Instrument alerts for HTTP backend.

An alert is sent whenever an endpoint returns
an error other than an explicit failure (e.g.,
it won't send an alert if a middleware intentionally
returns a {status: XXX} object).

lib/www/server/api/index.js

@@ -3,6 +3,7 @@ const http = require('http');
 const express = require('express');
 const cookieParser = require('cookie-parser')
 
+const maybeSendAlert = require("../lib/alerts");
 const mw = require('./middleware');
 
 const app = express();
@@ -153,14 +154,25 @@ app.map({
 // Generic error handler. Stops stack dumps
 // being sent to clients.
 app.use(function (err, req, res, next) {
+	const title = `HTTP backend error at ${req.method} ${req.originalUrl}`;
+	const description = err.message;
+	const message = err.message;
+	const alert = {title, message, description, error: err};
+
 	console.log("Error:", err);
+
 	if (err instanceof Error && err.name != "UnauthorizedError") {
 		console.error(err.stack);
 		res.status(500).send('General internal error');
+		maybeSendAlert(alert);
 	} else if (typeof err === 'string') {
 		res.status(500).send({message: err});
+		maybeSendAlert(alert);
 	} else {
 		res.status(err.status || 500).send({message: err.message || (err.inner && err.inner.message) || "Internal error"});
+		if (!res.status) {
+			maybeSendAlert(alert);
+		}
 	}
 });