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openmama 6.2 crash with dqstrategy disabled for subscription with multiple initials [I]

Igor Kovalenko
 

Classification: For internal use only

Thank you Aaron, I will give your suggestion a try.

 

To reproduce the issue you will need a transport returning multiple initial snapshots for your group subscription. Without that conditional I was referring to and with DQ strategy disabled crash will happen handling second snapshot from the group.

 

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Kind regards,
Igor Kovalenko
____________________________________________________



Igor Kovalenko

OOO "Deutsche Bank TechCentre"
Global Technology
Business Center Aquamarine, Ozerkovskaya naberezhnaya 24, 115184 Moscow, Russia
Tel. +7 495 783-0313
Email igor.kovalenko@...

 

From: Aaron Sneddon [mailto:asneddon@...]
Sent: 18 декабря 2018 г. 17:06
To: Igor Kovalenko <igor.kovalenko@...>; Frank Quinn <fquinn@...>; openmama-dev@...
Cc: Gary Molloy <gmolloy@...>; Philip McCausland <pmccausland@...>
Subject: FW: [Openmama-dev] openmama 6.2 crash with dqstrategy disabled for subscription with multiple initials

 

Hey Igor,

I find I am unable to reproduce your issue. I am using group subscriptions (to a feed handler) and have disabled dq.

I tried the various config options to reproduce the issue (as there are transport specific and global config options for disabling dq strategy). With regards to the missing conditional:  I can see that around the line of the change we have taken out the following conditional which I assume you are referring to:

 

I would just point out that this conditional statement hasn’t been removed, but was relocated to mamaPlugin_fireSubscriptionPreMsgHook.

Certainly, the return statement activated by that conditional now returns you to this function, from mamaPlugin_fireSubscriptionPreMsgHook. With previous functionality, this conditional would ensure you skip the code that you say causes the problem you are seeing, and that makes sense.

 

I cannot recommend duplicating the conditional statement, as this would be unnecessary and as I cannot reproduce your issue I can only make a suggestion that hopefully you could try?

 

At present mamaPlugin_fireSubscriptionPreMsgHook returns MAMA_STATUS_OK in all cases. My suggestion is, in dqstrategyplugin.c, at line 478, change MAMA_STATUS_OK to MAMA_STATUS_INVALID_ARG (for example).

Then, in listenermsgcallback.c, on line 380, add in a check to the return type, and if you do not receive MAMA_STATUS_OK, return from this function. This would look like:
    if (MAMA_STATUS_OK != mamaPlugin_fireSubscriptionPreMsgHook(subscription, msgType, msg))

    {

        return;

    }

 

This would now emulate the previous functionality (but does not duplicate the conditional).

 

I have done this myself and performed a quick check that it does not break anything and it looks fine. But as I say, I cannot replicate your issue and so cannot do a full check. I would therefore say that if it suits, you could change that single line in dqstrategyplugin.c and add the check in listenermsgcallback, and run a test to see if this fixes your issue.

 

I am still concerned as to why I cannot reproduce the same issue, but please let me know what you think.

 

Regards,

Aaron

 

From: Frank Quinn [mailto:fquinn@...]
Sent: 11 December 2018 17:16
Cc: igor.kovalenko@...; Aaron Sneddon <asneddon@...>; openmama-dev <openmama-dev@...>
Subject: Re: [Openmama-dev] openmama 6.2 crash with dqstrategy disabled for subscription with multiple initials

 

Aaron / Vela, could someone have a look please?

 

On 12 Nov 2018 19:36, Frank Quinn <frank@...> wrote:

Thanks Igor,

 

This was part of Vela's DQ strategy changes - Aaron could you have a look please?

 

Cheers,

Frank

 

On Mon, Nov 12, 2018 at 1:32 PM Igor Kovalenko <igor.kovalenko@...> wrote:

Classification: Public

Hi openmama team,

 

I see that commit 6de60350f40b4d9b0f181b7e64e0d192798b9f97 accidentally removed one conditional expression from around current line 393 of listenermsgcallbacks.c

 

Now if group subscription, or in fact any allowing multiple initials, receives first initial, then

- with dqstrategy disabled listenerMsgCallback_processMsg will unconditionally call mamaSubscription_stopWaitForResponse

- with dqstrategy enabled dqstrategy plugin implementation would only call mamaSubscription_stopWaitForResponse if mamaSubscription_getAcceptMultipleInitials() returns false

 

The code that stops waiting for response destroys related inbox object. This leads to easy crash with group subscriptions and dqstrategy disabled.

 

Hope it will be not hard to restore the conditional for openmama-6.2.x and later.

 

Thank you!

 

Kind regards,

Igor Kovalenko

 

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