StaticModule: Lazily initialize zip FileSystem

Java's zip FileSystem is rather memory-hungry, as it maintains the
full central directory in memory, among other internal state. In the
headless server case, we never actually need to serve a UI from the
war, so it's not necessary to even load the zip FileSystem.

Maintain a synchronized map of zip FileSystems in GerritLauncher,
since each one still needs to be a singleton, but we don't want to
eagerly load it just because we wanted to look up the war location.

Change-Id: Id186964b2a197a8a0e874f86c72c21e06fc1388f

gerrit-httpd/src/main/java/com/google/gerrit/httpd/raw/StaticModule.java

@@ -41,20 +41,17 @@ public class StaticModule extends ServletModule {
   static final String CACHE = "static_content";
 
   private final GerritOptions options;
-  private final FileSystem warFs;
-  private final Path buckOut;
-  private final Path unpackedWar;
+  private Paths paths;
 
   public StaticModule(GerritOptions options) {
     this.options = options;
-    warFs = getDistributionArchive();
-    if (warFs == null) {
-      buckOut = getDeveloperBuckOut();
-      unpackedWar = makeWarTempDir();
-    } else {
-      buckOut = null;
-      unpackedWar = null;
+  }
+
+  private Paths getPaths() {
+    if (paths == null) {
+      paths = new Paths();
     }
+    return paths;
   }
 
   @Override
@@ -69,128 +66,161 @@ public class StaticModule extends ServletModule {
       }
     });
     if (options.enablePolyGerrit()) {
-      servePolyGerritUi();
+      install(new PolyGerritUiModule());
     } else if (options.enableDefaultUi()) {
-      serveGwtUi();
+      install(new GwtUiModule());
     }
   }
 
-  private void serveGwtUi() {
-    serveRegex("^/gerrit_ui/(?!rpc/)(.*)$")
-        .with(Key.get(HttpServlet.class, Names.named(GWT_UI_SERVLET)));
-    if (warFs == null && buckOut != null) {
-      filter("/").through(new RecompileGwtUiFilter(buckOut, unpackedWar));
+  private class GwtUiModule extends ServletModule {
+    @Override
+    public void configureServlets() {
+      serveRegex("^/gerrit_ui/(?!rpc/)(.*)$")
+          .with(Key.get(HttpServlet.class, Names.named(GWT_UI_SERVLET)));
+      Paths p = getPaths();
+      if (p.warFs == null && p.buckOut != null) {
+        filter("/").through(new RecompileGwtUiFilter(p.buckOut, p.unpackedWar));
+      }
     }
-  }
 
