kpatelatwork commented on a change in pull request #10822:
URL: https://github.com/apache/kafka/pull/10822#discussion_r655749684



##########
File path: 
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java
##########
@@ -1063,6 +1076,132 @@ public int generation() {
         return generation;
     }
 
+    @Override
+    public void restartConnectorAndTasks(
+            RestartRequest request,
+            Callback<ConnectorStateInfo> callback
+    ) {
+        final String connectorName = request.connectorName();
+        addRequest(
+                () -> {
+                    if (checkRebalanceNeeded(callback)) {
+                        return null;
+                    }
+                    if 
(!configState.connectors().contains(request.connectorName())) {
+                        callback.onCompletion(new NotFoundException("Unknown 
connector: " + connectorName), null);
+                        return null;
+                    }
+                    if (isLeader()) {
+                        // Write a restart request to the config backing 
store, to be executed asynchronously in tick()
+                        configBackingStore.putRestartRequest(request);
+                        // Compute and send the response that this was accepted
+                        Optional<RestartPlan> maybePlan = 
buildRestartPlanFor(request);
+                        if (!maybePlan.isPresent()) {
+                            callback.onCompletion(new 
NotFoundException("Status for connector " + connectorName + " not found", 
null), null);
+                        } else {
+                            RestartPlan plan = maybePlan.get();
+                            callback.onCompletion(null, 
plan.restartConnectorStateInfo());
+                        }
+                    } else {
+                        callback.onCompletion(new NotLeaderException("Only the 
leader can process restart requests.", leaderUrl()), null);
+                    }
+
+                    return null;
+                },
+                forwardErrorCallback(callback)
+        );
+    }
+
+    /**
+     * Process all pending restart requests. There can be at most one request 
per connector.
+     *
+     * <p>This method is called from within the {@link #tick()} method.
+     */
+    void processRestartRequests() {
+        List<RestartRequest> restartRequests;
+        synchronized (this) {
+            if (pendingRestartRequests.isEmpty()) {
+                return;
+            }
+            //dequeue into a local list to minimize the work being done within 
the synchronized block
+            restartRequests = new ArrayList<>(pendingRestartRequests.values());
+            pendingRestartRequests.clear();
+        }
+        for (RestartRequest restartRequest : restartRequests) {
+            try {
+                doRestartConnectorAndTasks(restartRequest);
+            } catch (Exception e) {
+                log.warn("Unexpected error while trying to process " + 
restartRequest + ", the restart request will be skipped.", e);
+            }
+        }
+    }
+
+    /**
+     * Builds and and executes a restart plan for the connector and its tasks 
from <code>request</code>.
+     * Execution of a plan involves triggering the stop of eligible 
connector/tasks and then queuing the start for eligible connector/tasks.
+     *
+     * @param request the request to restart connector and tasks
+     */
+    protected synchronized void doRestartConnectorAndTasks(RestartRequest 
request) {
+        final String connectorName = request.connectorName();
+        Optional<RestartPlan> maybePlan = buildRestartPlanFor(request);
+        if (!maybePlan.isPresent()) {
+            log.debug("Skipping restart of connector '{}' since no status is 
available: {}", connectorName, request);
+            return;
+        }
+        RestartPlan plan = maybePlan.get();
+        log.info("Executing {}", plan);
+
+        // If requested, stop the connector and any tasks, marking each as 
restarting
+        final ExtendedAssignment currentAssignments = assignment;
+        final Collection<ConnectorTaskId> assignedIdsToRestart = 
plan.taskIdsToRestart()
+                                                                     .stream()
+                                                                     
.filter(taskId -> currentAssignments.tasks().contains(taskId))
+                                                                     
.collect(Collectors.toList());
+        final boolean restartConnector = plan.restartConnector() && 
currentAssignments.connectors().contains(connectorName);
+        final boolean restartTasks = !assignedIdsToRestart.isEmpty();
+        if (restartConnector) {
+            worker.stopAndAwaitConnector(connectorName);
+            recordRestarting(connectorName);
+        }
+        if (restartTasks) {
+            // Stop the tasks and mark as restarting
+            worker.stopAndAwaitTasks(assignedIdsToRestart);
+            assignedIdsToRestart.forEach(this::recordRestarting);
+        }
+
+        // Now restart the connector and tasks
+        if (restartConnector) {
+            try {
+                startConnector(connectorName, (error, targetState) -> {
+                    if (error == null) {
+                        log.info("Connector '{}' restart successful", 
connectorName);
+                    } else {
+                        log.error("Connector '{}' restart failed", 
connectorName, error);
+                    }
+                });
+            } catch (Throwable t) {
+                log.error("Connector '{}' restart failed", connectorName, t);
+            }

Review comment:
       @rhauch  I kinda agree with you but I had seen this code and it had 
try/catch around both startTask and startConnector .  I added try/catch around 
startTask so if one tasks fails we can see if others atleasst succeed. The 
try/catch around startConnector was because I saw the pattern.  But I am torn 
on this, if you think we should remove the try/catch on connector, I am open to 
removing the try/catch given its already caught at the higher layer, but IMHO 
we can keep the startTask try/catch. Wdyt?
   
   
https://github.com/apache/kafka/blob/1bd99c809b6546cd6711cc4f2d40785393ca584a/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java#L1437
   
https://github.com/apache/kafka/blob/1bd99c809b6546cd6711cc4f2d40785393ca584a/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java#L1490




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