Track locking metrics

src/database-backends/index.js

@@ -33,7 +33,7 @@ const isTaskObject = require("../validators/is-task-object");
 // FIXME: Verify that all internal method calls in the PostgreSQL backend are still valid after moving argument validation/normalization into this module
 
 module.exports = function (state) {
-	let { tasks } = state;
+	let { tasks, metrics } = state;
 
 	const backendModules = {
 		"postgresql": require("./postgresql")(state),
@@ -370,7 +370,15 @@ module.exports = function (state) {
 								}]
 							});
 		
-							return backend.lock(tx, options);
+							return Promise.try(() => {
+								return backend.lock(tx, options);
+							}).tap((succeeded) => {
+								if (succeeded) {
+									metrics.successfulLocks.labels({ task: task.name }).inc(1);
+								} else {
+									metrics.failedLocks.labels({ task: task.name }).inc(1);
+								}
+							});
 						},
 		
 						unlock: function (_tx, _options) {

src/prometheus/index.js

@@ -27,6 +27,18 @@ module.exports = function createPrometheus() {
 				help: "Amount of items that have failed during processing",
 				labelNames: [ "task" ]
 			}),
+			successfulLocks: new prometheusClient.Counter({
+				registers: [ prometheusRegistry ],
+				name: "srap_successful_locks_total",
+				help: "Amount of queue item lock attempts that were successful",
+				labelNames: [ "task" ]
+			}),
+			failedLocks: new prometheusClient.Counter({
+				registers: [ prometheusRegistry ],
+				name: "srap_failed_locks_total",
+				help: "Amount of queue item lock attempts that failed",
+				labelNames: [ "task" ]
+			}),
 			taskFetchTime: new prometheusClient.Gauge({
 				registers: [ prometheusRegistry ],
 				name: "srap_task_fetch_seconds",