Torsten Mielke created AMQ-4212:
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Summary: Broker may be unable to recover durable topic
subscription from the kahadb journal
Key: AMQ-4212
URL: https://issues.apache.org/jira/browse/AMQ-4212
Project: ActiveMQ
Issue Type: Bug
Components: Message Store
Affects Versions: 5.7.0
Environment: kahadb and durable topic subscribers
Reporter: Torsten Mielke
KahaDB is supposed to recover its index from the journal *completely*.
Such recovery can be enforced by stopping the broker, deleting the db.data
index file and restarting the broker.
The recovery process may however not be able to recover inactive durable topic
subscriptions.
This is because the kahadb cleanup task will not consider any active
subscription entries in the journal files when marking journal files for
deletion.
E.g. If a durable sub info was written to e.g. the journal file db-1.log but
kahadb has already rolled over to writing to db-2.log, the cleanup task may
delete db1.log (in case all msgs in db1.log got acked). The durable sub however
is still alive.
When stopping the broker this durable sub info is still present in the index
file and will be restored at broker restart.
If however the index file gets deleted in order to enforce a recovery of the
index from the journal, then the broker has lost the information about this
durable sub.
The broker is therefore not able to recover its state fully from the journal
files.
If the durable subscriber remains inactive (i.e. does not reconnect to broker
immediately after broker restart), it may miss messages as the broker has no
knowledge of this durable sub.
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