Re: Read Waiters growing

[Quanah Gibson-Mount]

--On Friday, February 26, 2010 9:46 AM +0100 Peter Mogensen a...@mutex.dk 
wrote:



Hi,

I see a strange thing in cn=Monitor. Suggestions needed.

I have a huge database, and performance is great as long as olcReadOnly
is TRUE.
But a soon as I enable writes, the number of Read Waiters are growing,
even though there's no or very few Write waiters.

# Read, Waiters, Monitor
dn: cn=Read,cn=Waiters,cn=Monitor
monitorCounter: 311

# Write, Waiters, Monitor
dn: cn=Write,cn=Waiters,cn=Monitor
monitorCounter: 0

# Current, Connections, Monitor
dn: cn=Current,cn=Connections,cn=Monitor
monitorCounter: 210

I have idletime=120 and connections do around 30 reads each before they
are retired, but not many writes. Like this:

# Connection 5389, Connections, Monitor
dn: cn=Connection 5389,cn=Connections,cn=Monitor
monitorConnectionNumber: 5389
monitorConnectionOpsReceived: 32
monitorConnectionOpsExecuting: 0
monitorConnectionOpsPending: 0
monitorConnectionOpsCompleted: 32
monitorConnectionGet: 32
monitorConnectionRead: 32
monitorConnectionWrite: 0

It's slapd 2.4.21, BDB 4.8.26 and back_bdb.

Any hint to what could cause that many read-waiters, but only while
writing is enabled and even though there's not that many writes?


It could be a bug in back-monitor...

--Quanah

--

Quanah Gibson-Mount
Principal Software Engineer
Zimbra, Inc

Zimbra ::  the leader in open source messaging and collaboration

Re: Read Waiters growing

[Peter Mogensen]

Quanah Gibson-Mount wrote:

It could be a bug in back-monitor...


I assume that delete operations are writes.

If so, you may be right.

I've just tried doing an ldapdelete -r on a subtree with several 
thousands entries and just before it finished the connection monitor 
entry was this:


# Connection 34616, Connections, Monitor
dn: cn=Connection 34616,cn=Connections,cn=Monitor
monitorConnectionNumber: 34616
monitorConnectionOpsReceived: 7983
monitorConnectionOpsExecuting: 1
monitorConnectionOpsPending: 0
monitorConnectionOpsCompleted: 7982
monitorConnectionGet: 7983
monitorConnectionRead: 7983
monitorConnectionWrite: 0



I'm sure this is the correct connection.

Every entry delete seems counted as a read.

Also - it took very long time to delete these entries. Over an hour.

(there's around 10 million entries in the database)

/Peter