Avoid creating HTTP Sessions for Git-over-HTTP

The Change-Id: Iffcd0fbd7 has involuntarily triggered the
creation of a new HTTP Session for every invocation a Git-over-HTTP
request.

All came from the mistake of tracing the HTTP session instead
of the Gerrit session in the audit record.
The HTTP Servlet API specs say that any attempt to access
the current session of an incoming request would result
in the creation of a brand-new session.

The session involuntarily created also had an expiry time
equal to zero, which prevented the session housekeeper
to reclaim them later on, even though they were unused.

The consequence of creating an empty session for every
Git-over-HTTP request isn't immediately tangible, because
the session is empty and doesn't occupy a significant
amount of memory. However, longer-term, the in-memory
hashtable that records all the sessions, each one using
750 bytes on average, will be causing the overload
of the JVM heap and the crash of the process because of
lack of available memory.

Use the correct Gerrit session-id, retrieving
from the Provider<WebSession> the proper session, if active
and logged in, and make sure in tests that no HTTP sessions
are created as a result of a Git-over-http request.

Bug: Issue 13858
Change-Id: I8c086fed54b196c3f46fa88ac78c127784524d30

java/com/google/gerrit/acceptance/GerritServer.java

@@ -541,6 +541,10 @@ public Injector getTestInjector() {
     return testInjector;
   }
 
+  public Injector getHttpdInjector() {
+    return daemon.getHttpdInjector();
+  }
+
   Description getDescription() {
     return desc;
   }

java/com/google/gerrit/httpd/GitOverHttpServlet.java

@@ -339,17 +339,20 @@ static class UploadFilter implements Filter {
     private final Provider<CurrentUser> userProvider;
     private final GroupAuditService groupAuditService;
     private final Metrics metrics;
+    private final Provider<WebSession> sessionProvider;
 
     @Inject
     UploadFilter(
         UploadValidators.Factory uploadValidatorsFactory,
         PermissionBackend permissionBackend,
         Provider<CurrentUser> userProvider,
+        Provider<WebSession> sessionProvider,
         GroupAuditService groupAuditService,
         Metrics metrics) {
       this.uploadValidatorsFactory = uploadValidatorsFactory;
       this.permissionBackend = permissionBackend;
       this.userProvider = userProvider;
+      this.sessionProvider = sessionProvider;
       this.groupAuditService = groupAuditService;
       this.metrics = metrics;
     }
@@ -367,7 +370,7 @@ public void doFilter(ServletRequest request, ServletResponse response, FilterCha
       HttpServletResponseWithStatusWrapper responseWrapper =
           new HttpServletResponseWithStatusWrapper((HttpServletResponse) response);
       HttpServletRequest httpRequest = (HttpServletRequest) request;
-      String sessionId = httpRequest.getSession().getId();
+      String sessionId = getSessionIdOrNull(sessionProvider);
 
       try {
         try {
@@ -457,17 +460,20 @@ static class ReceiveFilter implements Filter {
     private final Provider<CurrentUser> userProvider;
     private final GroupAuditService groupAuditService;
     private final Metrics metrics;
+    private final Provider<WebSession> sessionProvider;
 
     @Inject
     ReceiveFilter(
         @Named(ID_CACHE) Cache<AdvertisedObjectsCacheKey, Set<ObjectId>> cache,
         PermissionBackend permissionBackend,
         Provider<CurrentUser> userProvider,
+        Provider<WebSession> sessionProvider,
         GroupAuditService groupAuditService,
         Metrics metrics) {
       this.cache = cache;
       this.permissionBackend = permissionBackend;
       this.userProvider = userProvider;
+      this.sessionProvider = sessionProvider;
       this.groupAuditService = groupAuditService;
       this.metrics = metrics;
     }
@@ -509,7 +515,7 @@ public void doFilter(ServletRequest request, ServletResponse response, FilterCha
       } finally {
         groupAuditService.dispatch(
             new HttpAuditEvent(
-                httpRequest.getSession().getId(),
+                getSessionIdOrNull(sessionProvider),
                 userProvider.get(),
                 extractWhat(httpRequest),
                 TimeUtil.nowMs(),
@@ -565,4 +571,12 @@ public void init(FilterConfig arg0) {}
     @Override
     public void destroy() {}
   }
+
+  private static String getSessionIdOrNull(Provider<WebSession> sessionProvider) {
+    WebSession session = sessionProvider.get();
+    if (session.isSignedIn()) {
+      return session.getSessionId();
+    }
+    return null;
+  }
 }

java/com/google/gerrit/pgm/Daemon.java

@@ -217,6 +217,11 @@ public void setEnableHttpd(boolean enable) {
     httpd = enable;
   }
 
