Re: [Zope3-Users] recovering from a lost db connection
On Thu, Jan 11, 2007 at 09:55:28PM -0500, Roy Mathew wrote:
Brian Sutherland writes:
On Wed, Jan 10, 2007 at 08:13:27PM -0500, Roy Mathew wrote:
What is the recommended way to recover from a db connection that is
held by a Psycopgda adapter instance? If for some reason postgres
goes down, I get the following error:
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py,
line 83, in _runWithConnection
val = meth(conn, *args)
File
/usr/lib/python2.4/site-packages/SQLObject-0.8dev_r1814-py2.4.egg/sqlobject/dbconnection.p
, line 351, in _queryOne
self._executeRetry(conn, c, s)
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py,
line 77, in _executeRetry
raise DatabaseException(str(exc.args))
DatabaseException: ('no connection to the server\n',).
I then have no recourse but to restart the zope server. In the Java
world one would put a try/catch around the the SQL operation and
attempt a reconnect, but I am wondering if there is a better way
(read: automatic recovery) in a z3 world.
The way ZPsycopgDA does it is exactly that. But it can be a little
complex when you look at the detail.
In the Z3 case, I would:
* If the error is a concurrent update error, raise a Retry
exception. The same request gets tried again.
* If the error is an OperationalError, close the connection and
re-raise the error (perhaps as a Retry error, though I can think
of cases where this is a bad idea). On the next request, the
connection is re-opened.
Brian, Thanks for your response.
I am confused - that means that if this is being done *currently* in
Psycopgda, I should simply be able to repeat my client request and
succeed in the operation. Or is ZPsycopgda something other than plain
old psycopgda?
ZPsycopgDA is the zope 2 Product:) didn't realise it would be confused
with the zope 3 version psycopgda. Since I don't do much Zope3/RDB work
anymore, I havn't had a good look inside psycopgda.
I am essentially stuck once I get this error. The stacktrace above
shows that a retry was attempted but did not succeed. Sorry that I am
missing your point, but I don't get it!
Yeah, but that's a retry within the sqlobject/sqlos layer, which
probably is just confusing cruft.
It's because sqlobject is designed to directly manage connections, but
has been shoehorned into using zope.rdb for connections which also manages
connections. Things get a little complex after that.
* On other errors, let the error propagate.
All this stuff should probably be done at the zope.rdb level.
--
Thanks,
Roy Mathew.
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--
Brian Sutherland
Metropolis - it's the first movie with a robot. And she's a woman.
And she's EVIL!!
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Re: [Zope3-Users] recovering from a lost db connection
On Wed, Jan 10, 2007 at 08:13:27PM -0500, Roy Mathew wrote:
What is the recommended way to recover from a db connection that is
held by a Psycopgda adapter instance? If for some reason postgres
goes down, I get the following error:
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py,
line 83, in _runWithConnection
val = meth(conn, *args)
File
/usr/lib/python2.4/site-packages/SQLObject-0.8dev_r1814-py2.4.egg/sqlobject/dbconnection.p
, line 351, in _queryOne
self._executeRetry(conn, c, s)
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py,
line 77, in _executeRetry
raise DatabaseException(str(exc.args))
DatabaseException: ('no connection to the server\n',).
I then have no recourse but to restart the zope server. In the Java
world one would put a try/catch around the the SQL operation and
attempt a reconnect, but I am wondering if there is a better way
(read: automatic recovery) in a z3 world.
The way ZPsycopgDA does it is exactly that. But it can be a little
complex when you look at the detail.
In the Z3 case, I would:
* If the error is a concurrent update error, raise a Retry
exception. The same request gets tried again.
* If the error is an OperationalError, close the connection and
re-raise the error (perhaps as a Retry error, though I can think
of cases where this is a bad idea). On the next request, the
connection is re-opened.
* On other errors, let the error propagate.
All this stuff should probably be done at the zope.rdb level.
--
Thanks,
Roy Mathew.
___
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Zope3-users@zope.org
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--
Brian Sutherland
Metropolis - it's the first movie with a robot. And she's a woman.
And she's EVIL!!
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Re: [Zope3-Users] recovering from a lost db connection
Brian Sutherland writes:
On Wed, Jan 10, 2007 at 08:13:27PM -0500, Roy Mathew wrote:
What is the recommended way to recover from a db connection that is
held by a Psycopgda adapter instance? If for some reason postgres
goes down, I get the following error:
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py,
line 83, in _runWithConnection
val = meth(conn, *args)
File
/usr/lib/python2.4/site-packages/SQLObject-0.8dev_r1814-py2.4.egg/sqlobject/dbconnection.p
, line 351, in _queryOne
self._executeRetry(conn, c, s)
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py,
line 77, in _executeRetry
raise DatabaseException(str(exc.args))
DatabaseException: ('no connection to the server\n',).
I then have no recourse but to restart the zope server. In the Java
world one would put a try/catch around the the SQL operation and
attempt a reconnect, but I am wondering if there is a better way
(read: automatic recovery) in a z3 world.
The way ZPsycopgDA does it is exactly that. But it can be a little
complex when you look at the detail.
In the Z3 case, I would:
* If the error is a concurrent update error, raise a Retry
exception. The same request gets tried again.
* If the error is an OperationalError, close the connection and
re-raise the error (perhaps as a Retry error, though I can think
of cases where this is a bad idea). On the next request, the
connection is re-opened.
Brian, Thanks for your response.
I am confused - that means that if this is being done *currently* in
Psycopgda, I should simply be able to repeat my client request and
succeed in the operation. Or is ZPsycopgda something other than plain
old psycopgda?
I am essentially stuck once I get this error. The stacktrace above
shows that a retry was attempted but did not succeed. Sorry that I am
missing your point, but I don't get it!
* On other errors, let the error propagate.
All this stuff should probably be done at the zope.rdb level.
--
Thanks,
Roy Mathew.
___
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[Zope3-Users] recovering from a lost db connection
What is the recommended way to recover from a db connection that is
held by a Psycopgda adapter instance? If for some reason postgres
goes down, I get the following error:
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py, line
83, in _runWithConnection
val = meth(conn, *args)
File
/usr/lib/python2.4/site-packages/SQLObject-0.8dev_r1814-py2.4.egg/sqlobject/dbconnection.p
, line 351, in _queryOne
self._executeRetry(conn, c, s)
File
/var/lib/zope3/instances/instance.barry2007/lib/python/sqlos/adapter.py, line
77, in _executeRetry
raise DatabaseException(str(exc.args))
DatabaseException: ('no connection to the server\n',).
I then have no recourse but to restart the zope server. In the Java
world one would put a try/catch around the the SQL operation and
attempt a reconnect, but I am wondering if there is a better way
(read: automatic recovery) in a z3 world.
--
Thanks,
Roy Mathew.
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