Reuse the function for creating empty responses

src/serve_rendered.js

@@ -36,14 +36,6 @@ mbgl.on('message', function(e) {
   }
 });
 
-/**
- * Cache of response data by sharp output format.  The empty string represents
- * an unknown or unsupported format.
- */
-var cachedErrorResponses = {
-  '': new Buffer(0)
-};
-
 /**
  * Lookup of sharp output formats by file extension.
  */
@@ -54,24 +46,42 @@ var extensionToFormat = {
   '.webp': 'webp'
 };
 
+/**
+ * Cache of response data by sharp output format and color.  Entry for empty
+ * string is for unknown or unsupported formats.
+ */
+var cachedEmptyResponses = {
+  '': new Buffer(0)
+};
+
 /**
  * Create an appropriate mbgl response for http errors.
- * @param {Object} req The mbgl req object.
+ * @param {string} format The format (a sharp format or 'pbf').
- * @param {http.IncomingMessage} res The incoming response.
+ * @param {string} color The background color (or empty string for transparent).
  * @param {Function} callback The mbgl callback.
  */
-function createErrorResponse(req, res, callback) {
+function createEmptyResponse(format, color, callback) {
-  var parts = url.parse(req.url);
+  if (!format || format === 'pbf') {
-  var extension = path.extname(parts.pathname).toLowerCase();
+    callback(null, {data: cachedEmptyResponses['']});
-  var format = extensionToFormat[extension] || '';
+    return;
-  var data = cachedErrorResponses[format];
+  }
+
+  if (format === 'jpg') {
+    format = 'jpeg';
+  }
+  if (!color) {
+    color = 'rgba(255,255,255,0)';
+  }
+
+  var cacheKey = format + ',' + color;
+  var data = cachedEmptyResponses[cacheKey];
   if (data) {
     callback(null, {data: data});
     return;
   }
 
   // create an "empty" response image
-  var color = new Color('rgba(255,255,255,0)');
+  var color = new Color(color);
   var array = color.array();
   var channels = array.length == 4 && format != 'jpeg' ? 4 : 3;
   sharp(new Buffer(array), {
@@ -82,7 +92,7 @@ function createErrorResponse(req, res, callback) {
     }
   }).toFormat(format).toBuffer(function(err, buffer, info) {
     if (!err) {
-      cachedErrorResponses[format] = buffer;
+      cachedEmptyResponses[cacheKey] = buffer;
     }
     callback(null, {data: buffer});
   });
@@ -162,10 +172,11 @@ module.exports = function(options, repo, params, id, dataResolver) {
             source.getTile(z, x, y, function(err, data, headers) {
               if (err) {
                 //console.log('MBTiles error, serving empty', err);
-                callback(null, { data: source.emptyTile });
+                createEmptyResponse(source.format, source.color, callback);
-              } else {
+                return;
-                var response = {};
+              }
 
+              var response = {};
               if (headers['Last-Modified']) {
                 response.modified = new Date(headers['Last-Modified']);
               }
@@ -181,7 +192,6 @@ module.exports = function(options, repo, params, id, dataResolver) {
               }
 
               callback(null, response);
-              }
             });
           } else if (protocol == 'http' || protocol == 'https') {
             request({
@@ -189,12 +199,16 @@ module.exports = function(options, repo, params, id, dataResolver) {
                 encoding: null,
                 gzip: true
             }, function(err, res, body) {
-                if (err) {
+                var parts = url.parse(req.url);
-                  // console.log('HTTP request error', err);
+                var extension = path.extname(parts.pathname).toLowerCase();
-                  createErrorResponse(req, res, callback);
+                var format = extensionToFormat[extension] || '';
-                } else if (res.statusCode == 200) {
+                if (err || res.statusCode < 200 || res.statusCode >= 300) {
-                  var response = {};
+                  // console.log('HTTP error', err || res.statusCode);
+                  createEmptyResponse(format, '', callback);
+                  return;
+                }
 
+                var response = {};
                 if (res.headers.modified) {
                   response.modified = new Date(res.headers.modified);
                 }
@@ -206,12 +220,7 @@ module.exports = function(options, repo, params, id, dataResolver) {
                 }
 
                 response.data = body;
-
                 callback(null, response);
-                } else {
-                  // console.log('HTTP response error', req.url, res.statusCode);
-                  createErrorResponse(req, res, callback);
-                }
             });
           }
         }
@@ -321,26 +330,6 @@ module.exports = function(options, repo, params, id, dataResolver) {
               source = options.dataDecoratorFunc(name, 'tilejson', source);
             }
 
-            if (source.format == 'pbf') {
-              map.sources[name].emptyTile = new Buffer(0);
-            } else {
-              var color = new Color(source.color || 'rgba(255,255,255,0)');
-              var format = source.format;
-              if (format == 'jpg') {
-                format = 'jpeg';
-              }
-              var array = color.array();
-              var channels = array.length == 4 && format != 'jpeg' ? 4 : 3;
-              sharp(new Buffer(array), {
-                raw: {
-                  width: 1,
-                  height: 1,
-                  channels: channels
-                }
-              }).toFormat(format).toBuffer(function(err, buffer, info) {
-                map.sources[name].emptyTile = buffer;
-              });
-            }
             if (!attributionOverride &&
                 source.attribution && source.attribution.length > 0) {
               if (tileJSON.attribution.length > 0) {