Handle SQL API errors by logging them and requesting NO cache

SQL api is used to determine the list of source tables affected
by a query. Before this commit, the X-Cache-Channel header set
on sql api error was an arbitrary 'table' string, now the header
is omitted, the error logged and Cache-Control and Pragma headers
are sent as an attempt to request no caching.

The code includes test for this mechanism.

config/environments/test.js.example

@@ -48,8 +48,10 @@ var config = {
     }
     ,sqlapi: {
         protocol: 'http',
-        host: 'localhost.lan',
+        host: '',
-        port: 8080,
+        // This port will be used by "make check" for testing purposes
+        // It must be available
+        port: 1080,
         version: 'v1'
     }
     ,varnish: {

lib/cartodb/cache_validator.js

@@ -36,7 +36,7 @@ function generateCacheChannel(req, callback){
 
         // use cache if present
         if (!_.isNull(channelCache[sql_md5]) && !_.isUndefined(channelCache[sql_md5])) {
-            callback(channelCache[sql_md5]);
+            callback(null, channelCache[sql_md5]);
         } else{
             // strip out windshaft/mapnik inserted sql if present
             var sql = req.params.sql.match(/^\((.*)\)\sas\scdbq$/);
@@ -54,21 +54,28 @@ function generateCacheChannel(req, callback){
             }
 
             // call sql api
-            request.get({url:sqlapi, qs:qs, json:true}, function(err, response, body){
+            request.get({url:sqlapi, qs:qs, json:true}, function(err, res, body){
-                if (!err && response.statusCode == 200) {
+                var epref = 'could not detect source tables using SQL api at ' + sqlapi;
-                    tableNames = body.rows[0].cdb_querytables.split(/^\{(.*)\}$/)[1];
+                if (err){
-                } else {
+                  var msg = err.message ? err.message : err;
-                    //oops, no SQL API. Just cache using fallback 'table' key
+                  callback(new Error(epref + ': ' + msg));
-                    tableNames = 'table';
+                  return;
                 }
+                if (res.statusCode != 200) {
+                    var msg = res.body.error ? res.body.error : res.body;
+                    callback(new Error(epref + ': ' + msg));
+                    return;
+                } 
+                var qtables = body.rows[0].cdb_querytables;
+                tableNames = qtables.split(/^\{(.*)\}$/)[1];
                 cacheChannel = buildCacheChannel(dbName,tableNames);
                 channelCache[sql_md5] = cacheChannel; // store for caching
-                callback(cacheChannel);
+                callback(null, cacheChannel);
             });
         }
     } else {
         cacheChannel = buildCacheChannel(dbName,tableNames);
-        callback(cacheChannel);
+        callback(null, cacheChannel);
     }
 }
 

lib/cartodb/server_options.js

@@ -57,17 +57,27 @@ module.exports = function(){
         // skip non-GET requests, or requests for which there's no response
         if ( req.method != 'GET' || ! req.res ) { cb(null, null); return; }
         var res = req.res;
-        var ttl = global.environment.varnish.ttl || 86400;
+        var cache_policy = req.query.cache_policy;
-        Cache.generateCacheChannel(req, function(channel){
+        if ( cache_policy == 'persist' ) {
-            res.header('X-Cache-Channel', channel);
+          res.header('Cache-Control', 'public,max-age=31536000'); // 1 year
-            var cache_policy = req.query.cache_policy;
+        } else {
-            if ( cache_policy == 'persist' ) {
+          var ttl = global.environment.varnish.ttl || 86400;
-              res.header('Cache-Control', 'public,max-age=31536000'); // 1 year
+          res.header('Last-Modified', new Date().toUTCString());
+          res.header('Cache-Control', 'no-cache,max-age='+ttl+',must-revalidate, public');
+        }
+        Cache.generateCacheChannel(req, function(err, channel){
+            if ( ! err ) {
+              res.header('X-Cache-Channel', channel);
+              cb(null, channel); 
             } else {
-              res.header('Last-Modified', new Date().toUTCString());
+              // avoid caching this result
-              res.header('Cache-Control', 'no-cache,max-age='+ttl+',must-revalidate, public');
+              // (temptative, what Varnish does is out of our control)
+              res.header('Cache-Control', 'no-cache,no-store,max-age=0,must-revalidate');
+              res.header('Pragma', 'no-cache');
+              console.log('ERROR generating cache channel: ' + ( err.message ? err.message : err ));
+              // TODO: evaluate if we should bubble up the error instead
+              cb(null, 'ERROR');
             }
-            cb(null, channel); // add last-modified too ?
         });
     }
 
@@ -127,7 +137,7 @@ module.exports = function(){
                 if (!_.isNull(data))
                     _.extend(req.params, {geom_type: data});
 
-                that.addCacheChannel(req, function(err, chan) {
+                that.addCacheChannel(req, function(err) {
                   callback(err, req);
                 });
             }

test/acceptance/server.js

@@ -6,6 +6,8 @@ var querystring = require('querystring');
 var semver      = require('semver');
 var mapnik      = require('mapnik');
 var Step        = require('step');
+var http        = require('http');
+var url         = require('url');
 
 require(__dirname + '/../support/test_helper');
 
