Exception in MongoDB perl driver used under Mojolicious hypnotoad

[Cathe]

Hello,

The problem is exactly as it is described here: http://stackoverflow.com/questions/18140561/exceptions-in-mongodb-cursor-pm-line-161
Versions of MongoDB, MongoDB Perl driver are the most recent.

I suspect that something is wrong in the way how I connect to the mongodb: I do it from MyApp.pm before the startup { … } and it looks like connection is dropped sometimes (but not always) when hypnotoad restarts the workers, so they are forgetting about the connection.

I would be very grateful for your advice.

— Catherine.

[Abhijit Menon-Sen]

At 2014-07-02 04:02:44 -0700, jes...@gmail.com wrote:
>
> The problem is exactly as it is described here:
> http://stackoverflow.com/questions/18140561/exceptions-in-mongodb-cursor-pm-line-161

Could you please include the question in your post, instead of just the
URL? (It's more convenient for some readers, and makes the archive more
useful to boot.)

Thanks.

-- ams

[Per Carlson]

Hi.

Have you read the guidelines in the wiki
(https://github.com/kraih/mojo/wiki/Using-mongodb)?

[Cathe]

I'm sorry, this is the text (with correction for versions I use):

Using MongoDB 2.4.6 with version 0.704.1.0 of the Perl MongoDB driver, I frequently run into exceptions like these:

recv timed out (30000 ms) at ...MongoDB/Cursor.pm line 161.
couldn't get response to throw out at ...MongoDB/Cursor.pm line 161.
missed the response we wanted, please try again at ...MongoDB/Cursor.pm line 161
invalid header received at ...MongoDB/Cursor.pm line 161.
can't get db response, not connected at ...MongoDB/Cursor.pm line 161.

The exceptions are intermittent, and often vanish on the next request (this is a web app). Occasionally, the exceptions will persist over several consecutive requests.

[Cathe]

Hi,

Thanks a lot! I couldn't find this guidance. I guess this is exactly what I need.

[Cathe]

Hello again

I did everything as it as advised by the link above.
Didn't help actually.
May be this related to «Notes on Pooling for MongoDB Drivers» ( http://docs.mongodb.org/meta-driver/latest/legacy/notes-on-pooling-for-mongodb-drivers/ )
but I cannot get how to implement this with Mojolicious.

Sorry, but Perl driver for MongoDB is really erroneous and this happens already for years…

[sri]

Sorry, but Perl driver for MongoDB is really erroneous and this happens already for years…

You might have more luck trying the official MongoDB support channels, this does not seem like a Mojolicious problem.

--

sebastian 

[Cathe]

Hi Sebastian…

The thing is that apparently this issue happens after worker of hypnotoad is restarted, i.e. the corresponding processes (say I have only 1 worker) looks like that:
qapp   27672  0.0  0.9 243268 36004 ?        Ss   11:15   0:00 /net/qapp/live/app/script/sym
qapp   27688  0.4  1.1 251260 44256 ?        S    11:23   0:01 /net/qapp/live/app/script/sym

— 27688 was restarted at 11:23

and everything is fine when worker is running together with parent process:
qapp   27703  0.0  1.6 287576 63124 ?        Ss   11:29   0:00 /net/qapp/live/app/script/sym
qapp   27704  0.0  1.5 287708 62724 ?        S    11:29   0:00 /net/qapp/live/app/script/sym

I do not know why the worker has to be restarted and I have no control on this…

[Cathe]

oops…
doesn't depend no workers restart really…
yes, apparently something wrong withenv setting on server and/or MongoDB

[sri]

I do not know why the worker has to be restarted and I have no control on this…

This is factually incorrect, you have total control over the restart process.

    http://mojolicio.us/perldoc/Mojo/Server/Hypnotoad#SETTINGS

It is enabled by default because in our experience, most non-trivial Perl applications leak memory, if they are not carefully reviewed and profiled.

--

sebastian