Revert "Cache change /meta ref SHA1 for each REST API request"

This reverts commit 23db8a546b800b2c91629d80b6f5117ff635238a.

Reason: refs caching on stable-3.2 can be achieve using [1].

[1] https://gerrit.googlesource.com/modules/cached-refdb/

Release-Notes: skip
Change-Id: I44ad6fbe165bed57c3d639a6a0878f704139b7b3

5 files changed, 11 insertions, 86 deletions

diff --git a/java/com/google/gerrit/httpd/restapi/RestApiServlet.java b/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
index fb1f2353ff..d427caa0c6 100644
--- a/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
+++ b/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
@@ -326,7 +326,7 @@ public class RestApiServlet extends HttpServlet {
     try (TraceContext traceContext = enableTracing(req, res)) {
       List<IdString> path = splitPath(req);
 
-      try (PerThreadCache ignored = PerThreadCache.create(req)) {
+      try (PerThreadCache ignored = PerThreadCache.create()) {
         RequestInfo requestInfo = createRequestInfo(traceContext, requestUri(req), path);
         globals.requestListeners.runEach(l -> l.onRequest(requestInfo));
 
diff --git a/java/com/google/gerrit/server/cache/PerThreadCache.java b/java/com/google/gerrit/server/cache/PerThreadCache.java
index 609fce7b25..b4f79d10ab 100644
--- a/java/com/google/gerrit/server/cache/PerThreadCache.java
+++ b/java/com/google/gerrit/server/cache/PerThreadCache.java
@@ -21,9 +21,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 import com.google.gerrit.common.Nullable;
 import java.util.Map;
-import java.util.Optional;
 import java.util.function.Supplier;
-import javax.servlet.http.HttpServletRequest;
 
 /**
  * Caches object instances for a request as {@link ThreadLocal} in the serving thread.
@@ -60,12 +58,6 @@ public class PerThreadCache implements AutoCloseable {
   private static final int PER_THREAD_CACHE_SIZE = 25;
 
   /**
-   * Optional HTTP request associated with the per-thread cache, should the thread be associated
-   * with the incoming HTTP thread pool.
-   */
-  private final Optional<HttpServletRequest> httpRequest;
-
-  /**
    * Unique key for key-value mappings stored in PerThreadCache. The key is based on the value's
    * class and a list of identifiers that in combination uniquely set the object apart form others
    * of the same class.
@@ -110,9 +102,9 @@ public class PerThreadCache implements AutoCloseable {
     }
   }
 
-  public static PerThreadCache create(@Nullable HttpServletRequest httpRequest) {
+  public static PerThreadCache create() {
     checkState(CACHE.get() == null, "called create() twice on the same request");
-    PerThreadCache cache = new PerThreadCache(httpRequest);
+    PerThreadCache cache = new PerThreadCache();
     CACHE.set(cache);
     return cache;
   }
@@ -129,9 +121,7 @@ public class PerThreadCache implements AutoCloseable {
 
   private final Map<Key<?>, Object> cache = Maps.newHashMapWithExpectedSize(PER_THREAD_CACHE_SIZE);
 
-  private PerThreadCache(@Nullable HttpServletRequest req) {
-    httpRequest = Optional.ofNullable(req);
-  }
+  private PerThreadCache() {}
 
   /**
    * Returns an instance of {@code T} that was either loaded from the cache or obtained from the
@@ -149,19 +139,6 @@ public class PerThreadCache implements AutoCloseable {
     return value;
   }
 
-  /** Returns the optional HTTP request associated with the local thread cache. */
-  public Optional<HttpServletRequest> getHttpRequest() {
-    return httpRequest;
-  }
-
-  /** Returns true if there is an HTTP request associated and is a GET or HEAD */
-  public boolean hasReadonlyRequest() {
-    return httpRequest
-        .map(HttpServletRequest::getMethod)
-        .filter(m -> m.equalsIgnoreCase("GET") || m.equalsIgnoreCase("HEAD"))
-        .isPresent();
-  }
-
   @Override
   public void close() {
     CACHE.remove();
diff --git a/java/com/google/gerrit/server/git/RepoRefCache.java b/java/com/google/gerrit/server/git/RepoRefCache.java
index 9086da7fb5..6b2493a9f1 100644
--- a/java/com/google/gerrit/server/git/RepoRefCache.java
+++ b/java/com/google/gerrit/server/git/RepoRefCache.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.git;
 
-import com.google.gerrit.server.cache.PerThreadCache;
 import java.io.IOException;
 import java.util.Collections;
 import java.util.HashMap;
@@ -30,17 +29,6 @@ public class RepoRefCache implements RefCache {
   private final RefDatabase refdb;
   private final Map<String, Optional<ObjectId>> ids;
 
-  public static Optional<RefCache> getOptional(Repository repo) {
-    PerThreadCache cache = PerThreadCache.get();
-    if (cache != null && cache.hasReadonlyRequest()) {
-      return Optional.of(
-          cache.get(
-              PerThreadCache.Key.create(RepoRefCache.class, repo), () -> new RepoRefCache(repo)));
-    }
-
-    return Optional.empty();
-  }
-
   public RepoRefCache(Repository repo) {
     this.refdb = repo.getRefDatabase();
     this.ids = new HashMap<>();
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotes.java b/java/com/google/gerrit/server/notedb/ChangeNotes.java
index cc31115fe5..51acf16e52 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotes.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotes.java
@@ -56,7 +56,6 @@ import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
 import com.google.gerrit.server.git.RefCache;
-import com.google.gerrit.server.git.RepoRefCache;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -577,10 +576,6 @@ public class ChangeNotes extends AbstractChangeNotes<ChangeNotes> {
 
