On 11/07/2008 05:33 PM, Joe Orton wrote:
> On Fri, Nov 07, 2008 at 01:29:15PM +0100, "Plüm, Rüdiger, VF-Group" wrote:
>>> Would it be possible to substitute the backend ("fake") conn_rec's
>>> ->bucket_alloc pointer with the "real" r->connection->bucket_alloc,
>>> for the duration of the request/response to the backend? Wouldn't
>>> that ensure that all the buckets in question exactly have the
>>> correct lifetime?
>> I though about this as well, but I suppose this is a risky road to take.
>> Keep in mind that mod_ssl and the core network filters below might use this
>> bucket allocator and that we keep this backend connection alive while the
>> front
>> end connection might have died. So we might still have buckets in this
>> backend connection pipe created by the previous request that are dead on the
>> new request. This may cause segfaults when we start using the backend
>> connection again.
>
> Fair enough. Transmuting the buckets into TRANSIENTs seems like a
> reasonable solution, in any case, it's sort of saying "lifetime issues,
> buyer beware" in bucket-speak which exactly matches the problem in hand.
>
> In ap_proxy_buckets_lifetime_transform() is there any reason to restrict
> to:
>
> + if (APR_BUCKET_IS_HEAP(e) || APR_BUCKET_IS_TRANSIENT(e)
> + || APR_BUCKET_IS_IMMORTAL(e) || APR_BUCKET_IS_POOL(e)) {
> + apr_bucket_read(e, &data, &bytes, APR_BLOCK_READ);
>
> instead of simply:
>
> if (!APR_BUCKET_IS_METADATA(e)) {
> // ...likewise transmute to a TRANSIENT
>
> ? You already know that the brigade size is constrained, right, so
> there is no worry about memory consumption from morphing buckets, and
> the technique should should work equally well for any data bucket?
This is a valid and good point I have not though about before :-).
Especially that the length of the brigade is limited. And it seems better
in this case to possibly do a sub optimal conversion of a data bucket
(like an MMAP bucket or especially a file bucket) than to not convert it at
all. So I adjusted this part of the code. Thanks for reviewing.
Regards
Rüdiger
