过事件总线发送Node注册事件来注册到分发器。分发器读取它，然后尝试通过 HTTP 到达Node以确认它的存在。如果请求成功，Distributor注册节点并通过 GridModel 跟踪所有Node功能。

查询新会话队列并处理任何未决的新会话请求

当一个新的会话请求被发送到路由器时，它被转发到新会话队列，它将在队列中等待。 Distributor 将轮询新会话队列以查找未决的新会话请求，然后找到可以创建会话的合适Node。会话创建后，分发器将会话 ID 与正在执行会话的Node之间的关系存储在会话映射中。

会话映射（Session Map）

会话映射 是一个数据存储，用于保存会话 ID 和运行会话的Node之间的关系。它支持路由器在将请求转发到Node的过程中进行查询。路由器将向会话映射询问与会话 ID 关联的Node。

新会话队列（New Session Queue）

新会话队列按先进先出的顺序保存所有新会话请求。它具有可配置的参数，用于设置请求超时和请求重试间隔（检查超时的频率）。

路由器将新会话请求添加到新会话队列中并等待响应。新会话队列定期检查队列中是否有任何请求超时，如果是，则立即拒绝并将其删除。

分发器定期检查是否有可用的插槽。如果有可用的插槽，则分发器会轮询新会话队列以查找第一个匹配的请求。然后，分发器尝试创建新会话。

一旦请求的功能与任何空闲Node插槽的功能匹配，分发器将尝试获取可用插槽。如果所有插槽都已忙碌，则分发器将将请求发送回队列。如果请求在重试或添加到队列的前面时超时，则会被拒绝。

成功创建会话后，分发器将会话信息发送到新会话队列，该信息然后被发送回路由器，最终发送给客户端。

节点（Node）

一个Grid可以包含多个Node。每个Node管理它所在机器上可用浏览器的插槽。

Node通过事件总线向分发器注册自己，并将其配置作为注册消息发送。

默认情况下，Node会自动注册其所在机器上路径中可用的所有浏览器驱动程序。它还为基于Chromium的浏览器和Firefox创建每个可用CPU一个插槽。对于Safari，只创建一个插槽。通过特定的配置，它可以在Docker容器中运行会话或转发命令。

Node仅执行接收到的命令，不评估、不做出判断或控制任何除命令和响应流之外的东西。Node所在的机器不需要与其他组件具有相同的操作系统。例如，Windows节点可能具有在Edge上提供IE模式作为浏览器选项的能力，而在Linux或Mac上则不可能，网格可以配置多个具有Windows、Mac或Linux的Node。

事件总线（Event Bus）

事件总线作为节点、分发器、新会话队列和会话映射之间的通信路径。Grid 的大部分内部通信都通过消息进行，避免了频繁的HTTP调用。在完全分布式模式下启动Grid 时，事件总线应该是第一个组件。

4 - 配置组件

4.1 - 配置帮助

信息命令

Info命令提供以下主题的详细文档:

• 配置Selenium
• 安全
• 会话表配置
• 追踪

配置帮助

通过运行以下命令快速获取配置帮助:

java -jar selenium-server-<version>.jar info config

安全

获取构建网格服务器的详细信息, 用于安全通信和节点注册.

java -jar selenium-server-<version>.jar info security

会话表配置

默认情况下, 网格使用本地会话表来存储会话信息. 网格支持额外的存储选项, 比如Redis和JDBC-SQL支持的数据库. 要设置不同的会话存储, 请使用以下命令获取设置步骤:

java -jar selenium-server-<version>.jar info sessionmap

基于OpenTelemetry和Jaeger的追踪配置

默认情况下, 追踪是启用的. 要通过Jaeger导出追踪并将其可视化, 请使用以下命令进行说明:

java -jar selenium-server-<version>.jar info tracing

列出Selenium网格的命令

java -jar selenium-server-<version>.jar --config-help

上述命令将显示所有可用的命令及其描述.

组件帮助命令

在Selenium后面键入–help的配置选项, 以获取特定组件的配置信息.

Standalone

java -jar selenium-server-<version>.jar standalone --help

Hub

java -jar selenium-server-<version>.jar hub --help

Sessions

java -jar selenium-server-<version>.jar sessions --help

队列器

java -jar selenium-server-<version>.jar sessionqueue --help

Distributor

java -jar selenium-server-<version>.jar distributor --help

Router

java -jar selenium-server-<version>.jar router --help

Node

java -jar selenium-server-<version>.jar node --help

4.2 - CLI 选项

Different sections are available to configure a Grid. Each section has options can be configured through command line arguments.

A complete description of the component to section mapping can be seen below.

Sections

Distributor

Docker

Events

Logging

Network

Node

Relay

Router

Server

SessionQueue

Sessions

Configuration examples

All the options mentioned above can be used when starting the Grid components. They are a good way of exploring the Grid options, and trying out values to find a suitable configuration.

Command-line flags

To pass config options as command-line flags, identify the valid options for the component and follow the template below.

java -jar selenium-server-<version>.jar <component> --<option> value

Standalone, setting max sessions and main port

java -jar selenium-server-<version>.jar standalone --max-sessions 4 --port 4444

Hub, setting a new session request timeout, a main port, and disabling tracing

java -jar selenium-server-<version>.jar hub --session-request-timeout 500 --port 3333 --tracing false

Node, with 4 max sessions, with debug(fine) log, 7777 as port, and only with Firefox and Edge

java -jar selenium-server-<version>.jar node --max-sessions 4 --log-level "fine" --port 7777 --driver-implementation "firefox" --driver-implementation "edge"

Distributor, setting Session Map server url, Session Queue server url, and disabling bus

java -jar selenium-server-<version>.jar distributor --sessions http://localhost:5556 --sessionqueue http://localhost:5559 --bind-bus false

Setting custom capabilities for matching specific Nodes

Important: Custom capabilities need to be set in the configuration in all Nodes. They also need to be included always in every session request.

Start the Hub

java -jar selenium-server-<version>.jar hub

Start the Node A with custom cap set to true

java -jar selenium-server-<version>.jar node --detect-drivers false --driver-configuration display-name="Chrome (custom capability true)" max-sessions=1 stereotype='{"browserName":"chrome","gsg:customcap":true}' --port 6161

Start the Node B with custom cap set to false

java -jar selenium-server-<version>.jar node --detect-drivers false --driver-configuration display-name="Chrome (custom capability true)" max-sessions=1 stereotype='{"browserName":"chrome","gsg:customcap":false}' --port 6262

Matching Node A

ChromeOptions options = new ChromeOptions();
options.setCapability("gsg:customcap", true);
WebDriver driver = new RemoteWebDriver(new URL("http://localhost:4444"), options);
driver.get("https://selenium.dev");
driver.quit();

Set the custom capability to false in order to match the Node B.

Enabling Managed downloads by the Node

At times a test may need to access files that were downloaded by it on the Node. To retrieve such files, following can be done.

