Provide a way to configure each plugin. (#993)

Motivation:
Configuring user-defined plugins is currently difficult because there is no way to configure their properties via `dogma.json`.

Modifications:
- Added `PluginConfig` interface that represents a configuration of a plugin.
- Added `pluginConfigs` to `CentralDogmaConfig` that accepts a list of `PluginConfig`.
  - Users can now configure each plugin using `PluginConfig`.
- Moved mirroring plugin properties from `CentralDogmaConfig` to `MirroringServicePluginConfig`.
  - Compatibility was not maintained as few users are running the Central Dogma server, and they can be guided directly. Let me know if a different approach is preferred.

Result:
- Users can now specify plugin configurations in the `plugins` property.
  ```json
  {
    "dataDir": "./data",
    ...
    "pluginConfigs": [
      {
        "type": "com.example.MyPlugin",
        "enabled": true, // enabled by default
        "myPluginTimeout": 10
      },
      // Other plugins
    ]
  }
  ```
- (Breaking changes) `mirroringEnabled`, `numMirroringThreads`, `maxNumFilesPerMirror`, and `maxNumBytesPerMirror` have been removed from `CentralDogmaBuilder` and `CentralDogmaConfig`.
  - These properties should now be specified in the plugins property:
    ```json
    {
      "dataDir": "./data",
      ...
      "pluginConfigs": [
        {
          "type": "com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig",
          "enabled": true,
          "numMirroringThreads": 16,
          "maxNumFilesPerMirror": 8192
        }
      ]
    }
    ```

it/mirror/src/test/java/com/linecorp/centraldogma/it/mirror/git/ForceRefUpdateTest.java

@@ -51,6 +51,7 @@
 import com.linecorp.centraldogma.server.MirroringService;
 import com.linecorp.centraldogma.server.internal.mirror.MirrorState;
 import com.linecorp.centraldogma.server.mirror.MirrorDirection;
+import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
 import com.linecorp.centraldogma.server.storage.project.Project;
 import com.linecorp.centraldogma.testing.internal.TestUtil;
 import com.linecorp.centraldogma.testing.junit.CentralDogmaExtension;
@@ -72,7 +73,7 @@ protected boolean runForEachTest() {
     static final CentralDogmaExtension dogma = new CentralDogmaExtension() {
         @Override
         protected void configure(CentralDogmaBuilder builder) {
-            builder.mirroringEnabled(true);
+            builder.pluginConfigs(new MirroringServicePluginConfig(true));
         }
     };
 

it/mirror/src/test/java/com/linecorp/centraldogma/it/mirror/git/GitMirrorAuthTest.java

@@ -41,6 +41,7 @@
 import com.linecorp.centraldogma.server.CentralDogmaBuilder;
 import com.linecorp.centraldogma.server.MirroringService;
 import com.linecorp.centraldogma.server.internal.storage.repository.DefaultMetaRepository;
+import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
 import com.linecorp.centraldogma.server.storage.project.Project;
 import com.linecorp.centraldogma.testing.junit.CentralDogmaExtension;
 
@@ -50,7 +51,7 @@ class GitMirrorAuthTest {
     static final CentralDogmaExtension dogma = new CentralDogmaExtension() {
         @Override
         protected void configure(CentralDogmaBuilder builder) {
-            builder.mirroringEnabled(true);
+            builder.pluginConfigs(new MirroringServicePluginConfig(true));
         }
     };
 

it/mirror/src/test/java/com/linecorp/centraldogma/it/mirror/git/GitMirrorIntegrationTest.java

