jsancio commented on code in PR #19658:
URL: https://github.com/apache/kafka/pull/19658#discussion_r2082461965
##########
raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java:
##########
@@ -1048,14 +1053,18 @@ private void maybeHandleElectionLoss(NomineeState
state, long currentTimeMs) {
}
}
- private int binaryExponentialElectionBackoffMs(int retries) {
+ // visible for testing
+ static int binaryExponentialElectionBackoffMs(int backoffMaxMs, int
retries, Random random) {
if (retries <= 0) {
throw new IllegalArgumentException("Retries " + retries + " should
be larger than zero");
}
- // upper limit exponential co-efficients at 20 to avoid overflow
+ // Takes minimum of the following:
+ // 1. exponential backoff calculation (maxes out at 102.4 seconds)
+ // 2. configurable electionBackoffMaxMs + jitter
+ // The jitter is added to prevent deadlock of elections.
Review Comment:
I don't think deadlock is the correct term. The actors/replicas are not dead
or blocked. I think that livelock is a more accurate description of the issue.
The replicas are changing (i.e. holding election) but they are changing in a
way that they can't make process(i.e. elect a leader).
##########
raft/src/test/java/org/apache/kafka/raft/KafkaRaftClientTest.java:
##########
@@ -4569,6 +4574,55 @@ public void testObserverFetchWithNoLocalId(boolean
withKip853Rpc) throws Excepti
assertEquals(3, context.log.lastFetchedEpoch());
}
+ @Test
+ public void testExponentialElectionBackoffMs() {
Review Comment:
Did you consider having 3 parametrized tests? On each test invocation you
can create a new mocked `Random`. This should allow you to remove
`clearInvocations` and be sure that your mock objects are behaving correctly.
##########
raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java:
##########
@@ -1048,14 +1053,18 @@ private void maybeHandleElectionLoss(NomineeState
state, long currentTimeMs) {
}
}
- private int binaryExponentialElectionBackoffMs(int retries) {
+ // visible for testing
+ static int binaryExponentialElectionBackoffMs(int backoffMaxMs, int
retries, Random random) {
Review Comment:
How about moving this static method to `RaftUtil` and make it public? If you
do this you can also move the test to `RaftUtilTest`.
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