Grid

• 1: 独自のグリッドを設定する
• 2: グリッドを使用する場合
• 3: グリッドのコンポーネント
• 4: コンポーネントの構成
• 4.1: 構成ヘルプ
• 4.2: CLI Options
• 4.3: Toml Options
• 5: Grid Architecture
• 6: 高度な機能
• 6.1: Observability
• 6.2: GraphQLクエリのサポート
• 6.3: Grid Endpoints

1 - 独自のグリッドを設定する

Grid roles

Several components compose a Selenium Grid. Depending on your needs, you can start each one of them on its own, or a few at the same time by using a Grid role.

Standalone

Standalone is the union of all components, and to the user’s eyes, they are executed as one. A fully functional Grid of one is available after starting it in the Standalone mode.

Standalone is also the easiest mode to spin up a Selenium Grid. By default, the server will be listening on http://localhost:4444, and that’s the URL you should point your RemoteWebDriver tests. The server will detect the available drivers that it can use from the System PATH.

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

Hub and Node(s)

It enables the classic Hub & Node(s) setup. These roles are suitable for small and middle-sized Grids.

Hub

A Hub is the union of the following components:

• Router
• Distributor
• Session Map
• New Session Queue
• Event Bus

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

By default, the server will be listening on http://localhost:4444, and that’s the URL you should point your RemoteWebDriver tests.

Node(s)

One or more Nodes can be started in this setup, and the server will detect the available drivers that it can use from the System PATH.

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

Distributed

On Distributed mode, each component needs to be started on its own. This setup is more suitable for large Grids.

1. Event Bus: serves as a communication path to other Grid components in subsequent steps.

java -jar selenium-server-<version>.jar  event-bus

2. Session Map: responsible for mapping session IDs to the Node where the session is running.

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

3. New Session Queue: adds the new session request to a queue, then the distributor processes it.

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

4. Distributor: Nodes register to it, and assigns a Node for a session request.

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

5. Router: the Grid entrypoint, in charge of redirecting requests to the right component.

java -jar selenium-server-<version>.jar router --sessions http://localhost:5556 --distributor http://localhost:5553 --sessionqueue http://localhost:5559

6. Node(s)

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

Running tests

To run tests after starting successfully Selenium Grid, you can use a RemoteWebDriver. Head to the RemoteWebDriver section for more details.

Tests metadata

You can add metadata to your tests and consume it via GraphQL or visualize parts of it through the Selenium Grid UI. Metadata can be added by prefixing the metadata with se:.

Here is a quick example in Java showing how to do that.

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();

Querying Selenium Grid

After starting a Grid, there are mainly two ways of querying its status, through the Grid UI or via an API call.

The Grid UI can be reached by opening your preferred browser and heading to http://localhost:4444.

API calls can be done through the http://localhost:4444/status endpoint or using GraphQL

警告

Selenium Gridは、適切なファイアウォールアクセス許可を使用して外部アクセスから保護する必要があります。

グリッドを保護しないと、次の1つ以上が発生する可能性があります。

• グリッドインフラストラクチャへのオープンアクセスを提供します。
• サードパーティが内部Webアプリケーションおよびファイルにアクセスすることを許可します。
• サードパーティにカスタムバイナリの実行を許可します。

Detectify に関するこのブログ投稿をご覧ください。 これは、公開されたグリッドが悪用される可能性のある概要を示しています。 Don’t Leave your Grid Wide Open

2 - グリッドを使用する場合

一般的に、グリッドを使用する理由は2つあります。

• 複数のブラウザー、複数のバージョンのブラウザー、および異なるオペレーティングシステムで実行されているブラウザーに対してテストを実行するため。
• テストスイートがテストがパスするのに完了するのにかかる時間を短縮するため。

グリッドは、複数のマシンを使用してテストを並行して実行することにより、テストパスの実行を高速化するために使用されます。 たとえば、100個のテストスイートがあり、それらのテストを実行するために4つの異なるマシン（VMまたは個別の物理マシン）をサポートするようにグリッドをセットアップした場合、テストスイートは単一のマシンでテストを連続して実行した場合と比較して（およそ）4分の1の時間で完了します。 大規模なテストスイート、および大量のデータ検証を実行するような長時間実行されるテストスイートの場合、これは大幅な時間の節約になります。 一部のテストスイートの実行には数時間かかる場合があります。 スイートの実行に費やす時間を増やすもう1つの理由は、開発者がAUTのコードをチェックインした後のテスト結果の所要時間を短縮することです。 アジャイルソフトウェア開発を実践しているソフトウェアチームは、一晩テストパスを一晩待つのではなく、できるだけ早くテストフィードバックを求めています。

