Reduce sql-api communication timeout, and allow overriding it

Introduces new sqlapi.timeout directive, defaults to 100 ms
Includes testcase.
Closes #167

NEWS.md

@@ -8,6 +8,8 @@ Enhancements:
  - Improve speed of instanciating a map (#147, #159, #165)
  - Give meaningful error on attempts to use map tokens
    with attribute service (#156)
+ - Reduce sql-api communication timeout, and allow overriding (#167)
+   [ new sqlapi.timeout directive, defaults to 100 ms ]
 
 1.8.2 -- 2014-02-25
 -------------------

config/environments/development.js.example

@@ -106,7 +106,10 @@ var config = {
         // Maximum lenght of SQL query for GET
         // requests. Longer queries will be sent
         // using POST. Defaults to 2048
-        max_get_sql_length: 2048
+        max_get_sql_length: 2048,
+        // Maximum time to wait for a response,
+        // in milliseconds. Defaults to 100.
+        timeout: 100
     }
     ,varnish: {
         host: 'localhost',

config/environments/production.js.example

@@ -100,7 +100,10 @@ var config = {
         // Maximum lenght of SQL query for GET
         // requests. Longer queries will be sent
         // using POST. Defaults to 2048
-        max_get_sql_length: 2048
+        max_get_sql_length: 2048,
+        // Maximum time to wait for a response,
+        // in milliseconds. Defaults to 100.
+        timeout: 100
     }
     ,varnish: {
         host: 'localhost',

config/environments/staging.js.example

@@ -100,7 +100,10 @@ var config = {
         // Maximum lenght of SQL query for GET
         // requests. Longer queries will be sent
         // using POST. Defaults to 2048
-        max_get_sql_length: 2048
+        max_get_sql_length: 2048,
+        // Maximum time to wait for a response,
+        // in milliseconds. Defaults to 100.
+        timeout: 100
     }
     ,varnish: {
         host: 'localhost',

config/environments/test.js.example

@@ -102,7 +102,10 @@ var config = {
         // Maximum lenght of SQL query for GET
         // requests. Longer queries will be sent
         // using POST. Defaults to 2048
-        max_get_sql_length: 2048
+        max_get_sql_length: 2048,
+        // Maximum time to wait for a response,
+        // in milliseconds. Defaults to 100.
+        timeout: 100
     }
     ,varnish: {
         host: '',

lib/cartodb/server_options.js

@@ -116,13 +116,15 @@ module.exports = function(){
       //
       var maxSockets = global.environment.maxConnections || 128;
       var maxGetLen = api.max_get_sql_length || 2048;
+      var maxSQLTime = api.timeout || 100; // 1/10 of a second by default
       var reqSpec = {
             url:sqlapi,
             json:true,
             headers:{host: sqlapihostname}
             // http://nodejs.org/api/http.html#http_agent_maxsockets
             ,pool:{maxSockets:maxSockets}
-            //,timeout:100
+            // timeout in milliseconds
+            ,timeout:maxSQLTime
       }
       if ( sql.length > maxGetLen ) {
         reqSpec.method = 'POST';

test/acceptance/multilayer.js

@@ -1128,6 +1128,47 @@ suite('multilayer', function() {
       );
     });
 
+    // See https://github.com/CartoDB/Windshaft-cartodb/issues/167
+    test("lack of response from sql-api will result in a timeout", function(done) {
+
+      var layergroup =  {
+        version: '1.0.0',
+        layers: [
+           { options: {
+               sql: "select *, 'SQLAPINOANSWER' from test_table",
+               cartocss: '#layer { marker-fill:red; marker-width:32; marker-allow-overlap:true; }', 
+               cartocss_version: '2.1.0'
+             } }
+        ]
+      };
+
+      Step(
+        function do_post()
+        {
+          var next = this;
+          assert.response(server, {
+              url: '/tiles/layergroup',
+              method: 'POST',
+              headers: {host: 'localhost', 'Content-Type': 'application/json' },
+              data: JSON.stringify(layergroup)
+          }, {}, function(res, err) { next(err, res); });
+        },
+        function check_post(err, res) {
+          if ( err ) throw err;
+          assert.equal(res.statusCode, 400, res.statusCode + ': ' + res.body);
+          var parsed = JSON.parse(res.body);
+          assert.ok(parsed.errors, 'Missing "errors" in response: ' + JSON.stringify(parsed));
+          assert.equal(parsed.errors.length, 1);
+          var msg = parsed.errors[0];
+          assert.equal(msg, 'Error: could not fetch source tables: ETIMEDOUT');
+          return null;
+        },
+        function finish(err) {
+          done(err);
+        }
+      );
+    });
+
 
     suiteTeardown(function(done) {
 

test/support/SQLAPIEmu.js

@@ -42,6 +42,9 @@ o.prototype.handleQuery = function(query, res) {
     if ( query.q.match('SQLAPIERROR') ) {
       res.statusCode = 400;
       res.write(JSON.stringify({'error':'Some error occurred'}));
+    } else if ( query.q.match('SQLAPINOANSWER') ) {
+      console.log("SQLAPIEmulator will never respond, on request");
+      return;
     } else if ( query.q.match('EPOCH.* as max') ) {
       // This is the structure of the known query sent by tiler
       var row = {