On 02/02/2008 07:08 PM, Nick Kew wrote:
> On Sat, 02 Feb 2008 16:35:40 -0000
> [EMAIL PROTECTED] wrote:
>
>
>> +static int is_idempotent(request_rec *r)
>> +{
>> + /*
>> + * If the request has arguments it might not be idempotent as it
>> might have
>> + * side-effects.
>> + */
>> + if (r->args) {
>> + return 0;
>> + }
>
> That breaks RFC compliance, as soon as someone uses it to test
> idempotence.
Thats the question: On one side you are correct that the RFC clearly states
in 9.1.2 that GET / HEAD is idempotent. OTOH in 13.9 the RFC says that GET /
HEAD
requests with arguments can have significant side effects and therefore
responses
to these queries should be only cached if the response contains an expiration
time.
I may chose a bad name with is_idempotent as the purpose is to determine if we
can retry this request again once it has been sent to a backend (partially) and
the real main argument for retrying or not retrying seems to me if the already
sent request can cause side-effects that prohibit to sent it again.
Non idempotent methods are said to have these, so we cannot sent them again.
>
>> + /*
>> + * RFC2616 (9.1.2): GET, HEAD, PUT, DELETE, OPTIONS, TRACE are
>> considered
>> + * idempotent. Hint: HEAD requests use M_GET as method number as
>> well.
>> + */
>> + switch (r->method_number) {
>> + case M_GET:
>> + case M_DELETE:
>> + case M_PUT:
>> + case M_OPTIONS:
>> + case M_TRACE:
>> + return 1;
>> + /* Everything else is not considered idempotent. */
>> + default:
>> + return 0;
>> + }
>> +}
>
> Suggested solution: an enum, with a third value for an idempotent
> method with arguments. The caller then determines how to use it.
So you think of something like this (ok, no enum, but similar):
#define METHOD_NON_IDEMPOTENT 0
#define METHOD_IDEMPOTENT 1
#define METHOD_IDEMPOTENT_WITH_ARGS 2
static int is_idempotent(request_rec *r)
{
/*
* RFC2616 (9.1.2): GET, HEAD, PUT, DELETE, OPTIONS, TRACE are considered
* idempotent. Hint: HEAD requests use M_GET as method number as well.
*/
switch (r->method_number) {
case M_GET:
case M_DELETE:
case M_PUT:
case M_OPTIONS:
case M_TRACE:
/*
* If the request has arguments it might have side-effects and thus
* it might be undesirable to resent it to a backend again·
* automatically.
*/
if (r->args) {
return METHOD_IDEMPOTENT_WITH_ARGS;
}
return METHOD_IDEMPOTENT;
/* Everything else is not considered idempotent. */
default:
return METHOD_NON_IDEMPOTENT;
}
}
>
> That's in response to your post to [EMAIL PROTECTED] OTTOMH it seems to me
> to work as a core function. How many existing handlers apply
> an equivalent test?
>
I know of none currently, but I assume that at least in mod_proxy(_http) the
need for this test will rise, once we try to finally solve the race problem in
mod_proxy_http when it sends a request over a connection that is closed just
at this moment.
Regards
Rüdiger
