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Arrange the bybusyness logic and prevent bad busy values
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this closes #383


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1912245 13f79535-47bb-0310-9956-ffa450edef68
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@jfclere
jfclere committed Sep 11, 2023
1 parent a077812 commit 1b9292a
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Showing 4 changed files with 168 additions and 17 deletions.
13 changes: 10 additions & 3 deletions modules/proxy/balancers/mod_lbmethod_bybusyness.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
*/

#include "mod_proxy.h"
#include "proxy_util.h"
#include "scoreboard.h"
#include "ap_mpm.h"
#include "apr_version.h"
Expand All @@ -25,18 +26,24 @@ module AP_MODULE_DECLARE_DATA lbmethod_bybusyness_module;
static APR_OPTIONAL_FN_TYPE(proxy_balancer_get_best_worker)
*ap_proxy_balancer_get_best_worker_fn = NULL;


static int is_best_bybusyness(proxy_worker *current, proxy_worker *prev_best, void *baton)
{
int *total_factor = (int *)baton;
apr_size_t current_busy = getbusy_count(current);
apr_size_t prev_best_busy = 0;

current->s->lbstatus += current->s->lbfactor;
*total_factor += current->s->lbfactor;
if (prev_best)
prev_best_busy = getbusy_count(prev_best);


return (
!prev_best
|| (current->s->busy < prev_best->s->busy)
|| (current_busy < prev_best_busy)
|| (
(current->s->busy == prev_best->s->busy)
(current_busy == prev_best_busy)
&& (current->s->lbstatus > prev_best->s->lbstatus)
)
);
Expand Down Expand Up @@ -65,7 +72,7 @@ static apr_status_t reset(proxy_balancer *balancer, server_rec *s)
worker = (proxy_worker **)balancer->workers->elts;
for (i = 0; i < balancer->workers->nelts; i++, worker++) {
(*worker)->s->lbstatus = 0;
(*worker)->s->busy = 0;
setbusy_count(*worker, 0);
}
return APR_SUCCESS;
}
Expand Down
18 changes: 4 additions & 14 deletions modules/proxy/mod_proxy_balancer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
/* Load balancer module for Apache proxy */

#include "mod_proxy.h"
#include "proxy_util.h"
#include "scoreboard.h"
#include "ap_mpm.h"
#include "apr_version.h"
Expand Down Expand Up @@ -486,17 +487,6 @@ static void force_recovery(proxy_balancer *balancer, server_rec *s)
}
}

static apr_status_t decrement_busy_count(void *worker_)
{
proxy_worker *worker = worker_;

if (worker->s->busy) {
worker->s->busy--;
}

return APR_SUCCESS;
}

static int proxy_balancer_pre_request(proxy_worker **worker,
proxy_balancer **balancer,
request_rec *r,
Expand Down Expand Up @@ -635,7 +625,7 @@ static int proxy_balancer_pre_request(proxy_worker **worker,
*worker = runtime;
}

(*worker)->s->busy++;
increment_busy_count(*worker);
apr_pool_cleanup_register(r->pool, *worker, decrement_busy_count,
apr_pool_cleanup_null);

Expand Down Expand Up @@ -1575,7 +1565,7 @@ static void balancer_display_page(request_rec *r, proxy_server_conf *conf,
"</httpd:redirect>\n", NULL);
ap_rprintf(r,
" <httpd:busy>%" APR_SIZE_T_FMT "</httpd:busy>\n",
worker->s->busy);
getbusy_count(worker));
ap_rprintf(r, " <httpd:lbset>%d</httpd:lbset>\n",
worker->s->lbset);
/* End proxy_worker_stat */
Expand Down Expand Up @@ -1748,7 +1738,7 @@ static void balancer_display_page(request_rec *r, proxy_server_conf *conf,
ap_rvputs(r, ap_proxy_parse_wstatus(r->pool, worker), NULL);
ap_rputs("</td>", r);
ap_rprintf(r, "<td>%" APR_SIZE_T_FMT "</td>", worker->s->elected);
ap_rprintf(r, "<td>%" APR_SIZE_T_FMT "</td>", worker->s->busy);
ap_rprintf(r, "<td>%" APR_SIZE_T_FMT "</td>", getbusy_count(worker));
ap_rprintf(r, "<td>%d</td><td>", worker->s->lbstatus);
ap_rputs(apr_strfsize(worker->s->transferred, fbuf), r);
ap_rputs("</td><td>", r);
Expand Down
119 changes: 119 additions & 0 deletions modules/proxy/proxy_util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include "apr_version.h"
#include "apr_strings.h"
#include "apr_hash.h"
#include "apr_atomic.h"
#include "http_core.h"
#include "proxy_util.h"
#include "ajp.h"
Expand Down Expand Up @@ -4984,6 +4985,124 @@ PROXY_DECLARE(apr_status_t) ap_proxy_tunnel_create(proxy_tunnel_rec **ptunnel,
return APR_SUCCESS;
}

PROXY_DECLARE(apr_status_t) decrement_busy_count(void *worker_)
{
apr_size_t val;
proxy_worker *worker = worker_;

