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Use anonymous shared memory segments for mod_tile.so #459

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merged 4 commits into from
Jul 17, 2024
Merged

Use anonymous shared memory segments for mod_tile.so #459

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077a874
Use anonymous shared memory segments here
hummeltech Mar 14, 2024
e40839e
Rename delay_mutex to delaypool_mutex (to match stats)
hummeltech Jul 10, 2024
203266f
Use P_tmpdir rather than /tmp
hummeltech Jul 10, 2024
398ebc2
Don't comingle the two mutexes mutexfilenames
hummeltech Jul 10, 2024
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1 change: 0 additions & 1 deletion .github/workflows/build-and-test.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,6 @@ jobs:
INSTALL_PREFIX: /usr/local
INSTALL_RUNSTATEDIR: /var/run
LDFLAGS: -undefined dynamic_lookup
TEST_PARALLEL_LEVEL: 1
name: >-
${{ matrix.os }}
(${{ matrix.build_system }})
Expand Down
57 changes: 21 additions & 36 deletions src/mod_tile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,12 +81,11 @@ APLOG_USE_MODULE(tile);

apr_shm_t *stats_shm;
apr_shm_t *delaypool_shm;
char *shmfilename;
char *shmfilename_delaypool;
apr_global_mutex_t *stats_mutex;
apr_global_mutex_t *delay_mutex;
apr_global_mutex_t *delaypool_mutex;

char *mutexfilename;
char *stats_mutexfilename;
char *delaypool_mutexfilename;
int layerCount = 0;
int global_max_zoom = 0;

Expand Down Expand Up @@ -818,7 +817,7 @@ static int delay_allowed(request_rec *r, enum tileState state)
return 1;
}

if (get_global_lock(r, delay_mutex) == 0) {
if (get_global_lock(r, delaypool_mutex) == 0) {
ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, "Could not acquire lock, skipping delay pool accounting\n");
return 1;
};
Expand Down Expand Up @@ -847,11 +846,11 @@ static int delay_allowed(request_rec *r, enum tileState state)
if (delay > 0) {
/* If we are on the second round, we really hit an empty delaypool, timeout for a while to slow down clients */
if (j > 0) {
apr_global_mutex_unlock(delay_mutex);
apr_global_mutex_unlock(delaypool_mutex);
ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, "Delaypool: Client %s has hit its limits, throttling (%i)\n", ip_addr, delay);
sleep(CLIENT_PENALTY);

if (get_global_lock(r, delay_mutex) == 0) {
if (get_global_lock(r, delaypool_mutex) == 0) {
ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, "Could not acquire lock, but had to delay\n");
return 0;
};
Expand Down Expand Up @@ -897,7 +896,7 @@ static int delay_allowed(request_rec *r, enum tileState state)
delay = 0;
}

apr_global_mutex_unlock(delay_mutex);
apr_global_mutex_unlock(delaypool_mutex);

if (delay > 0) {
ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, "Delaypool: Client %s has hit its limits, rejecting (%i)\n", ip_addr, delay);
Expand Down Expand Up @@ -1673,37 +1672,25 @@ static int mod_tile_post_config(apr_pool_t *pconf, apr_pool_t *plog,
return OK;
} /* Kilroy was here */

/* Create the shared memory segment */

/*
* Create a unique filename using our pid. This information is
* stashed in the global variable so the children inherit it.
* TODO get the location from the environment $TMPDIR or somesuch.
*/
shmfilename = apr_psprintf(pconf, "/tmp/httpd_shm.%ld", (long int)getpid());
shmfilename_delaypool = apr_psprintf(pconf, "/tmp/httpd_shm_delay.%ld", (long int)getpid());

/* Now create that segment
/* Create the shared memory segment
* would prefer to use scfg->configs->nelts here but that does
* not seem to be set at this stage, so rely on previously set layerCount */

rs = apr_shm_create(&stats_shm, sizeof(stats_data) + layerCount * 2 * sizeof(apr_uint64_t),
(const char *)shmfilename, pconf);
NULL, pconf);

if (rs != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ERR, rs, s,
"Failed to create shared memory segment on file %s",
shmfilename);
"Failed to create 'stats' shared memory segment");
return HTTP_INTERNAL_SERVER_ERROR;
}

rs = apr_shm_create(&delaypool_shm, sizeof(delaypool),
(const char *)shmfilename_delaypool, pconf);
NULL, pconf);

if (rs != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ERR, rs, s,
"Failed to create shared memory segment on file %s",
shmfilename_delaypool);
"Failed to create 'delaypool' shared memory segment");
return HTTP_INTERNAL_SERVER_ERROR;
}

Expand Down Expand Up @@ -1770,16 +1757,15 @@ static int mod_tile_post_config(apr_pool_t *pconf, apr_pool_t *plog,
* depending on OS and locking mechanism of choice, the file
* may or may not be actually created.
*/
mutexfilename = apr_psprintf(pconf, "/tmp/httpd_mutex.%ld",
(long int)getpid());
stats_mutexfilename = apr_psprintf(pconf, "%s/httpd_mutex_stats.%ld", P_tmpdir, (long int)getpid());

rs = apr_global_mutex_create(&stats_mutex, (const char *)mutexfilename,
rs = apr_global_mutex_create(&stats_mutex, (const char *)stats_mutexfilename,
APR_LOCK_DEFAULT, pconf);

if (rs != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ERR, rs, s,
"Failed to create mutex on file %s",
mutexfilename);
stats_mutexfilename);
return HTTP_INTERNAL_SERVER_ERROR;
}

Expand All @@ -1800,21 +1786,20 @@ static int mod_tile_post_config(apr_pool_t *pconf, apr_pool_t *plog,
* depending on OS and locking mechanism of choice, the file
* may or may not be actually created.
*/
mutexfilename = apr_psprintf(pconf, "/tmp/httpd_mutex_delay.%ld",
(long int)getpid());
delaypool_mutexfilename = apr_psprintf(pconf, "%s/httpd_mutex_delaypool.%ld", P_tmpdir, (long int)getpid());

rs = apr_global_mutex_create(&delay_mutex, (const char *)mutexfilename,
rs = apr_global_mutex_create(&delaypool_mutex, (const char *)delaypool_mutexfilename,
APR_LOCK_DEFAULT, pconf);

if (rs != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ERR, rs, s,
"Failed to create mutex on file %s",
mutexfilename);
delaypool_mutexfilename);
return HTTP_INTERNAL_SERVER_ERROR;
}

#ifdef MOD_TILE_SET_MUTEX_PERMS
rs = ap_unixd_set_global_mutex_perms(delay_mutex);
rs = ap_unixd_set_global_mutex_perms(delaypool_mutex);

if (rs != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rs, s,
Expand Down Expand Up @@ -1846,13 +1831,13 @@ static void mod_tile_child_init(apr_pool_t *p, server_rec *s)
* the mutex pointer global here.
*/
rs = apr_global_mutex_child_init(&stats_mutex,
(const char *)mutexfilename,
(const char *)stats_mutexfilename,
p);

if (rs != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rs, s,
"Failed to reopen mutex on file %s",
shmfilename);
stats_mutexfilename);
/* There's really nothing else we can do here, since
* This routine doesn't return a status. */
exit(1); /* Ugly, but what else? */
Expand Down
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