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core: follow up to r1891148: WC bucket defaulting to FLUSH bucket.

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Define WC bucket semantics as:
/**
 * @brief Write Completion (WC) bucket
 *
 * A WC bucket is a FLUSH bucket with special ->data == &ap_bucket_wc_data,
 * still both AP_BUCKET_IS_WC() and APR_BUCKET_IS_FLUSH() hold for them so
 * they have the same semantics for most filters, namely:
 *   Everything produced before shall be passed to the next filter, including
 *   the WC/FLUSH bucket itself.
 * The distinction between WC and FLUSH buckets is only for filters that care
 * about write completion (calling ap_filter_reinstate_brigade() with non-NULL
 * flush_upto), those can setaside WC buckets and the preceding data provided
 * they have first determined that the next filter(s) have pending data
 * already, usually by calling ap_filter_should_yield(f->next).
 */

The only filters that care about write completion for now are
ap_core_output_filter() and ssl_io_filter_output(), which try to fill
in the pipe as much as possible, using ap_filter_reinstate_brigade(&flush_upto)
to determine whether they should flush (blocking) or setaside their remaining
data.

So ap_filter_reinstate_brigade() is made to not treat WC as FLUSH buckets and
keep the above filters working as before (and correctly w.r.t. above WC bucket
semantics).

* include/ap_mmn.h, include/util_filter.h:
  Axe specific ap_bucket_type_wc and define global &ap_bucket_wc_data address to
  mark WC buckets checked by AP_BUCKET_IS_WC().

* server/util_filter.c (ap_filter_reinstate_brigade):
  Don't treat WC buckets as FLUSH buckets.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1892468 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Yann Ylavic
2021-08-20 09:36:19 +00:00
parent 8f8793bcc6
commit 324ae13e8e
4 changed files with 41 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/ap_mmn.h
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@ -673,7 +673,7 @@
* ap_proxy_tunnel_conn_get_transferred() change
* ap_proxy_transfer_between_connections() sent to apr_off_t *.
* 20210531.0 (2.5.1-dev) add conn_rec->outgoing and ap_ssl_bind_outgoing()
* 20210531.1 (2.5.1-dev) Add ap_bucket_type_wc, ap_bucket_wc_make() and
* 20210531.1 (2.5.1-dev) Add ap_bucket_wc_data, ap_bucket_wc_make() and
* ap_bucket_wc_create() to util_filter.h
* 20210531.2 (2.5.1-dev) Add ap_proxy_get_worker_ex() and
* ap_proxy_define_worker_ex() to mod_proxy.h

22
include/util_filter.h
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@ -763,15 +763,31 @@ AP_DECLARE(void) ap_filter_protocol(ap_filter_t* f, unsigned int proto_flags);
/** Filter is incompatible with "Cache-Control: no-transform" */
#define AP_FILTER_PROTO_TRANSFORM 0x20
/** Write Completion (WC) bucket */
AP_DECLARE_DATA extern const apr_bucket_type_t ap_bucket_type_wc;
/**
* @brief Write Completion (WC) bucket
*
* A WC bucket is a FLUSH bucket with special ->data == &ap_bucket_wc_data,
* still both AP_BUCKET_IS_WC() and APR_BUCKET_IS_FLUSH() hold for them so
* they have the same semantics for most filters, namely:
* Everything produced before shall be passed to the next filter, including
* the WC/FLUSH bucket itself.
* The distinction between WC and FLUSH buckets is only for filters that care
* about write completion (calling ap_filter_reinstate_brigade() with non-NULL
* flush_upto), those can setaside WC buckets and the preceding data provided
* they have first determined that the next filter(s) have pending data
* already, usually by calling ap_filter_should_yield(f->next).
*/
/** Write Completion (WC) bucket data mark */
AP_DECLARE_DATA extern const char ap_bucket_wc_data;
/**
* Determine if a bucket is a Write Completion (WC) bucket
* @param e The bucket to inspect
* @return true or false
*/
#define AP_BUCKET_IS_WC(e) ((e)->type == &ap_bucket_type_wc)
#define AP_BUCKET_IS_WC(e) (APR_BUCKET_IS_FLUSH(e) && \
(e)->data == (void *)&ap_bucket_wc_data)
/**
* Make the bucket passed in a Write Completion (WC) bucket

