Add healthcheck endpoint (close #140)

docs/endpoints.rst

@@ -64,3 +64,10 @@ Array of all TileJSONs is at ``/index.json`` (``/rendered.json``; ``/data.json``
 List of available fonts
 =======================
 Array of names of the available fonts is at ``/fonts.json``
+
+Health check
+============
+Endpoint reporting health status is at ``/health`` and currently returns:
+
+  * ``503`` Starting - for a short period before everything is initialized
+  * ``200`` OK - when the server is running

src/server.js

@@ -375,8 +375,17 @@ function start(opts) {
     return data;
   });
 
+  var startupComplete = false;
   var startupPromise = Promise.all(startupPromises).then(function() {
     console.log('Startup complete');
+    startupComplete = true;
+  });
+  app.get('/health', function(req, res, next) {
+    if (startupComplete) {
+      return res.status(200).send('OK');
+    } else {
+      return res.status(503).send('Starting');
+    }
   });
 
   var server = app.listen(process.env.PORT || opts.port, process.env.BIND || opts.bind, function() {

test/metadata.js

@@ -38,6 +38,14 @@ var testTileJSON = function(url) {
 };
 
 describe('Metadata', function() {
+  describe('/health', function() {
+    it('returns 200', function(done) {
+      supertest(app)
+        .get('/health')
+        .expect(200, done);
+    });
+  });
+
   testTileJSONArray('/index.json');
   testTileJSONArray('/rendered.json');
   testTileJSONArray('/data.json');