Add "information" command and information about tracing

java/client/src/org/openqa/selenium/os/BUILD.bazel

@@ -3,8 +3,6 @@ java_library(
     srcs = glob(["*.java"]),
     visibility = [
         "//java/client/src/org/openqa/selenium:__pkg__",
-        "//java/client/src/org/openqa/selenium/firefox:__pkg__",
-        "//java/client/src/org/openqa/selenium/firefox/xpi:__pkg__",
         "//java/client/src/org/openqa/selenium/remote:__pkg__",
         "//java/client/test/org/openqa/selenium:__subpackages__",
         "//java/client/test/org/openqa/selenium/build:__pkg__",

java/server/src/org/openqa/selenium/grid/commands/BUILD.bazel

@@ -1,6 +1,7 @@
 java_library(
     name = "commands",
     srcs = glob(["*.java"]),
+    resources = glob(["*.txt"]),
     visibility = [
         "//java/server/src/org/openqa/selenium/grid:__pkg__",
     ],

java/server/src/org/openqa/selenium/grid/commands/InfoCommand.java

@@ -0,0 +1,125 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.openqa.selenium.grid.commands;
+
+import com.beust.jcommander.JCommander;
+import com.beust.jcommander.ParameterException;
+import com.google.auto.service.AutoService;
+import com.google.common.io.Resources;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.StringReader;
+import java.nio.charset.StandardCharsets;
+import org.openqa.selenium.cli.CliCommand;
+import org.openqa.selenium.cli.WrappedPrintWriter;
+import org.openqa.selenium.grid.server.HelpFlags;
+
+import java.io.PrintWriter;
+import java.util.Collections;
+
+
+@AutoService(CliCommand.class)
+public class InfoCommand implements CliCommand {
+
+  public String getName() {
+    return "info";
+  }
+
+  public String getDescription() {
+    return "Prints information for commands and topics.";
+  }
+
+  public Executable configure(String... args) {
+    HelpFlags help = new HelpFlags();
+    InfoFlags topic = new InfoFlags();
+
+    JCommander commander = JCommander.newBuilder()
+      .programName("selenium")
+      .addObject(help)
+      .addObject(topic)
+      .build();
+
+    return () -> {
+      try {
+        commander.parse(args);
+      } catch (ParameterException e) {
+        System.err.println(e.getMessage());
+        commander.usage();
+        return;
+      }
+
+      if (help.displayHelp(commander, System.out)) {
+        return;
+      }
+
+      String toDisplay;
+      String title;
+      switch (topic.topic) {
+        case "tracing":
+          title = "About Tracing";
+          toDisplay = "tracing.txt";
+          break;
+
+        case "help":
+        default:
+          title = "Help";
+          toDisplay = "help.txt";
+          break;
+      }
+
+      String path = getClass().getPackage().getName().replaceAll("\\.", "/") + "/" + toDisplay;
+      String content = readContent(path);
+
+      PrintWriter out = new WrappedPrintWriter(System.out, 72, 0);
+
+      out.printf("\n%s\n%s\n\n", title, String.join("", Collections.nCopies(title.length(), "=")));
+      out.print(content);
+      out.println("\n\n");
+    };
+  }
+
+  private String readContent(String path) throws IOException {
+    String unformattedText = Resources.toString(Resources.getResource(path), StandardCharsets.UTF_8);
+    StringBuilder formattedText = new StringBuilder();
+    try (BufferedReader reader = new BufferedReader(new StringReader(unformattedText))) {
+      boolean inCode = false;
+
+      for (String line = reader.readLine(); line != null; line = reader.readLine()) {
+        if (line.isEmpty()) {
+          if (inCode) {
+            formattedText.append("\n");
+          } else {
+            formattedText.append("\n\n");
+          }
+        } else if ("```".equals(line)) {
+          inCode = !inCode;
+        } else {
+          formattedText.append(line);
+          if (inCode || line.startsWith("* ")) {
+            formattedText.append("\n");
+          } else {
+            formattedText.append(" ");
+          }
+        }
+      }
+    }
+
+    return formattedText.toString();
+  }
+}

java/server/src/org/openqa/selenium/grid/commands/InfoFlags.java

@@ -0,0 +1,26 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.openqa.selenium.grid.commands;
+
+import com.beust.jcommander.Parameter;
+
+public class InfoFlags {
+
+  @Parameter(description = "Topic to gather additional help on")
+  String topic = "help";
+}

java/server/src/org/openqa/selenium/grid/commands/help.txt

@@ -0,0 +1,7 @@
+You can find out more about topics concerning Selenium Grid by running
+the "help" command followed by:
+
+* tracing - Help on how distributed tracing works with selenium
+
+Each topic will give you enough information to help you get started, and
+contains some pointers on our site to provide more complete information.

java/server/src/org/openqa/selenium/grid/commands/tracing.txt

@@ -0,0 +1,68 @@
+Selenium Grid ships with support for distributed tracing, backed by
+the OpenTracing APIs. This allows admins and devops engineers to trace
+the flow of control through the Grid for each and every command.
+
+To enable this support, you must first provide a "Tracer"
+implementation that should be used. We use OpenTracing's own
+TracerResolver to find the Tracer to use, so if your chosen tracing
+library supports this mechanism to (and most do!) you should be good
+to go. If you are using the standalone selenium jar, updating the
+classpath to contain your tracer can be done using the `--ext` flag to
+selenium. As a worked example, using Jaeger as the tracing library and
+running on macOS or Linux:
+
+```
+  java -jar selenium.jar \
+       --ext $(coursier fetch -p io.jaegertracing:jaeger-client:1.0.0) \
+       standalone
+```
+
+This example uses a tool called "coursier" to generate a full
+classpath, but you can also write this manually. When started this
+way, the selenium server will inform you that it has found a tracer on
+stdout.
+
+However, just making the tracer available is seldom enough. You must
+also configure it to send diagnostics back. In the case of Jaeger,
+this can be done via system properties. Modifying our example:
+
+```
+  java -DJAEGER_SERVICE_NAME="selenium-standalone" \
+       -DJAEGER_AGENT_HOST=localhost \
+       -DJAEGER_AGENT_PORT=6831 \
+       -DJAEGER_SAMPLER_TYPE=const \
+       -DJAEGER_SAMPLER_PARAM=1 \
+       -jar selenium.jar \
+       --ext $(coursier fetch -p io.jaegertracing:jaeger-client:1.0.0) \
+       standalone
+```
+
+There are other popular tracing libraries that are supported by
+OpenTracing, so please check their documentation for more information
+on how to configure them.
+
+You will also need to be running a tracing server somewhere. In the
+case of Jaeger, you can do this using docker to fire up something
+locally:
+
+```
+  docker run --rm -it  -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 \
+    -p 5775:5775/udp \
+    -p 6831:6831/udp \
+    -p 6832:6832/udp \
+    -p 5778:5778 \
+    -p 16686:16686 \
+    -p 14268:14268 \
+    -p 9411:9411 \
+    jaegertracing/all-in-one:1.14
+```
+
+Now run some tests, and then point a browser at
+http://localhost:16686/ to view the outputs.
+
+More information can be found at:
+
+* OpenTracing: https://opentracing.io
+* TracerResolver: https://github.com/opentracing-contrib/java-tracerresolver
+* Jaeger: https://www.jaegertracing.io
+* Coursier: https://get-coursier.io