1
modules/proxy/proxy_util.c
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@ -4551,6 +4551,7 @@ PROXY_DECLARE(apr_status_t) ap_proxy_transfer_between_connections(
APR_BRIGADE_INSERT_TAIL(bb_o, b);
}
else {
/* Prevent setaside/coalescing by intermediate filters. */
b = ap_bucket_wc_create(bb_o->bucket_alloc);
APR_BRIGADE_INSERT_TAIL(bb_o, b);
}

45
server/util_filter.c
View File

@ -976,7 +976,9 @@ AP_DECLARE(apr_status_t) ap_filter_setaside_brigade(ap_filter_t *f,
e = next) {
next = APR_BUCKET_NEXT(e);
/* Strip WC buckets added by ap_filter_output_pending(). */
/* WC buckets will be added back by ap_filter_output_pending()
* at the tail.
*/
if (AP_BUCKET_IS_WC(e)) {
apr_bucket_delete(e);
continue;
@ -1069,6 +1071,7 @@ AP_DECLARE(apr_status_t) ap_filter_reinstate_brigade(ap_filter_t *f,
int eor_buckets_in_brigade, opaque_buckets_in_brigade;
struct ap_filter_private *fp = f->priv;
core_server_config *conf;
int is_flush;
ap_log_cerror(APLOG_MARK, APLOG_TRACE6, 0, f->c,
"reinstate %s brigade to %s brigade in '%s' %sput filter",
@ -1132,7 +1135,15 @@ AP_DECLARE(apr_status_t) ap_filter_reinstate_brigade(ap_filter_t *f,
bucket = next) {
next = APR_BUCKET_NEXT(bucket);
if (AP_BUCKET_IS_EOR(bucket)) {
/* When called with flush_upto != NULL, we assume that the caller does
* the right thing to potentially setaside WC buckets (per semantics),
* so we don't treat them as FLUSH(_upto) here.
*/
is_flush = (APR_BUCKET_IS_FLUSH(bucket) && !AP_BUCKET_IS_WC(bucket));
if (is_flush) {
/* handled below */
}
else if (AP_BUCKET_IS_EOR(bucket)) {
eor_buckets_in_brigade++;
}
else if (bucket->length == (apr_size_t)-1) {
@ -1145,14 +1156,14 @@ AP_DECLARE(apr_status_t) ap_filter_reinstate_brigade(ap_filter_t *f,
}
}
if (APR_BUCKET_IS_FLUSH(bucket)
if (is_flush
|| (memory_bytes_in_brigade > conf->flush_max_threshold)
|| (conf->flush_max_pipelined >= 0
&& eor_buckets_in_brigade > conf->flush_max_pipelined)) {
/* this segment of the brigade MUST be sent before returning. */
if (APLOGctrace6(f->c)) {
char *reason = APR_BUCKET_IS_FLUSH(bucket) ?
char *reason = is_flush ?
"FLUSH bucket" :
(memory_bytes_in_brigade > conf->flush_max_threshold) ?
"max threshold" : "max requests in pipeline";
@ -1400,22 +1411,15 @@ AP_DECLARE(void) ap_filter_protocol(ap_filter_t *f, unsigned int flags)
f->frec->proto_flags = flags ;
}
/* Write Completion (WC) bucket implementation */
static apr_status_t wc_bucket_read(apr_bucket *b, const char **str,
apr_size_t *len, apr_read_type_e block)
{
*str = NULL;
*len = 0;
return APR_SUCCESS;
}
AP_DECLARE_DATA const char ap_bucket_wc_data;
AP_DECLARE(apr_bucket *) ap_bucket_wc_make(apr_bucket *b)
{
b->length = 0;
b->start = 0;
b->data = NULL;
b->type = &ap_bucket_type_wc;
/* FLUSH bucket with special ->data mark (instead of NULL) */
b = apr_bucket_flush_make(b);
b->data = (void *)&ap_bucket_wc_data;
return b;
}
@ -1428,12 +1432,3 @@ AP_DECLARE(apr_bucket *) ap_bucket_wc_create(apr_bucket_alloc_t *list)
b->list = list;
return ap_bucket_wc_make(b);
}
AP_DECLARE_DATA const apr_bucket_type_t ap_bucket_type_wc = {
"WC", 5, APR_BUCKET_METADATA,
apr_bucket_destroy_noop,
wc_bucket_read,
apr_bucket_setaside_noop,
apr_bucket_split_notimpl,
apr_bucket_simple_copy
};