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Re: NIO support

From: Vitalii Tymchyshyn <tivv00(at)gmail(dot)com>
To: Dave Cramer <pg(at)fastcrypt(dot)com>
Cc: PG-JDBC Mailing List <pgsql-jdbc(at)postgresql(dot)org>
Subject: Re: NIO support
Date: 2012-01-31 14:37:12
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-jdbc
I still call your code to send request to server with another 
connection, so it's same thing, simply without additional thread.

Talking about query timeout, the question is what benefit do we get this 
way instead of server-side timeout. It server connection is stable, 
server-side timeout is good. If it's not - the current schema won't work 
property. As for me, there should be two timeouts - first one is where 
we start trying to stop query (either current way or by simple asking 
server beforehand), second - when we return from query execute call, no 
matter if we could cancel query. Latter may lead to connection close.

31.01.12 16:29, Dave Cramer написав(ла):
> Vitalli,
> I've given this some thought. Without using a timer you are
> implementing the timeout by having the read timeout on the client end.
> This will leave the query running on the server. Is this what we want
> ? Using a timer to do this we actually cancel the query on the server.
> Dave Cramer
> dave.cramer(at)credativ(dot)ca
> 2012/1/22 Dave Cramer<pg(at)fastcrypt(dot)com>:
>> Vitalii,
>> My github repository is not current, so it is not a good place to branch from.
>> We require context patches to be submitted to the list
>> The ssl tests are documented in the current docs if you check them out
>> of the project.
>> Dave Cramer
>> dave.cramer(at)credativ(dot)ca
>> 2012/1/21 Віталій Тимчишин<tivv00(at)gmail(dot)com>:
>>> Hello.
>>> I've fixed 1.4.2 compiling problems (moved from PriorityQueue to TreeSet +
>>> removed some generics). Tests pass on 1.4.2.
>>> I've created a fork from your github repository as it's much easier to work
>>> with. New patch is
>>> here:
>>> Are there any hints/guides on running SSL tests?
>>> Best regards, Vitalii Tymchyshyn
>>> 20 січня 2012 р. 16:06 Dave Cramer<pg(at)fastcrypt(dot)com>  написав:
>>>> Vitalii,
>>>>   Does this compile and run on java 1.4 ?
>>>> Thanks for the note on the current bug.
>>>> Dave Cramer
>>>> dave.cramer(at)credativ(dot)ca
>>>> On Fri, Jan 20, 2012 at 8:54 AM, Vitalii Tymchyshyn<tivv00(at)gmail(dot)com>
>>>> wrote:
>>>>> Hello.
>>>>> This patch provides timeouts without additional threads.
>>>>> I am going to enhance it to additionally solve next problems (as for me
>>>>> this
>>>>> problem are easily solvable with NIO):
>>>>> 1) DeadLock when client and server send buffers fill up. This is rare
>>>>> case
>>>>> because it requires query to start generation output (e.g. notices)
>>>>> before
>>>>> all query data is sent to server. AFAIR this can be provoked by copying
>>>>> to
>>>>> table with trigger outputting notices.
>>>>> 2) When SSL is enabled, getNotifications does not return notifications
>>>>> until
>>>>> server is asked for anything.
>>>>> Also move to NIO may produce better performance, but this is still
>>>>> something
>>>>> to be checked. It may be needed to select carefully if Heap or Off-heap
>>>>> buffers should be used to get performance benefit.
>>>>> P.S. Unrelated to NIO, current setQueryTimeout code has bug since it
>>>>> treats
>>>>> timeout as being specified in milliseconds, while javadoc says it's in
>>>>> seconds.
>>>>> 20.01.12 14:05, Dave Cramer написав(ла):
>>>>>> Can you confirm that this patch is just to add time out ?
>>>>>> If not can you outline what problem you are trying to solve ?
>>>>>> Dave Cramer
>>>>>> dave.cramer(at)credativ(dot)ca
>>>>>> 2012/1/19 Віталій Тимчишин<tivv00(at)gmail(dot)com>:
>>>>>>> OK, I finally have first try of NIO support in the patch attached.
>>>>>>> The only current feature is query timeout without any additional
>>>>>>> threads.
>>>>>>> Please note that current driver has a bug: JDBC specs says timeout is
>>>>>>> in
>>>>>>> seconds and driver takes it as millis, fixed in my patch.
>>>>>>> Also current query timeout schema limitation is that query timeout
>>>>>>> processing still requires server round trips that are not under
>>>>>>> timeout
>>>>>>> control. I really don't see how much this differ from simply setting
>>>>>>> server-side timeout for fast connections. For slow connections it's
>>>>>>> still
>>>>>>> unreliable. Good thing that it is may be possible to enforce some kind
>>>>>>> of
>>>>>>> hard timeout with NIO schema as it's easy to control blocking calls.
>>>>>>> Limitations: only for V3 non-secure connections. Other connections use
>>>>>>> regular stream-based implementation.
>>>>>>> Planned features:
>>>>>>>   * SSL with NIO. This should allow to receive notifications without
>>>>>>> server
>>>>>>> roundtrip in SSL mode
>>>>>>>   * Read answer while sending query. This should make go away the
>>>>>>> problem
>>>>>>> when large query is blocked because answer must be read to send more
>>>>>>> data
>>>>>>> to
>>>>>>> server.
>>>>>>> Note that I have never worked with CVS and have problems to make patch
>>>>>>> with
>>>>>>> new files (AFAICS I can't add it to CVS with RO access).
>>>>>>> Comments are welcome.
>>>>>>> P.S. To work with SSL I need to start SSL tests. Any hints?
>>>>>>> --
>>>>>>> Best regards,
>>>>>>>   Vitalii Tymchyshyn
>>>>>>> --
>>>>>>> Sent via pgsql-jdbc mailing list (pgsql-jdbc(at)postgresql(dot)org)
>>>>>>> To make changes to your subscription:
>>> --
>>> Best regards,
>>>   Vitalii Tymchyshyn

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