blocking vs non-blocking apr_bucket_read()

[Christina Fu]

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