グリッドは、複数のランタイム環境、特に異なるブラウザーに対して同時に実行するテストをサポートするためにも使用されます。 たとえば、仮想マシンの"グリッド"は、テスト対象のアプリケーションがサポートする必要がある異なるブラウザーをサポートするようにセットアップできます。 したがって、マシン1にはInternet Explorer 8、マシン2、Internet Explorer 9、マシン3は最新のChrome、マシン4は最新のFirefoxを持っています。 テストスイートが実行されると、Selenium-Gridは各テストブラウザーの組み合わせを受け取り、必要なブラウザーに対して実行する各テストを割り当てます。

さらに、すべて同じブラウザ、タイプ、およびバージョンのグリッドを持つことができます。 たとえば、それぞれがFirefox 70の3つのインスタンスを実行する4台のマシンのグリッドを持つことができ、利用可能なFirefoxインスタンスの"ある意味"での"サーバーファーム"を可能にします。 スイートが実行されると、各テストはグリッドに渡され、グリッドは次に利用可能なFirefoxインスタンスにテストを割り当てます。 この方法で、おそらく12のテストがすべて同時に並行して実行されるテストパスを取得し、テストパスの完了に必要な時間を大幅に短縮します。

グリッドは非常に柔軟です。 これらの2つの例を組み合わせて、各ブラウザタイプとバージョンの複数のインスタンスを許可することができます。 このような構成では、迅速にテストがパスすることを完了するための並列実行と、複数のブラウザタイプおよびバージョンの同時サポートの両方が提供されます。

3 - グリッドのコンポーネント

ルーター

ルーターがリクエストを正しいコンポーネントに転送します。

これはGridのエントリポイントであり、すべての外部リクエストはGridによって受信されます。 ルーターの動作は、リクエストによって異なります。 新しいセッション要求の場合、ルーターはそれをディストリビュータに転送します（新しいセッションの作成が処理されます）。 リクエストが既存のセッションに属している場合、ルーターはセッションIDをセッションマップに送信し、 セッションマップはセッションが実行されているノードを返します。 この後、ルーターはリクエストをノードに転送します。

ルーターは、プロセスで不要なコンポーネントをオーバーロードすることなく、 より適切に処理できるコンポーネントにリクエストを送信することにより、 Grid内の負荷のバランスをとることを目的としています。

ディストリビューター

ディストリビューターは、すべてのノードとそのケイパビリティを認識しています。 その主な役割は、新しいセッション要求を受け取り、セッションを作成できる適切なノードを見つけることです。 セッションが作成されると、ディストリビューターは、 セッションIDとセッションが実行されているノードとの関係をセッションマップに格納します。

ノード

ノードはGrid内に数回存在することができます。 各ノードは、それが実行されているマシンの利用可能なブラウザのスロットを管理します。

ノードは、イベントバスを介して自身をディストリビューターに登録し、その構成は登録メッセージの一部として送信されます。

By default, the Node auto-registers all browser drivers available on the path of the machine where it runs. It also creates one slot per available CPU for Chromium based browsers and Firefox. For Safari and Internet Explorer, only one slot is created. Through a specific configuration, it can run sessions in Docker containers or relay commands. You can see more configuration details in setting up your own grid.

ノードは受信したコマンドを実行するだけで、評価、判断、制御は行いません。 ノードが実行されているマシンは、他のコンポーネントと同じオペレーティングシステムを持つ必要はありません。 たとえば、WindowsノードにはInternet Explorerをブラウザーオプションとして提供する機能がありますが、 これはLinuxまたはMacでは不可能です。

Session Map

The Session Map is a data store that keeps the information of the session id and the Node where the session is running. It serves as a support for the Router in the process of forwarding a request to the Node. The Router will ask the Session Map for the Node associated to a session id.

New Session Queue

New Session Queue holds all the new session requests in a FIFO order. It has configurable parameters for setting the request timeout and request retry interval.

The Router adds the new session request to the New Session Queue and waits for the response. The New Session Queue regularly checks if any request in the queue has timed out, if so the request is rejected and removed immediately.

The Distributor regularly checks if a slot is available. If so, the Distributor requests the New Session Queue for the first matching request. The Distributor then attempts to create a new session.

Once the requested capabilities match the capabilities of any of the free Node slots, the Distributor attempts to get the available slot. If all the slots are busy, the Distributor will ask the queue to add the request to the front of the queue. If request times out while retrying or adding to the front of the queue it is rejected.

After a session is created successfully, the Distributor sends the session information to the New Session Queue. The New Session Queue sends the response back to the client.

Event Bus

The Event Bus serves as a communication path between the Nodes, Distributor, New Session Queue, and Session Map. The Grid does most of its internal communication through messages, avoiding expensive HTTP calls. When starting the Grid in its fully distributed mode, the Event Bus is the first component that should be started.

