blocking vs non-blocking apr_bucket_read()

[Christina Fu <fu...@gmail.com>]

Hi,

I am writing a connection level input and output filter. I have 
confusions about whether to use APR_NONBLOCK_READ or APR_BLOCK_READ when 
calling apr_bucket_read() function. Could someone advise the guidelines 
of using blocking vs non-blocking bucket read?

I have seen situations when I use APR_NONBLOCK_READ to read a heap 
bucket, it returns status of APR_SUCCESS but length is zero. Is this 
case, what shall I do with this bucket? shall I read it again with 
blocking? or pass it and process the next bucket?

Thanks a lot for the help!

Christina

Re: blocking vs non-blocking apr_bucket_read()

[Nick Kew <ni...@webthing.com>]

On Sat, 12 Jan 2008 19:18:10 -0500
Christina Fu <fu...@gmail.com> wrote:

> Hi,
> 
> I am writing a connection level input and output filter. I have 
> confusions about whether to use APR_NONBLOCK_READ or APR_BLOCK_READ
> when calling apr_bucket_read() function. Could someone advise the
> guidelines of using blocking vs non-blocking bucket read?

There's nothing specific to Apache.  Blocking reads are easier to
work with, but preclude certain forms of optimisation.

> I have seen situations when I use APR_NONBLOCK_READ to read a heap 
> bucket, it returns status of APR_SUCCESS but length is zero.

Sounds unlikely, unless the bucket had length zero.  It should
only make a difference on streaming bucket types.

>    Is this 
> case, what shall I do with this bucket? shall I read it again with 
> blocking? or pass it and process the next bucket?

If you've nothing better to do, then yes.  A filter function can
also return to its caller if you don't want blocking.

-- 
Nick Kew

Application Development with Apache - the Apache Modules Book
http://www.apachetutor.org/