Allow host:port specification for MemcacheD storage backend (#369)

So that MemcacheD hosts and ports other than `localhost` and `11211` can be used.

_Also_:
- Added `ctest --parallel` execution support
- Added tests for custom `MemcacheD` {host}:{port}
- Added tests for `AddTileConfig`/`AddTileMimeConfig`

etc/apache2/renderd-example-map.conf

@@ -14,7 +14,11 @@ Redirect /renderd-example-map/leaflet/leaflet.min.js https://unpkg.com/leaflet/d
 
 Listen 8081
 <VirtualHost *:8081>
-
+    # Specify the location under which (meta)tiles are stored.
+    # This can be a directory path, or, when using storage backends other than "file", a URI.
+    #
+    # I.E.:
+    #   "memcached://{memcached_host}:{memcached_port}" for MemcacheD
     ModTileTileDir /var/cache/renderd/tiles
 
     # You can manually configure each tile set with AddTileConfig or AddTileMimeConfig.

etc/renderd/renderd.conf.examples

@@ -19,7 +19,15 @@ tile_dir=/var/cache/renderd/tiles
 ;iphostname=::1
 ;ipport=7654
 ;num_threads=8
-;tile_dir=memcached://
+;tile_dir=memcached:// ; Defaults to "localhost:11211" when host:port is not specified
+;pid_file=/run/renderd/renderd_memcached.pid
+;stats_file=/run/renderd/renderd.stats
+
+;[renderd]
+;iphostname=::1
+;ipport=7654
+;num_threads=8
+;tile_dir=memcached://memcached_host:11212 ; You may also specify a custom host:port
 ;pid_file=/run/renderd/renderd_memcached.pid
 ;stats_file=/run/renderd/renderd.stats
 
@@ -70,3 +78,19 @@ XML=/var/www/example-map/mapnik.xml
 ;ATTRIBUTION=&copy;<a href=\"http://www.openstreetmap.org/\">OpenStreetMap</a> and <a href=\"http://wiki.openstreetmap.org/wiki/Contributors\">contributors</a>, <a href=\"http://opendatacommons.org/licenses/odbl/\">ODbL</a>
 ;SERVER_ALIAS=http://localhost/
 ;CORS=*
+
+;[style3]
+;URI=/osm_tiles3/
+;TILEDIR=memcached://
+;TILESIZE=512
+;XML=/usr/share/renderd/openstreetmap/osm-local3.xml
+;HOST=tile.openstreetmap.org
+;HTCPHOST=proxy.openstreetmap.org
+;** config options used by mod_tile, but not renderd **
+;MINZOOM=0
+;MAXZOOM=22
+;TYPE=png image/png png256 ; Values are: <extension> <mime-type> <output-format> (for more information about output format see https://github.com/mapnik/mapnik/wiki/Image-IO)
+;DESCRIPTION=This is a description of the tile layer used in the tile json request
+;ATTRIBUTION=&copy;<a href=\"http://www.openstreetmap.org/\">OpenStreetMap</a> and <a href=\"http://wiki.openstreetmap.org/wiki/Contributors\">contributors</a>, <a href=\"http://opendatacommons.org/licenses/odbl/\">ODbL</a>
+;SERVER_ALIAS=http://localhost/
+;CORS=*

src/store_memcached.c

@@ -284,8 +284,20 @@ struct storage_backend * init_storage_memcached(const char * connection_string)
 		return NULL;
 	}
 
+	if (strcmp(connection_string, "memcached://")) {
+		int connection_string_len = strnlen(connection_string, PATH_MAX);
+		connection_str = malloc(sizeof(char) * connection_string_len);
+		// The length of the string "memcached://" is 12
+		snprintf(connection_str, connection_string_len - 2, "--server=%.*s", connection_string_len - 12, connection_string + 12);
+	}
+
+	g_logger(G_LOG_LEVEL_DEBUG, "init_storage_memcached: Creating memcached ctx with options '%s'", connection_str);
 	ctx = memcached(connection_str, strlen(connection_str));
 
+	if (strcmp(connection_string, "memcached://")) {
+		free(connection_str);
+	}
+
 	if (ctx == NULL) {
 		g_logger(G_LOG_LEVEL_ERROR, "init_storage_memcached: Failed to create memcached ctx");
 		free(store);