Re: [opendds-main] Possible memory leak in v 2.3-RT14855-1

[Adam M. <mi...@oc...>]

Hi Leeland,

On 11/8/2011 11:13 AM, Leeland Artra wrote:
>
> Hello Adam,
>
> Your comment on the history keeping might indeed be the issue. I found 
> another section of code that had this additional comment:
>
>   //We don't want to lose any messages so setting the history to keep 
> all and set limits to unlimited
>
>   dr_qos.history.kind = DDS::KEEP_ALL_HISTORY_QOS;
>
> Which seems wrong to me. What we really want is for all messages to be 
> assured of being passed on to the subscribers. What would you 
> recommend I set these parameters to?
>
>

I don't think there's one right answer to the HISTORY QoS settings.  The 
snippet of code you've shown is "dr_qos", so I assume that's for the 
DataReader.  KEEP_ALL_HISTORY_QOS should be OK here unless you notice a 
lot of memory use.  Your application code will most likely be calling 
some form of take() on the Data Reader so it doesn't need to hold on to 
the data forever.

Setting HISTORY on the Data Writer can be more difficult.  KEEP_ALL can 
lead to large memory use (not leak) in the Data Writer, but too small a 
number can lead to samples being replaced before they're sent.  I think 
this large memory use may be an implementation artifact so let us know 
if you're interested in developing or funding a fix for that.

> As far as the id_ I am still trying to figure out where that is set, 
> how it is tracked, etc.

None of the HISTORY settings will make much sense for your application 
until you determine how you'd like to divide the data samples into 
instances.  Is there only one instance (no key fields), or one instance 
per data sample (one key field with a different value for each sample), 
or something in between?

Thanks,
Adam Mitz
Senior Software Engineer
Object Computing, Inc.