first commit

batch/job_canceller.js

@@ -0,0 +1,78 @@
+'use strict';
+
+var PSQL = require('cartodb-psql');
+
+function JobCanceller() {
+}
+
+module.exports = JobCanceller;
+
+JobCanceller.prototype.cancel = function (job, callback) {
+
+    const dbConfiguration = {
+        host: job.data.host,
+        port: job.data.port,
+        dbname: job.data.dbname,
+        user: job.data.dbuser,
+        pass: job.data.pass,
+    };
+
+    doCancel(job.data.job_id, dbConfiguration, callback);
+};
+
+function doCancel(job_id, dbConfiguration, callback) {
+    var pg = new PSQL(dbConfiguration);
+
+    getQueryPID(pg, job_id, function (err, pid) {
+        if (err) {
+            return callback(err);
+        }
+
+        if (!pid) {
+            return callback();
+        }
+
+        doCancelQuery(pg, pid, function (err, isCancelled) {
+            if (err) {
+                return callback(err);
+            }
+
+            if (!isCancelled) {
+                return callback(new Error('Query has not been cancelled'));
+            }
+
+            callback();
+        });
+    });
+}
+
+function getQueryPID(pg, job_id, callback) {
+    var getPIDQuery = "SELECT pid FROM pg_stat_activity WHERE query LIKE '/* " + job_id + " */%'";
+
+    pg.query(getPIDQuery, function(err, result) {
+        if (err) {
+            return callback(err);
+        }
+
+        if (!result.rows[0] || !result.rows[0].pid) {
+            // query is not running actually, but we have to callback w/o error to cancel the job anyway.
+            return callback();
+        }
+
+        callback(null, result.rows[0].pid);
+    });
+}
+
+function doCancelQuery(pg, pid, callback) {
+    var cancelQuery = 'SELECT pg_cancel_backend(' + pid + ')';
+
+    pg.query(cancelQuery, function (err, result) {
+        if (err) {
+            return callback(err);
+        }
+
+        var isCancelled = result.rows[0].pg_cancel_backend;
+
+        callback(null, isCancelled);
+    });
+}