Adds an onTileErrorStrategy that intercepts error timeout

- returns an fallback image without error

config/environments/development.js.example

@@ -196,6 +196,8 @@ var config = {
 
     // Use this as a feature flags enabling/disabling mechanism
     ,enabledFeatures: {
+        // whether it should intercept tile render errors an act based on them, enabled by default.
+        onTileErrorStrategy: true,
         // whether the affected tables for a given SQL must query directly postgresql or use the SQL API
         cdbQueryTablesFromPostgres: true
     }

config/environments/production.js.example

@@ -196,6 +196,8 @@ var config = {
 
     // Use this as a feature flags enabling/disabling mechanism
     ,enabledFeatures: {
+        // whether it should intercept tile render errors an act based on them, enabled by default.
+        onTileErrorStrategy: true,
         // whether the affected tables for a given SQL must query directly postgresql or use the SQL API
         cdbQueryTablesFromPostgres: true
     }

config/environments/staging.js.example

@@ -196,6 +196,8 @@ var config = {
 
     // Use this as a feature flags enabling/disabling mechanism
     ,enabledFeatures: {
+        // whether it should intercept tile render errors an act based on them, enabled by default.
+        onTileErrorStrategy: true,
         // whether the affected tables for a given SQL must query directly postgresql or use the SQL API
         cdbQueryTablesFromPostgres: true
     }

config/environments/test.js.example

@@ -192,6 +192,8 @@ var config = {
 
     // Use this as a feature flags enabling/disabling mechanism
     ,enabledFeatures: {
+        // whether it should intercept tile render errors an act based on them, enabled by default.
+        onTileErrorStrategy: true,
         // whether the affected tables for a given SQL must query directly postgresql or use the SQL API
         cdbQueryTablesFromPostgres: true
     }

lib/cartodb/server_options.js

@@ -10,6 +10,9 @@ var TemplateMaps = require('./template_maps.js');
 var MapConfigNamedLayersAdapter = require('./models/mapconfig_named_layers_adapter');
 var CdbRequest = require('./models/cdb_request');
 
+var timeoutErrorTilePath = __dirname + '/../../assets/render-timeout-fallback.png';
+var timeoutErrorTile = require('fs').readFileSync(timeoutErrorTilePath, {encoding: null});
+
 // Whitelist query parameters and attach format
 var REQUEST_QUERY_PARAMS_WHITELIST = [
     'config',
@@ -242,6 +245,17 @@ module.exports = function(redisPool) {
         });
     };
 
+
+    if (global.environment.enabledFeatures.onTileErrorStrategy !== false) {
+        me.renderer.onTileErrorStrategy = function(err, tile, headers, stats, format, callback) {
+            if (err && err.message === 'Render timed out' && format === 'png') {
+                return callback(null, timeoutErrorTile, { 'Content-Type': 'image/png' }, {});
+            } else {
+                return callback(err, tile, headers, stats);
+            }
+        };
+    }
+
     me.renderCache.beforeRendererCreate = function(req, callback) {
         var user = cdbRequest.userByReq(req);