-  private void servePolyGerritUi() {
-    serve("/").with(PolyGerritUiIndexServlet.class);
-    serve("/c/*").with(PolyGerritUiIndexServlet.class);
-    serve("/q/*").with(PolyGerritUiIndexServlet.class);
-    serve("/x/*").with(PolyGerritUiIndexServlet.class);
-    serve("/admin/*").with(PolyGerritUiIndexServlet.class);
-    serve("/dashboard/*").with(PolyGerritUiIndexServlet.class);
-    serve("/settings/*").with(PolyGerritUiIndexServlet.class);
-    // TODO(dborowitz): These fragments conflict with the REST API namespace, so
-    // they will need to use a different path.
-    //serve("/groups/*").with(PolyGerritUiIndexServlet.class);
-    //serve("/projects/*").with(PolyGerritUiIndexServlet.class);
-
-    if (warFs == null) {
-      serve("/bower_components/*")
-          .with(Key.get(PolyGerritUiServlet.class, Names.named(BOWER_SERVLET)));
-    }
-    serve("/*").with(PolyGerritUiServlet.class);
-  }
-
-  @Provides
-  @Singleton
-  @Named(GWT_UI_SERVLET)
-  HttpServlet getGwtUiServlet(@Named(CACHE) Cache<Path, Resource> cache)
-      throws IOException {
-    if (warFs != null) {
-      return new WarGwtUiServlet(cache, warFs);
-    } else {
-      return new DeveloperGwtUiServlet(cache, unpackedWar);
-    }
-  }
-
-  @Provides
-  @Singleton
-  PolyGerritUiIndexServlet getPolyGerritUiIndexServlet(
-      @Named(CACHE) Cache<Path, Resource> cache) {
-    return new PolyGerritUiIndexServlet(cache, polyGerritBasePath());
-  }
-
-  @Provides
-  @Singleton
-  PolyGerritUiServlet getPolyGerritUiServlet(
-      @Named(CACHE) Cache<Path, Resource> cache) {
-    return new PolyGerritUiServlet(cache, polyGerritBasePath());
-  }
-
-  @Provides
-  @Singleton
-  @Named(BOWER_SERVLET)
-  PolyGerritUiServlet getPolyGerritUiBowerServlet(
-      @Named(CACHE) Cache<Path, Resource> cache) {
-    return new PolyGerritUiServlet(cache,
-        polyGerritBasePath().resolveSibling("bower_components"));
-  }
-
-  private Path polyGerritBasePath() {
-    return warFs != null
-        ? warFs.getPath("/polygerrit_ui")
-        : buckOut.getParent().resolve("polygerrit-ui").resolve("app");
-  }
-
-  private static FileSystem getDistributionArchive() {
-    try {
-      return GerritLauncher.getDistributionArchiveFileSystem();
-    } catch (IOException e) {
-      if ((e instanceof FileNotFoundException)
-          && GerritLauncher.NOT_ARCHIVED.equals(e.getMessage())) {
-        return null;
+    @Provides
+    @Singleton
+    @Named(GWT_UI_SERVLET)
+    HttpServlet getGwtUiServlet(@Named(CACHE) Cache<Path, Resource> cache)
+        throws IOException {
+      Paths p = getPaths();
+      if (p.warFs != null) {
+        return new WarGwtUiServlet(cache, p.warFs);
       } else {
+        return new DeveloperGwtUiServlet(cache, p.unpackedWar);
+      }
+    }
+  }
+
+  private class PolyGerritUiModule extends ServletModule {
+    @Override
+    public void configureServlets() {
+      serve("/").with(PolyGerritUiIndexServlet.class);
+      serve("/c/*").with(PolyGerritUiIndexServlet.class);
+      serve("/q/*").with(PolyGerritUiIndexServlet.class);
+      serve("/x/*").with(PolyGerritUiIndexServlet.class);
+      serve("/admin/*").with(PolyGerritUiIndexServlet.class);
+      serve("/dashboard/*").with(PolyGerritUiIndexServlet.class);
+      serve("/settings/*").with(PolyGerritUiIndexServlet.class);
+      // TODO(dborowitz): These fragments conflict with the REST API namespace,
+      // so they will need to use a different path.
+      //serve("/groups/*").with(PolyGerritUiIndexServlet.class);
+      //serve("/projects/*").with(PolyGerritUiIndexServlet.class);
+
+      if (getPaths().warFs == null) {
+        serve("/bower_components/*").with(
+            Key.get(PolyGerritUiServlet.class, Names.named(BOWER_SERVLET)));
+      }
+      serve("/*").with(PolyGerritUiServlet.class);
+    }
+
+    @Provides
+    @Singleton
+    PolyGerritUiIndexServlet getPolyGerritUiIndexServlet(
+        @Named(CACHE) Cache<Path, Resource> cache) {
+      return new PolyGerritUiIndexServlet(cache, polyGerritBasePath());
+    }
+
+    @Provides
+    @Singleton
+    PolyGerritUiServlet getPolyGerritUiServlet(
+        @Named(CACHE) Cache<Path, Resource> cache) {
+      return new PolyGerritUiServlet(cache, polyGerritBasePath());
+    }
+
+    @Provides
+    @Singleton
+    @Named(BOWER_SERVLET)
+    PolyGerritUiServlet getPolyGerritUiBowerServlet(
+        @Named(CACHE) Cache<Path, Resource> cache) {
+      return new PolyGerritUiServlet(cache,
+          polyGerritBasePath().resolveSibling("bower_components"));
+    }
+
+    private Path polyGerritBasePath() {
+      Paths p = getPaths();
+      return p.warFs != null
+          ? p.warFs.getPath("/polygerrit_ui")
+          : p.buckOut.getParent().resolve("polygerrit-ui").resolve("app");
+    }
+  }
+
+  private static class Paths {
+    private final FileSystem warFs;
+    private final Path buckOut;
+    private final Path unpackedWar;
+
+    private Paths() {
+      try {
+        warFs = getDistributionArchive();
+        if (warFs == null) {
+          buckOut = getDeveloperBuckOut();
+          unpackedWar = makeWarTempDir();
+        } else {
+          buckOut = null;
+          unpackedWar = null;
+        }
+      } catch (IOException e) {
+        throw new ProvisionException(
+            "Error initializing static content paths", e);
+      }
+    }
+
+    private static FileSystem getDistributionArchive() throws IOException {
+      File war;
+      try {
+        war = GerritLauncher.getDistributionArchive();
+      } catch (IOException e) {
+        if ((e instanceof FileNotFoundException)
+            && GerritLauncher.NOT_ARCHIVED.equals(e.getMessage())) {
+          return null;
+        } else {
+          ProvisionException pe =
+              new ProvisionException("Error reading gerrit.war");
+          pe.initCause(e);
+          throw pe;
+        }
+      }
+      return GerritLauncher.getZipFileSystem(war.toPath());
+    }
+
+    private static Path getDeveloperBuckOut() {
+      try {
+        return GerritLauncher.getDeveloperBuckOut();
+      } catch (FileNotFoundException e) {
+        return null;
+      }
+    }
+
+    private static Path makeWarTempDir() {
+      // Obtain our local temporary directory, but it comes back as a file
+      // so we have to switch it to be a directory post creation.
+      //
+      try {
+        File dstwar = GerritLauncher.createTempFile("gerrit_", "war");
+        if (!dstwar.delete() || !dstwar.mkdir()) {
+          throw new IOException("Cannot mkdir " + dstwar.getAbsolutePath());
+        }
+
+        // Jetty normally refuses to serve out of a symlinked directory, as
+        // a security feature. Try to resolve out any symlinks in the path.
+        //
+        try {
+          return dstwar.getCanonicalFile().toPath();
+        } catch (IOException e) {
+          return dstwar.getAbsoluteFile().toPath();
+        }
+      } catch (IOException e) {
         ProvisionException pe =
-            new ProvisionException("Error reading gerrit.war");
+            new ProvisionException("Cannot create war tempdir");
         pe.initCause(e);
         throw pe;
       }
     }
   }
-
-  private static Path getDeveloperBuckOut() {
-    try {
-      return GerritLauncher.getDeveloperBuckOut();
-    } catch (FileNotFoundException e) {
-      return null;
-    }
-  }
-
-  private static Path makeWarTempDir() {
-    // Obtain our local temporary directory, but it comes back as a file
-    // so we have to switch it to be a directory post creation.
-    //
-    try {
-      File dstwar = GerritLauncher.createTempFile("gerrit_", "war");
-      if (!dstwar.delete() || !dstwar.mkdir()) {
-        throw new IOException("Cannot mkdir " + dstwar.getAbsolutePath());
-      }
-
-      // Jetty normally refuses to serve out of a symlinked directory, as
-      // a security feature. Try to resolve out any symlinks in the path.
-      //
-      try {
-        return dstwar.getCanonicalFile().toPath();
-      } catch (IOException e) {
-        return dstwar.getAbsoluteFile().toPath();
-      }
-    } catch (IOException e) {
-      ProvisionException pe =
-          new ProvisionException("Cannot create war tempdir");
-      pe.initCause(e);
-      throw pe;
-    }
-  }
 }

