httpd-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Yann Ylavic <ylavic....@gmail.com>
Subject Re: svn commit: r1696960 - in /httpd/httpd/trunk: CHANGES docs/log-message-tags/next-number modules/proxy/mod_proxy_balancer.c
Date Tue, 25 Aug 2015 13:15:21 GMT
Well, if one adds a new balancer before restarting, at post_config
time conf->balancers->nelts is +1 wrt the previous load...

On Tue, Aug 25, 2015 at 2:46 PM, Jim Jagielski <jim@jagunet.com> wrote:
> But the number of balancers does not change yet... And when it
> is implemented the overall size of the storage slot should *never*
> change. It must be constant, ala the scoreboard.
>
>> On Aug 25, 2015, at 8:39 AM, Yann Ylavic <ylavic.dev@gmail.com> wrote:
>>
>> At every startup, in balancer_post_config:
>>    conf->max_balancers = conf->balancers->nelts + conf->bgrowth;
>>
>> which means that if you add a balancer and restart, storage->create()
>> (eg. slotmem_create) will try to find an existing slot with this ID
>> and the exact ALIGNED_PROXY_BALANCER_SHARED_SIZE * conf->max_balancers
>> size, and fail:
>>    if (apr_shm_size_get(shm) != size) {
>>        apr_shm_detach(shm);
>>        ap_log_error(APLOG_MARK, APLOG_ERR, 0, ap_server_conf, APLOGNO(02599)
>>                     "existing shared memory for %s could not be used
>> (failed size check)",
>>                     fname);
>>        return APR_EINVAL;
>>    }
>>
>> By using storage->attach() first (which is based on the ID only and
>> returns the existing item_size and item_num), we can do the check
>> ourselves and fail only if conf->max_balancers > item_num, allowing
>> for balancers to be added thanks to growth margin used at startup.
>>
>> On Tue, Aug 25, 2015 at 2:12 PM, Jim Jagielski <jim@jagunet.com> wrote:
>>> How and when do ALIGNED_PROXY_BALANCER_SHARED_SIZE and conf->max_balancers
>>> change???
>>>
>>>> On Aug 21, 2015, at 8:34 AM, ylavic@apache.org wrote:
>>>>
>>>> Author: ylavic
>>>> Date: Fri Aug 21 12:34:02 2015
>>>> New Revision: 1696960
>>>>
>>>> URL: http://svn.apache.org/r1696960
>>>> Log:
>>>> mod_proxy_balancer: Fix balancers and balancer members reuse on
>>>> restart when new ones are added.  PR 58024.
>>>>
>>>> Since slotmem_create() issues a strict check on the size of an existing
>>>> slot before reusing it, it won't reuse existing balancers and members when
>>>> new ones are added during restart (whereas growth margins would allow it).
>>>> Fix this by using slotmem_attach() first and if it succeeds do the checks
>>>> based on the returned previous number of existing entries.
>>>>
>>>> Modified:
>>>>   httpd/httpd/trunk/CHANGES
>>>>   httpd/httpd/trunk/docs/log-message-tags/next-number
>>>>   httpd/httpd/trunk/modules/proxy/mod_proxy_balancer.c
>>>>
>>>> Modified: httpd/httpd/trunk/CHANGES
>>>> URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/CHANGES?rev=1696960&r1=1696959&r2=1696960&view=diff
>>>> ==============================================================================
>>>> --- httpd/httpd/trunk/CHANGES [utf-8] (original)
>>>> +++ httpd/httpd/trunk/CHANGES [utf-8] Fri Aug 21 12:34:02 2015
>>>> @@ -1,6 +1,9 @@
>>>>                                                         -*- coding: utf-8
-*-
>>>> Changes with Apache 2.5.0
>>>>
>>>> +  *) mod_proxy_balancer: Fix balancers and balancer members reuse on
>>>> +     restart when new ones are added.  PR 58024.  [Yann Ylavic]
>>>> +
>>>>  *) mod_socache_memcache: Add the 'MemcacheConnTTL' directive to control
how
>>>>     long to keep idle connections with the memcache server(s).
