Introduce environment component

communication/src/main/java/datadog/communication/ddagent/ExternalAgentLauncher.java

@@ -5,8 +5,8 @@
 import static datadog.trace.util.ProcessSupervisor.Health.NEVER_CHECKED;
 import static datadog.trace.util.ProcessSupervisor.Health.READY_TO_START;
 
+import datadog.environment.OperatingSystem;
 import datadog.trace.api.Config;
-import datadog.trace.api.Platform;
 import datadog.trace.util.ProcessSupervisor;
 import java.io.Closeable;
 import java.io.File;
@@ -17,7 +17,7 @@ public class ExternalAgentLauncher implements Closeable {
   private static final Logger log = LoggerFactory.getLogger(ExternalAgentLauncher.class);
 
   private static final ProcessBuilder.Redirect DISCARD =
-      ProcessBuilder.Redirect.to(new File((Platform.isWindows() ? "NUL" : "/dev/null")));
+      ProcessBuilder.Redirect.to(new File((OperatingSystem.isWindows() ? "NUL" : "/dev/null")));
 
   private ProcessSupervisor traceProcessSupervisor;
   private ProcessSupervisor dogStatsDProcessSupervisor;

communication/src/main/java/datadog/communication/monitor/DDAgentStatsDConnection.java

@@ -8,8 +8,8 @@
 import com.timgroup.statsd.NoOpDirectStatsDClient;
 import com.timgroup.statsd.NonBlockingStatsDClientBuilder;
 import com.timgroup.statsd.StatsDClientErrorHandler;
+import datadog.environment.OperatingSystem;
 import datadog.trace.api.Config;
-import datadog.trace.api.Platform;
 import datadog.trace.relocate.api.IOLogger;
 import datadog.trace.util.AgentTaskScheduler;
 import datadog.trace.util.AgentThreadFactory;
@@ -136,7 +136,7 @@ private void doConnect() {
           if (bufferSize != null) {
             clientBuilder.socketBufferSize(bufferSize);
           }
-          int packetSize = Platform.isMac() ? 2048 : 8192;
+          int packetSize = OperatingSystem.isMacOs() ? 2048 : 8192;
           if (bufferSize != null && bufferSize < packetSize) {
             packetSize = bufferSize;
           }
@@ -185,7 +185,7 @@ private void discoverConnectionSettings() {
     }
 
     if (null == host) {
-      if (!Platform.isWindows() && new File(DEFAULT_DOGSTATSD_SOCKET_PATH).exists()) {
+      if (!OperatingSystem.isWindows() && new File(DEFAULT_DOGSTATSD_SOCKET_PATH).exists()) {
         log.info("Detected {}.  Using it to send StatsD data.", DEFAULT_DOGSTATSD_SOCKET_PATH);
         host = DEFAULT_DOGSTATSD_SOCKET_PATH;
         port = 0; // tells dogstatsd client to treat host as a socket path

components/environment/build.gradle.kts

@@ -0,0 +1,18 @@
+plugins {
+  `java-library`
+}
+
+apply(from = "$rootDir/gradle/java.gradle")
+
+extra.set("minimumInstructionCoverage", 0.7)
+val excludedClassesCoverage by extra {
+  listOf(
+    "datadog.environment.JavaVirtualMachine", // depends on OS and JVM vendor
+    "datadog.environment.JavaVirtualMachine.JvmOptionsHolder", // depends on OS and JVM vendor
+    "datadog.environment.JvmOptions", // depends on OS and JVM vendor
+    "datadog.environment.OperatingSystem", // depends on OS
+  )
+}
+val excludedClassesBranchCoverage by extra {
+  listOf("datadog.environment.CommandLine") // tested using forked process
+}

components/environment/src/main/java/datadog/environment/CommandLine.java

@@ -0,0 +1,45 @@
+package datadog.environment;
+
+import static java.util.Collections.emptyList;
+
+import de.thetaphi.forbiddenapis.SuppressForbidden;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Fetches and captures the command line, both command and its arguments. It relies on a
+ * non-standard {@code sun.java.command} system property and was tested on:
+ *
+ * <ul>
+ *   <li>OracleJDK,
+ *   <li>OpenJDK,
+ *   <li>Temurin based JDK,
+ *   <li>IMB JDK,
+ *   <li>Azul Zulu,
+ *   <li>Amazon Coretto,
+ * </ul>
+ */
+class CommandLine {
+  private static final String SUN_JAVA_COMMAND_PROPERTY = "sun.java.command";
+  final List<String> fullCommand = findFullCommand();
+  final String command = getCommand();
+  final List<String> arguments = getCommandArguments();
+
+  @SuppressForbidden // split on single-character uses fast path
+  private List<String> findFullCommand() {
+    String command = SystemProperties.getOrDefault(SUN_JAVA_COMMAND_PROPERTY, "").trim();
+    return command.isEmpty() ? emptyList() : Arrays.asList(command.split(" "));
+  }
+
+  private String getCommand() {
+    return fullCommand.isEmpty() ? null : fullCommand.get(0);
+  }
+
+  private List<String> getCommandArguments() {
+    if (fullCommand.isEmpty()) {
+      return fullCommand;
+    } else {
+      return fullCommand.subList(1, fullCommand.size());
+    }
+  }
+}

components/environment/src/main/java/datadog/environment/EnvironmentVariables.java

@@ -0,0 +1,41 @@
+package datadog.environment;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * Safely queries environment variables against security manager.
+ *
+ * @see <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/SecurityManager.html">Security
+ *     Manager</a>
+ */
+public final class EnvironmentVariables {
+  private EnvironmentVariables() {}
+
+  /**
+   * Gets an environment variable value.
+   *
+   * @param name The environment variable name.
+   * @return The environment variable value, {@code null} if missing or can't be retrieved.
+   */
+  public static @Nullable String get(String name) {
+    return getOrDefault(name, null);
+  }
+
+  /**
+   * Gets an environment variable value, or default value if missing or can't be retrieved.
+   *
+   * @param name The environment variable name.
+   * @param defaultValue The default value to return if the environment variable is missing or can't
+   *     be retrieved.
+   * @return The environment variable value, {@code defaultValue} if missing or can't be retrieved.
+   */
+  public static String getOrDefault(@Nonnull String name, String defaultValue) {
+    try {
+      String value = System.getenv(name);
+      return value == null ? defaultValue : value;
+    } catch (SecurityException e) {
+      return defaultValue;
+    }
+  }
+}