gerrit-launcher/src/main/java/com/google/gerrit/launcher/GerritLauncher.java

@@ -38,7 +38,9 @@ import java.security.CodeSource;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.SortedMap;
 import java.util.TreeMap;
 import java.util.jar.Attributes;
@@ -300,9 +302,10 @@ public final class GerritLauncher {
   }
 
   private static volatile File myArchive;
-  private static volatile FileSystem myArchiveFs;
   private static volatile File myHome;
 
+  private static final Map<Path, FileSystem> zipFileSystems = new HashMap<>();
+
   /**
    * Locate the JAR/WAR file we were launched from.
    *
@@ -319,19 +322,24 @@ public final class GerritLauncher {
           return result;
         }
         result = locateMyArchive();
-        myArchiveFs = FileSystems.newFileSystem(
-            URI.create("jar:" + result.toPath().toUri()),
-            Collections.<String, String> emptyMap());
         myArchive = result;
       }
     }
     return result;
   }
 
-  public static FileSystem getDistributionArchiveFileSystem()
-      throws FileNotFoundException, IOException {
-    getDistributionArchive();
-    return myArchiveFs;
+  public static synchronized FileSystem getZipFileSystem(Path zip)
+      throws IOException {
+    // FileSystems canonicalizes the path, so we should too.
+    zip = zip.toRealPath();
+    FileSystem zipFs = zipFileSystems.get(zip);
+    if (zipFs == null) {
+      zipFs = FileSystems.newFileSystem(
+          URI.create("jar:" + zip.toUri()),
+          Collections.<String, String> emptyMap());
+      zipFileSystems.put(zip, zipFs);
+    }
+    return zipFs;
   }
 
   private static File locateMyArchive() throws FileNotFoundException {