HDFS-17242. Make congestion backoff time configurable. (#6227)

Reviewed-by: Xing Lin <xinglin@linkedin.com>
Reviewed-by: Ayush Saxena <ayushsaxena@apache.org>
Signed-off-by: Tao Li <tomscut@apache.org>

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DataStreamer.java

@@ -46,6 +46,7 @@ import java.util.concurrent.atomic.AtomicReference;
 import org.apache.hadoop.classification.VisibleForTesting;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.StorageType;
+import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.BlockWrite;
 import org.apache.hadoop.hdfs.client.impl.DfsClientConf;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
@@ -528,9 +529,8 @@ class DataStreamer extends Daemon {
   // are congested
   private final List<DatanodeInfo> congestedNodes = new ArrayList<>();
   private final Map<DatanodeInfo, Integer> slowNodeMap = new HashMap<>();
-  private static final int CONGESTION_BACKOFF_MEAN_TIME_IN_MS = 5000;
-  private static final int CONGESTION_BACK_OFF_MAX_TIME_IN_MS =
-      CONGESTION_BACKOFF_MEAN_TIME_IN_MS * 10;
+  private int congestionBackOffMeanTimeInMs;
+  private int congestionBackOffMaxTimeInMs;
   private int lastCongestionBackoffTime;
   private int maxPipelineRecoveryRetries;
   private int markSlowNodeAsBadNodeThreshold;
@@ -564,6 +564,35 @@ class DataStreamer extends Daemon {
     this.addBlockFlags = flags;
     this.maxPipelineRecoveryRetries = conf.getMaxPipelineRecoveryRetries();
     this.markSlowNodeAsBadNodeThreshold = conf.getMarkSlowNodeAsBadNodeThreshold();
+    congestionBackOffMeanTimeInMs = dfsClient.getConfiguration().getInt(
+        HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME,
+        HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME_DEFAULT);
+    congestionBackOffMaxTimeInMs = dfsClient.getConfiguration().getInt(
+        HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME,
+        HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME_DEFAULT);
+    if (congestionBackOffMeanTimeInMs <= 0) {
+      LOG.warn("Configuration: {} is not appropriate, using default value: {}",
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME,
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME_DEFAULT);
+    }
+    if (congestionBackOffMaxTimeInMs <= 0) {
+      LOG.warn("Configuration: {} is not appropriate, using default value: {}",
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME,
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME_DEFAULT);
+    }
+    if (congestionBackOffMaxTimeInMs < congestionBackOffMeanTimeInMs) {
+      LOG.warn("Configuration: {} can not less than {}, using their default values.",
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME,
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME);
+    }
+    if (congestionBackOffMeanTimeInMs <= 0 || congestionBackOffMaxTimeInMs <= 0 ||
+        congestionBackOffMaxTimeInMs < congestionBackOffMeanTimeInMs) {
+      congestionBackOffMeanTimeInMs =
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME_DEFAULT;
+      congestionBackOffMaxTimeInMs =
+          HdfsClientConfigKeys.DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME_DEFAULT;
+    }
+
   }
 
   /**
@@ -1998,10 +2027,10 @@ class DataStreamer extends Daemon {
           sb.append(' ').append(i);
         }
         int range = Math.abs(lastCongestionBackoffTime * 3 -
-                                CONGESTION_BACKOFF_MEAN_TIME_IN_MS);
+            congestionBackOffMeanTimeInMs);
         int base = Math.min(lastCongestionBackoffTime * 3,
-                            CONGESTION_BACKOFF_MEAN_TIME_IN_MS);
-        t = Math.min(CONGESTION_BACK_OFF_MAX_TIME_IN_MS,
+            congestionBackOffMeanTimeInMs);
+        t = Math.min(congestionBackOffMaxTimeInMs,
                      (int)(base + Math.random() * range));
         lastCongestionBackoffTime = t;
         sb.append(" are congested. Backing off for ").append(t).append(" ms");

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/client/HdfsClientConfigKeys.java

@@ -287,6 +287,15 @@ public interface HdfsClientConfigKeys {
       "dfs.client.output.stream.uniq.default.key";
   String DFS_OUTPUT_STREAM_UNIQ_DEFAULT_KEY_DEFAULT = "DEFAULT";
 
+  String DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME =
+      "dfs.client.congestion.backoff.mean.time";
+  int DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME_DEFAULT = 5000;
+
+  String DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME =
+      "dfs.client.congestion.backoff.max.time";
+  int DFS_CLIENT_CONGESTION_BACKOFF_MAX_TIME_DEFAULT =
+      DFS_CLIENT_CONGESTION_BACKOFF_MEAN_TIME_DEFAULT * 10;
+
   /**
    * These are deprecated config keys to client code.
    */

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -6559,6 +6559,22 @@
       If the namespace is DEFAULT, it's best to change this conf to other value.
     </description>
   </property>
+  <property>
+    <name>dfs.client.congestion.backoff.mean.time</name>
+    <value>5000</value>
+    <description>
+      The mean time in milliseconds which is used to compute
+      client congestion backoff sleep time.
+    </description>
+  </property>
+  <property>
+    <name>dfs.client.congestion.backoff.max.time</name>
+    <value>50000</value>
+    <description>
+      The max time in milliseconds which is used to restrict
+      the upper limit backoff sleep time for client.
+    </description>
+  </property>
   <property>
     <name>dfs.client.rbf.observer.read.enable</name>
     <value>false</value>

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSOutputStream.java

@@ -275,6 +275,8 @@ public class TestDFSOutputStream {
   public void testCongestionBackoff() throws IOException {
     DfsClientConf dfsClientConf = mock(DfsClientConf.class);
     DFSClient client = mock(DFSClient.class);
+    Configuration conf = mock(Configuration.class);
+    when(client.getConfiguration()).thenReturn(conf);
     when(client.getConf()).thenReturn(dfsClientConf);
     when(client.getTracer()).thenReturn(FsTracer.get(new Configuration()));
     client.clientRunning = true;
@@ -306,6 +308,8 @@ public class TestDFSOutputStream {
   public void testCongestionAckDelay() {
     DfsClientConf dfsClientConf = mock(DfsClientConf.class);
     DFSClient client = mock(DFSClient.class);
+    Configuration conf = mock(Configuration.class);
+    when(client.getConfiguration()).thenReturn(conf);
     when(client.getConf()).thenReturn(dfsClientConf);
     when(client.getTracer()).thenReturn(FsTracer.get(new Configuration()));
     client.clientRunning = true;
@@ -325,7 +329,7 @@ public class TestDFSOutputStream {
     ArrayList<DatanodeInfo> congestedNodes = (ArrayList<DatanodeInfo>)
             Whitebox.getInternalState(stream, "congestedNodes");
     int backOffMaxTime = (int)
-            Whitebox.getInternalState(stream, "CONGESTION_BACK_OFF_MAX_TIME_IN_MS");
+            Whitebox.getInternalState(stream, "congestionBackOffMaxTimeInMs");
     DFSPacket[] packet = new DFSPacket[100];
     AtomicBoolean isDelay = new AtomicBoolean(true);