Set X-Cache-Channel to NONE when the SQL may write to the database

Note that "may write" allows for false positive, so there could be
less cache hits than possibly allowable. If this will be a problem
for any real use case we could still improve the regular expression
used to detect "writing" queries.

Automated tests are added to check for the X-Cache-Channel header
with both writing and read-only queries performed by authenticated
requests.

Closes #27
Closes #43

app/controllers/app.js

@@ -38,6 +38,21 @@ app.all('/api/v1/sql',     function(req, res) { handleQuery(req, res) } );
 app.all('/api/v1/sql.:f',  function(req, res) { handleQuery(req, res) } );
 app.get('/api/v1/cachestatus',  function(req, res) { handleCacheStatus(req, res) } );
 
+// Return true of the given query may write to the database
+//
+// NOTE: this is a fuzzy check, the return could be true even
+//       if the query doesn't really write anything.
+//       But you can be pretty sure of a false return.
+//
+function queryMayWrite(sql) {
+  var mayWrite = false;  
+  var pattern = RegExp("(insert|update|delete|create|drop)", "i");
+  if ( pattern.test(sql) ) {
+    mayWrite = true;
+  }
+  return mayWrite;
+}
+
 // request handlers
 function handleQuery(req, res) {
 
@@ -81,6 +96,8 @@ function handleQuery(req, res) {
         // placeholder for connection
         var pg;
 
+        var authenticated;
+
         // 1. Get database from redis via the username stored in the host header subdomain
         // 2. Run the request through OAuth to get R/W user id if signed
         // 3. Get the list of tables affected by the query
@@ -119,11 +136,13 @@ function handleQuery(req, res) {
                 // store postgres connection
                 pg = new PSQL(user_id, database, limit, offset);
 
+                authenticated = ! _.isNull(user_id);
+
                 // get all the tables from Cache or SQL
                 if (!_.isNull(tableCache[sql_md5]) && !_.isUndefined(tableCache[sql_md5])){
                    tableCache[sql_md5].hits++;
                    return true;
-                } else{
+                } else {
                    pg.query("SELECT CDB_QueryTables($quotesql$" + sql + "$quotesql$)", this);
                 }
             },
@@ -133,6 +152,7 @@ function handleQuery(req, res) {
                 // store explain result in local Cache
                 if (_.isUndefined(tableCache[sql_md5])){
                     tableCache[sql_md5] = result;
+                    tableCache[sql_md5].may_write = queryMayWrite(sql);
                     tableCache[sql_md5].hits = 1; //initialise hit counter
                 }
 
@@ -176,8 +196,8 @@ function handleQuery(req, res) {
 
                 // set cache headers
                 res.header('Last-Modified', new Date().toUTCString());
-                res.header('Cache-Control', 'no-cache,max-age=3600,must-revalidate, public');
+                res.header('Cache-Control', 'no-cache,max-age=3600,must-revalidate,public');
-                res.header('X-Cache-Channel', generateCacheKey(database, tableCache[sql_md5]));
+                res.header('X-Cache-Channel', generateCacheKey(database, tableCache[sql_md5], authenticated));
 
                 return result;
             },
@@ -392,8 +412,12 @@ function setCrossDomain(res){
     res.header("Access-Control-Allow-Headers", "X-Requested-With");
 }
 
-function generateCacheKey(database,tables){
+function generateCacheKey(database,tables,is_authenticated){
+    if ( is_authenticated && tables.may_write ) {
+      return "NONE";
+    } else {
       return database + ":" + tables.rows[0].cdb_querytables.split(/^\{(.*)\}$/)[1];   
+    }
 }
 
 function generateMD5(data){

test/acceptance/app.test.js

@@ -24,7 +24,7 @@ app.setMaxListeners(0);
 
 suite('app.test', function() {
 
-var real_oauth_header = 'OAuth realm="http://vizzuality.testhost.lan/",oauth_consumer_key="fZeNGv5iYayvItgDYHUbot1Ukb5rVyX6QAg8GaY2",oauth_token="l0lPbtP68ao8NfStCiA3V3neqfM03JKhToxhUQTR",oauth_signature_method="HMAC-SHA1", oauth_signature="o4hx4hWP6KtLyFwggnYB4yPK8xI%3D",oauth_timestamp="1313581372",oauth_nonce="W0zUmvyC4eVL8cBd4YwlH1nnPTbxW0QBYcWkXTwe4",oauth_version="1.0"';
+var expected_cache_control = 'no-cache,max-age=3600,must-revalidate,public';
 
 // use dec_sep for internationalization
 var checkDecimals = function(x, dec_sep){
@@ -54,11 +54,14 @@ test('GET /api/v1/sql with SQL parameter on SELECT only. No oAuth included ', fu
         method: 'GET'
     },{ }, function(res) {
         assert.equal(res.statusCode, 200, res.body);
+        // Check cache headers
+        // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+        assert.equal(res.headers['x-cache-channel'], 'cartodb_test_user_1_db:untitle_table_4');
+        assert.equal(res.headers['cache-control'], expected_cache_control);
         done();
     });
 });
 
-
 test('GET /api/v1/sql with SQL parameter on SELECT only. no database param, just id using headers', function(done){
     assert.response(app, {
         url: '/api/v1/sql?q=SELECT%20*%20FROM%20untitle_table_4',
@@ -70,6 +73,22 @@ test('GET /api/v1/sql with SQL parameter on SELECT only. no database param, just
     });
 });
 
