Benoit Tellier created JAMES-3403:
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Summary: IMAP Fetch: UidMSNConverter :: get MSN is slow
Key: JAMES-3403
URL: https://issues.apache.org/jira/browse/JAMES-3403
Project: James Server
Issue Type: Bug
Components: IMAPServer
Affects Versions: master
Reporter: Benoit Tellier
Fix For: master, 3.6.0
# What?
Following openpaas-1.7.15-rc2 deployment, and the use of VAVR immutable
datastructures in UidMsnConverter, I notice some offending slow FETCH requests.
A closer look shows Cassandra is not to blame here
Flame graphs correlate the analysis
On our prod set up 40k messages are enough to trigger endless FETCHs.
# Why ?
Fetch is calling getMSN(uid) one by one.
Previous code was "getMSN optimized" as it uses an array as the underlying data
structure. O(1) upon reads * n messages.
The later code uses a red-black tree as an underlying data structure. I'm usure
about the complexity here (because I am not a VAVR expert) but it is at least
O(log n) * n messages.
# Short term reaction
Revert uneeded changes added in UidMsnConverter as part of work on JAMES-3177.
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