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HDFS-15419. RBF: Router should retry communicate with NN when cluster is unavailable using configurable time interval #2082

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HDFS-15419. RBF: Router should retry communicate with NN when cluster is unavailable using configurable time interval #2082

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Merge pull request #1 from apache/trunk
bhji123 Jun 18, 2020
2bba65f
router retry communicate with NN using configurable time interval whe…
bhji123 Jun 19, 2020
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Binary file added hadoop-common-project/hadoop-common/.debug.log.crc
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5 changes: 5 additions & 0 deletions .../hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/client/HdfsClientConfigKeys.java
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Original file line number Diff line number Diff line change
Expand Up @@ -250,6 +250,11 @@ public interface HdfsClientConfigKeys {
String DFS_LEASE_HARDLIMIT_KEY = "dfs.namenode.lease-hard-limit-sec";
long DFS_LEASE_HARDLIMIT_DEFAULT = 20 * 60;

String DFS_ROUTER_RPC_RETRY_INTERVAL_KEY = "dfs.router.rpc.retry.interval.seconds";
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Technically is not seconds but time duration.

int DFS_ROUTER_RPC_RETRY_INTERVAL_DEFAULT = 10;
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Make it TimeUnit.SECONDS.toXXXX(10)

String DFS_ROUTER_RPC_RETRY_COUNT_KEY = "dfs.router.rpc.retry.count";
int DFS_ROUTER_RPC_RETRY_COUNT_DEFAULT = 3;

/**
* These are deprecated config keys to client code.
*/
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26 changes: 25 additions & 1 deletion ...fs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcClient.java
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Expand Up @@ -112,6 +112,10 @@ public class RouterRpcClient {
private final ThreadPoolExecutor executorService;
/** Retry policy for router -> NN communication. */
private final RetryPolicy retryPolicy;
/** Retry time interval for router -> NN communication when cluster is unavailable. */
private long retryTimeInterval;
/** Maximum number of retries for router -> NN communication when cluster is unavailable. */
private int maxRetryCount;
/** Optional perf monitor. */
private final RouterRpcMonitor rpcMonitor;

Expand Down Expand Up @@ -172,6 +176,13 @@ public RouterRpcClient(Configuration conf, Router router,
this.retryPolicy = RetryPolicies.failoverOnNetworkException(
RetryPolicies.TRY_ONCE_THEN_FAIL, maxFailoverAttempts, maxRetryAttempts,
failoverSleepBaseMillis, failoverSleepMaxMillis);
this.retryTimeInterval = conf.getTimeDuration(
HdfsClientConfigKeys.DFS_ROUTER_RPC_RETRY_INTERVAL_KEY,
HdfsClientConfigKeys.DFS_ROUTER_RPC_RETRY_INTERVAL_DEFAULT,
TimeUnit.SECONDS);
this.maxRetryCount = conf.getInt(
HdfsClientConfigKeys.DFS_ROUTER_RPC_RETRY_COUNT_KEY,
HdfsClientConfigKeys.DFS_ROUTER_RPC_RETRY_COUNT_DEFAULT);
}

/**
Expand Down Expand Up @@ -357,7 +368,7 @@ private RetryDecision shouldRetry(final IOException ioe, final int retryCount,
// check for the case of cluster unavailable state
if (isClusterUnAvailable(nsId)) {
// we allow to retry once if cluster is unavailable
if (retryCount == 0) {
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This logic starts with this counter at a value and then decreases, it makes sense to keep it as such.

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In fact, not all clients are so smart, they may not configred appropriately. When those clients encounter this problem, they complain about router not retry more.

if (retryCount < maxRetryCount) {
return RetryDecision.RETRY;
} else {
throw new NoNamenodesAvailableException(nsId, ioe);
Expand Down Expand Up @@ -557,6 +568,19 @@ private Object invoke(String nsId, int retryCount, final Method method,
}

// retry
try {
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The idea before was for us to surface the unavailability to the client and then the client retry with the regular client logic.

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In fact, not all clients are so smart, they may not configred appropriately. When those clients encounter this problem, they complain about router not retry more.

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Sure, but we should change the logic to match the old style or at least to not have the two styles together.

for (int i = 0; i < maxRetryCount; i++) {
if (retryCount == i) {
TimeUnit.SECONDS.sleep(retryTimeInterval * i);
break;
}
}
} catch (InterruptedException ex) {
LOG.warn("Router rpc retry sleep encounter exception.");
} finally {
LOG.info("Router rpc retry, maxRetryCount={}, retryCount={}, method={}, params={} ",
maxRetryCount, retryCount, method, params);
}
return invoke(nsId, ++retryCount, method, obj, params);
} else if (decision == RetryDecision.FAILOVER_AND_RETRY) {
// failover, invoker looks for standby exceptions for failover.
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4 changes: 2 additions & 2 deletions ...test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterRPCClientRetries.java
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Expand Up @@ -139,7 +139,7 @@ public void testRetryWhenAllNameServiceDown() throws Exception {
// Verify the retry times, it should only retry one time.
FederationRPCMetrics rpcMetrics = routerContext.getRouter()
.getRpcServer().getRPCMetrics();
assertEquals(1, rpcMetrics.getProxyOpRetries());
assertEquals(3, rpcMetrics.getProxyOpRetries());
}

@Test
Expand All @@ -158,7 +158,7 @@ public void testRetryWhenOneNameServiceDown() throws Exception {
// Verify the retry times, it will retry one time for ns0.
FederationRPCMetrics rpcMetrics = routerContext.getRouter()
.getRpcServer().getRPCMetrics();
assertEquals(1, rpcMetrics.getProxyOpRetries());
assertEquals(3, rpcMetrics.getProxyOpRetries());
}

/**
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