4 - コンポーネントの構成

4.1 - 構成ヘルプ

Info コマンド

infoコマンドは、次のトピックに関する詳細なドキュメントを提供します。

• Seleniumの構成
• セキュリティ
• セッションマップの設定
• トレース

構成ヘルプ

クイック設定のヘルプと概要は、以下を実行することで提供されます。

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

セキュリティ

安全な通信とノード登録のためのグリッドサーバーの設定の詳細を取得するには、以下を実行します。

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

セッションマップの設定

デフォルトでは、グリッドはローカルセッションマップを使用してセッション情報を保存します。 グリッドは、RedisやJDBC-SQLがサポートするデータベースなどの追加のストレージオプションをサポートしています。 別のセッションストレージをセットアップするには、次のコマンドを使用してセットアップ手順を取得します。

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

OpenTelemetryとJaegerを使用したトレースの設定

デフォルトでは、トレースは有効になっています。 トレースをエクスポートしてJaeger経由で視覚化するには、次のコマンドを使用して手順を実行します。

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

SeleniumGridコマンドを一覧表示する

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

使用可能なすべてのコマンドとそれぞれの説明が表示されます。

コンポーネントヘルプコマンド

Seleniumロールの後に–help configオプションを渡して、コンポーネント固有の構成情報を取得します。

スタンドアロン

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

ハブ

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

セッション

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

新しいセッションキューラー

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

ディストリビューター

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

ルーター

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

ノード

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

4.2 - CLI Options

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.

4.3 - Toml Options

All the options shown in CLI options can be configured through a TOML file. This page shows configuration examples for the different Grid components.

Overview

Selenium Grid uses TOML format for config files. The config file consists of sections and each section has options and its respective value(s).

Refer to the TOML documentation for detailed usage guidance. In case of parsing errors, validate the config using TOML linter.

The general configuration structure has the following pattern:

[section1]
option1="value"

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

Below are some examples of Grid components configured with a Toml file, the component can be started in the following way:

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

Standalone

A Standalone server, running on port 4449, and a new session request timeout of 500 seconds.

[server]
port = 4449

[sessionqueue]
session-request-timeout = 500

Specific browsers and a limit of max sessions

A Standalone server or a Node which only has Firefox and Chrome enabled by default.

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

Configuring and customising drivers

Standalone or Node server with customised drivers, which allows things like having Firefox Beta or Nightly, and having different browser versions.

[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'

Standalone or Node with Docker

A Standalone or Node server that is able to run each new session in a Docker container. Disabling drivers detection, having maximum 2 concurrent sessions. Stereotypes configured need to be mapped to a Docker image, and the Docker daemon needs to be exposed via http/tcp. In addition, it is possible to define which device files, accessible on the host, will be available in containers through the devices property. Refer to the docker documentation for more information about how docker device mapping works.

[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"

Relaying commands to a service endpoint that supports WebDriver

It is useful to connect an external service that supports WebDriver to Selenium Grid. An example of such service could be a cloud provider or an Appium server. In this way, Grid can enable more coverage to platforms and versions not present locally.

The following is an en example of connecting an Appium server to Grid.

[server]
port = 5555

[node]
detect-drivers = false

[relay]
# Default Appium server endpoint
url = "http://localhost:4723/wd/hub"
status-endpoint = "/status"
# Stereotypes supported by the service
configs = [
  "1", "{\"browserName\": \"chrome\", \"platformName\": \"android\", \"appium:platformVersion\": \"11\"}"
]

Basic auth enabled

It is possible to protect a Grid with basic auth by configuring the Router/Hub/Standalone with a username and password. This user/password combination will be needed when loading the Grid UI or starting a new session.

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

Here is a Java example showing how to start a session using the configured user and password.

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();

5 - Grid Architecture

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.

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 - 高度な機能

6.1 - Observability

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クエリのサポート

GraphQLは、APIのクエリ言語であり、既存のデータでこれらのクエリを実行するためのランタイムです。 これにより、ユーザーは必要なものだけを正確に要求することができます。

列挙型(Enum)

列挙型は、フィールドの可能な値のセットを表します。

たとえば、 Node オブジェクトには status というフィールドがあります。 UP 、 DRAINING 、または UNAVAILABLE の可能性があるため、状態は、 列挙型（具体的には、Status タイプ）です。

スカラー

スカラーはプリミティブ値です： Int 、 Float 、 String 、 Boolean 、または ID 。

GraphQL APIを呼び出すときは、スカラーのみを返すまでネストされたサブフィールドを指定する必要があります。

スキーマの構造

グリッドスキーマの構造は次のとおりです。

{
    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
                }
            }
        ]
    }
}