Start the Hub

java -jar selenium-server-<version>.jar hub

Start the Node with manage downloads enabled

java -jar selenium-server-<version>.jar node --enable-managed-downloads true

Set the capability at the test level

Tests that want to use this feature should set the capability "se:downloadsEnabled"to true

options.setCapability("se:downloadsEnabled", true);

How does this work

• The Grid infrastructure will try to match a session request with "se:downloadsEnabled" against ONLY those nodes which were started with --enable-managed-downloads true
• If a session is matched, then the Node automatically sets the required capabilities to let the browser know, as to where should a file be downloaded.
• The Node now allows a user to:
  • List all the files that were downloaded for a specific session and
  • Retrieve a specific file from the list of files.
• The directory into which files were downloaded for a specific session gets automatically cleaned up when the session ends (or) timesout due to inactivity.

Note: Currently this capability is ONLY supported on:

• Edge
• Firefox and
• Chrome browser

Listing files that can be downloaded for current session:

• The endpoint to GET from is /session/<sessionId>/se/files.
• The session needs to be active in order for the command to work.
• The raw response looks like below:

{
  "value": {
    "names": [
      "Red-blue-green-channel.jpg"
    ]
  }
}

In the response the list of file names appear under the key names.

Dowloading a file:

• The endpoint to POST from is /session/<sessionId>/se/files with a payload of the form {"name": "fileNameGoesHere}
• The session needs to be active in order for the command to work.
• The raw response looks like below:

{
  "value": {
    "filename": "Red-blue-green-channel.jpg",
    "contents": "Base64EncodedStringContentsOfDownloadedFileAsZipGoesHere"
  }
}

• The response blob contains two keys,
  • filename - The file name that was downloaded.
  • contents - Base64 encoded zipped contents of the file.
• The file contents are Base64 encoded and they need to be unzipped.

List files that can be downloaded

The below mentioned curl example can be used to list all the files that were downloaded by the current session in the Node, and which can be retrieved locally.

curl -X GET "http://localhost:4444/session/90c0149a-2e75-424d-857a-e78734943d4c/se/files"

A sample response would look like below:

{
  "value": {
    "names": [
      "Red-blue-green-channel.jpg"
    ]
  }
}

Retrieve a downloaded file

Assuming the downloaded file is named Red-blue-green-channel.jpg, and using curl, the file could be downloaded with the following command:

curl -H "Accept: application/json" \
-H "Content-Type: application/json; charset=utf-8" \
-X POST -d '{"name":"Red-blue-green-channel.jpg"}' \
"http://localhost:4444/session/18033434-fa4f-4d11-a7df-9e6d75920e19/se/files"

A sample response would look like below:

{
  "value": {
    "filename": "Red-blue-green-channel.jpg",
    "contents": "UEsDBBQACAgIAJpagVYAAAAAAAAAAAAAAAAaAAAAUmVkLWJsAAAAAAAAAAAAUmVkLWJsdWUtZ3JlZW4tY2hhbm5lbC5qcGdQSwUGAAAAAAEAAQBIAAAAcNkAAAAA"
  }
}

Complete sample code in Java

Below is an example in Java that does the following:

• Sets the capability to indicate that the test requires automatic managing of downloaded files.
• Triggers a file download via a browser.
• Lists the files that are available for retrieval from the remote node (These are essentially files that were downloaded in the current session)
• Picks one file and downloads the file from the remote node to the local machine.

import com.google.common.collect.ImmutableMap;

import org.openqa.selenium.By;
import org.openqa.selenium.io.Zip;
import org.openqa.selenium.json.Json;
import org.openqa.selenium.remote.RemoteWebDriver;
import org.openqa.selenium.remote.http.HttpClient;
import org.openqa.selenium.remote.http.HttpRequest;
import org.openqa.selenium.remote.http.HttpResponse;

import java.io.File;
import java.net.URL;
import java.nio.file.Files;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.TimeUnit;

import static org.openqa.selenium.remote.http.Contents.asJson;
import static org.openqa.selenium.remote.http.Contents.string;
import static org.openqa.selenium.remote.http.HttpMethod.GET;
import static org.openqa.selenium.remote.http.HttpMethod.POST;

public class DownloadsSample {

  public static void main(String[] args) throws Exception {
    // Assuming the Grid is running locally.
    URL gridUrl = new URL("http://localhost:4444");
    ChromeOptions options = new ChromeOptions();
    options.setCapability("se:downloadsEnabled", true);
    RemoteWebDriver driver = new RemoteWebDriver(gridUrl, options);
    try {
      demoFileDownloads(driver, gridUrl);
    } finally {
      driver.quit();
    }
  }

	private static void demoFileDownloads(RemoteWebDriver driver, URL gridUrl) throws Exception {
		driver.get("https://www.selenium.dev/selenium/web/downloads/download.html");
		// Download the two available files on the page
		driver.findElement(By.id("file-1")).click();
		driver.findElement(By.id("file-2")).click();

		// The download happens in a remote Node, which makes it difficult to know when the file
		// has been completely downloaded. For demonstration purposes, this example uses a
		// 10-second sleep which should be enough time for a file to be downloaded.
		// We strongly recommend to avoid hardcoded sleeps, and ideally, to modify your
		// application under test, so it offers a way to know when the file has been completely
		// downloaded.
		TimeUnit.SECONDS.sleep(10);

		//This is the endpoint which will provide us with list of files to download and also to
		//let us download a specific file.
		String downloadsEndpoint = String.format("/session/%s/se/files", driver.getSessionId());

		String fileToDownload;

		try (HttpClient client = HttpClient.Factory.createDefault().createClient(gridUrl)) {
			// To list all files that are were downloaded on the remote node for the current session
			// we trigger GET request.
			HttpRequest request = new HttpRequest(GET, downloadsEndpoint);
			HttpResponse response = client.execute(request);
			Map<String, Object> jsonResponse = new Json().toType(string(response), Json.MAP_TYPE);
			@SuppressWarnings("unchecked")
			Map<String, Object> value = (Map<String, Object>) jsonResponse.get("value");
			@SuppressWarnings("unchecked")
			List<String> names = (List<String>) value.get("names");
			// Let's say there were "n" files downloaded for the current session, we would like
			// to retrieve ONLY the first file.
			fileToDownload = names.get(0);
		}

		// Now, let's download the file
		try (HttpClient client = HttpClient.Factory.createDefault().createClient(gridUrl)) {
			// To retrieve a specific file from one or more files that were downloaded by the current session
			// on a remote node, we use a POST request.
			HttpRequest request = new HttpRequest(POST, downloadsEndpoint);
			request.setContent(asJson(ImmutableMap.of("name", fileToDownload)));
			HttpResponse response = client.execute(request);
			Map<String, Object> jsonResponse = new Json().toType(string(response), Json.MAP_TYPE);
			@SuppressWarnings("unchecked")
			Map<String, Object> value = (Map<String, Object>) jsonResponse.get("value");
			// The returned map would contain 2 keys,
			// filename - This represents the name of the file (same as what was provided by the test)
			// contents - Base64 encoded String which contains the zipped file.
			String zippedContents = value.get("contents").toString();
			// The file contents would always be a zip file and has to be unzipped.
			File downloadDir = Zip.unzipToTempDir(zippedContents, "download", "");
			// Read the file contents
			File downloadedFile = Optional.ofNullable(downloadDir.listFiles()).orElse(new File[]{})[0];
			String fileContent = String.join("", Files.readAllLines(downloadedFile.toPath()));
			System.out.println("The file which was "
					+ "downloaded in the node is now available in the directory: "
					+ downloadDir.getAbsolutePath() + " and has the contents: " + fileContent);
		}
	}


}

4.3 - Toml配置选项

CLI选项 中 显示的所有选项都可以通过 TOML 文件进行配置. 此页面显示不同Grid组件的配置示例.

