Add a command for dumping Redis SLOWLOG output.

service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java

@@ -155,6 +155,7 @@ import org.whispersystems.textsecuregcm.websocket.ProvisioningConnectListener;
 import org.whispersystems.textsecuregcm.websocket.WebSocketAccountAuthenticator;
 import org.whispersystems.textsecuregcm.workers.CertificateCommand;
 import org.whispersystems.textsecuregcm.workers.DeleteUserCommand;
+import org.whispersystems.textsecuregcm.workers.GetRedisSlowlogCommand;
 import org.whispersystems.textsecuregcm.workers.VacuumCommand;
 import org.whispersystems.textsecuregcm.workers.ZkParamsCommand;
 import org.whispersystems.websocket.WebSocketResourceProviderFactory;
@@ -189,6 +190,7 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     bootstrap.addCommand(new DeleteUserCommand());
     bootstrap.addCommand(new CertificateCommand());
     bootstrap.addCommand(new ZkParamsCommand());
+    bootstrap.addCommand(new GetRedisSlowlogCommand());
 
     bootstrap.addBundle(new NameableMigrationsBundle<WhisperServerConfiguration>("accountdb", "accountsdb.xml") {
       @Override

service/src/main/java/org/whispersystems/textsecuregcm/redis/FaultTolerantRedisCluster.java

@@ -101,6 +101,10 @@ public class FaultTolerantRedisCluster {
         clusterClient.shutdown();
     }
 
+    public String getName() {
+        return name;
+    }
+
     public void useCluster(final Consumer<StatefulRedisClusterConnection<String, String>> consumer) {
         useConnection(stringConnection, consumer);
     }

service/src/main/java/org/whispersystems/textsecuregcm/workers/GetRedisSlowlogCommand.java

@@ -0,0 +1,54 @@
+package org.whispersystems.textsecuregcm.workers;
+
+import io.dropwizard.cli.ConfiguredCommand;
+import io.dropwizard.setup.Bootstrap;
+import net.sourceforge.argparse4j.inf.Namespace;
+import net.sourceforge.argparse4j.inf.Subparser;
+import org.whispersystems.textsecuregcm.WhisperServerConfiguration;
+import org.whispersystems.textsecuregcm.redis.FaultTolerantRedisCluster;
+import org.whispersystems.textsecuregcm.util.SystemMapper;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class GetRedisSlowlogCommand extends ConfiguredCommand<WhisperServerConfiguration> {
+
+    public GetRedisSlowlogCommand() {
+        super("redisslowlog", "Dump a JSON blob describing slow Redis operations");
+    }
+
+    @Override
+    public void configure(final Subparser subparser) {
+        super.configure(subparser);
+
+        subparser.addArgument("-n", "--entries")
+                 .dest("entries")
+                 .type(Integer.class)
+                 .required(false)
+                 .setDefault(128)
+                 .help("The maximum number of SLOWLOG entries to retrieve per cluster node");
+    }
+
+    @Override
+    protected void run(final Bootstrap<WhisperServerConfiguration> bootstrap, final Namespace namespace, final WhisperServerConfiguration config) throws Exception {
+        final int entries = namespace.getInt("entries");
+
+        final FaultTolerantRedisCluster cacheCluster         = new FaultTolerantRedisCluster("main_cache_cluster", config.getCacheClusterConfiguration());
+        final FaultTolerantRedisCluster messagesCacheCluster = new FaultTolerantRedisCluster("messages_cluster", config.getMessageCacheConfiguration().getRedisClusterConfiguration());
+        final FaultTolerantRedisCluster metricsCluster       = new FaultTolerantRedisCluster("metrics_cluster", config.getMetricsClusterConfiguration());
+
+        final Map<String, List<Object>> slowlogsByUri = new HashMap<>();
+
+        for (final FaultTolerantRedisCluster cluster : List.of(cacheCluster, messagesCacheCluster, metricsCluster)) {
+            cluster.useCluster(connection -> connection.sync()
+                                                       .masters()
+                                                       .commands()
+                                                       .slowlogGet(entries)
+                                                       .asMap()
+                                                       .forEach((node, slowlogs) -> slowlogsByUri.put(node.getUri().toString(), slowlogs)));
+        }
+
+        SystemMapper.getMapper().writeValue(System.out, slowlogsByUri);
+    }
+}