FreeTDS Development Group

[Craig Jackson <cejackson51 AT gmail.com>]

How long does it stop? By default, a TCP connection can take as 10 minutes
to time out.

Are you specifying timeouts on your freetds calls?

Craig

On Thu, Oct 26, 2017 at 4:40 AM, LacaK <lacak AT zoznam.sk> wrote:

>
> Thank you very much Frediano,
>>>
>>> now , when I increase number of rows in table I can reproduce network
>>> failure.
>>>
>>> But behavior is other than I have expected.
>>>
>>> I was expecting, that dbnextrow() will return FAIL, but it seems, that
>>> call
>>> to dbnextrow() never returns ... it freezes somewhere in dblib.dll
>>> (I can not debug more because I use dblib.dll from Pascal program)
>>>
>>> Is it expected behavior?
>>>
>>> L.
>>>
>>> No, should return an error.
>> TDSDUMP could help.
>>
> I have recompiled dblib from todays git master to ensure that problem
> persist.
> And yes persists.
> When rows are reading in loop and I unplug network cable loop stops.
> When I plug-in cable in few seconds loop continues and rows are returned.
> But when I unplug for longer time say 1 minute loop does not continue and
> program freezes.
>
> Then I must force end of program. Here are last lines in tdsdump (nothing
> special IMO):
> Whole dump has 265MB (as I transfer big rows with TEXT fields)
>
> 10:29:32.620 (dblib.c:2064):dbnextrow(032F9D10)
> 10:29:32.620 (dblib.c:2070):dbnextrow() dbresults_state = 2
> (_DB_RES_RESULTSET_ROWS)
> 10:29:32.620 (token.c:532):tds_process_tokens(032F14A8, 015BFDE0,
> 00000000, 0x1508)
> 10:29:32.620 (util.c:165):Changed query state from PENDING to READING
> 10:29:32.620 (token.c:547):processing result tokens.  marker is d2(NBC_ROW)
> 10:29:32.620 (token.c:1969):tds_process_nbcrow(): reading column 0
> 10:29:32.620 (data.c:740):tds_get_data: type 56, varint size 0
> 10:29:32.620 (data.c:784):tds_get_data(): wire column size is 4
> 10:29:32.620 (token.c:1969):tds_process_nbcrow(): reading column 1
> 10:29:32.620 (data.c:740):tds_get_data: type 56, varint size 0
> 10:29:32.620 (data.c:784):tds_get_data(): wire column size is 4
> 10:29:32.620 (token.c:1969):tds_process_nbcrow(): reading column 2
> 10:29:32.620 (data.c:740):tds_get_data: type 39, varint size 2
> 10:29:32.620 (data.c:784):tds_get_data(): wire column size is 4
> 10:29:32.620 (token.c:1969):tds_process_nbcrow(): reading column 3
> 10:29:32.620 (token.c:1969):tds_process_nbcrow(): reading column 4
> 10:29:32.620 (data.c:740):tds_get_data: type 35, varint size 4
> 10:29:32.620 (data.c:784):tds_get_data(): wire column size is 5000
> 10:29:32.620 (packet.c:640):Received packet
> ...follows binary dump of packet
>
> Thank you
> L.
>
> Hi *,
>>>>>
>>>>> I would like to ask how FreeTDS performs buffering on client side.
>>>>> I use dblib as my client library (I do not set there DBBUFFER using
>>>>> "dbsetopt")
>>>>>
>>>>> I am trying simulate network failure in such way:
>>>>> 1. connect to MS SQL Server using dbopen()
>>>>> 2. I send SQL select using dbcmd(), dbsqlexec()
>>>>> 3. then I call dbresults()
>>>>> 4. here I pause program and unplug network cable to simulate network
>>>>> error
>>>>> 5. next I process rows in loop calling dbnextrow()
>>>>>
>>>>> Strange thing is that I can perform step 5 also when network cable is
>>>>> unpluged. So I have suspection, that all rows from select are already
>>>>> somewhere on client side. Probably handled already by underlaying
>>>>> libtds
>>>>> ?
>>>>>
>>>>> What is going to happen? Why I can still read rows when there is
>>>>> already
>>>>> broken network connection ?
>>>>> Thanks
>>>>>
>>>>> -Laco.
>>>>>
>>>>> There are a lot of caching in between.
>>>> The server execute the query and starts sending back results.
>>>> Probably the results you are expecting are already sent by the server
>>>> when you disconnect the cable and are in the tcp socket buffer ready
>>>> to be parsed from your program. Try to return 1000000 rows and at
>>>> some point the program will fail (unless connection is really fast and
>>>> network buffer is big enough!).
>>>>
>>>> Frediano
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