Refactor addCacheChannel using Step

lib/cartodb/server_options.js

@@ -201,50 +201,72 @@ module.exports = function(){
 
       // use key to call sql api with sql request if present, else
       // just return dbname and table name base key
-      var dbName     = req.params.dbname;
+      var dbName = req.params.dbname;
 
       var cacheKey = [ dbName ];
       if ( req.params.token ) cacheKey.push(req.params.token);
       else if ( req.params.sql ) cacheKey.push( me.generateMD5(req.params.sql) );
       cacheKey = cacheKey.join(':');
 
-      if ( me.channelCache.hasOwnProperty(cacheKey) ) {
-        callback(null, me.channelCache[cacheKey]);
-        return;
-      }
-      else if ( req.params.token ) {
-        // cached cache channel for token-based access should be constructed
-        // at cache creation time
-        callback(new Error('missing channel cache for token ' + req.params.token));
-        return;
-      }
+      var that = this;
 
-      if ( ! req.params.sql && ! req.params.token ) {
-        var cacheChannel = me.buildCacheChannel(dbName, [req.params.table]);
-        // not worth caching this
-        callback(null, cacheChannel);
-        return;
-      }
+      Step (
+        function checkCached() {
+          if ( me.channelCache.hasOwnProperty(cacheKey) ) {
+            callback(null, me.channelCache[cacheKey]);
+            return;
+          }
+          return null;
+        },
+        function extractSQL(err) {
+          if ( err ) throw err;
 
-      if ( ! req.params.sql ) {
-        callback(new Error("this request doesn't need an X-Cache-Channel generated"));
-        return;
-      }
+          if ( req.params.token ) {
+            // TODO: cached cache channel for token-based access should
+            //       be constructed at renderer cache creation time
+            // See http://github.com/CartoDB/Windshaft-cartodb/issues/152
+            throw new Error('missing channel cache for token ' + req.params.token);
+            return;
+          }
+          else if ( ! req.params.sql ) {
+            return null; // no sql
+          }
 
-      var dbName     = req.params.dbname;
-      var username   = this.userByReq(req);
+          // We have sql, and no token...
 
-      // strip out windshaft/mapnik inserted sql if present
-      var sql = req.params.sql.match(/^\((.*)\)\sas\scdbq$/);
-      sql = (sql != null) ? sql[1] : req.params.sql;
+          // strip out windshaft/mapnik inserted sql if present
+          var sql = req.params.sql.match(/^\((.*)\)\sas\scdbq$/);
+          sql = (sql != null) ? sql[1] : req.params.sql;
 
-      me.affectedTables(username, req.params.map_key, sql, function(err, tableNames) {
-          if ( err ) { callback(err); return; }
+          return sql;
+        },
+        function findAffectedTables(err, sql) {
+          if ( err ) throw err;
+          if ( ! sql ) {
+            if ( ! req.params.table ) {
+              throw new Error("this request doesn't need an X-Cache-Channel generated");
+            }
+            return [req.params.table];
+          }
+          var username   = that.userByReq(req);
+          me.affectedTables(username, req.params.map_key, sql, this);
+        },
+        function buildCacheChannel(err, tableNames) {
+          if ( err ) throw err;
+
+          var dbName     = req.params.dbname;
           var cacheChannel = me.buildCacheChannel(dbName,tableNames);
           // store for caching from me.generateCacheChannel
-          me.channelCache[cacheKey] = cacheChannel;
-          callback(null, cacheChannel);
-      });
+          // (not worth when table was specified in params)
+          if ( ! req.params.table ) {
+            me.channelCache[cacheKey] = cacheChannel;
+          }
+          return cacheChannel;
+        },
+        function finish(err, cacheChannel) {
+          callback(err, cacheChannel);
+        }
+      );
     };
 
     // Set the cache chanel info to invalidate the cache on the frontend server

test/acceptance/server.js

@@ -1111,7 +1111,7 @@ suite('server', function() {
             var ct = res.headers['content-type'];
             assert.equal(ct, 'image/png');
             var cc = res.headers['x-cache-channel'];
-            assert(cc);
+            assert(cc, 'Missing X-Cache-Channel');
             var dbname = 'test_cartodb_user_1_db'
             assert.equal(cc.substring(0, dbname.length), dbname);
             var jsonquery = cc.substring(dbname.length+1);