Gary Tully created AMQ-7082:
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Summary: KahaDB index, recover free pages in parallel with start
Key: AMQ-7082
URL: https://issues.apache.org/jira/browse/AMQ-7082
Project: ActiveMQ
Issue Type: Bug
Components: KahaDB
Affects Versions: 5.15.0
Reporter: Gary Tully
Assignee: Gary Tully
Fix For: 5.16.0
AMQ-6590 fixes free page loss through recovery. The recover process can be
timely, which prevents fast failover, doing recovery on shutdown is preferable,
but it is still not ideal b/c it will hold onto the kahadb lock. It also can
stall shutdown unexpectedly.
AMQ-7080 is going to tackle checkpointing the free list. This should help avoid
the need for recovery but it may still be necessary. If the perf hit is
significant this may need to be optional.
There will still be the need to walk the index to find the free list.
It is possible to run with no free list and grow, and we can do that while we
recover the free list in parallel, then merge the two at a safe point. This we
can do at startup.
In cases where the disk is the bottleneck this won't help much, but it will
help failover and it will help shutdown, with a bit of luck the recovery will
complete before we stop.
Initially I thought this would be too complex, but if we concede some growth
while we recover, ie: start with an empty free list, it is should be straight
forward to merge with a recovered one.
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