I'm experimenting a random problem on my PC. Sometimes a sql query
executed with Statement never returns. The code is blocked at a line
like this one:

rs = stmt.executeQuery("select true");

The query is not important: it fails with any type of query, at random,
even with the one above.

I never get an exception.

Now the logs. I've enable logging at the database level and I have set
"statement_timeout = 3000". I have searched for the query in
postgresql's log but I cannot find the query which is blocking in my
java code so I guess that it means that the query never reached postgresql.

I've enabled jdbc logging with "loglevel=2" and this is what I get:

simple execute,
handler=org.postgresql.jdbc2.AbstractJdbc2Statemen t$StatementResultHandler@996cca,
maxRows=0, fetchSize=0, flags=17
FE=> Parse(stmt=null,query="i've remove the select query",oids={})
FE=> Bind(stmt=null,portal=null)
FE=> Describe(portal=null)
FE=> Execute(portal=null,limit=0)
FE=> Sync

... and nothing else. No "<=BE ..." follow the " FE=> Sync" log entry.


I've also tried to put "stmt.setQueryTimeout(3);" but it doesn't seem to
do anything.

I'm using postgresql 8.1.4 on Windows 2000 Pro SP4 and the driver is
"8.1-407 JDBC 3". I'm also using java 1.5.0_06-b05.


I guess that there is a bug in the driver. If I'm wrong, please tell me
how to solve it. If I'm right, could you try to fix it?

__________________________________________________ _______________
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This sort of behavior often indicates some kind of unsafe concurrent
usage of the JDBC Connection. Is this running in a multi-threaded
environment? If so, are there measures in place to ensure that only one
thread uses the connection at a time?

It would also be useful if you could do a thread dump while it's hanging
and send a stack trace of the affected thread.

-- Mark

On Wed, 2006-08-09 at 10:21 +0000, James Im wrote:
> I'm experimenting a random problem on my PC. Sometimes a sql query
> executed with Statement never returns. The code is blocked at a line
> like this one:
>
> rs = stmt.executeQuery("select true");
>
> The query is not important: it fails with any type of query, at random,
> even with the one above.
>
> I never get an exception.
>
> Now the logs. I've enable logging at the database level and I have set
> "statement_timeout = 3000". I have searched for the query in
> postgresql's log but I cannot find the query which is blocking in my
> java code so I guess that it means that the query never reached postgresql.
>
> I've enabled jdbc logging with "loglevel=2" and this is what I get:
>
> simple execute,
> handler=org.postgresql.jdbc2.AbstractJdbc2Statemen t$StatementResultHandler@996cca,
> maxRows=0, fetchSize=0, flags=17
> FE=> Parse(stmt=null,query="i've remove the select query",oids={})
> FE=> Bind(stmt=null,portal=null)
> FE=> Describe(portal=null)
> FE=> Execute(portal=null,limit=0)
> FE=> Sync
>
> .. and nothing else. No "<=BE ..." follow the " FE=> Sync" log entry.
>
>
> I've also tried to put "stmt.setQueryTimeout(3);" but it doesn't seem to
> do anything.
>
> I'm using postgresql 8.1.4 on Windows 2000 Pro SP4 and the driver is
> "8.1-407 JDBC 3". I'm also using java 1.5.0_06-b05.
>
>
> I guess that there is a bug in the driver. If I'm wrong, please tell me
> how to solve it. If I'm right, could you try to fix it?
>
> __________________________________________________ _______________
> Log p MSN Messenger direkte p nettet: http://webmessenger.msn.com
>
>
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James,

We will need more information in order to help you here.

As Mark said, are you using this concurrently ?

Dave
On 9-Aug-06, at 6:21 AM, James Im wrote:

> I'm experimenting a random problem on my PC. Sometimes a sql query
> executed with Statement never returns. The code is blocked at a line
> like this one:
>
> rs = stmt.executeQuery("select true");
>
> The query is not important: it fails with any type of query, at
> random,
> even with the one above.
>
> I never get an exception.
>
> Now the logs. I've enable logging at the database level and I have set
> "statement_timeout = 3000". I have searched for the query in
> postgresql's log but I cannot find the query which is blocking in my
> java code so I guess that it means that the query never reached
> postgresql.
>
> I've enabled jdbc logging with "loglevel=2" and this is what I get:
>
> simple execute,
> handler=org.postgresql.jdbc2.AbstractJdbc2Statemen t
> $StatementResultHandler@996cca,
> maxRows=0, fetchSize=0, flags=17
> FE=> Parse(stmt=null,query="i've remove the select query",oids={})
> FE=> Bind(stmt=null,portal=null)
> FE=> Describe(portal=null)
> FE=> Execute(portal=null,limit=0)
> FE=> Sync
>
> .. and nothing else. No "<=BE ..." follow the " FE=> Sync" log entry.
>
>
> I've also tried to put "stmt.setQueryTimeout(3);" but it doesn't
> seem to
> do anything.
>
> I'm using postgresql 8.1.4 on Windows 2000 Pro SP4 and the driver is
> "8.1-407 JDBC 3". I'm also using java 1.5.0_06-b05.
>
>
> I guess that there is a bug in the driver. If I'm wrong, please
> tell me
> how to solve it. If I'm right, could you try to fix it?
>
> __________________________________________________ _______________
> Log på MSN Messenger direkte på nettet: http://webmessenger.msn.com
>
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 1: if posting/reading through Usenet, please send an appropriate
> subscribe-nomail command to majordomo@postgresql.org so that
> your
> message can get through to the mailing list cleanly
>


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James Im wrote:
> I'm experimenting a random problem on my PC. Sometimes a sql query
> executed with Statement never returns.

> simple execute,
> handler=org.postgresql.jdbc2.AbstractJdbc2Statemen t$StatementResultHandler@996cca,
>
> maxRows=0, fetchSize=0, flags=17
> FE=> Parse(stmt=null,query="i've remove the select query",oids={})
> FE=> Bind(stmt=null,portal=null)
> FE=> Describe(portal=null)
> FE=> Execute(portal=null,limit=0)
> FE=> Sync
>
> .. and nothing else. No "<=BE ..." follow the " FE=> Sync" log entry.

This seems normal enough. What is logged immediately before before this?

Can you capture the network traffic between the server and JDBC driver?
If it's a concurrency issue we should see something at the connection
level. I'm not familiar with what windows tools are available to take
network captures (in the unix world I'd use tcpdump/snoop/ethereal), but
if you manage to get something in a format that ethereal will read, send
me the raw capture off-list and I'll take a look.

> I've also tried to put "stmt.setQueryTimeout(3);" but it doesn't seem to
> do anything.

setQueryTimeout() is a no-op in the current driver.

-O

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