@@ -17,6 +19,7 @@ server.setMaxListeners(0);
 suite('server', function() {
 
     var redis_client = redis.createClient(global.environment.redis.port);
+    var sqlapi_server;
 
     var default_style = semver.satisfies(mapnik.versions.mapnik, '<2.1.0')
     ?
@@ -30,7 +33,19 @@ suite('server', function() {
     var test_style_black_200 = "#test_table{marker-fill:black;marker-line-color:red;marker-width:10}";
     var test_style_black_210 = "#test_table{marker-fill:black;marker-line-color:red;marker-width:20}";
     
-    suiteSetup(function(){
+    suiteSetup(function(done){
+      sqlapi_server = http.createServer(function(req,res) {
+        var query = url.parse(req.url, true).query;
+        if ( query.q.match('SQLAPIERROR') ) {
+          res.statusCode = 400;
+          res.write(JSON.stringify({'error':'Some error occurred'}));
+        } else {
+          res.write(JSON.stringify({rows: [ { 'cdb_querytables': '{' +
+            JSON.stringify(query) + '}' } ]}));
+        }
+        res.end();
+      });
+      sqlapi_server.listen(global.environment.sqlapi.port, done);
     });
 
     /////////////////////////////////////////////////////////////////////////////////
@@ -916,6 +931,69 @@ suite('server', function() {
       );
     });
 
+    test("uses sqlapi to figure source data of query", function(done){
+        var qo = {
+          sql: "SELECT g.cartodb_id, g.codineprov, t.the_geom_webmercator "
+              + "FROM gadm4 g, test_table t "
+              + "WHERE g.cartodb_id = t.cartodb_id",
+          map_key: 1234
+        };
+        var sqlapi;
+        Step(
+          function sendRequest(err) {
+            assert.response(server, {
+                headers: {host: 'localhost'},
+                url: '/tiles/gadm4/6/31/24.png?' + querystring.stringify(qo),
+                method: 'GET'
+            },{}, this);
+          },
+          function checkResponse(res) {
+            assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+            var ct = res.headers['content-type'];
+            assert.equal(ct, 'image/png');
+            var cc = res.headers['x-cache-channel'];
+            var dbname = 'cartodb_test_user_1_db'
+            assert.equal(cc.substring(0, dbname.length), dbname);
+            var jsonquery = cc.substring(dbname.length+1);
+            var sentquery = JSON.parse(jsonquery);
+            assert.equal(sentquery.api_key, qo.map_key);
+            assert.equal(sentquery.q, 'SELECT CDB_QueryTables($windshaft$' + qo.sql + '$windshaft$)');
+            done();
+          }
+        );
+    });
+
+    test("requests to skip cache on sqlapi error", function(done){
+        var qo = {
+          sql: "SELECT g.cartodb_id, g.codineprov, t.the_geom_webmercator "
+              + ", 'SQLAPIERROR' is not null "
+              + "FROM gadm4 g, test_table t "
+              + "WHERE g.cartodb_id = t.cartodb_id",
+          map_key: 1234
+        };
+        var sqlapi;
+        Step(
+          function sendRequest(err) {
+            assert.response(server, {
+                headers: {host: 'localhost'},
+                url: '/tiles/gadm4/6/31/24.png?' + querystring.stringify(qo),
+                method: 'GET'
+            },{}, this);
+          },
+          function checkResponse(res) {
+            assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+            var ct = res.headers['content-type'];
+            assert.equal(ct, 'image/png');
+            // does NOT send an x-cache-channel
+            assert.ok(!res.headers.hasOwnProperty('x-cache-channel'));
+            // attempts to tell varnish NOT to cache
+            assert.equal(res.headers['cache-control'], 'no-cache,no-store,max-age=0,must-revalidate');
+            assert.equal(res.headers['pragma'], 'no-cache');
+            done();
+          }
+        );
+    });
+
     /////////////////////////////////////////////////////////////////////////////////
     //
     // DELETE CACHE 
@@ -1040,7 +1118,7 @@ suite('server', function() {
         // 'map_style|null|publicuser|my_table',
         redis_client.keys("map_style|*", function(err, matches) {
             _.each(matches, function(k) { redis_client.del(k); });
-            done();
+            sqlapi_server.close(done);
         });
     });
     

test/support/sql/gadm4.sql

@@ -97,8 +97,6 @@ ALTER TABLE ONLY gadm4
 
 CREATE INDEX bdll25_provincias_4326_2_the_geom_webmercator_idx ON gadm4 USING gist (the_geom_webmercator);
 
--- development_cartodb_user_3 role
+GRANT ALL ON TABLE gadm4 TO test_cartodb_user_1;
-CREATE USER development_cartodb_user_3;
-GRANT ALL ON TABLE gadm4 TO development_cartodb_user_3;
 GRANT SELECT ON TABLE gadm4 TO publicuser;