   @Override
   protected ObjectId readRef(Repository repo) throws IOException {
-    Optional<RefCache> refsCache =
-        Optional.ofNullable(refs).map(Optional::of).orElse(RepoRefCache.getOptional(repo));
-    return refsCache.isPresent()
-        ? refsCache.get().get(getRefName()).orElse(null)
-        : super.readRef(repo);
+    return refs != null ? refs.get(getRefName()).orElse(null) : super.readRef(repo);
   }
 }
diff --git a/javatests/com/google/gerrit/server/cache/PerThreadCacheTest.java b/javatests/com/google/gerrit/server/cache/PerThreadCacheTest.java
index 9d0e0e0665..0453fa1532 100644
--- a/javatests/com/google/gerrit/server/cache/PerThreadCacheTest.java
+++ b/javatests/com/google/gerrit/server/cache/PerThreadCacheTest.java
@@ -18,10 +18,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth8.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 
-import com.google.gerrit.util.http.testutil.FakeHttpServletRequest;
 import java.util.function.Supplier;
-import javax.servlet.http.HttpServletRequest;
-import javax.servlet.http.HttpServletRequestWrapper;
 import org.junit.Test;
 
 public class PerThreadCacheTest {
@@ -43,7 +40,7 @@ public class PerThreadCacheTest {
 
   @Test
   public void endToEndCache() {
-    try (PerThreadCache ignored = PerThreadCache.create(null)) {
+    try (PerThreadCache ignored = PerThreadCache.create()) {
       PerThreadCache cache = PerThreadCache.get();
       PerThreadCache.Key<String> key1 = PerThreadCache.Key.create(String.class);
 
@@ -61,7 +58,7 @@ public class PerThreadCacheTest {
   @Test
   public void cleanUp() {
     PerThreadCache.Key<String> key = PerThreadCache.Key.create(String.class);
-    try (PerThreadCache ignored = PerThreadCache.create(null)) {
+    try (PerThreadCache ignored = PerThreadCache.create()) {
       PerThreadCache cache = PerThreadCache.get();
       String value1 = cache.get(key, () -> "value1");
       assertThat(value1).isEqualTo("value1");
@@ -69,7 +66,7 @@ public class PerThreadCacheTest {
 
     // Create a second cache and assert that it is not connected to the first one.
     // This ensures that the cleanup is actually working.
-    try (PerThreadCache ignored = PerThreadCache.create(null)) {
+    try (PerThreadCache ignored = PerThreadCache.create()) {
       PerThreadCache cache = PerThreadCache.get();
       String value1 = cache.get(key, () -> "value2");
       assertThat(value1).isEqualTo("value2");
@@ -78,48 +75,16 @@ public class PerThreadCacheTest {
 
   @Test
   public void doubleInstantiationFails() {
-    try (PerThreadCache ignored = PerThreadCache.create(null)) {
+    try (PerThreadCache ignored = PerThreadCache.create()) {
       IllegalStateException thrown =
-          assertThrows(IllegalStateException.class, () -> PerThreadCache.create(null));
+          assertThrows(IllegalStateException.class, () -> PerThreadCache.create());
       assertThat(thrown).hasMessageThat().contains("called create() twice on the same request");
     }
   }
 
   @Test
-  public void isAssociatedWithHttpReadonlyRequest() {
-    HttpServletRequest getRequest = new FakeHttpServletRequest();
-    try (PerThreadCache cache = PerThreadCache.create(getRequest)) {
-      assertThat(cache.getHttpRequest()).hasValue(getRequest);
-      assertThat(cache.hasReadonlyRequest()).isTrue();
-    }
-  }
-
-  @Test
-  public void isAssociatedWithHttpWriteRequest() {
-    HttpServletRequest putRequest =
-        new HttpServletRequestWrapper(new FakeHttpServletRequest()) {
-          @Override
-          public String getMethod() {
-            return "PUT";
-          }
-        };
-    try (PerThreadCache cache = PerThreadCache.create(putRequest)) {
-      assertThat(cache.getHttpRequest()).hasValue(putRequest);
-      assertThat(cache.hasReadonlyRequest()).isFalse();
-    }
-  }
-
-  @Test
-  public void isNotAssociatedWithHttpRequest() {
-    try (PerThreadCache cache = PerThreadCache.create(null)) {
-      assertThat(cache.getHttpRequest()).isEmpty();
-      assertThat(cache.hasReadonlyRequest()).isFalse();
-    }
-  }
-
-  @Test
   public void enforceMaxSize() {
-    try (PerThreadCache cache = PerThreadCache.create(null)) {
+    try (PerThreadCache cache = PerThreadCache.create()) {
       // Fill the cache
       for (int i = 0; i < 50; i++) {
         PerThreadCache.Key<String> key = PerThreadCache.Key.create(String.class, i);