@@ -69,6 +69,7 @@
 import com.linecorp.centraldogma.server.MirrorException;
 import com.linecorp.centraldogma.server.MirroringService;
 import com.linecorp.centraldogma.server.internal.JGitUtil;
+import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
 import com.linecorp.centraldogma.server.storage.project.Project;
 import com.linecorp.centraldogma.testing.internal.TemporaryFolderExtension;
 import com.linecorp.centraldogma.testing.internal.TestUtil;
@@ -85,9 +86,7 @@ class GitMirrorIntegrationTest {
     static final CentralDogmaExtension dogma = new CentralDogmaExtension() {
         @Override
         protected void configure(CentralDogmaBuilder builder) {
-            builder.mirroringEnabled(true);
-            builder.maxNumFilesPerMirror(MAX_NUM_FILES);
-            builder.maxNumBytesPerMirror(MAX_NUM_BYTES);
+            builder.pluginConfigs(new MirroringServicePluginConfig(true, 1, MAX_NUM_FILES, MAX_NUM_BYTES));
         }
     };
 

it/mirror/src/test/java/com/linecorp/centraldogma/it/mirror/git/LocalToRemoteGitMirrorTest.java

@@ -61,6 +61,7 @@
 import com.linecorp.centraldogma.server.MirroringService;
 import com.linecorp.centraldogma.server.internal.mirror.MirrorState;
 import com.linecorp.centraldogma.server.mirror.MirrorDirection;
+import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
 import com.linecorp.centraldogma.server.storage.project.Project;
 import com.linecorp.centraldogma.testing.internal.TestUtil;
 import com.linecorp.centraldogma.testing.junit.CentralDogmaExtension;
@@ -78,9 +79,7 @@ class LocalToRemoteGitMirrorTest {
     static final CentralDogmaExtension dogma = new CentralDogmaExtension() {
         @Override
         protected void configure(CentralDogmaBuilder builder) {
-            builder.mirroringEnabled(true);
-            builder.maxNumFilesPerMirror(MAX_NUM_FILES);
-            builder.maxNumBytesPerMirror(MAX_NUM_BYTES);
+            builder.pluginConfigs(new MirroringServicePluginConfig(true, 1, MAX_NUM_FILES, MAX_NUM_BYTES));
         }
     };
 

it/server/src/test/java/com/linecorp/centraldogma/it/ReplicationWriteQuotaTest.java

@@ -47,6 +47,7 @@
 import com.linecorp.centraldogma.server.ZooKeeperReplicationConfig;
 import com.linecorp.centraldogma.server.ZooKeeperServerConfig;
 import com.linecorp.centraldogma.server.auth.AuthProviderFactory;
+import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
 import com.linecorp.centraldogma.testing.internal.FlakyTest;
 import com.linecorp.centraldogma.testing.internal.TemporaryFolderExtension;
 import com.linecorp.centraldogma.testing.internal.auth.TestAuthMessageUtil;
@@ -131,7 +132,7 @@ private static CompletableFuture<Void> startNewReplica(
                 .port(port, SessionProtocol.HTTP)
                 .administrators(TestAuthMessageUtil.USERNAME)
                 .authProviderFactory(factory)
-                .mirroringEnabled(false)
+                .pluginConfigs(new MirroringServicePluginConfig(false))
                 .writeQuotaPerRepository(5, 1)
                 .gracefulShutdownTimeout(new GracefulShutdownTimeout(0, 0))
                 .replication(new ZooKeeperReplicationConfig(serverId, servers))

it/server/src/test/java/com/linecorp/centraldogma/it/TestAllReplicasPlugin.java

@@ -41,4 +41,10 @@ public CompletionStage<Void> start(PluginContext context) {
     public CompletionStage<Void> stop(PluginContext context) {
         return UnmodifiableFuture.completedFuture(null);
     }
+
+    @Override
+    public Class<?> configType() {
+        // Return the plugin class itself because it does not have a configuration.
+        return TestAllReplicasPlugin.class;
+    }
 }

server-mirror-git/src/test/java/com/linecorp/centraldogma/server/internal/mirror/MirroringMigrationServiceClusterTest.java