概述

Selenium Grid对配置文件使用 TOML 格式. 配置文件由多个部分组成, 每个部分都有选项及其各自的值.

有关详细的使用指南, 请参阅TOML文档 . 如果出现解析错误, 请使用 TOML linter 验证配置.

一般配置结构具有以下模式:

[section1]
option1="value"

[section2]
option2=["value1","value2"]
option3=true

下面是一些使用Toml文件配置的 Grid组件示例, 该组件可以 从下面的方式开始:

java -jar selenium-server-<version>.jar <component> --config /path/to/file/<file-name>.toml

单机模式

单机服务器, 在端口4449上运行, 新会话请求超时500秒.

[server]
port = 4449

[sessionqueue]
session-request-timeout = 500

特定浏览器和最大会话数限制

默认情况下仅启用Firefox 和Chrome的单机服务器或节点.

[node]
drivers = ["chrome", "firefox"]
max-sessions = 3

配置和定制驱动程序

具有定制驱动程序的单机或节点服务器, 允许使用Firefox试用或者每日构建的功能, 并且有不同的浏览器版本.

[node]
detect-drivers = false
[[node.driver-configuration]]
max-sessions = 100
display-name = "Firefox Nightly"
stereotype = "{\"browserName\": \"firefox\", \"browserVersion\": \"93\", \"platformName\": \"MAC\", \"moz:firefoxOptions\": {\"binary\": \"/Applications/Firefox Nightly.app/Contents/MacOS/firefox-bin\"}}"
[[node.driver-configuration]]
display-name = "Chrome Beta"
stereotype = "{\"browserName\": \"chrome\", \"browserVersion\": \"94\", \"platformName\": \"MAC\", \"goog:chromeOptions\": {\"binary\": \"/Applications/Google Chrome Beta.app/Contents/MacOS/Google Chrome Beta\"}}"
[[node.driver-configuration]]
display-name = "Chrome Dev"
stereotype = "{\"browserName\": \"chrome\", \"browserVersion\": \"95\", \"platformName\": \"MAC\", \"goog:chromeOptions\": {\"binary\": \"/Applications/Google Chrome Dev.app/Contents/MacOS/Google Chrome Dev\"}}"
webdriver-executable = '/path/to/chromedriver/95/chromedriver'

带Docker的单机或节点

单机或节点服务器能够在Docker容器中运行每个新会话. 禁用驱动程序检测, 则最多有2个并发会话. 原型配置需要映射一个Docker映像, Docker的守护进程需要通过http/tcp公开. 此外，可以通过 devices 属性定义在主机上可访问的哪些设备文件将在容器中可用。 有关 docker 设备映射如何工作的更多信息，请参阅 docker 文档。

[node]
detect-drivers = false
max-sessions = 2

[docker]
configs = [
    "selenium/standalone-chrome:93.0", "{\"browserName\": \"chrome\", \"browserVersion\": \"91\"}", 
    "selenium/standalone-firefox:92.0", "{\"browserName\": \"firefox\", \"browserVersion\": \"92\"}"
]
#Optionally define all device files that should be mapped to docker containers
#devices = [
#    "/dev/kvm:/dev/kvm"
#]
url = "http://localhost:2375"
video-image = "selenium/video:latest"

将命令中继到支持WebDriver的服务端点

连接到支持WebDriver外部服务 的Selenium Grid非常有用. 这种服务的一个例子可以是 云提供商或Appium服务器. 这样, Grid可以实现对本地不存在的平台和版本的更多覆盖.

下面是一个将Appium服务器连接到Grid的示例.

[node]
detect-drivers = false

[relay]
# Default Appium/Cloud server endpoint
url = "http://localhost:4723/wd/hub"
status-endpoint = "/status"
# Stereotypes supported by the service. The initial number is "max-sessions", and will allocate 
# that many test slots to that particular configuration
configs = [
  "5", "{\"browserName\": \"chrome\", \"platformName\": \"android\", \"appium:platformVersion\": \"11\"}"
]

启用基本身份验证

通过配置包含用户名和密码的 路由器/集线器/单机的方式, 可以使用这样的基本身份验证保护Grid. 加载Grid UI或者开始一个新的会话时 需要此用户/密码组合.

[router]
username = "admin"
password = "myStrongPassword"

下面是一个Java示例, 演示如何使用配置的用户和密码启动会话.

URL gridUrl = new URL("http://admin:myStrongPassword@localhost:4444");
RemoteWebDriver webDriver = new RemoteWebDriver(gridUrl, new ChromeOptions());

Setting custom capabilities for matching specific Nodes

Important: Custom capabilities need to be set in the configuration in all Nodes. They also need to be included always in every session request.

[node]
detect-drivers = false

[[node.driver-configuration]]
display-name = "firefox"
stereotype = '{"browserName": "firefox", "platformName": "macOS", "browserVersion":"96", "networkname:applicationName":"node_1", "nodename:applicationName":"app_1" }'
max-sessions = 5

Here is a Java example showing how to match that Node

FirefoxOptions options = new FirefoxOptions();
options.setCapability("networkname:applicationName", "node_1");
options.setCapability("nodename:applicationName", "app_1");
options.setBrowserVersion("96");
options.setPlatformName("macOS");
WebDriver driver = new RemoteWebDriver(new URL("http://localhost:4444"), options);
driver.get("https://selenium.dev");
driver.quit();

Enabling Managed downloads by the Node.

The Node can be instructed to manage downloads automatically. This will cause the Node to save all files that were downloaded for a particular session into a temp directory, which can later be retrieved from the node. To turn this capability on, use the below configuration:

[node]
enable-managed-downloads = true

Refer to the CLI section for a complete example.

5 - Grid架构

The Grid is designed as a set of components that all fulfill a role in maintaining the Grid. It can seem quite complicated, but hopefully this document can help clear up any confusion.

The Key Components

The main components of the Grid are:

Event Bus

Used for sending messages which may be received asynchronously between the other components.

New Session Queue

Maintains a list of incoming sessions which have yet to be assigned to a Node by the Distributor.

Distributor

Responsible for maintaining a model of the available locations in the Grid where a session may run (known as "slots") and taking any incoming new session requests and assigning them to a slot.

Node

Runs a WebDriver session. Each session is assigned to a slot, and each node has one or more slots.

Session Map

Maintains a mapping between the session ID and the address of the Node the session is running on.

Router

Acts as the front-end of the Grid. This is the only part of the Grid which may be exposed to the wider Web (though we strongly caution against it). This routes incoming requests to either the New Session Queue or the Node on which the session is running.

