Don't check if sandbox is supported over and over again.

RELNOTES: None
PiperOrigin-RevId: 203454741

3 files changed, 22 insertions, 8 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java
index bde1a99692..ced76adba9 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java
@@ -65,9 +65,12 @@ final class DarwinSandboxedSpawnRunner extends AbstractSandboxSpawnRunner {
   @VisibleForTesting
   static String sandboxExecBinary = "/usr/bin/sandbox-exec";
 
+  // Since checking if sandbox is supported is expensive, we remember what we've checked.
+  private static Boolean isSupported = null;
+
   /**
    * Returns whether the darwin sandbox is supported on the local machine by running a small command
-   * in it. This is expensive!
+   * in it.
    */
   public static boolean isSupported(CommandEnvironment cmdEnv) {
     if (OS.getCurrent() != OS.DARWIN) {
@@ -76,7 +79,13 @@ final class DarwinSandboxedSpawnRunner extends AbstractSandboxSpawnRunner {
     if (!ProcessWrapperUtil.isSupported(cmdEnv)) {
       return false;
     }
+    if (isSupported == null) {
+      isSupported = computeIsSupported();
+    }
+    return isSupported;
+  }
 
+  private static boolean computeIsSupported() {
     List<String> args = new ArrayList<>();
     args.add(sandboxExecBinary);
     args.add("-p");
diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java
index b0a7ed652a..5be9cd18f7 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java
@@ -41,6 +41,7 @@ import com.google.devtools.build.lib.vfs.Symlinks;
 import java.io.File;
 import java.io.IOException;
 import java.time.Duration;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.SortedMap;
 import javax.annotation.Nullable;
@@ -48,22 +49,28 @@ import javax.annotation.Nullable;
 /** Spawn runner that uses linux sandboxing APIs to execute a local subprocess. */
 final class LinuxSandboxedSpawnRunner extends AbstractSandboxSpawnRunner {
 
+  // Since checking if sandbox is supported is expensive, we remember what we've checked.
+  private static final Map<Path, Boolean> isSupportedMap = new HashMap<>();
+
   /**
    * Returns whether the linux sandbox is supported on the local machine by running a small command
-   * in it. This is expensive!
+   * in it.
    */
-  public static boolean isSupported(CommandEnvironment cmdEnv) {
+  public static boolean isSupported(final CommandEnvironment cmdEnv) {
     if (OS.getCurrent() != OS.LINUX) {
       return false;
     }
     if (!LinuxSandboxUtil.isSupported(cmdEnv)) {
       return false;
     }
+    Path linuxSandbox = LinuxSandboxUtil.getLinuxSandbox(cmdEnv);
+    return isSupportedMap.computeIfAbsent(
+        linuxSandbox, linuxSandboxPath -> computeIsSupported(cmdEnv, linuxSandboxPath));
+  }
 
+  private static boolean computeIsSupported(CommandEnvironment cmdEnv, Path linuxSandbox) {
     ImmutableList<String> linuxSandboxArgv =
-        LinuxSandboxUtil.commandLineBuilder(
-                LinuxSandboxUtil.getLinuxSandbox(cmdEnv), ImmutableList.of("/bin/true"))
-            .build();
+        LinuxSandboxUtil.commandLineBuilder(linuxSandbox, ImmutableList.of("/bin/true")).build();
     ImmutableMap<String, String> env = ImmutableMap.of();
     Path execRoot = cmdEnv.getExecRoot();
     File cwd = execRoot.getPathFile();
diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java b/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java
index a331f55b3d..a177598036 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java
@@ -144,9 +144,7 @@ public final class SandboxModule extends BlazeModule {
         cmdEnv.getOptions().getOptions(LocalExecutionOptions.class).getLocalSigkillGraceSeconds();
 
     boolean processWrapperSupported = ProcessWrapperSandboxedSpawnRunner.isSupported(cmdEnv);
-    // LinuxSandboxedSpawnRunner.isSupported is expensive! It runs the sandbox as a subprocess.
     boolean linuxSandboxSupported = LinuxSandboxedSpawnRunner.isSupported(cmdEnv);
-    // DarwinSandboxedSpawnRunner.isSupported is expensive! It runs the sandbox as a subprocess.
     boolean darwinSandboxSupported = DarwinSandboxedSpawnRunner.isSupported(cmdEnv);
 
     // This works on most platforms, but isn't the best choice, so we put it first and let later