@@ -74,6 +74,7 @@
 import com.linecorp.centraldogma.server.ZooKeeperReplicationConfig;
 import com.linecorp.centraldogma.server.ZooKeeperServerConfig;
 import com.linecorp.centraldogma.server.auth.AuthProviderFactory;
+import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
 import com.linecorp.centraldogma.server.storage.project.Project;
 import com.linecorp.centraldogma.testing.internal.TemporaryFolderExtension;
 import com.linecorp.centraldogma.testing.internal.auth.TestAuthMessageUtil;
@@ -106,7 +107,7 @@ void shouldMigrateMirrorConfigsWithZooKeeper() throws Exception {
                                  final int port = ports[i * 3 + 2];
                                  return new CentralDogmaBuilder(data)
                                          .port(port, SessionProtocol.HTTP)
-                                         .mirroringEnabled(false)
+                                         .pluginConfigs(new MirroringServicePluginConfig(false))
                                          .authProviderFactory(factory)
                                          .replication(replicationConfig)
                                          .administrators(TestAuthMessageUtil.USERNAME)
@@ -155,7 +156,6 @@ void shouldMigrateMirrorConfigsWithZooKeeper() throws Exception {
                            server.stop().join();
                            return new CentralDogmaBuilder(server.config().dataDir())
                                    .port(port, SessionProtocol.HTTP)
-                                   .mirroringEnabled(true)
                                    .replication(server.config().replicationConfig())
                                    .build();
                        })

server/src/main/java/com/linecorp/centraldogma/server/CentralDogma.java

@@ -212,8 +212,7 @@ public class CentralDogma implements AutoCloseable {
      */
     public static CentralDogma forConfig(File configFile) throws IOException {
         requireNonNull(configFile, "configFile");
-        return new CentralDogma(Jackson.readValue(configFile, CentralDogmaConfig.class),
-                                Flags.meterRegistry());
+        return new CentralDogma(CentralDogmaConfig.load(configFile), Flags.meterRegistry());
     }
 
     private final SettableHealthChecker serverHealth = new SettableHealthChecker(false);

server/src/main/java/com/linecorp/centraldogma/server/CentralDogmaBuilder.java

@@ -49,6 +49,7 @@
 import com.linecorp.centraldogma.server.auth.AuthProvider;
 import com.linecorp.centraldogma.server.auth.AuthProviderFactory;
 import com.linecorp.centraldogma.server.auth.Session;
+import com.linecorp.centraldogma.server.plugin.PluginConfig;
 import com.linecorp.centraldogma.server.storage.repository.Repository;
 
 import io.micrometer.core.instrument.MeterRegistry;
@@ -71,9 +72,6 @@ public final class CentralDogmaBuilder {
     private static final ServerPort DEFAULT_PORT = new ServerPort(36462, SessionProtocol.HTTP);
 
     static final int DEFAULT_NUM_REPOSITORY_WORKERS = 16;
-    static final int DEFAULT_NUM_MIRRORING_THREADS = 16;
-    static final int DEFAULT_MAX_NUM_FILES_PER_MIRROR = 8192;
-    static final long DEFAULT_MAX_NUM_BYTES_PER_MIRROR = 32 * 1048576; // 32 MiB
     static final long DEFAULT_MAX_REMOVED_REPOSITORY_AGE_MILLIS = 604_800_000;  // 7 days
 
     static final String DEFAULT_REPOSITORY_CACHE_SPEC =
@@ -84,13 +82,19 @@ public final class CentralDogmaBuilder {
     // Note that we use nullable types here for optional properties.
     // When a property is null, the default value will be used implicitly.
     private final List<ServerPort> ports = new ArrayList<>(2);
+    @Nullable
     private TlsConfig tls;
-    private List<String> trustedProxyAddresses = new ArrayList<>();
-    private List<String> clientAddressSources = new ArrayList<>();
+    private final List<String> trustedProxyAddresses = new ArrayList<>();
+    private final List<String> clientAddressSources = new ArrayList<>();
+    @Nullable
     private Integer numWorkers;
+    @Nullable
     private Integer maxNumConnections;
+    @Nullable
     private Long requestTimeoutMillis;
+    @Nullable
     private Long idleTimeoutMillis;
+    @Nullable
     private Integer maxFrameLength;
 