While discussing the Grid, there are some other useful concepts to keep in mind:

• A slot is the place where a session can run.
• Each slot has a stereotype. This is the minimal set of capabilities that a new session session request must match before the Distributor will send that request to the Node owning the slot.
• The Grid Model is how the Distributor tracks the state of the Grid. As the name suggests, this may sometimes fall out of sync with reality (perhaps because the Distributor has only just started). It is used in preference to querying each Node so that the Distributor can quickly assign a slot to a New Session request.

Synchronous and Asynchronous Calls

There are two main communication mechanisms used within the Grid:

1. Synchronous “REST-ish” JSON over HTTP requests.
2. Asynchronous events sent to the Event Bus.

How do we pick which communication mechanism to use? After all, we could model the entire Grid in an event-based way, and it would work out just fine.

The answer is that if the action being performed is synchronous (eg. most WebDriver calls), or if missing the response would be problematic, the Grid uses a synchronous call. If, instead, we want to broadcast information to anyone who’s interested, or if missing the response doesn’t matter, then we prefer to use the event bus.

One interesting thing to note is that the async calls are more decoupled from their listeners than the synchronous calls are.

Start Up Sequence and Dependencies Between Components

Although the Grid is designed to allow components to start up in any order, conceptually the order in which components starts is:

1. The Event Bus and Session Map start first. These have no other dependencies, not even on each other, and so are safe to start in parallel.
2. The Session Queue starts next.
3. It is now possible to start the Distributor. This will periodically connect to the Session Queue and poll for jobs, though this polling might be initiated either by an event (that a New Session has been added to the queue) or at regular intervals.
4. The Router(s) can be started. New Session requests will be directed to the Session Queue, and the Distributor will attempt to find a slot to run the session on.
5. We are now able to start a Node. See below for details about how the Node is registered with the Grid. Once registration is complete, the Grid is ready to serve traffic.

You can picture the dependencies between components this way, where a “✅” indicates that there is a synchronous dependency between the components.

Node Registration

The process of registering a new Node to the Grid is lightweight.

1. When the Node starts, it should emit a “heart beat” event on a regular basis. This heartbeat contains the node status.
2. The Distributor listens for the heart beat events. When it sees one, it attempts to GET the /status endpoint of the Node. It is from this information that the Grid is set up.

The Distributor will use the same /status endpoint to check the Node on a regular basis, but the Node should continue sending heart beat events even after started so that a Distributor without a persistent store of the Grid state can be restarted and will (eventually) be up to date and correct.

The Node Status Object

The Node Status is a JSON blob with the following fields:

It is recommended to put values in all fields.

The Slot Object

The Slot object represents a single slot within a Node. A “slot” is where a single session may be run. It is possible that a Node will have more slots than it can run concurrently. For example, a node may be able to run up 10 sessions, but they could be any combination of Chrome, Edge, or Firefox; in this case, the Node would indicate a “max session count” of 10, and then also say it has 10 slots for Chrome, 10 for Edge, and 10 for Firefox.

The Session Object

This represents a running session within a slot

6 - 高级功能

6.1 - 可观测性

Table of Contents

• Selenium Grid
• Observability
  • Distributed tracing
  • Event logging
• Grid Observability
  • Visualizing Traces
  • Leveraging event logs
• References

Selenium Grid

Grid aids in scaling and distributing tests by executing tests on various browser and operating system combinations.

Observability

Observability has three pillars: traces, metrics and logs. Since Selenium Grid 4 is designed to be fully distributed, observability will make it easier to understand and debug the internals.

Distributed tracing

A single request or transaction spans multiple services and components. Tracing tracks the request lifecycle as each service executes the request. It is useful in debugging in an error scenario. Some key terms used in tracing context are:

Trace Tracing allows one to trace a request through multiple services, starting from its origin to its final destination. This request’s journey helps in debugging, monitoring the end-to-end flow, and identifying failures. A trace depicts the end-to-end request flow. Each trace has a unique id as its identifier.

Span Each trace is made up of timed operations called spans. A span has a start and end time and it represents operations done by a service. The granularity of span depends on how it is instrumented. Each span has a unique identifier. All spans within a trace have the same trace id.

Span Attributes Span attributes are key-value pairs which provide additional information about each span.

Events Events are timed-stamped logs within a span. They provide additional context to the existing spans. Events also contain key-value pairs as event attributes.

Event logging

Logging is essential to debug an application. Logging is often done in a human-readable format. But for machines to search and analyze the logs, it has to have a well-defined format. Structured logging is a common practice of recording logs consistently in a fixed format. It commonly contains fields like:

• Timestamp
• Logging level
• Logger class
• Log message (This is further broken down into fields relevant to the operation where the log was recorded)

Logs and events are closely related. Events encapsulate all the possible information available to do a single unit of work. Logs are essentially subsets of an event. At the crux, both aid in debugging. Refer following resources for detailed understanding:

1. https://www.honeycomb.io/blog/how-are-structured-logs-different-from-events/
2. https://charity.wtf/2019/02/05/logs-vs-structured-events/

Grid Observability

Selenium server is instrumented with tracing using OpenTelemetry. Every request to the server is traced from start to end. Each trace consists of a series of spans as a request is executed within the server. Most spans in the Selenium server consist of two events:

1. Normal event - records all information about a unit of work and marks successful completion of the work.
2. Error event - records all information till the error occurs and then records the error information. Marks an exception event.

Running Selenium server

1. Standalone
2. Hub and Node
3. Fully Distributed
4. Docker

Visualizing Traces

All spans, events and their respective attributes are part of a trace. Tracing works while running the server in all of the above-mentioned modes.

By default, tracing is enabled in the Selenium server. Selenium server exports the traces via two exporters:

1. Console - Logs all traces and their included spans at FINE level. By default, Selenium server prints logs at INFO level and above. The log-level flag can be used to pass a logging level of choice while running the Selenium Grid jar/s.

java -jar selenium-server-4.0.0-<selenium-version>.jar standalone --log-level FINE

2. Jaeger UI - OpenTelemetry provides the APIs and SDKs to instrument traces in the code. Whereas Jaeger is a tracing backend, that aids in collecting the tracing telemetry data and providing querying, filtering and visualizing features for the data.

Detailed instructions of visualizing traces using Jaeger UI can be obtained by running the command :

java -jar selenium-server-4.0.0-<selenium-version>.jar info tracing

A very good example and scripts to run the server and send traces to Jaeger

Leveraging event logs

Tracing has to be enabled for event logging as well, even if one does not wish to export traces to visualize them.
By default, tracing is enabled. No additional parameters need to be passed to see logs on the console. All events within a span are logged at FINE level. Error events are logged at WARN level.

