don't hold thread while waiting after failure from server (#4795)

java-util/src/main/java/io/druid/java/util/common/RetryUtils.java

@@ -81,7 +81,7 @@ public class RetryUtils
     return retry(f, shouldRetry, 0, maxTries);
   }
 
-  private static void awaitNextRetry(Throwable e, final int nTry, final boolean quiet) throws InterruptedException
+  private static void awaitNextRetry(final Throwable e, final int nTry, final boolean quiet) throws InterruptedException
   {
 
     final long sleepMillis = nextRetrySleepMillis(nTry);
@@ -95,7 +95,7 @@ public class RetryUtils
     Thread.sleep(sleepMillis);
   }
 
-  public static long nextRetrySleepMillis(final int nTry) throws InterruptedException
+  public static long nextRetrySleepMillis(final int nTry)
   {
     final long baseSleepMillis = 1000;
     final long maxSleepMillis = 60000;

server/src/main/java/io/druid/client/HttpServerInventoryView.java

@@ -31,7 +31,6 @@ import com.google.common.net.HostAndPort;
 import com.google.common.util.concurrent.FutureCallback;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
-import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.google.inject.Inject;
 import com.metamx.emitter.EmittingLogger;
 import com.metamx.http.client.HttpClient;
@@ -50,6 +49,7 @@ import io.druid.java.util.common.ISE;
 import io.druid.java.util.common.Pair;
 import io.druid.java.util.common.RetryUtils;
 import io.druid.java.util.common.StringUtils;
+import io.druid.java.util.common.concurrent.ScheduledExecutors;
 import io.druid.java.util.common.lifecycle.LifecycleStart;
 import io.druid.java.util.common.lifecycle.LifecycleStop;
 import io.druid.server.coordination.DataSegmentChangeRequest;
@@ -75,9 +75,8 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
 import java.util.concurrent.LinkedBlockingDeque;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -103,7 +102,7 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
   // For each queryable server, a name -> DruidServerHolder entry is kept
   private final ConcurrentHashMap<String, DruidServerHolder> servers = new ConcurrentHashMap<>();
 
-  private volatile ExecutorService executor;
+  private volatile ScheduledExecutorService executor;
 
   // the work queue, all items in this are sequentially processed by main thread setup in start()
   // used to call inventoryInitialized on all SegmentCallbacks and
@@ -145,9 +144,9 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
       log.info("Starting HttpServerInventoryView.");
 
       try {
-        executor = Executors.newFixedThreadPool(
+        executor = ScheduledExecutors.fixed(
             config.getNumThreads(),
-            new ThreadFactoryBuilder().setDaemon(true).setNameFormat("HttpServerInventoryView-%s").build()
+            "HttpServerInventoryView-%s"
         );
 
         executor.execute(
@@ -433,10 +432,23 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
     private volatile long unstableStartTime = -1;
     private volatile int consecutiveFailedAttemptCount = 0;
 
+    private final Runnable addToQueueRunnable;
+
     DruidServerHolder(DruidServer druidServer)
     {
       this.druidServer = druidServer;
       this.serverHostAndPort = HostAndPort.fromString(druidServer.getHost());
+
+      this.addToQueueRunnable = () -> {
+        queue.add(
+            () -> {
+              DruidServerHolder holder = servers.get(druidServer.getName());
+              if (holder != null) {
+                holder.updateSegmentsListAsync();
+              }
+            }
+        );
+      };
     }
 
     //wait for first fetch of segment listing from server.
@@ -571,10 +583,21 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
                   consecutiveFailedAttemptCount = 0;
                 }
                 catch (Exception ex) {
-                  log.error(ex, "error processing segment list response from server [%s]", druidServer.getName());
+                  String logMsg = StringUtils.nonStrictFormat(
+                      "Error processing segment list response from server [%s]. Reason [%s]",
+                      druidServer.getName(),
+                      ex.getMessage()
+                  );
+
+                  if (incrementFailedAttemptAndCheckUnstabilityTimeout()) {
+                    log.error(ex, logMsg);
+                  } else {
+                    log.info("Temporary Failure. %s", logMsg);
+                    log.debug(ex, logMsg);
+                  }
                 }
                 finally {
-                  addNextSyncToWorkQueue(druidServer.getName());
+                  addNextSyncToWorkQueue();
                 }
               }
 
@@ -603,17 +626,9 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
                       log.debug(logMsg);
                     }
                   }
-
-                  // sleep for a bit so that retry does not happen immediately.
-                  try {
-                    Thread.sleep(RetryUtils.nextRetrySleepMillis(consecutiveFailedAttemptCount));
-                  }
-                  catch (InterruptedException ex) {
-                    Thread.currentThread().interrupt();
-                  }
                 }
                 finally {
-                  addNextSyncToWorkQueue(druidServer.getName());
+                  addNextSyncToWorkQueue();
                 }
               }
             },
@@ -632,17 +647,9 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
             log.info("Temporary Failure. %s", logMsg);
             log.debug(th, logMsg);
           }
-
-          // sleep for a bit so that retry does not happen immediately.
-          try {
-            Thread.sleep(RetryUtils.nextRetrySleepMillis(consecutiveFailedAttemptCount));
-          }
-          catch (InterruptedException ex) {
-            Thread.currentThread().interrupt();
-          }
         }
         finally {
-          addNextSyncToWorkQueue(druidServer.getName());
+          addNextSyncToWorkQueue();
         }
       }
     }
@@ -696,16 +703,28 @@ public class HttpServerInventoryView implements ServerInventoryView, FilteredSer
       }
     }
 
-    private void addNextSyncToWorkQueue(final String serverId)
+    private void addNextSyncToWorkQueue()
     {
-      queue.add(
+      if (consecutiveFailedAttemptCount > 0) {
-          () -> {
+        try {
-            DruidServerHolder holder = servers.get(serverId);
+          long sleepMillis = RetryUtils.nextRetrySleepMillis(consecutiveFailedAttemptCount);
-            if (holder != null) {
+          log.info("Scheduling next syncup in [%d] millis from server [%s].", sleepMillis, druidServer.getName());
-              holder.updateSegmentsListAsync();
+          executor.schedule(
-            }
+              addToQueueRunnable,
-          }
+              sleepMillis,
-      );
+              TimeUnit.MILLISECONDS
+          );
+        }
+        catch (Exception ex) {
+          log.makeAlert(
+              ex,
+              "WTF! Couldn't schedule next sync. Server[%s] is not being synced any more, restarting Druid process on that server might fix the issue.",
+              druidServer.getName()
+          ).emit();
+        }
+      } else {
+        addToQueueRunnable.run();
+      }
     }
 
     private boolean incrementFailedAttemptAndCheckUnstabilityTimeout()