Handle error in graphs code

src/routes/graphs.js

@@ -5,6 +5,7 @@ exports = module.exports = {
 };
 
 var middleware = require('../middleware/index.js'),
+    HttpError = require('connect-lastmile').HttpError,
     url = require('url');
 
 // for testing locally: curl 'http://127.0.0.1:8417/graphite-web/render?format=json&from=-1min&target=absolute(collectd.localhost.du-docker.capacity-usage)'
@@ -24,6 +25,14 @@ function getGraphs(req, res, next) {
     // nginx still has a request timeout which can deal with this then.
     req.clearTimeout();
 
-    graphiteProxy(req, res, next);
+    graphiteProxy(req, res, function (error) {
+        if (!error) return next();
+
+        if (error.code === 'ECONNREFUSED') return next(new HttpError(424, 'Unable to connect to graphite'));
+        // ECONNRESET here is most likely because of a bug in the query or the uwsgi buffer size is too small
+        if (error.code === 'ECONNRESET') return next(new HttpError(424, 'Unable to query graphite'));
+
+        next(new HttpError(500, error));
+    });
 }