+  @VisibleForTesting
+  public Injector getHttpdInjector() {
+    return httpdInjector;
+  }
+
   public void setSlave(boolean slave) {
     this.slave = slave;
   }

java/com/google/gerrit/pgm/http/jetty/JettyServer.java

@@ -17,6 +17,7 @@
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Strings;
 import com.google.gerrit.extensions.client.AuthType;
 import com.google.gerrit.extensions.events.LifecycleListener;
@@ -40,8 +41,11 @@
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
 import javax.servlet.DispatcherType;
 import javax.servlet.Filter;
+import javax.servlet.http.HttpSessionEvent;
+import javax.servlet.http.HttpSessionListener;
 import org.eclipse.jetty.http.HttpScheme;
 import org.eclipse.jetty.io.ConnectionStatistics;
 import org.eclipse.jetty.jmx.MBeanContainer;
@@ -198,6 +202,8 @@ public long getSentBytes() {
   private final Metrics metrics;
   private boolean reverseProxy;
   private ConnectionStatistics connStats;
+  private final SessionHandler sessionHandler;
+  private final AtomicLong sessionsCounter;
 
   @Inject
   JettyServer(
@@ -216,8 +222,27 @@ public long getSentBytes() {
       connector.addBean(connStats);
     }
     metrics = new Metrics(pool, connStats);
+    sessionHandler = new SessionHandler();
+    sessionsCounter = new AtomicLong();
 
-    Handler app = makeContext(env, cfg);
+    /* Code used for testing purposes for making assertions
+     * on the number of active HTTP sessions.
+     */
+    sessionHandler.addEventListener(
+        new HttpSessionListener() {
+
+          @Override
+          public void sessionDestroyed(HttpSessionEvent se) {
+            sessionsCounter.decrementAndGet();
+          }
+
+          @Override
+          public void sessionCreated(HttpSessionEvent se) {
+            sessionsCounter.incrementAndGet();
+          }
+        });
+
+    Handler app = makeContext(env, cfg, sessionHandler);
     if (cfg.getBoolean("httpd", "requestLog", !reverseProxy)) {
       RequestLogHandler handler = new RequestLogHandler();
       handler.setRequestLog(httpLogFactory.get());
@@ -244,6 +269,11 @@ public long getSentBytes() {
     httpd.setStopAtShutdown(false);
   }
 
+  @VisibleForTesting
+  public long numActiveSessions() {
+    return sessionsCounter.longValue();
+  }
+
   Metrics getMetrics() {
     return metrics;
   }
@@ -443,7 +473,7 @@ private QueuedThreadPool threadPool(Config cfg, ThreadSettingsConfig threadSetti
     return pool;
   }
 
-  private Handler makeContext(JettyEnv env, Config cfg) {
+  private Handler makeContext(JettyEnv env, Config cfg, SessionHandler sessionHandler) {
     final Set<String> paths = new HashSet<>();
     for (URI u : listenURLs(cfg)) {
       String p = u.getPath();
@@ -458,7 +488,7 @@ private Handler makeContext(JettyEnv env, Config cfg) {
 
     final List<ContextHandler> all = new ArrayList<>();
     for (String path : paths) {
-      all.add(makeContext(path, env, cfg));
+      all.add(makeContext(path, env, cfg, sessionHandler));
     }
 
     if (all.size() == 1) {
@@ -476,13 +506,14 @@ private Handler makeContext(JettyEnv env, Config cfg) {
     return r;
   }
 
-  private ContextHandler makeContext(final String contextPath, JettyEnv env, Config cfg) {
+  private ContextHandler makeContext(
+      final String contextPath, JettyEnv env, Config cfg, SessionHandler sessionHandler) {
     final ServletContextHandler app = new ServletContextHandler();
 
     // This enables the use of sessions in Jetty, feature available
     // for Gerrit plug-ins to enable user-level sessions.
     //
-    app.setSessionHandler(new SessionHandler());
+    app.setSessionHandler(sessionHandler);
     app.setErrorHandler(new HiddenErrorHandler());
 
