Raidb1 load balancer and WaitForCompletionPolicy=first doesnot work
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Key: SEQUOIA-955
URL: https://forge.continuent.org/jira/browse/SEQUOIA-955
Project: Sequoia
Type: Bug
Components: Core
Versions: Sequoia 2.10.8
Environment: Windows XP
Reporter: xavier roques
Priority: Critical
If have a VirtualDatabase with two backends db1 and db2, the load balancer is
the Raiddb1 and the waitForCompletionPolicy is First.
DB1 and DB2 are up. My application makes a lot of updates and after some time
one of the Database is disabled.
I don't undertstand why, because the database is up.
After some searches I find out that database was disabled because of a timeout
while trying to get a new connection.
My pool of connection 50 was full ? But I released all my connections ...
So now, I will explain why it does not work.
There is a load balancer with two backends: Db1 and DB2. Each backend has its
own queue and the queue of each backend is managed by different a thread.
A lot of updates are sent to the virtualdatabase.
The load balancer dispatches the requests on each backend. Now let's us suppose
that the two following requests arrive.
Request 1 (update)
Request 2 (commit)
The load balancer sends the request 1 on each backend and wait for the first
completion.
If the thread managing the DB1 executes the request 1 and send the result to
the load balancer. It is possible that the load balancer dispatch the request 2
even if the Request 1 has not been started on the DB2.
The code of the loadBalancer RAIDDB1.commit is:
{code}
for (int i = 0; i < nbOfThreads; i++)
{
DatabaseBackend backend = (DatabaseBackend) enabledBackends.get(i);
if (backend.isStartedTransaction(lTid))
commitList.add(backend);
}
{code}
Unfortunately when this code is executed the backend DB2 may not have started
to execute the request 1 so the commit will only be pushed on the backend 1.
So when the request 1 will be executed on DB2, a new connection will be open
and it will never be released because the commit will never be executed on the
backend DB2.
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