chia7712 commented on code in PR #16753:
URL: https://github.com/apache/kafka/pull/16753#discussion_r1703058596
##########
clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java:
##########
@@ -1196,16 +1196,31 @@ private long maybeDrainPendingCalls(long now) {
long pollTimeout = Long.MAX_VALUE;
log.trace("Trying to choose nodes for {} at {}", pendingCalls,
now);
- Iterator<Call> pendingIter = pendingCalls.iterator();
- while (pendingIter.hasNext()) {
- Call call = pendingIter.next();
+ List<Call> toRemove = new ArrayList<>();
+ // Using for-loop instead of iterator to avoid
ConcurrentModificationException with following sequence:
+ // 1. In maybeDrainPendingCalls, pendingCalls.iterator() create a
iterator.
+ // 2. In maybeDrainPendingCall, call.nodeProvider.provide() throws
UnsupportedVersionException error.
+ // 3. In call.fail, runnable.pendingCalls.add modify the
pendingCalls list.
+ // Using pendingCalls.size() to get the list size before the
for-loop to avoid infinite loop.
+ // If call.fail keeps adding the call to pendingCalls,
+ // the loop like for (int i = 0; i < pendingCalls.size(); i++)
can't stop.
+ int pendingSize = pendingCalls.size();
+ for (int i = 0; i < pendingSize; i++) {
+ Call call = pendingCalls.get(i);
// If the call is being retried, await the proper backoff
before finding the node
if (now < call.nextAllowedTryMs) {
pollTimeout = Math.min(pollTimeout, call.nextAllowedTryMs
- now);
- } else if (maybeDrainPendingCall(call, now)) {
- pendingIter.remove();
+ continue;
+ }
+ if (maybeDrainPendingCall(call, now)) {
Review Comment:
If we change it from `else if` to `if`, it will drain the pending call even
though the call is not being retried. why we need this change?
##########
clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java:
##########
@@ -1196,16 +1196,31 @@ private long maybeDrainPendingCalls(long now) {
long pollTimeout = Long.MAX_VALUE;
log.trace("Trying to choose nodes for {} at {}", pendingCalls,
now);
- Iterator<Call> pendingIter = pendingCalls.iterator();
- while (pendingIter.hasNext()) {
- Call call = pendingIter.next();
+ List<Call> toRemove = new ArrayList<>();
+ // Using for-loop instead of iterator to avoid
ConcurrentModificationException with following sequence:
+ // 1. In maybeDrainPendingCalls, pendingCalls.iterator() create a
iterator.
Review Comment:
Maybe we can simply say "pendingCalls could be modified in this loop, hence
...."?
##########
clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java:
##########
@@ -1196,16 +1196,31 @@ private long maybeDrainPendingCalls(long now) {
long pollTimeout = Long.MAX_VALUE;
log.trace("Trying to choose nodes for {} at {}", pendingCalls,
now);
- Iterator<Call> pendingIter = pendingCalls.iterator();
- while (pendingIter.hasNext()) {
- Call call = pendingIter.next();
+ List<Call> toRemove = new ArrayList<>();
+ // Using for-loop instead of iterator to avoid
ConcurrentModificationException with following sequence:
+ // 1. In maybeDrainPendingCalls, pendingCalls.iterator() create a
iterator.
+ // 2. In maybeDrainPendingCall, call.nodeProvider.provide() throws
UnsupportedVersionException error.
+ // 3. In call.fail, runnable.pendingCalls.add modify the
pendingCalls list.
+ // Using pendingCalls.size() to get the list size before the
for-loop to avoid infinite loop.
+ // If call.fail keeps adding the call to pendingCalls,
+ // the loop like for (int i = 0; i < pendingCalls.size(); i++)
can't stop.
Review Comment:
It seems to me the loop can stop but we don't want to verify the re-enqueue
call right now, right?
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