All event logs have the following fields :

Sample log

FINE [LoggingOptions$1.lambda$export$1] - {
  "traceId": "fc8aef1d44b3cc8bc09eb8e581c4a8eb",
  "spanId": "b7d3b9865d3ddd45",
  "spanKind": "INTERNAL",
  "eventTime": 1597819675128886121,
  "eventName": "Session request execution complete",
  "attributes": {
    "http.status_code": 200,
    "http.handler_class": "org.openqa.selenium.grid.router.HandleSession",
    "http.url": "\u002fsession\u002fdd35257f104bb43fdfb06242953f4c85",
    "http.method": "DELETE",
    "session.id": "dd35257f104bb43fdfb06242953f4c85"
  }
}

In addition to the above fields, based on OpenTelemetry specification error logs consist of :

Sample error log

WARN [LoggingOptions$1.lambda$export$1] - {
  "traceId": "7efa5ea57e02f89cdf8de586fe09f564",
  "spanId": "914df6bc9a1f6e2b",
  "spanKind": "INTERNAL",
  "eventTime": 1597820253450580272,
  "eventName": "exception",
  "attributes": {
    "exception.type": "org.openqa.selenium.ScriptTimeoutException",
    "exception.message": "Unable to execute request: java.sql.SQLSyntaxErrorException: Table 'mysql.sessions_mappa' doesn't exist ..." (full message will be printed),
    "exception.stacktrace": "org.openqa.selenium.ScriptTimeoutException: java.sql.SQLSyntaxErrorException: Table 'mysql.sessions_mappa' doesn't exist\nBuild info: version: '4.0.0-alpha-7', revision: 'Unknown'\nSystem info: host: 'XYZ-MacBook-Pro.local', ip: 'fe80:0:0:0:10d5:b63a:bdc6:1aff%en0', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.13.6', java.version: '11.0.7'\nDriver info: driver.version: unknown ...." (full stack will be printed),
    "http.handler_class": "org.openqa.selenium.grid.distributor.remote.RemoteDistributor",
    "http.url": "\u002fsession",
    "http.method": "POST"
  }
}

Note: Logs are pretty printed above for readability. Pretty printing for logs is turned off in Selenium server.

The steps above should set you up for seeing traces and logs.

References

1. Understanding Tracing
2. OpenTelemetry Tracing API Specification
3. Selenium Wiki
4. Structured logs vs events
5. Jaeger framework

6.2 - GraphQL查询支持

GraphQL 是一种用于API的查询语言, 也是用于使用现有数据完成这些查询的运行时. 其仅仅是使用户能够准确地获取所需.

枚举

枚举是表示字段的可能值的集合.

例如, Node对象具有一个称为status的字段. 状态是一个枚举 (特别是Status类型) , 因为它可能是UP , DRAINING 或 UNAVAILABLE.

标量

标量是基本类型的值: Int, Float, String, Boolean, 或 ID.

在调用GraphQL API时, 必须指定嵌套子字段, 直到只返回标量.

模式的结构

网格模式的结构如下:

{
    session(id: "<session-id>") : {
        id,
        capabilities,
        startTime,
        uri,
        nodeId,
        nodeUri,
        sessionDurationMillis
        slot : {
            id,
            stereotype,
            lastStarted
        }
    }
    grid: {
        uri,
        totalSlots,
        nodeCount,
        maxSession,
        sessionCount,
        version,
        sessionQueueSize
    }
    sessionsInfo: {
        sessionQueueRequests,
        sessions: [
            {
                id,
                capabilities,
                startTime,
                uri,
                nodeId,
                nodeUri,
                sessionDurationMillis
                slot : {
                    id,
                    stereotype,
                    lastStarted
                }
            }
        ]
    }
    nodesInfo: {
        nodes : [
            {
                id,
                uri,
                status,
                maxSession,
                slotCount,
                sessions: [
                    {
                        id,
                        capabilities,
                        startTime,
                        uri,
                        nodeId,
                        nodeUri,
                        sessionDurationMillis
                        slot : {
                            id,
                            stereotype,
                            lastStarted
                        }
                    }
                ],
                sessionCount,
                stereotypes,
                version,
                osInfo: {
                    arch,
                    name,
                    version
                }
            }
        ]
    }
}

查询 GraphQL

查询GraphQL的最佳方法是使用curl请求. GraphQL允许您仅获取所需的数据, 仅此而已.

下面给出了一些GraphQL查询的示例. 您可以根据需要构建自己的查询.

查询网格中 maxSession 和 sessionCount 的数量:

curl -X POST -H "Content-Type: application/json" --data '{"query": "{ grid { maxSession, sessionCount } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

通常在本地机器上 <LINK_TO_GRAPHQL_ENDPOINT> 会是 http://localhost:4444/graphql

查询全部会话、及节点以及网格的详情 :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ grid { uri, maxSession, sessionCount }, nodesInfo { nodes { id, uri, status, sessions { id, capabilities, startTime, uri, nodeId, nodeUri, sessionDurationMillis, slot { id, stereotype, lastStarted } }, slotCount, sessionCount }} }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询以获取当前网格的会话总数 :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ grid { sessionCount } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询以获取网格中的最大会话数量 :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ grid { maxSession } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询以获取网格中所有节点的全部会话详情 :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ sessionsInfo { sessions { id, capabilities, startTime, uri, nodeId, nodeId, sessionDurationMillis } } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询以获取网格中每个节点中所有会话的插槽信息 :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ sessionsInfo { sessions { id, slot { id, stereotype, lastStarted } } } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询以获取给定会话的会话信息查询以获取给定会话的会话信息 :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ session (id: \"<session-id>\") { id, capabilities, startTime, uri, nodeId, nodeUri, sessionDurationMillis, slot { id, stereotype, lastStarted } } } "}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询网格中每个节点的功能 :

curl -X POST -H "Content-Type: application/json" --data '{"query": "{ nodesInfo { nodes { stereotypes } } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询网格中每个节点的状态 :

curl -X POST -H "Content-Type: application/json" --data '{"query": "{ nodesInfo { nodes { status } } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

查询每个节点和网格的 URI :

curl -X POST -H "Content-Type: application/json" --data '{"query": "{ nodesInfo { nodes { uri } } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

Query for getting the current requests in the New Session Queue:

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ sessionsInfo { sessionQueueRequests } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

Query for getting the New Session Queue size :

curl -X POST -H "Content-Type: application/json" --data '{"query":"{ grid { sessionQueueSize } }"}' -s <LINK_TO_GRAPHQL_ENDPOINT>

6.3 - Grid端点

Grid

Grid 状态

Grid状态提供Grid的当前状态. 它包含每个注册节点的详细信息. 对于每个节点, 状态包括有关节点可用性、会话和插槽的信息.

cURL GET 'http://localhost:4444/status'

在独立模式下, Grid URL是独立服务器的地址.

在集线器节点模式下, Grid URL是集线器服务器的地址.

在完全分布式模式下, Grid URL是路由服务器的地址.

以上所有模式的默认URL皆为http://localhost:4444.

分发器

删除节点

要从Grid中删除节点, 请使用下面列出的cURL命令. 它不会停止在该节点上运行的任何持续中的会话. 除非显式终止, 否则节点将继续按原样运行. 分发器不再知晓该节点, 因此任何匹配的新会话请求 也不会转发到该节点.

在独立模式下, 分发器URL是独立服务器的地址.

