I have an odd one here. I was unable to find it with a search of the maili=
ng lists. I've spent a few hours trying to create a simple test case, but =
so far these simple cases aren't showing the problem. I want to make sure =
this isn't a know problem before investing more time trying to come up with=
a test case suffiently complex to expose the problem.
=20
The problem is this: a single thread is submitting database updates throug=
h a middle tier which has a pool of connections. There are no guarantees o=
f which connection will be used for any request. Each request is commited =
as its own database transaction before the middle tier responds to the requ=
ester, which then immediately submits the next request. Nothing else it hi=
tting the database. We are getting serialization errors.
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If we add a 1 ms delay on the client side between requests to the middle ti=
er, the frequency of these errors drops by about two orders of magnitude. =
With a 100 ms delay, we haven't seen any.
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The pattern of activity which causes the problem involves a single database=
transaction with inserts and updates to many tables, including one with a =
potentially large blob, followed by an update to a numeric column in a row =
which tracks progress. The serialization errors are happening on this fina=
l update. My simple test cases use a single thread on two JDBC connection =
emulating just this final update, and the problem does not show up.
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We have the same behavior on 8.0.3 and the develpment snapshot from yesterd=
ay. (I haven't gotten a test run from today's beta release yet -- I need t=
o coordinate the test with someone else who's not here right now. I'll fol=
low up if the beta release changes this behavior.)
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The server is SuSE 9.3 with dual xeons and xfs on a SAN. The client and mi=
ddle tier for these tests have been on Windows XP. The requests are going =
through JDBC.
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Does this behavior sound familiar to anyone?
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-Kevin
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