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 <j...@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....@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 <j...@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, yla...@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;
>>>>
>>>>
>>>
>
