saintstack commented on a change in pull request #954: HBASE-23305: Master
based registry implementation
URL: https://github.com/apache/hbase/pull/954#discussion_r360503952
##########
File path:
hbase-client/src/main/java/org/apache/hadoop/hbase/client/MasterRegistry.java
##########
@@ -0,0 +1,364 @@
+package org.apache.hadoop.hbase.client;
+
+import static org.apache.hadoop.hbase.HConstants.DEFAULT_HBASE_RPC_TIMEOUT;
+import static org.apache.hadoop.hbase.HConstants.HBASE_RPC_TIMEOUT_KEY;
+import static org.apache.hadoop.hbase.HConstants.MASTER_ADDRS_DEFAULT;
+import static org.apache.hadoop.hbase.HConstants.MASTER_ADDRS_KEY;
+import static
org.apache.hadoop.hbase.HConstants.MASTER_REGISTRY_NUM_HEDGED_REQS_DEFAULT;
+import static
org.apache.hadoop.hbase.HConstants.MASTER_REGISTRY_NUM_HEDGED_REQS_KEY;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.HRegionLocation;
+import org.apache.hadoop.hbase.RegionLocations;
+import org.apache.hadoop.hbase.ServerName;
+import org.apache.hadoop.hbase.exceptions.MasterRegistryFetchException;
+import org.apache.hadoop.hbase.ipc.RpcClient;
+import org.apache.hadoop.hbase.ipc.RpcClientFactory;
+import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
+import org.apache.hadoop.hbase.security.User;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import
org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
+import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
+import
org.apache.hbase.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
+import org.apache.hbase.thirdparty.com.google.protobuf.ServiceException;
+import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.ClientMetaService;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetActiveMasterRequest;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetActiveMasterResponse;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetClusterIdRequest;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetClusterIdResponse;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetMetaRegionLocationsRequest;
+import
org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetMetaRegionLocationsResponse;
+
+/**
+ * Master based registry implementation. Makes RPCs to the configured master
addresses from config
+ * {@value HConstants#MASTER_ADDRS_KEY}.
+ *
+ * It has the ability to burst the same RPC to multiple masters as a batch and
returns whatever
+ * comes back first (a.k.a hedged RPCs). Number of target masters in a single
batch is controlled
+ * via {@value HConstants#MASTER_REGISTRY_NUM_HEDGED_REQS_KEY}. If it is set
to 1 (default), it is
+ * equivalent to picking a random master from the configured list.
+ *
+ * TODO: Handle changes to the configuration dynamically without having to
restart the client.
Review comment:
More detail on how hedged read works? Do we read from all always? Or a delay
before we read from others? Thanks.
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