GraphQLで照会する

GraphQLをクエリする最良の方法は、 curl リクエストを使用することです。 GraphQLを使用すると、必要なデータのみをフェッチできます。それ以上でもそれ以下でもありません。

GraphQLクエリの例のいくつかを以下に示します。 必要に応じて独自のクエリを作成できます。

グリッド内の maxSessionと sessionCountの数を照会する

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

通常、ローカルマシンでは、 <LINK_TO_GRAPHQL_ENDPOINT> は http://localhost:4444/graphql になります。

セッション、ノード、グリッドのすべての詳細を照会する

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>

グリッドで現在のセッション数を取得するためのクエリ

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

グリッドで最大セッション数を取得するためのクエリ

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

グリッド内のすべてのノードのすべてのセッションの詳細を取得するためのクエリ

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

グリッド内の各ノードのすべてのセッションのスロット情報を取得するためのクエリ

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

特定のセッションのセッション情報を取得するためのクエリ

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>

グリッド内の各ノードのcapabilityを照会する

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

グリッド内の各ノードのステータスを照会する

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

各ノードとグリッドのURIを照会する

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

新しいセッションキューで現在のリクエストを取得するためのクエリ

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

新しいセッションキューのサイズを取得するためのクエリ

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

6.3 - Grid Endpoints

Grid

Grid Status

Grid status provides the current state of the Grid. It consists of details about every registered Node. For every Node, the status includes information regarding Node availability, sessions, and slots.

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

In the Standalone mode, the Grid URL is the Standalone server address.

In the Hub-Node mode, the Grid URL is the Hub server address.

In the fully distributed mode, the Grid URL is the Router server address.

Default URL for all the above modes is http://localhost:4444.

Distributor

Remove Node

To remove the Node from the Grid, use the cURL command enlisted below. It does not stop any ongoing session running on that Node. The Node continues running as it is unless explicitly killed. The Distributor is no longer aware of the Node and hence any matching new session request will not be forwarded to that Node.

In the Standalone mode, the Distributor URL is the Standalone server address.

In the Hub-Node mode, the Distributor URL is the Hub server address.

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

In the fully distributed mode, the URL is the Distributor server address.

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

If no registration secret has been configured while setting up the Grid, then use

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

Drain Node

Node drain command is for graceful node shutdown. Draining a Node stops the Node after all the ongoing sessions are complete. However, it does not accept any new session requests.

In the Standalone mode, the Distributor URL is the Standalone server address.

In the Hub-Node mode, the Distributor URL is the Hub server address.

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

In the fully distributed mode, the URL is the Distributor server address.

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

If no registration secret has been configured while setting up the Grid, then use

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

Node

The endpoints in this section are applicable for Hub-Node mode and fully distributed Grid mode where the Node runs independently. The default Node URL is http://localhost:5555 in case of one Node. In case of multiple Nodes, use Grid status to get all Node details and locate the Node address.

Status

The Node status is essentially a health-check for the Node. Distributor pings the node status are regular intervals and updates the Grid Model accordingly. The status includes information regarding availability, sessions, and slots.

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

Drain

Distributor passes the drain command to the appropriate node identified by the node-id. To drain the Node directly, use the cuRL command enlisted below. Both endpoints are valid and produce the same result. Drain finishes the ongoing sessions before stopping the Node.

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

If no registration secret has been configured while setting up the Grid, then use

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

Check session owner

To check if a session belongs to a Node, use the cURL command enlisted below.

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

If no registration secret has been configured while setting up the Grid, then use

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

It will return true if the session belongs to the Node else it will return false.

Delete session

Deleting the session terminates the WebDriver session, quits the driver and removes it from the active sessions map. Any request using the removed session-id or reusing the driver instance will throw an error.

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

If no registration secret has been configured while setting up the Grid, then use

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

New Session Queue

Clear New Session Queue

New Session Request Queue holds the new session requests. To clear the queue, use the cURL command enlisted below. Clearing the queue rejects all the requests in the queue. For each such request, the server returns an error response to the respective client. The result of the clear command is the total number of deleted requests.

In the Standalone mode, the Queue URL is the Standalone server address.

In the Hub-Node mode, the Queue URL is the Hub server address.

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

In the fully distributed mode, the Queue URL is New Session Queue server address.

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

If no registration secret has been configured while setting up the Grid, then use

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

Get New Session Queue Requests

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.

In the Standalone mode, the Queue URL is the Standalone server address.

In the Hub-Node mode, the Queue URL is the Hub server address.

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

In the fully distributed mode, the Queue URL is New Session Queue server address.

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