Fix for #3307: Make isWorking synchronized to avoid read/write problems with mutable working field. Check whether git is working once per JVM run and don't recheck every time.

Author: azakkerman

opengrok-indexer/src/main/java/org/opengrok/indexer/history/GitRepository.java

@@ -49,6 +49,7 @@
 import org.opengrok.indexer.util.BufferSink;
 import org.opengrok.indexer.util.Executor;
 import org.opengrok.indexer.util.HeadHandler;
+import org.opengrok.indexer.util.LazilyInstantiate;
 import org.opengrok.indexer.util.StringUtils;
 import org.opengrok.indexer.util.Version;
 
@@ -95,6 +96,12 @@ public class GitRepository extends Repository {
      */
     private static final Version MINIMUM_VERSION = new Version(2, 1, 2);
 
+    /**
+     * This is a static replacement for 'working' field. Effectively, check if git is working once in a JVM
+     * instead of calling it for every GitRepository instance.
+     */
+    private static final LazilyInstantiate<Boolean> GIT_IS_WORKING = LazilyInstantiate.using(GitRepository::isGitWorking);
+
     public GitRepository() {
         type = "git";
         /*
@@ -109,6 +116,21 @@ public GitRepository() {
         ignoredFiles.add(".git");
     }
 
+    private static boolean isGitWorking() {
+        String repoCommand = getCommand(GitRepository.class, CMD_PROPERTY_KEY, CMD_FALLBACK);
+        Executor exec = new Executor(new String[] {repoCommand, "--version"});
+        if (exec.exec(false) == 0) {
+            final String outputVersion = exec.getOutputString();
+            final String version = outputVersion.replaceAll(".*? version (\\d+(\\.\\d+)*).*", "$1");
+            try {
+                return Version.from(version).compareTo(MINIMUM_VERSION) >= 0;
+            } catch (NumberFormatException ex) {
+                LOGGER.log(Level.WARNING, String.format("Unable to detect git version from %s", outputVersion), ex);
+            }
+        }
+        return false;
+    }
+
     /**
      * Get an executor to be used for retrieving the history log for the named
      * file.
@@ -521,21 +543,7 @@ boolean isNestable() {
     @Override
     public boolean isWorking() {
         if (working == null) {
-            ensureCommand(CMD_PROPERTY_KEY, CMD_FALLBACK);
-            Executor exec = new Executor(new String[]{RepoCommand, "--version"});
-
-            if (exec.exec(false) == 0) {
-                final String outputVersion = exec.getOutputString();
-                final String version = outputVersion.replaceAll(".*? version (\\d+(\\.\\d+)*).*", "$1");
-                try {
-                    working = Version.from(version).compareTo(MINIMUM_VERSION) >= 0;
-                } catch (NumberFormatException ex) {
-                    LOGGER.log(Level.WARNING, String.format("Unable to detect git version from %s", outputVersion), ex);
-                    working = false;
-                }
-            } else {
-                working = false;
-            }
+            working = GIT_IS_WORKING.get();
         }
 
         return working;

opengrok-indexer/src/main/java/org/opengrok/indexer/history/Repository.java

@@ -117,7 +117,7 @@ public Repository() {
 
     /**
      * Gets the instance's repository command, primarily for testing purposes.
-     * @return null if not {@link isWorking}, or otherwise a defined command
+     * @return null if not {@link #isWorking()}, or otherwise a defined command
      */
     public String getRepoCommand() {
         isWorking();
@@ -548,6 +548,17 @@ static Boolean checkCmd(String... args) {
         return exec.exec(false) == 0;
     }
 
+    protected static String getCommand(Class<? extends Repository> repoClass, String propertyKey, String fallbackCommand) {
+        RuntimeEnvironment env = RuntimeEnvironment.getInstance();
+        String className = repoClass.getCanonicalName();
+        String command = env.getRepoCmd(className);
+        if (command == null) {
+            command = System.getProperty(propertyKey, fallbackCommand);
+            env.setRepoCmd(className, command);
+        }
+        return command;
+    }
+
     /**
      * Set the name of the external client command that should be used to access
      * the repository wrt. the given parameters. Does nothing, if this
@@ -561,18 +572,10 @@ static Boolean checkCmd(String... args) {
      * @see #RepoCommand
      */
     protected String ensureCommand(String propertyKey, String fallbackCommand) {
-        RuntimeEnvironment env = RuntimeEnvironment.getInstance();
-        
-        if (RepoCommand != null) {
-            return RepoCommand;
-        }
-        
-        RepoCommand = env.getRepoCmd(this.getClass().getCanonicalName());
         if (RepoCommand == null) {
-            RepoCommand = System.getProperty(propertyKey, fallbackCommand);
-            env.setRepoCmd(this.getClass().getCanonicalName(), RepoCommand);
+            RepoCommand = getCommand(this.getClass(), propertyKey, fallbackCommand);
         }
-        
+
         return RepoCommand;
     }