bharathv commented on a change in pull request #954: HBASE-23305: Master based registry implementation URL: https://github.com/apache/hbase/pull/954#discussion_r362718926
########## File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/MasterRegistry.java ########## @@ -0,0 +1,218 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.hadoop.hbase.client; + +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_ENABLE_HEDGED_READS_DEFAULT; +import static org.apache.hadoop.hbase.HConstants.MASTER_REGISTRY_ENABLE_HEDGED_READS_KEY; +import java.io.IOException; +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.concurrent.CompletableFuture; +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.HBaseRpcController; +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.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting; +import org.apache.hbase.thirdparty.com.google.common.base.Function; +import org.apache.hbase.thirdparty.com.google.common.base.Preconditions; +import org.apache.hbase.thirdparty.com.google.common.net.HostAndPort; +import org.apache.hbase.thirdparty.com.google.protobuf.RpcCallback; +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 org.apache.hadoop.hbase.HConstants#MASTER_ADDRS_KEY}. + * + * It supports hedged reads, which can be enabled by setting + * {@value org.apache.hadoop.hbase.HConstants#MASTER_REGISTRY_ENABLE_HEDGED_READS_KEY} to True. Fan + * out the requests batch is controlled by + * {@value org.apache.hadoop.hbase.HConstants#HBASE_RPCS_HEDGED_REQS_FANOUT_KEY}. + * + * TODO: Handle changes to the configuration dynamically without having to restart the client. + */ +@InterfaceAudience.Private +public class MasterRegistry implements AsyncRegistry { + private static final String MASTER_ADDRS_CONF_SEPARATOR = ","; + + // Configured list of masters to probe the meta information from. + private final List<ServerName> masterServers; + + // RPC client used to talk to the masters. + private final RpcClient rpcClient; + private final RpcControllerFactory rpcControllerFactory; + private final int rpcTimeoutMs; + + MasterRegistry(Configuration conf) { + boolean hedgedReadsEnabled = conf.getBoolean(MASTER_REGISTRY_ENABLE_HEDGED_READS_KEY, + MASTER_REGISTRY_ENABLE_HEDGED_READS_DEFAULT); + Configuration finalConf; + if (!hedgedReadsEnabled) { + // If hedged reads are disabled, it is equivalent to setting a fan out of 1. We make a copy of + // the configuration so that other places reusing this reference is not affected. + finalConf = new Configuration(conf); + finalConf.setInt(HConstants.HBASE_RPCS_HEDGED_REQS_FANOUT_KEY, 1); + } else { + finalConf = conf; + } + rpcTimeoutMs = (int) Math.min(Integer.MAX_VALUE, conf.getLong(HConstants.HBASE_RPC_TIMEOUT_KEY, + HConstants.DEFAULT_HBASE_RPC_TIMEOUT)); + masterServers = new ArrayList<>(); + parseMasterAddrs(finalConf); + rpcClient = RpcClientFactory.createClient(finalConf, HConstants.CLUSTER_ID_DEFAULT); + rpcControllerFactory = RpcControllerFactory.instantiate(finalConf); + } + + /** + * @return Stub needed to make RPC using a hedged channel to the master end points. + */ + private ClientMetaService.Interface getMasterStub() throws IOException { + return ClientMetaService.newStub( + rpcClient.createHedgedRpcChannel(masterServers, User.getCurrent(), rpcTimeoutMs)); + } + + /** + * Parses the list of master addresses from the provided configuration. Supported format is + * comma separated host[:port] values. If no port number if specified, default master port is + * assumed. + * @param conf Configuration to parse from. + */ + private void parseMasterAddrs(Configuration conf) { + String configuredMasters = conf.get(MASTER_ADDRS_KEY, MASTER_ADDRS_DEFAULT); + for (String masterAddr: configuredMasters.split(MASTER_ADDRS_CONF_SEPARATOR)) { + HostAndPort masterHostPort = + HostAndPort.fromString(masterAddr.trim()).withDefaultPort(HConstants.DEFAULT_MASTER_PORT); + masterServers.add(ServerName.valueOf(masterHostPort.toString(), ServerName.NON_STARTCODE)); + } + Preconditions.checkArgument(!masterServers.isEmpty(), "At least one master address is needed"); + } + + @VisibleForTesting + public List<ServerName> getParsedMasterServers() { + return Collections.unmodifiableList(masterServers); + } + + /** + * Returns a call back that can be passed along to the non-blocking rpc call. It is invoked once + * the rpc finishes and the response is propagated to the passed future. + * @param future Result future to which the rpc response is propagated. + * @param isValidResp Checks if the rpc response has a valid result. + * @param transformResult Transforms the result to a different form as expected by callers. + * @param hrc RpcController instance for this rpc. + * @param <T> RPC result type. + * @param <R> Transformed type of the result. + * @return A call back that can be embedded in the non-blocking rpc call. + */ + private <T, R> RpcCallback<T> getRpcCallBack(CompletableFuture<R> future, + Function<T, Boolean> isValidResp, Function<T, R> transformResult, HBaseRpcController hrc) { + return rpcResult -> { + if (rpcResult == null) { + future.completeExceptionally( + new MasterRegistryFetchException(masterServers, hrc.getFailed())); + } + if (!isValidResp.apply(rpcResult)) { + // Rpc returned ok, but result was malformed. Review comment: > I take it failures that warrant a DoNotRetryIOException are handled by the RPC layer. Is there a reason why an RPC would succeed but the isValidResp would need to fail with a DNRIOE ? It happens when the server doing the RPC does not have enough information to service the request. For example, if there is no active master in the cluster but someone does a "get active master" request. The rPC resturns ok but no server name set. The predicate catches such scenarios. >It would be nice if this was an interface was enriched to support adding meaningful logging into the loop. For instance, it would be nice to have DEBUG logging that said something like "GetClusterIdResponse does not contain a clusterId value. retrying." Right now it's just RPC into the void over and over without leaving a trail as to the error scenario. My original implementation had something like that. It made the code ugly. Fwiw, the stack trace will have the actual failing RPC in the protobuf stack. However it is probably not as readable to a user, unless they know how to interpret it. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
