Okay, I've found a pretty nasty bug in the PostGIS driver.
My dataset is a table with about 250 rows in it. Each row has the VMAP0
dataset polygon of a country in. Each row is large.
If you look closely at the JDBC datastore, you'll notice that it will
fetch 200 rows at a time - which means its pretty much loading in the
entire dataset for each query - thats about 250mb.
This doesnt fit into the memory allocated to geoserver (especially if
you're doing multiple requests at the same time), so an OutOfMemory
error gets thrown and the reader is closed. So far, so good.
Closing the reader will release the result set and the statement - this
frees up about 60mb of memory. It then tries to close the DB
connection. This fails - most likely because it was in the middle of
reading a tuple when it was rudely interupted by running out of memory.
It actually runs out of memory in PGStream.ReceiveTupleV3(), called from
QueryExecutorImpl.processResults().
Later, the connection is closed and the
PooledConnectionImpl$ConnectionHandler.invoke() is called, which
(because we're not AutoCommit) attempt to rollback the transaction with
a con.rollback(). This is where the problem occurs.
Inside QueryExecutorImpl.processResults(), it gets a "\" from the server
(highly likely from the bytea returned in the original query). It, of
course, doesnt understand this and throws an "An I/O error occured while
sending to the backend." error.
The end result is that the connection doesnt appear to be closed and
released back to the connectionpool. This means that connections to the
database are being leaked, and probably a fair amount of memory. This,
of course, causes the OutOfMemory error to happen more often.
I'm probably going to have to talk to the postgresql JDBC people, but I
thought I would ask here first incase people know something about. Are
we doing anything "funny" with the connection pooling - I noticed there
was a "funny" proxy object there?
dave
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