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Posted to bugs@httpd.apache.org by bu...@apache.org on 2009/05/11 10:50:31 UTC
DO NOT REPLY [Bug 47180] New: DBM ssl_scache setting can cause
extreme performance degradation
https://issues.apache.org/bugzilla/show_bug.cgi?id=47180
Summary: DBM ssl_scache setting can cause extreme performance
degradation
Product: Apache httpd-2
Version: 2.2.11
Platform: Sun
OS/Version: Solaris
Status: NEW
Severity: normal
Priority: P2
Component: mod_ssl
AssignedTo: bugs@httpd.apache.org
ReportedBy: mick.sheppard@cpp.co.uk
We are running Apache 2.2 on Solaris 10 with the following SSL cache settings:-
SSLSessionCache dbm:/usr/local/apache2/logs/ssl_scache
SSLSessionCacheTimeout 300
We have connections from clients using client certificates for authentication.
These connections are programs rather than interactive. As such each connection
exists for a single discrete request.
The session cache is checked each SSLSessionCacheTimeout seconds for expired
SSL session information. This is performed by all httpd processes
independently. This check consists of at least one sequential search of the DBM
file. During this all other SSL operations are blocked.
We have seen that under load the size of the DBM file grow to between 1 and 2
GB. As the file grows in size it takes longer to traverse it and the server
suffers intermittent performance issues. Once the time to traverse the file
exceeds the SSLSessionCacheTimeout the server responds to requests at the rate
of one per SSLSessionCacheTimeout.
It is possible to workaround this by disabling the session cache or changing to
use shared memory.
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