saintstack commented on a change in pull request #954: HBASE-23305: Master
based registry implementation
URL: https://github.com/apache/hbase/pull/954#discussion_r360511377
##########
File path:
hbase-client/src/main/java/org/apache/hadoop/hbase/client/MasterRegistry.java
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@@ -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.
+ */
+@InterfaceAudience.Private
+public class MasterRegistry implements AsyncRegistry {
+ private static final Logger LOG =
LoggerFactory.getLogger(MasterRegistry.class);
+
+ // Configured list of masters to probe the meta information from.
+ private final List<ServerName> masterServers;
+ // Controls the fan out of the hedged requests. Requests are made in batches
of this number until
+ // all the servers are exhausted. The first returned result is passed back
to the client.
+ private final int requestFanOut;
+ private ExecutorService masterRpcPool;
+
+ // RPC client used to talk to the masters.
+ private final RpcClient rpcClient;
+ private final RpcControllerFactory rpcControllerFactory;
+ private final int rpcTimeoutNs;
+
+ // A simple interface that callers can implement to make an RPC to master.
This is used to
+ // abstract out the logic needed to hedge the requests to multiple masters.
For more details, look
+ // at doRPCs().
+ @VisibleForTesting
+ @FunctionalInterface
+ public interface RpcCall<RESP> {
+ RESP doRpc(ClientMetaService.BlockingInterface stub) throws
ServiceException;
+ }
+
+ /**
+ * A shared RPC context between a batch of hedged RPCs. Tracks the state and
helpers needed to
+ * synchronize on multiple RPCs to different masters fetching the result.
All the methods are
+ * thread-safe.
+ * @param <RESP> Return response type for the RPCs.
+ */
+ private class BatchRpcCtx<RESP> {
+ // Result set by the thread finishing first. Set only once.
+ private AtomicReference<RESP> result;
+ // Caller waits on this latch being set.
+ private CountDownLatch resultsReady;
+ // Book-keeping for number of failed RPCs.
+ private AtomicInteger failedRPCs;
+
+ BatchRpcCtx() {
+ result = new AtomicReference<>();
+ // We set this to 1, so that the first successful RPC result is returned
to the client.
+ resultsReady = new CountDownLatch(1);
+ failedRPCs = new AtomicInteger(0);
+ }
+
+ /**
+ * Sets the result only if it is not already set by another thread. Thread
that successfully
+ * sets the result also count downs the latch.
+ * @param result Result to be set.
+ */
+ public void setResultIfNotSet(RESP result) {
+ if (this.result.compareAndSet(null, result)) {
+ resultsReady.countDown();
+ }
+ }
+
+ /**
+ * Caller can use this method to wait for results to be fetched.
+ * @param timeoutNs Waits until this timeout hits or the results are set.
Whatever happens
+ * first.
+ * @return True if the results are ready. False otherwise.
+ */
+ public boolean waitForResults(int timeoutNs) {
+ try {
+ return resultsReady.await(timeoutNs, TimeUnit.NANOSECONDS);
+ } catch (InterruptedException e) {
+ LOG.warn("Interrupted while waiting for batched master RPC results.
Aborting wait.", e);
+ return false;
+ }
+ }
+
+ /**
+ * Helper to increment the number of failed RPCs.
+ */
+ public void incrementFailedRPCs() {
+ failedRPCs.incrementAndGet();
+ }
+
+ /**
+ * Onus is on the caller to wait for the results and call this.
+ * @return the current result.
+ */
+ public RESP getResult() {
+ return result.get();
+ }
+ }
+
+ /**
+ * A runnable implementation of an RPC call to a given master. Updates the
results in a shared
+ * rpc context.
+ * @param <RESP> Response type of the RPC.
+ */
+ private class MasterRpc<RESP> implements Runnable {
+ private final BatchRpcCtx<RESP> rpcCtx;
+ private final ServerName master;
+ private final RpcCall<RESP> rpcCall;
+ private final Function<RESP, Boolean> isValidResp;
+ private final String debugStr;
+
+ MasterRpc(BatchRpcCtx<RESP> rpcCtx, ServerName master, RpcCall<RESP>
rpcCall,
Review comment:
We have a whole world of Callable+Call and it seems like this is introducing
a new one of RpcCall... We need this new one? (I don't know.... just asking...
because it gets hard tracking Callable/Call/Caller... and adding variants makes
for more to decipher... FYI).
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