在集线器节点模式下, 分发器URL是集线器服务器的地址.

cURL --request DELETE 'http://localhost:4444/se/grid/distributor/node/<node-id>' --header 'X-REGISTRATION-SECRET: <secret> '

在完全分布式模式下, URL是分发器的地址.

cURL --request DELETE 'http://localhost:5553/se/grid/distributor/node/<node-id>' --header 'X-REGISTRATION-SECRET: <secret>'

如果在设置Grid时未配置注册密码, 则使用

cURL --request DELETE 'http://<Distributor-URL>/se/grid/distributor/node/<node-id>' --header 'X-REGISTRATION-SECRET;'

放空节点

节点放空命令用于优雅地关闭节点. 放空节点将在所有持续中的会话完成后停止节点. 但是, 它不接受任何新的会话请求.

在独立模式下, 分发器URL是独立服务器的地址.

在集线器节点模式下, 分发器URL是集线器服务器的地址.

cURL --request POST 'http://localhost:4444/se/grid/distributor/node/<node-id>/drain' --header 'X-REGISTRATION-SECRET: <secret> '

在完全分布式模式下, URL是分发服务器的地址.

cURL --request POST 'http://localhost:5553/se/grid/distributor/node/<node-id>/drain' --header 'X-REGISTRATION-SECRET: <secret>'

如果在设置Grid时未配置注册密码, 则使用

cURL --request POST 'http://<Distributor-URL>/se/grid/distributor/node/<node-id>/drain' --header 'X-REGISTRATION-SECRET;'

节点

本节中的端点适用于 集线器节点模式和 节点独立运行的完全分布式网格模式. 在一个节点的情况下, 默认节点的URL为 http://localhost:5555 . 如果有多个节点, 请使用 Grid 状态 获取所有节点详细信息 以及定位地址.

状态

节点状态本质上是节点的运行状况检查. 分发器定期ping节点状态， 并相应地更新Grid模型. 状态包括相关的可用性, 会话和插槽的信息.

cURL --request GET 'http://localhost:5555/status'

放空

分发器将 放空 命令传递给 由node-id标识的相应节点. 要直接放空节点, 请使用下面列出的cuRL命令. 两个端点都有效并产生相同的结果. 放空会等待持续中的会话完成后 才停止节点.

cURL --request POST 'http://localhost:5555/se/grid/node/drain' --header 'X-REGISTRATION-SECRET: <secret>'

如果在设置Grid时未配置注册密码, 则使用

cURL --request POST 'http://<node-URL>/se/grid/node/drain' --header 'X-REGISTRATION-SECRET;'

检查会话所有者

要检查会话是否属于某一节点, 请使用下面列出的cURL命令.

cURL --request GET 'http://localhost:5555/se/grid/node/owner/<session-id>' --header 'X-REGISTRATION-SECRET: <secret>'

如果在设置Grid时未配置注册密码, 则使用

cURL --request GET 'http://<node-URL>/se/grid/node/owner/<session-id>' --header 'X-REGISTRATION-SECRET;'

如果会话属于该节点, 则返回true, 否则返回false.

删除会话

删除会话将终止WebDriver会话, 退出驱动程序 并将其从活动会话集合中删除. 任何使用删除的会话id 或重用驱动程序实例的请求 都将抛出错误.

cURL --request DELETE 'http://localhost:5555/se/grid/node/session/<session-id>' --header 'X-REGISTRATION-SECRET: <secret>'

如果在设置Grid时未配置注册密码, 则使用

cURL --request DELETE 'http://<node-URL>/se/grid/node/session/<session-id>' --header 'X-REGISTRATION-SECRET;'

新会话队列

清除新会话队列

新会话请求队列保存新会话请求. 要清除队列, 请使用下面列出的cURL命令. 清除队列将拒绝队列中的所有请求. 对于每个这样的请求, 服务器都会向相应的客户端返回一个错误响应. 清除命令的返回结果是 已删除请求的总数.

在独立模式下, 队列URL是独立服务器的地址. 在集线器节点模式下, 队列URL是集线器服务器的地址.

cURL --request DELETE 'http://localhost:4444/se/grid/newsessionqueue/queue' --header 'X-REGISTRATION-SECRET: <secret>'

在完全分布式模式下, 队列URL是新会话队列服务器的地址.

cURL --request DELETE 'http://localhost:5559/se/grid/newsessionqueue/queue' --header 'X-REGISTRATION-SECRET: <secret>'

如果在设置Grid时未配置注册密码, 则使用

cURL --request DELETE 'http://<URL>/se/grid/newsessionqueue/queue' --header 'X-REGISTRATION-SECRET;'

获取新会话队列请求

New Session Request Queue holds the new session requests. To get the current requests in the queue, use the cURL command enlisted below. The response returns the total number of requests in the queue and the request payloads. 新会话请求队列保存新会话请求. 要获取队列中的当前请求, 请使用下面列出的cURL命令. 响应会返回队列中的请求总数以及请求内容.

在独立模式下, 队列URL是独立服务器的地址. 在集线器节点模式下, 队列URL是集线器服务器的地址.

cURL --request GET 'http://localhost:4444/se/grid/newsessionqueue/queue'

在完全分布式模式下, 队列URL是新会话队列服务器的地址.

cURL --request GET 'http://localhost:5559/se/grid/newsessionqueue/queue'

6.4 - Customizing a Node

How to customize a Node

There are times when we would like a Node to be customized to our needs.

For e.g., we may like to do some additional setup before a session begins execution and some clean-up after a session runs to completion.

Following steps can be followed for this:

• Create a class that extends org.openqa.selenium.grid.node.Node

• Add a static method (this will be our factory method) to the newly created class whose signature looks like this:

  public static Node create(Config config). Here:

  • Node is of type org.openqa.selenium.grid.node.Node
  • Config is of type org.openqa.selenium.grid.config.Config

• Within this factory method, include logic for creating your new Class.

• To wire in this new customized logic into the hub, start the node and pass in the fully qualified class name of the above class to the argument --node-implementation

Let’s see an example of all this:

Custom Node as an uber jar

1. Create a sample project using your favourite build tool (Maven|Gradle).
2. Add the below dependency to your sample project.
   • org.seleniumhq.selenium/selenium-grid
3. Add your customized Node to the project.
4. Build an uber jar to be able to start the Node using java -jar command.
5. Now start the Node using the command:

java -jar custom_node-server.jar node \
--node-implementation org.seleniumhq.samples.DecoratedLoggingNode

Note: If you are using Maven as a build tool, please prefer using maven-shade-plugin instead of maven-assembly-plugin because maven-assembly plugin seems to have issues with being able to merge multiple Service Provider Interface files (META-INF/services)

Custom Node as a regular jar

1. Create a sample project using your favourite build tool (Maven|Gradle).
2. Add the below dependency to your sample project.
   • org.seleniumhq.selenium/selenium-grid
3. Add your customized Node to the project.
4. Build a jar of your project using your build tool.
5. Now start the Node using the command:

java -jar selenium-server-4.6.0.jar \
--ext custom_node-1.0-SNAPSHOT.jar node \
--node-implementation org.seleniumhq.samples.DecoratedLoggingNode