     // This is the path we are accessed by clients within our domain.

javatests/com/google/gerrit/acceptance/git/AbstractGitOverHttpServlet.java

@@ -19,11 +19,15 @@
 import com.google.common.collect.ImmutableList;
 import com.google.gerrit.acceptance.FakeGroupAuditService;
 import com.google.gerrit.acceptance.Sandboxed;
-import com.google.gerrit.server.AnonymousUser;
+import com.google.gerrit.pgm.http.jetty.JettyServer;
+import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.server.audit.HttpAuditEvent;
 import com.google.inject.Inject;
+import java.util.Optional;
 import javax.servlet.http.HttpServletResponse;
 import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.transport.CredentialsProvider;
 import org.eclipse.jgit.transport.RefSpec;
@@ -33,9 +37,11 @@
 
 public class AbstractGitOverHttpServlet extends AbstractPushForReview {
   @Inject protected FakeGroupAuditService auditService;
+  private JettyServer jettyServer;
 
   @Before
   public void beforeEach() throws Exception {
+    jettyServer = server.getHttpdInjector().getInstance(JettyServer.class);
     CredentialsProvider.setDefault(
         new UsernamePasswordCredentialsProvider(admin.username(), admin.httpPassword()));
     selectProtocol(AbstractPushForReview.Protocol.HTTP);
@@ -71,29 +77,52 @@ public void receivePackAuditEventLog() throws Exception {
 
   @Test
   @Sandboxed
-  public void uploadPackAuditEventLog() throws Exception {
+  public void anonymousUploadPackAuditEventLog() throws Exception {
+    uploadPackAuditEventLog(Constants.DEFAULT_REMOTE_NAME, Optional.empty());
+  }
+
+  @Test
+  @Sandboxed
+  public void authenticatedUploadPackAuditEventLog() throws Exception {
+    String remote = "authenticated";
+    Config cfg = testRepo.git().getRepository().getConfig();
+
+    String uri = admin.getHttpUrl(server) + "/a/" + project.get();
+    cfg.setString("remote", remote, "url", uri);
+    cfg.setString("remote", remote, "fetch", "+refs/heads/*:refs/remotes/origin/*");
+
+    uploadPackAuditEventLog(remote, Optional.of(admin.id()));
+  }
+
+  private void uploadPackAuditEventLog(String remote, Optional<Account.Id> accountId)
+      throws Exception {
     auditService.drainHttpAuditEvents();
     // testRepo is already a clone. Make a server-side change so we have something to fetch.
     try (Repository repo = repoManager.openRepository(project);
         TestRepository<?> testRepo = new TestRepository<>(repo)) {
       testRepo.branch("master").commit().create();
     }
-    testRepo.git().fetch().call();
+    testRepo.git().fetch().setRemote(remote).call();
 
     ImmutableList<HttpAuditEvent> auditEvents = auditService.drainHttpAuditEvents();
     assertThat(auditEvents).hasSize(2);
 
     HttpAuditEvent lsRemote = auditEvents.get(0);
     // Repo URL doesn't include /a, so fetching doesn't cause authentication.
-    assertThat(lsRemote.who).isInstanceOf(AnonymousUser.class);
+    assertThat(lsRemote.who.toString())
+        .isEqualTo(
+            accountId.map(id -> "IdentifiedUser[account " + id.get() + "]").orElse("ANONYMOUS"));
     assertThat(lsRemote.what).endsWith("/info/refs?service=git-upload-pack");
     assertThat(lsRemote.params).containsExactly("service", "git-upload-pack");
     assertThat(lsRemote.httpStatus).isEqualTo(HttpServletResponse.SC_OK);
 
     HttpAuditEvent uploadPack = auditEvents.get(1);
-    assertThat(lsRemote.who).isInstanceOf(AnonymousUser.class);
+    assertThat(lsRemote.who.toString())
+        .isEqualTo(
+            accountId.map(id -> "IdentifiedUser[account " + id.get() + "]").orElse("ANONYMOUS"));
     assertThat(uploadPack.what).endsWith("/git-upload-pack");
     assertThat(uploadPack.params).isEmpty();
     assertThat(uploadPack.httpStatus).isEqualTo(HttpServletResponse.SC_OK);
+    assertThat(jettyServer.numActiveSessions()).isEqualTo(0);
   }
 }