#if APR_SIZEOF_VOIDP == 4
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint32_t));
val = apr_atomic_read32(&worker->s->busy);
while (val > 0) {
apr_size_t old = val;
val = apr_atomic_cas32(&worker->s->busy, val - 1, old);
if (val == old) {
break;
}
}
#elif APR_VERSION_AT_LEAST(1,7,4) /* APR 64bit atomics not safe before 1.7.4 */
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint64_t));
val = apr_atomic_read64(&worker->s->busy);
while (val > 0) {
apr_size_t old = val;
val = apr_atomic_cas64(&worker->s->busy, val - 1, old);
if (val == old) {
break;
}
}
#else /* Use atomics for (64bit) pointers */
void *volatile *busy_p = (void *)&worker->s->busy;
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(void*));
AP_DEBUG_ASSERT((apr_uintptr_t)busy_p % sizeof(void*) == 0);
val = (apr_uintptr_t)apr_atomic_casptr((void *)busy_p, NULL, NULL);
while (val > 0) {
apr_size_t old = val;
val = (apr_uintptr_t)apr_atomic_casptr((void *)busy_p,
(void *)(apr_uintptr_t)(val - 1),
(void *)(apr_uintptr_t)old);
if (val == old) {
break;
}
}
#endif
return APR_SUCCESS;
}

PROXY_DECLARE(void) increment_busy_count(proxy_worker *worker)
{
apr_size_t val;
#if APR_SIZEOF_VOIDP == 4
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint32_t));
val = apr_atomic_read32(&worker->s->busy);
while (val < APR_INT32_MAX) {
apr_size_t old = val;
val = apr_atomic_cas32(&worker->s->busy, val + 1, old);
if (val == old) {
break;
}
}
#elif APR_VERSION_AT_LEAST(1,7,4) /* APR 64bit atomics not safe before 1.7.4 */
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint64_t));
val = apr_atomic_read64(&worker->s->busy);
while (val < APR_INT64_MAX) {
apr_size_t old = val;
val = apr_atomic_cas64(&worker->s->busy, val + 1, old);
if (val == old) {
break;
}
}
#else /* Use atomics for (64bit) pointers */
void *volatile *busy_p = (void *)&worker->s->busy;
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(void*));
AP_DEBUG_ASSERT((apr_uintptr_t)busy_p % sizeof(void*) == 0);
val = (apr_uintptr_t)apr_atomic_casptr((void *)busy_p, NULL, NULL);
while (val < APR_INT64_MAX) {
apr_size_t old = val;
val = (apr_uintptr_t)apr_atomic_casptr((void *)busy_p,
(void *)(apr_uintptr_t)(val + 1),
(void *)(apr_uintptr_t)old);
if (val == old) {
break;
}
}
#endif
}

PROXY_DECLARE(apr_size_t) getbusy_count(proxy_worker *worker)
{
apr_size_t val;
#if APR_SIZEOF_VOIDP == 4
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint32_t));
val = apr_atomic_read32(&worker->s->busy);
#elif APR_VERSION_AT_LEAST(1,7,4) /* APR 64bit atomics not safe before 1.7.4 */
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint64_t));
val = apr_atomic_read64(&worker->s->busy);
#else /* Use atomics for (64bit) pointers */
void *volatile *busy_p = (void *)&worker->s->busy;
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(void*));
AP_DEBUG_ASSERT((apr_uintptr_t)busy_p % sizeof(void*) == 0);
val = (apr_uintptr_t)apr_atomic_casptr((void *)busy_p, NULL, NULL);
#endif

return val;
}

PROXY_DECLARE(void) setbusy_count(proxy_worker *worker, apr_size_t to)
{
#if APR_SIZEOF_VOIDP == 4
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint32_t));
apr_atomic_set32(&worker->s->busy, to);
#elif APR_VERSION_AT_LEAST(1,7,4) /* APR 64bit atomics not safe before 1.7.4 */
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(apr_uint64_t));
apr_atomic_set64(&worker->s->busy, to);
#else /* Use atomics for (64bit) pointers */
void *volatile *busy_p = (void *)&worker->s->busy;
AP_DEBUG_ASSERT(sizeof(apr_size_t) == sizeof(void*));
AP_DEBUG_ASSERT((apr_uintptr_t)busy_p % sizeof(void*) == 0);
apr_atomic_xchgptr((void *)busy_p, (void *)(apr_uintptr_t)to);
#endif
}

static void add_pollset(apr_pollset_t *pollset, apr_pollfd_t *pfd,
apr_int16_t events)
{
Expand Down
35 changes: 35 additions & 0 deletions modules/proxy/proxy_util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,41 @@ extern PROXY_DECLARE_DATA const apr_strmatch_pattern *ap_proxy_strmatch_domain;
*/
void proxy_util_register_hooks(apr_pool_t *p);

/*
* Get the busy counter from the shared worker memory
*
* @param worker Pointer to the worker structure.
* @return apr_size_t value atomically read for the worker.
*/
PROXY_DECLARE(apr_size_t) getbusy_count(proxy_worker *worker);

/*
* Set the busy counter from the shared worker memory
*
* @param worker Pointer to the worker structure.
* @param to value to set the busy counter.
* @return void
*/
PROXY_DECLARE(void) setbusy_count(proxy_worker *worker, apr_size_t to);

/*
* decrement the busy counter from the shared worker memory
* note it is called by apr_pool_cleanup_register()
* therfore the void * and apr_status_t.
*
* @param worker_ Pointer to the worker structure.
* @return apr_status_t returns APR_SUCCESS.
*/
PROXY_DECLARE(apr_status_t) decrement_busy_count(void *worker_);

/*
* increment the busy counter from the shared worker memory
*
* @param worker Pointer to the worker structure.
* @return void
*/
PROXY_DECLARE(void) increment_busy_count(proxy_worker *worker);

/** @} */

#endif /* PROXY_UTIL_H_ */

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