Below is a sample that just prints some messages on to the console whenever there’s an activity of interest (session created, session deleted, a webdriver command executed etc.,) on the Node.

package org.seleniumhq.samples;

import java.net.URI;
import java.util.UUID;
import org.openqa.selenium.Capabilities;
import org.openqa.selenium.NoSuchSessionException;
import org.openqa.selenium.WebDriverException;
import org.openqa.selenium.grid.config.Config;
import org.openqa.selenium.grid.data.CreateSessionRequest;
import org.openqa.selenium.grid.data.CreateSessionResponse;
import org.openqa.selenium.grid.data.NodeId;
import org.openqa.selenium.grid.data.NodeStatus;
import org.openqa.selenium.grid.data.Session;
import org.openqa.selenium.grid.log.LoggingOptions;
import org.openqa.selenium.grid.node.HealthCheck;
import org.openqa.selenium.grid.node.Node;
import org.openqa.selenium.grid.node.local.LocalNodeFactory;
import org.openqa.selenium.grid.security.Secret;
import org.openqa.selenium.grid.security.SecretOptions;
import org.openqa.selenium.grid.server.BaseServerOptions;
import org.openqa.selenium.internal.Either;
import org.openqa.selenium.remote.SessionId;
import org.openqa.selenium.remote.http.HttpRequest;
import org.openqa.selenium.remote.http.HttpResponse;
import org.openqa.selenium.remote.tracing.Tracer;

public class DecoratedLoggingNode extends Node {

  private Node node;

  protected DecoratedLoggingNode(Tracer tracer, URI uri, Secret registrationSecret) {
    super(tracer, new NodeId(UUID.randomUUID()), uri, registrationSecret);
  }

  public static Node create(Config config) {
    LoggingOptions loggingOptions = new LoggingOptions(config);
    BaseServerOptions serverOptions = new BaseServerOptions(config);
    URI uri = serverOptions.getExternalUri();
    SecretOptions secretOptions = new SecretOptions(config);

    // Refer to the foot notes for additional context on this line.
    Node node = LocalNodeFactory.create(config);

    DecoratedLoggingNode wrapper = new DecoratedLoggingNode(loggingOptions.getTracer(),
        uri, secretOptions.getRegistrationSecret());
    wrapper.node = node;
    return wrapper;
  }

  @Override
  public Either<WebDriverException, CreateSessionResponse> newSession(
      CreateSessionRequest sessionRequest) {
    System.out.println("Before newSession()");
    try {
      return this.node.newSession(sessionRequest);
    } finally {
      System.out.println("After newSession()");
    }
  }

  @Override
  public HttpResponse executeWebDriverCommand(HttpRequest req) {
    try {
      System.out.println("Before executeWebDriverCommand(): " + req.getUri());
      return node.executeWebDriverCommand(req);
    } finally {
      System.out.println("After executeWebDriverCommand()");
    }
  }

  @Override
  public Session getSession(SessionId id) throws NoSuchSessionException {
    try {
      System.out.println("Before getSession()");
      return node.getSession(id);
    } finally {
      System.out.println("After getSession()");
    }
  }

  @Override
  public HttpResponse uploadFile(HttpRequest req, SessionId id) {
    try {
      System.out.println("Before uploadFile()");
      return node.uploadFile(req, id);
    } finally {
      System.out.println("After uploadFile()");
    }
  }

  @Override
  public void stop(SessionId id) throws NoSuchSessionException {
    try {
      System.out.println("Before stop()");
      node.stop(id);
    } finally {
      System.out.println("After stop()");
    }
  }

  @Override
  public boolean isSessionOwner(SessionId id) {
    try {
      System.out.println("Before isSessionOwner()");
      return node.isSessionOwner(id);
    } finally {
      System.out.println("After isSessionOwner()");
    }
  }

  @Override
  public boolean isSupporting(Capabilities capabilities) {
    try {
      System.out.println("Before isSupporting");
      return node.isSupporting(capabilities);
    } finally {
      System.out.println("After isSupporting()");
    }
  }

  @Override
  public NodeStatus getStatus() {
    try {
      System.out.println("Before getStatus()");
      return node.getStatus();
    } finally {
      System.out.println("After getStatus()");
    }
  }

  @Override
  public HealthCheck getHealthCheck() {
    try {
      System.out.println("Before getHealthCheck()");
      return node.getHealthCheck();
    } finally {
      System.out.println("After getHealthCheck()");
    }
  }

  @Override
  public void drain() {
    try {
      System.out.println("Before drain()");
      node.drain();
    } finally {
      System.out.println("After drain()");
    }

  }

  @Override
  public boolean isReady() {
    try {
      System.out.println("Before isReady()");
      return node.isReady();
    } finally {
      System.out.println("After isReady()");
    }
  }
}

Foot Notes:

In the above example, the line Node node = LocalNodeFactory.create(config); explicitly creates a LocalNode.

There are basically 2 types of user facing implementations of org.openqa.selenium.grid.node.Node available.

These classes are good starting points to learn how to build a custom Node and also to learn the internals of a Node.

• org.openqa.selenium.grid.node.local.LocalNode - Used to represent a long running Node and is the default implementation that gets wired in when you start a node.
  • It can be created by calling LocalNodeFactory.create(config);, where:
    • LocalNodeFactory belongs to org.openqa.selenium.grid.node.local
    • Config belongs to org.openqa.selenium.grid.config
• org.openqa.selenium.grid.node.k8s.OneShotNode - This is a special reference implementation wherein the Node gracefully shuts itself down after servicing one test session. This class is currently not available as part of any pre-built maven artifact.
  • You can refer to the source code here to understand its internals.
  • To build it locally refer here.
  • It can be created by calling OneShotNode.create(config), where:
    • OneShotNode belongs to org.openqa.selenium.grid.node.k8s
    • Config belongs to org.openqa.selenium.grid.config

6.5 - External datastore

Table of Contents

• Introduction
• Setup
• Database backed Session Map
  • Steps
• Redis backed Session Map
  • Steps

Introduction

Selenium Grid allows you to persist information related to currently running sessions into an external data store. The external data store could be backed by your favourite database (or) Redis Cache system.

Setup

• Coursier - As a dependency resolver, so that we can download maven artifacts on the fly and make them available in our classpath
• Docker - To manage our PostGreSQL/Redis docker containers.

Database backed Session Map

For the sake of this illustration, we are going to work with PostGreSQL database.

We will spin off a PostGreSQL database as a docker container using a docker compose file.

Steps

You can skip this step if you already have a PostGreSQL database instance available at your disposal.