+test('GET /api/v1/sql with SQL parameter on SELECT only. no database param, just id using headers. Authenticated.',
+function(done){
+    assert.response(app, {
+        url: '/api/v1/sql?q=SELECT%20cartodb_id*2%20FROM%20untitle_table_4&api_key=1234',
+        headers: {host: 'vizzuality.cartodb.com'},
+        method: 'GET'
+    },{ }, function(res) {
+        assert.equal(res.statusCode, 200, res.body);
+        // Check cache headers
+        // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+        assert.equal(res.headers['x-cache-channel'], 'cartodb_test_user_1_db:untitle_table_4');
+        assert.equal(res.headers['cache-control'], expected_cache_control);
+        done();
+    });
+});
+
 
 test('POST /api/v1/sql with SQL parameter on SELECT only. no database param, just id using headers', function(done){
     assert.response(app, {
@@ -129,6 +148,10 @@ test('INSERT returns affected rows', function(done){
         assert.ok(out.hasOwnProperty('time'));
         assert.equal(out.total_rows, 2);
         assert.equal(out.rows.length, 0);
+        // Check cache headers
+        // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+        assert.equal(res.headers['x-cache-channel'], 'NONE');
+        assert.equal(res.headers['cache-control'], expected_cache_control);
         done();
     });
 });
@@ -151,6 +174,10 @@ test('UPDATE returns affected rows', function(done){
         assert.ok(out.hasOwnProperty('time'));
         assert.equal(out.total_rows, 2);
         assert.equal(out.rows.length, 0);
+        // Check cache headers
+        // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+        assert.equal(res.headers['x-cache-channel'], 'NONE');
+        assert.equal(res.headers['cache-control'], expected_cache_control);
         done();
     });
 });
@@ -173,6 +200,10 @@ test('DELETE returns affected rows', function(done){
         assert.ok(out.hasOwnProperty('time'));
         assert.equal(out.total_rows, 2);
         assert.equal(out.rows.length, 0);
+        // Check cache headers
+        // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+        assert.equal(res.headers['x-cache-channel'], 'NONE');
+        assert.equal(res.headers['cache-control'], expected_cache_control);
         done();
     });
 });
@@ -261,6 +292,97 @@ test('GET /api/v1/sql with SQL parameter on DROP DATABASE only.header based db -
     });
 });
 
+test('CREATE TABLE with GET and auth', function(done){
+    assert.response(app, {
+        url: "/api/v1/sql?" + querystring.stringify({
+          q: 'CREATE TABLE create_table_test(a int)',
+          api_key: 1234
+        }),
+        headers: {host: 'vizzuality.cartodb.com'},
+        method: 'GET'
+    },{}, function(res) {
+      assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+      // Check cache headers
+      // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+      assert.equal(res.headers['x-cache-channel'], 'NONE');
+      assert.equal(res.headers['cache-control'], expected_cache_control);
+      done();
+    });
+});
+
+// TODO: test COPY
+//test('COPY TABLE with GET and auth', function(done){
+//    assert.response(app, {
+//        url: "/api/v1/sql?" + querystring.stringify({
+//          q: 'COPY TABLE create_table_test FROM stdin; 1\n\\.\n',
+//          api_key: 1234
+//        }),
+//        headers: {host: 'vizzuality.cartodb.com'},
+//        method: 'GET'
+//    },{}, function(res) {
+//      assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+//      // Check cache headers
+//      // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+//      assert.equal(res.headers['x-cache-channel'], 'NONE');
+//      assert.equal(res.headers['cache-control'], expected_cache_control);
+//      done();
+//    });
+//});
+
+test('DROP TABLE with GET and auth', function(done){
+    assert.response(app, {
+        url: "/api/v1/sql?" + querystring.stringify({
+          q: 'DROP TABLE create_table_test',
+          api_key: 1234
+        }),
+        headers: {host: 'vizzuality.cartodb.com'},
+        method: 'GET'
+    },{}, function(res) {
+      assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+      // Check cache headers
+      // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+      assert.equal(res.headers['x-cache-channel'], 'NONE');
+      assert.equal(res.headers['cache-control'], expected_cache_control);
+      done();
+    });
+});
+
+test('CREATE FUNCTION with GET and auth', function(done){
+    assert.response(app, {
+        url: "/api/v1/sql?" + querystring.stringify({
+          q: 'CREATE FUNCTION create_func_test(a int) RETURNS INT AS \'SELECT 1\' LANGUAGE \'sql\'',
+          api_key: 1234
+        }),
+        headers: {host: 'vizzuality.cartodb.com'},
+        method: 'GET'
+    },{}, function(res) {
+      assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+      // Check cache headers
+      // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+      assert.equal(res.headers['x-cache-channel'], 'NONE');
+      assert.equal(res.headers['cache-control'], expected_cache_control);
+      done();
+    });
+});
+
+test('DROP FUNCTION with GET and auth', function(done){
+    assert.response(app, {
+        url: "/api/v1/sql?" + querystring.stringify({
+          q: 'DROP FUNCTION create_func_test(a int)',
+          api_key: 1234
+        }),
+        headers: {host: 'vizzuality.cartodb.com'},
+        method: 'GET'
+    },{}, function(res) {
+      assert.equal(res.statusCode, 200, res.statusCode + ': ' + res.body);
+      // Check cache headers
+      // See https://github.com/Vizzuality/CartoDB-SQL-API/issues/43
+      assert.equal(res.headers['x-cache-channel'], 'NONE');
+      assert.equal(res.headers['cache-control'], expected_cache_control);
+      done();
+    });
+});
+
 test('GET /api/v1/sql with SQL parameter and geojson format, ensuring content-disposition set to geojson', function(done){
     assert.response(app, {
         url: '/api/v1/sql?q=SELECT%20*%20FROM%20untitle_table_4&format=geojson',