Add child init hook for cache backends (#290)

* Some cache backends might need to call specific code at startup of a process. In the case of Apache mpm_event, child_init is executed after process start (fork) and before starting any threads that will do actual request processing.

* Use single noop child init function for all cache backends

* mapcache_cache_child_init needs a DLL export to not cause linking problems on Windows

Author: marisn

apache/mod_mapcache.c

@@ -307,11 +307,17 @@ static int write_http_response(mapcache_context_apache_request *ctx, mapcache_ht
 
 static void mod_mapcache_child_init(apr_pool_t *pool, server_rec *s)
 {
+  mapcache_context *ctx;
+  ctx = (mapcache_context*)create_apache_server_context(s,pool);
   for( ; s ; s=s->next) {
     mapcache_server_cfg* cfg = ap_get_module_config(s->module_config, &mapcache_module);
     int i,rv;
     for(i=0;i<cfg->aliases->nelts;i++) {
       mapcache_alias_entry *alias_entry = APR_ARRAY_IDX(cfg->aliases,i,mapcache_alias_entry*);
+      mapcache_cache_child_init(ctx,alias_entry->cfg,pool);
+      if (GC_HAS_ERROR(ctx)) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s, "%s", ctx->get_error_message(ctx));
+      }
       rv = mapcache_connection_pool_create(alias_entry->cfg, &(alias_entry->cp),pool);
       ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, "creating a child process mapcache connection pool on server %s for alias %s", s->server_hostname, alias_entry->endpoint);
       if(rv!=APR_SUCCESS) {
@@ -320,6 +326,10 @@ static void mod_mapcache_child_init(apr_pool_t *pool, server_rec *s)
     }
     for(i=0;i<cfg->quickaliases->nelts;i++) {
       mapcache_alias_entry *alias_entry = APR_ARRAY_IDX(cfg->quickaliases,i,mapcache_alias_entry*);
+      mapcache_cache_child_init(ctx,alias_entry->cfg,pool);
+      if (GC_HAS_ERROR(ctx)) {
+        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s, "%s", ctx->get_error_message(ctx));
+      }
       rv = mapcache_connection_pool_create(alias_entry->cfg, &(alias_entry->cp),pool);
       ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, "creating a child process mapcache connection pool on server %s for alias %s", s->server_hostname, alias_entry->endpoint);
       if(rv!=APR_SUCCESS) {

cgi/mapcache.c

@@ -213,6 +213,8 @@ static void load_config(mapcache_context *ctx, char *filename)
     apr_pool_destroy(config_pool);
   }
   config_pool = tmp_config_pool;
+  mapcache_cache_child_init(ctx,cfg,config_pool);
+  if (GC_HAS_ERROR(ctx)) goto failed_load;
   mapcache_connection_pool_create(cfg, &ctx->connection_pool, config_pool);
 
   return;

contrib/mapcache_detail/mapcache_detail.c

@@ -714,6 +714,8 @@ int main(int argc, char * argv[])
   mapcache_context_init(&ctx);
   ctx.config = mapcache_configuration_create(ctx.pool);
   ctx.log = mapcache_log;
+  mapcache_cache_child_init(&ctx,ctx.config,ctx.pool);
+  if (GC_HAS_ERROR(&ctx)) goto failure;
   mapcache_connection_pool_create(ctx.config, &ctx.connection_pool, ctx.pool);
 
 

include/mapcache.h

@@ -369,6 +369,7 @@ struct mapcache_cache {
 
   void (*configuration_parse_xml)(mapcache_context *ctx, ezxml_t xml, mapcache_cache * cache, mapcache_cfg *config);
   void (*configuration_post_config)(mapcache_context *ctx, mapcache_cache * cache, mapcache_cfg *config);
+  void (*child_init)(mapcache_context *ctx, mapcache_cache *cache, apr_pool_t *pchild);
 };
 
 MS_DLL_EXPORT int mapcache_cache_tile_get(mapcache_context *ctx, mapcache_cache *cache, mapcache_tile *tile);
@@ -377,6 +378,9 @@ MS_DLL_EXPORT int mapcache_cache_tile_exists(mapcache_context *ctx, mapcache_cac
 MS_DLL_EXPORT void mapcache_cache_tile_set(mapcache_context *ctx, mapcache_cache *cache, mapcache_tile *tile);
 void mapcache_cache_tile_multi_set(mapcache_context *ctx, mapcache_cache *cache, mapcache_tile *tiles, int ntiles);
 
