Hi Nick,
Is ap_hook_monitor available in httpd 2.2.15?
Thanks,
Alin
________________________________
From: Nick Kew <[email protected]>
To: [email protected]
Sent: Sat, April 17, 2010 12:10:46 PM
Subject: Fwd: Process lifetime and hooks to use
My reply seems to be lost in the ether ... try again.
Begin forwarded message:
> On 16 Apr 2010, at 20:51, Some Guy wrote:
>
>> Hi all,
>>
>> I would like to develop a module that periodically needs to fetch a file
>> from a remote site and update some data used by the child processes. Is it
>> safe to create this thread in the post config hook? I would like to do
>> something like:
>>
>> Global thread fetches a file, and loads content
>> Thread signals that it has new data
>> A separate thread in each of the child processes gets the signal and updates
>> the cache in the child process. The cache is only updated by this thread
>> and owned by the child process, so I lock it with a rwlock. The cache is
>> read by request handlers, so I don't want to use a global lock since the
>> documentation implied it could be a performance issue.
>>
>> Is this doable and which hooks / threading issues will I run into with this
>> approach? It would be nice for the threads in the child process to be able
>> to concurrently read the data from the global thread after the global thread
>> has signaled new data is ready. I did not see any type of global rw lock.
>
> It's doable, with some reservations (and re your last sentence,
> see apr_global_mutex). The hardest part will be to avoid leaking
> memory in the fetch.
>
> However, it might be over-complicated. Instead of your own thread
> in the parent process, why not use ap_hook_monitor? And the mtime
> of the fetched file should work nicely as the signal to the children.
>
> --
> Nick Kew