     // Central Dogma properties
@@ -103,13 +107,11 @@ public final class CentralDogmaBuilder {
     private boolean webAppEnabled = true;
     @Nullable
     private String webAppTitle;
-    private boolean mirroringEnabled = true;
-    private int numMirroringThreads = DEFAULT_NUM_MIRRORING_THREADS;
-    private int maxNumFilesPerMirror = DEFAULT_MAX_NUM_FILES_PER_MIRROR;
-    private long maxNumBytesPerMirror = DEFAULT_MAX_NUM_BYTES_PER_MIRROR;
+
     @Nullable
     private GracefulShutdownTimeout gracefulShutdownTimeout;
     private ReplicationConfig replicationConfig = ReplicationConfig.NONE;
+    @Nullable
     private String accessLogFormat;
 
     // AuthConfig properties
@@ -129,6 +131,8 @@ public final class CentralDogmaBuilder {
     @Nullable
     private CorsConfig corsConfig;
 
+    private final List<PluginConfig> pluginConfigs = new ArrayList<>();
+
     /**
      * Creates a new builder with the specified data directory.
      */
@@ -370,42 +374,6 @@ public CentralDogmaBuilder webAppTitle(String webAppTitle) {
         return this;
     }
 
-    /**
-     * Sets whether {@link MirroringService} is enabled or not.
-     * If unspecified, {@link MirroringService} is enabled.
-     */
-    public CentralDogmaBuilder mirroringEnabled(boolean mirroringEnabled) {
-        this.mirroringEnabled = mirroringEnabled;
-        return this;
-    }
-
-    /**
-     * Sets the number of worker threads dedicated to mirroring between repositories.
-     * If unspecified, {@value #DEFAULT_NUM_MIRRORING_THREADS} threads are created at maximum.
-     */
-    public CentralDogmaBuilder numMirroringThreads(int numMirroringThreads) {
-        this.numMirroringThreads = numMirroringThreads;
-        return this;
-    }
-
-    /**
-     * Sets the maximum allowed number of files in a mirrored tree.
-     * If unspecified, {@value #DEFAULT_MAX_NUM_FILES_PER_MIRROR} files are allowed at maximum.
-     */
-    public CentralDogmaBuilder maxNumFilesPerMirror(int maxNumFilesPerMirror) {
-        this.maxNumFilesPerMirror = maxNumFilesPerMirror;
-        return this;
-    }
-
-    /**
-     * Sets the maximum allowed number of bytes in a mirrored tree.
-     * If unspecified, {@value #DEFAULT_MAX_NUM_BYTES_PER_MIRROR} bytes are allowed at maximum.
-     */
-    public CentralDogmaBuilder maxNumBytesPerMirror(long maxNumBytesPerMirror) {
-        this.maxNumBytesPerMirror = maxNumBytesPerMirror;
-        return this;
-    }
-
     /**
      * Sets the graceful shutdown timeout. If unspecified, graceful shutdown is disabled.
      */
@@ -552,6 +520,15 @@ public CentralDogmaBuilder cors(CorsConfig corsConfig) {
         return this;
     }
 
+    /**
+     * Adds the {@link PluginConfig}s.
+     */
+    public CentralDogmaBuilder pluginConfigs(PluginConfig... pluginConfigs) {
+        requireNonNull(pluginConfigs, "pluginConfigs");
+        this.pluginConfigs.addAll(ImmutableList.copyOf(pluginConfigs));
+        return this;
+    }
+
     /**
      * Returns a newly-created {@link CentralDogma} server.
      */
@@ -583,9 +560,8 @@ private CentralDogmaConfig buildConfig() {
                                       requestTimeoutMillis, idleTimeoutMillis, maxFrameLength,
                                       numRepositoryWorkers, repositoryCacheSpec,
                                       maxRemovedRepositoryAgeMillis, gracefulShutdownTimeout,
-                                      webAppEnabled, webAppTitle, mirroringEnabled, numMirroringThreads,
-                                      maxNumFilesPerMirror, maxNumBytesPerMirror, replicationConfig,
+                                      webAppEnabled, webAppTitle,replicationConfig,
                                       null, accessLogFormat, authCfg, quotaConfig,
-                                      corsConfig);
+                                      corsConfig, pluginConfigs);
     }
 }