+MS_DLL_EXPORT void mapcache_cache_child_init(mapcache_context *ctx, mapcache_cfg *config, apr_pool_t *pchild);
+static inline void mapcache_cache_child_init_noop(mapcache_context *ctx, mapcache_cache *cache, apr_pool_t *pchild) {
+};
 
 
 /**

lib/cache.c

@@ -174,3 +174,16 @@ void mapcache_cache_tile_multi_set(mapcache_context *ctx, mapcache_cache *cache,
     }
   }
 }
+
+void mapcache_cache_child_init(mapcache_context *ctx, mapcache_cfg *config, apr_pool_t *pchild)
+{
+  apr_hash_index_t *cachei = apr_hash_first(pchild,config->caches);
+  while(cachei) {
+    mapcache_cache *cache;
+    const void *key;
+    apr_ssize_t keylen;
+    apr_hash_this(cachei,&key,&keylen,(void**)&cache);
+    cache->child_init(ctx,cache,pchild);
+    cachei = apr_hash_next(cachei);
+  }
+}

lib/cache_bdb.c

@@ -417,6 +417,7 @@ mapcache_cache* mapcache_cache_bdb_create(mapcache_context *ctx)
   cache->cache._tile_multi_set = _mapcache_cache_bdb_multiset;
   cache->cache.configuration_post_config = _mapcache_cache_bdb_configuration_post_config;
   cache->cache.configuration_parse_xml = _mapcache_cache_bdb_configuration_parse_xml;
+  cache->cache.child_init = mapcache_cache_child_init_noop;
   cache->basedir = NULL;
   cache->key_template = NULL;
   return (mapcache_cache*)cache;

lib/cache_composite.c

@@ -262,5 +262,6 @@ mapcache_cache* mapcache_cache_composite_create(mapcache_context *ctx)
   cache->cache._tile_multi_set = _mapcache_cache_composite_tile_multi_set;
   cache->cache.configuration_post_config = _mapcache_cache_composite_configuration_post_config;
   cache->cache.configuration_parse_xml = _mapcache_cache_composite_configuration_parse_xml;
+  cache->cache.child_init = mapcache_cache_child_init_noop;
   return (mapcache_cache*)cache;
 }

lib/cache_couchbase.c

@@ -466,6 +466,7 @@ mapcache_cache* mapcache_cache_couchbase_create(mapcache_context *ctx) {
    cache->cache.tile_delete = _mapcache_cache_couchbase_delete;
    cache->cache.configuration_parse_xml = _mapcache_cache_couchbase_configuration_parse_xml;
    cache->cache.configuration_post_config = _mapcache_cache_couchbase_configuration_post_config;
+   cache->cache.child_init = mapcache_cache_child_init_noop;
    cache->host = NULL;
    cache->username = NULL;
    cache->password = NULL;

lib/cache_disk.c

@@ -768,6 +768,7 @@ mapcache_cache* mapcache_cache_disk_create(mapcache_context *ctx)
   cache->cache._tile_set = _mapcache_cache_disk_set;
   cache->cache.configuration_post_config = _mapcache_cache_disk_configuration_post_config;
   cache->cache.configuration_parse_xml = _mapcache_cache_disk_configuration_parse_xml;
+  cache->cache.child_init = mapcache_cache_child_init_noop;
   return (mapcache_cache*)cache;
 }
 

lib/cache_fallback.c

@@ -190,6 +190,7 @@ mapcache_cache* mapcache_cache_fallback_create(mapcache_context *ctx)
   cache->cache._tile_multi_set = _mapcache_cache_fallback_tile_multi_set;
   cache->cache.configuration_post_config = _mapcache_cache_fallback_configuration_post_config;
   cache->cache.configuration_parse_xml = _mapcache_cache_fallback_configuration_parse_xml;
+  cache->cache.child_init = mapcache_cache_child_init_noop;
   return (mapcache_cache*)cache;
 }