• Create a sql file named init.sql with the below contents:

CREATE TABLE IF NOT EXISTS sessions_map(
    session_ids varchar(256),
    session_caps text,
    session_uri varchar(256),
    session_stereotype text,
    session_start varchar(256)
 );

• In the same directory as the init.sql, create a file named docker-compose.yml with its contents as below:

version: '3.8'
services:
  db:
    image: postgres:9.6-bullseye
    restart: always
    environment:
      - POSTGRES_USER=seluser
      - POSTGRES_PASSWORD=seluser
      - POSTGRES_DB=selenium_sessions
    ports:
      - "5432:5432"
    volumes:
    - ./init.sql:/docker-entrypoint-initdb.d/init.sql

We can now start our database container by running:

docker-compose up -d

Our database name is selenium_sessions with its username and password set to seluser

If you are working with an already running PostGreSQL DB instance, then you just need to create a database named selenium_sessions and the table sessions_map using the above mentioned SQL statement.

• Create a Selenium Grid configuration file named sessions.toml with the below contents:

[sessions]
implementation = "org.openqa.selenium.grid.sessionmap.jdbc.JdbcBackedSessionMap"
jdbc-url = "jdbc:postgresql://localhost:5432/selenium_sessions"
jdbc-user = "seluser"
jdbc-password = "seluser"

Note: If you plan to use an existing PostGreSQL DB instance, then replace localhost:5432 with the actual host and port number of your instance.

• Below is a simple shell script (let’s call it distributed.sh) that we will use to bring up our distributed Grid.

SE_VERSION=<current_selenium_version>
JAR_NAME=selenium-server-${SE_VERSION}.jar
PUBLISH="--publish-events tcp://localhost:4442"
SUBSCRIBE="--subscribe-events tcp://localhost:4443"
SESSIONS="--sessions http://localhost:5556"
SESSIONS_QUEUE="--sessionqueue http://localhost:5559"
echo 'Starting Event Bus'
java -jar $JAR_NAME event-bus $PUBLISH $SUBSCRIBE --port 5557 &
echo 'Starting New Session Queue'
java -jar $JAR_NAME sessionqueue --port 5559 &
echo 'Starting Sessions Map'
java -jar $JAR_NAME \
--ext $(coursier fetch -p org.seleniumhq.selenium:selenium-session-map-jdbc:${SE_VERSION} org.postgresql:postgresql:42.3.1) \
sessions $PUBLISH $SUBSCRIBE --port 5556 --config sessions.toml &
echo 'Starting Distributor'
java -jar $JAR_NAME  distributor $PUBLISH $SUBSCRIBE $SESSIONS $SESSIONS_QUEUE --port 5553 --bind-bus false &
echo 'Starting Router'
java -jar $JAR_NAME router $SESSIONS --distributor http://localhost:5553 $SESSIONS_QUEUE --port 4444 &
echo 'Starting Node'
java -jar $JAR_NAME node $PUBLISH $SUBSCRIBE &

• At this point the current directory should contain the following files:

  • docker-compose.yml
  • init.sql
  • sessions.toml
  • distributed.sh

• You can now spawn the Grid by running distributed.sh shell script and quickly run a test. You will notice that the Grid now stores session information into the PostGreSQL database.

In the line which spawns a SessionMap on a machine:

export SE_VERSION=<current_selenium_version>
java -jar selenium-server-${SE_VERSION}.jar \
--ext $(coursier fetch -p org.seleniumhq.selenium:selenium-session-map-jdbc:${SE_VERSION} org.postgresql:postgresql:42.3.1) \
sessions --publish-events tcp://localhost:4442 \
--subscribe-events tcp://localhost:4443 \
--port 5556 --config sessions.toml 

• The variable names from the above script have been replaced with their actual values for clarity.
• Remember to substitute localhost with the actual hostname of the machine where your Event-Bus is running.
• The arguments being passed to coursier are basically the GAV (Group Artifact Version) Maven co-ordinates of:
  • selenium-session-map-jdbc which is needed to help us store sessions information in database
  • postgresql which is needed to help us talk PostGreSQL database.
• sessions.toml is the configuration file that we created earlier.

Redis backed Session Map

We will spin off a Redis Cache docker container using a docker compose file.

Steps

You can skip this step if you already have a Redis Cache instance available at your disposal.

• Create a file named docker-compose.yml with its contents as below:

version: '3.8'
services:
  redis:
    image: redis:bullseye
    restart: always
    ports:
      - "6379:6379"

We can now start our Redis container by running:

docker-compose up -d

• Create a Selenium Grid configuration file named sessions.toml with the below contents:

[sessions]
scheme = "redis"
implementation = "org.openqa.selenium.grid.sessionmap.redis.RedisBackedSessionMap"
hostname = "localhost"
port = 6379

Note: If you plan to use an existing Redis Cache instance, then replace localhost and 6379 with the actual host and port number of your instance.

• Below is a simple shell script (let’s call it distributed.sh) that we will use to bring up our distributed grid.

SE_VERSION=<current_selenium_version>
JAR_NAME=selenium-server-${SE_VERSION}.jar
PUBLISH="--publish-events tcp://localhost:4442"
SUBSCRIBE="--subscribe-events tcp://localhost:4443"
SESSIONS="--sessions http://localhost:5556"
SESSIONS_QUEUE="--sessionqueue http://localhost:5559"
echo 'Starting Event Bus'
java -jar $JAR_NAME event-bus $PUBLISH $SUBSCRIBE --port 5557 &
echo 'Starting New Session Queue'
java -jar $JAR_NAME sessionqueue --port 5559 &
echo 'Starting Session Map'
java -jar $JAR_NAME \
--ext $(coursier fetch -p org.seleniumhq.selenium:selenium-session-map-redis:${SE_VERSION}) \
sessions $PUBLISH $SUBSCRIBE --port 5556 --config sessions.toml &
echo 'Starting Distributor'
java -jar $JAR_NAME  distributor $PUBLISH $SUBSCRIBE $SESSIONS $SESSIONS_QUEUE --port 5553 --bind-bus false &
echo 'Starting Router'
java -jar $JAR_NAME router $SESSIONS --distributor http://localhost:5553 $SESSIONS_QUEUE --port 4444 &
echo 'Starting Node'
java -jar $JAR_NAME node $PUBLISH $SUBSCRIBE &

• At this point the current directory should contain the following files:

  • docker-compose.yml
  • sessions.toml
  • distributed.sh

• You can now spawn the Grid by running distributed.sh shell script and quickly run a test. You will notice that the Grid now stores session information into the Redis instance. You can perhaps make use of a Redis GUI such as TablePlus to see them (Make sure that you have setup a debug point in your test, because the values will get deleted as soon as the test runs to completion).

In the line which spawns a SessionMap on a machine:

export SE_VERSION=<current_selenium_version>
java -jar selenium-server-${SE_VERSION}.jar \
--ext $(coursier fetch -p org.seleniumhq.selenium:selenium-session-map-redis:${SE_VERSION}) \
sessions --publish-events tcp://localhost:4442 \
--subscribe-events tcp://localhost:4443 \
--port 5556 --config sessions.toml 

• The variable names from the above script have been replaced with their actual values for clarity.
• Remember to substitute localhost with the actual hostname of the machine where your Event-Bus is running.
• The arguments being passed to coursier are basically the GAV (Group Artifact Version) Maven co-ordinates of:
  • selenium-session-map-redis which is needed to help us store sessions information in Redis Cache.
• sessions.toml is the configuration file that we created earlier.