merlimat opened a new pull request #7715:
URL: https://github.com/apache/pulsar/pull/7715
### Motivation
When forcifully deleting a topic that has active readers, there is a race
condition that lead to a failure in deleting the topic.
The race is
1. Connected readers are closed and removed
2. Since there's no active consumer on a non-durable subscription (eg: the
reader sub), then we trigger the removal of the subscription and its cursor.
That happens in background, in order to avoid deadlocking. See
https://github.com/apache/pulsar/blob/26c49a85dd89d4282a625f02d16959de595d282f/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentSubscription.java#L274
3. Once all consumers are closed, we then proceed in deleting the
managed-ledger
4. To delete the managed-ledger, we get the current list of cursors and
delete all of them in parallel
5. Since the cursors are removed in background, the list that we got might
contain cursors that don't exist anymore when we try to delete them.
```
org.apache.bookkeeper.mledger.ManagedLedgerException: ManagedCursor not
found: reader-7d300cd535
at
org.apache.pulsar.broker.service.persistent.PersistentTopic$4.deleteLedgerFailed(PersistentTopic.java:884)
~[org.apache.pulsar-pulsar-broker-2.6.0.jar:2.6.0]
at
org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl$16.deleteCursorFailed(ManagedLedgerImpl.java:2177)
~[org.apache.pulsar-managed-ledger-2.6.0.jar:2.6.0]
at
org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.asyncDeleteCursor(ManagedLedgerImpl.java:766)
~[org.apache.pulsar-managed-ledger-2.6.0.jar:2.6.0]
at
org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.asyncDelete(ManagedLedgerImpl.java:2156)
~[org.apache.pulsar-managed-ledger-2.6.0.jar:2.6.0]
at
org.apache.pulsar.broker.service.persistent.PersistentTopic.lambda$null$19(PersistentTopic.java:859)
~[org.apache.pulsar-pulsar-broker-2.6.0.jar:2.6.0]
at
java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:859)
~[?:?]
at
java.util.concurrent.CompletableFuture.uniWhenCompleteStage(CompletableFuture.java:883)
~[?:?]
at
java.util.concurrent.CompletableFuture.whenComplete(CompletableFuture.java:2251)
~[?:?]
at
org.apache.pulsar.broker.service.persistent.PersistentTopic.lambda$delete$20(PersistentTopic.java:853)
~[org.apache.pulsar-pulsar-broker-2.6.0.jar:2.6.0]
at
java.util.concurrent.CompletableFuture.uniAcceptNow(CompletableFuture.java:753)
~[?:?]
at
java.util.concurrent.CompletableFuture.uniAcceptStage(CompletableFuture.java:731)
~[?:?]
at
java.util.concurrent.CompletableFuture.thenAccept(CompletableFuture.java:2108)
~[?:?]
at
org.apache.pulsar.broker.service.persistent.PersistentTopic.delete(PersistentTopic.java:843)
~[org.apache.pulsar-pulsar-broker-2.6.0.jar:2.6.0]
at
org.apache.pulsar.broker.service.persistent.PersistentTopic.deleteForcefully(PersistentTopic.java:791)
~[org.apache.pulsar-pulsar-broker-2.6.0.jar:2.6.0]
at
org.apache.pulsar.broker.service.BrokerService.deleteTopic(BrokerService.java:719)
~[org.apache.pulsar-pulsar-broker-2.6.0.jar:2.6.0]
Caused by: org.apache.bookkeeper.mledger.ManagedLedgerException:
ManagedCursor not found: reader-7d300cd535
```
On topic deletion, we should be more tolerant of disappearing cursors and
instead proceed as a success case.
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