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Hi,
We have a setup including two real servers each of which runs an
instance of MySql with the max_connections option set to 1000. In this
setup we have run some performance tests with mysqlslap two determine
the throughput of the setup. These tests involve simulating many
simultaneous users querying the database. Under these conditions we have
encountered some problems with the load balancer. Specifically, using
ipvsadm -L -n to monitor the connections during the performance test
there are intitially many connections represented as inactive. After a
few seconds the inactive connections are represented as active in the
respective real server. This causes a problem when the Least-Connection
Scheduling algorithm is used because the connections are not equally
between the two real hosts. The two real hosts are almost equal in terms
of processing capacities.
In the following the output of ipvsadm -L -n is shown which probably
explains the problem better.
ipvsadm -L -n a few seconds in the test simulating 200 MySql clients
connecting simultaneously.
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.0.1.5:3306 lc
-> 10.0.1.2:3306 Route 1 71 0
-> 10.0.1.4:3306 Route 1 70 60
ipvsadm -L -n after 30 seconds in the test simulating 200 MySql clients
connecting simultaneously. Note that the load balancer uses the
Least-Connection scheduling algorithm.
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.0.1.5:3306 lc
-> 10.0.1.2:3306 Route 1 71 0
-> 10.0.1.4:3306 Route 1 130 0
The problem does not occur if the connections are made sequentially and
if the number of total connections is below about 100.
Is there anything we can do to avoid these problems?
Best regards
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