>>>>     Change default value from 600 usec (!) to 15 sec. PR 58091
>>>>
>>>> Modified: httpd/httpd/trunk/docs/log-message-tags/next-number
>>>> URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/log-message-tags/next-number?rev=1696960&r1=1696959&r2=1696960&view=diff
>>>> ==============================================================================
>>>> --- httpd/httpd/trunk/docs/log-message-tags/next-number (original)
>>>> +++ httpd/httpd/trunk/docs/log-message-tags/next-number Fri Aug 21 12:34:02
2015
>>>> @@ -1 +1 @@
>>>> -2964
>>>> +2966
>>>>
>>>> Modified: httpd/httpd/trunk/modules/proxy/mod_proxy_balancer.c
>>>> URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/modules/proxy/mod_proxy_balancer.c?rev=1696960&r1=1696959&r2=1696960&view=diff
>>>> ==============================================================================
>>>> --- httpd/httpd/trunk/modules/proxy/mod_proxy_balancer.c (original)
>>>> +++ httpd/httpd/trunk/modules/proxy/mod_proxy_balancer.c Fri Aug 21 12:34:02
2015
>>>> @@ -761,8 +761,11 @@ static int balancer_post_config(apr_pool
>>>>        char *id;
>>>>        proxy_balancer *balancer;
>>>>        ap_slotmem_type_t type;
>>>> +        apr_size_t attached_size;
>>>> +        unsigned int attached_num;
>>>>        void *sconf = s->module_config;
>>>>        conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);
>>>> +
>>>>        /*
>>>>         * During create_proxy_config() we created a dummy id. Now that
>>>>         * we have identifying info, we can create the real id
>>>> @@ -794,11 +797,39 @@ static int balancer_post_config(apr_pool
>>>>                         (int)ALIGNED_PROXY_BALANCER_SHARED_SIZE,
>>>>                         (int)conf->balancers->nelts, conf->max_balancers);
>>>>
>>>> -            rv = storage->create(&new, conf->id,
>>>> -                                 ALIGNED_PROXY_BALANCER_SHARED_SIZE,
>>>> -                                 conf->max_balancers, type, pconf);
>>>> +            /* First try to attach() since the number of configured balancers
>>>> +             * may have changed during restart, and we don't want create()
to
>>>> +             * fail because the overall size * number of entries is not
stricly
>>>> +             * identical to the previous run.  There may still be enough
room
>>>> +             * for this new run thanks to bgrowth margin, so if attach()
>>>> +             * succeeds we can only check for the number of available entries
>>>> +             * to be *greater or* equal to what we need now.  If attach()
fails
>>>> +             * we simply fall back to create().
>>>> +             */
>>>> +            rv = storage->attach(&new, conf->id,
>>>> +                                 &attached_size, &attached_num,
>>>> +                                 pconf);
>>>> +            if (rv != APR_SUCCESS) {
>>>> +                rv = storage->create(&new, conf->id,
>>>> +                                     ALIGNED_PROXY_BALANCER_SHARED_SIZE,
>>>> +                                     conf->max_balancers, type, pconf);
>>>> +            }
>>>> +            else {
>>>> +                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(02964)
>>>> +                             "Balancers attached: %d, %d (%d)",
>>>> +                             (int)ALIGNED_PROXY_BALANCER_SHARED_SIZE,
>>>> +                             (int)attached_num, conf->max_balancers);
>>>> +                if (attached_size == ALIGNED_PROXY_BALANCER_SHARED_SIZE
>>>> +                        && attached_num >= conf->balancers->nelts)
{
>>>> +                    conf->max_balancers = attached_num;
>>>> +                }
>>>> +                else {
>>>> +                    rv = APR_ENOSPC;
>>>> +                }
>>>> +            }
>>>>            if (rv != APR_SUCCESS) {
>>>> -                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01179)
"balancer slotmem_create failed");
>>>> +                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01179)
>>>> +                             "balancer slotmem create or attach failed");
>>>>                return !OK;
>>>>            }
>>>>            conf->bslot = new;
>>>> @@ -864,11 +895,32 @@ static int balancer_post_config(apr_pool
>>>>                         (int)ALIGNED_PROXY_WORKER_SHARED_SIZE,
>>>>                         (int)balancer->max_workers, i);
>>>>
>>>> -            rv = storage->create(&new, balancer->s->sname,
>>>> -                                 ALIGNED_PROXY_WORKER_SHARED_SIZE,
>>>> -                                 balancer->max_workers, type, pconf);
>>>> +            /* try to attach first (see rationale from balancers above)
*/
>>>> +            rv = storage->attach(&new, balancer->s->sname,
>>>> +                                 &attached_size, &attached_num,
>>>> +                                 pconf);
>>>> +            if (rv != APR_SUCCESS) {
>>>> +                rv = storage->create(&new, balancer->s->sname,
>>>> +                                     ALIGNED_PROXY_WORKER_SHARED_SIZE,
>>>> +                                     balancer->max_workers, type, pconf);
>>>> +            }
>>>> +            else {
>>>> +                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(02965)
>>>> +                             "Workers attached: %s (%s), %d, %d (%d) [%u]",
>>>> +                             balancer->s->name, balancer->s->sname,
>>>> +                             (int)ALIGNED_PROXY_WORKER_SHARED_SIZE,
>>>> +                             (int)attached_num, balancer->max_workers,
i);
>>>> +                if (attached_size == ALIGNED_PROXY_WORKER_SHARED_SIZE
>>>> +                        && attached_num >= balancer->workers->nelts)
{
>>>> +                    balancer->max_workers = attached_num;
>>>> +                }
>>>> +                else {
>>>> +                    rv = APR_ENOSPC;
>>>> +                }
>>>> +            }
>>>>            if (rv != APR_SUCCESS) {
>>>> -                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01185)
"worker slotmem_create failed");
>>>> +                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01185)
>>>> +                             "worker slotmem create or attach failed");
>>>>                return !OK;
>>>>            }
>>>>            balancer->wslot = new;
>>>>
>>>>
>>>
>

Mime
View raw message