create metrics only if not already existing

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

plugins/catalog-backend/src/next/DefaultCatalogProcessingEngine.ts

@@ -25,6 +25,7 @@ import stableStringify from 'fast-json-stable-stringify';
 import { DateTime } from 'luxon';
 import { Logger } from 'winston';
 import { ProcessingDatabase, RefreshStateItem } from './database/types';
+import { createCounterMetric, createSummaryMetric } from './metrics';
 import { CatalogProcessingOrchestrator } from './processing/types';
 import { Stitcher } from './stitching/Stitcher';
 import { startTaskPipeline } from './TaskPipeline';
@@ -34,7 +35,6 @@ import {
   EntityProviderConnection,
   EntityProviderMutation,
 } from './types';
-import { Counter, Summary } from 'prom-client';
 
 class Connection implements EntityProviderConnection {
   readonly validateEntityEnvelope = entityEnvelopeSchemaValidator();
@@ -87,15 +87,15 @@ class Connection implements EntityProviderConnection {
 export class DefaultCatalogProcessingEngine implements CatalogProcessingEngine {
   private stopFunc?: () => void;
   private readonly metrics = {
-    processedEntities: new Counter({
+    processedEntities: createCounterMetric({
       name: 'catalog_processed_entities_count',
       help: 'Amount of entities processed',
     }),
-    processingDuration: new Summary({
+    processingDuration: createSummaryMetric({
       name: 'catalog_processing_duration_seconds',
       help: 'Processing duration',
     }),
-    processingQueueDelay: new Summary({
+    processingQueueDelay: createSummaryMetric({
       name: 'catalog_processing_queue_delay_seconds',
       help: 'The amount of delay between being scheduled for processing, and the start of actually being processed',
     }),

plugins/catalog-backend/src/next/database/DefaultProcessingDatabase.ts

@@ -480,12 +480,10 @@ export class DefaultProcessingDatabase implements ProcessingDatabase {
         next_update_at:
           tx.client.config.client === 'sqlite3'
             ? tx.raw(`datetime('now', ?)`, [
-                `${this.options.refreshIntervalSeconds} seconds`,
+                `${this.options.refreshInterval()} seconds`,
               ])
             : tx.raw(
-                `now() + interval '${Number(
-                  this.options.refreshIntervalSeconds,
-                )} seconds'`,
+                `now() + interval '${this.options.refreshInterval()} seconds'`,
               ),
       });
 

plugins/catalog-backend/src/next/database/metrics.ts

@@ -15,14 +15,14 @@
  */
 
 import { Knex } from 'knex';
-import { Gauge } from 'prom-client';
 import { DbLocationsRow } from '../../database/types';
+import { createGaugeMetric } from '../metrics';
 import { DbRefreshStateRow, DbRelationsRow } from './tables';
 
 export function initDatabaseMetrics(knex: Knex) {
   const seen = new Set<string>();
   return {
-    entities_count: new Gauge({
+    entities_count: createGaugeMetric({
       name: 'catalog_entities_count',
       help: 'Total amount of entities in the catalog',
       labelNames: ['kind'],
@@ -48,7 +48,7 @@ export function initDatabaseMetrics(knex: Knex) {
         });
       },
     }),
-    registered_locations: new Gauge({
+    registered_locations: createGaugeMetric({
       name: 'catalog_registered_locations_count',
       help: 'Total amount of registered locations in the catalog',
       async collect() {
@@ -56,7 +56,7 @@ export function initDatabaseMetrics(knex: Knex) {
         this.set(total[0]['count(*)'] as number);
       },
     }),
-    relations: new Gauge({
+    relations: createGaugeMetric({
       name: 'catalog_relations_count',
       help: 'Total amount of relations between entities',
       async collect() {

plugins/catalog-backend/src/next/metrics.ts

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  Counter,
+  CounterConfiguration,
+  Gauge,
+  GaugeConfiguration,
+  Histogram,
+  HistogramConfiguration,
+  register,
+  Summary,
+  SummaryConfiguration,
+} from 'prom-client';
+
+export function createCounterMetric<T extends string>(
+  config: CounterConfiguration<T>,
+): Counter<T> {
+  const existing = register.getSingleMetric(config.name) as Counter<T>;
+  return existing || new Counter<T>(config);
+}
+
+export function createGaugeMetric<T extends string>(
+  config: GaugeConfiguration<T>,
+): Gauge<T> {
+  const existing = register.getSingleMetric(config.name) as Gauge<T>;
+  return existing || new Gauge<T>(config);
+}
+
+export function createSummaryMetric<T extends string>(
+  config: SummaryConfiguration<T>,
+): Summary<T> {
+  const existing = register.getSingleMetric(config.name) as Summary<T>;
+  return existing || new Summary<T>(config);
+}
+
+export function createHistogramMetric<T extends string>(
+  config: HistogramConfiguration<T>,
+): Histogram<T> {
+  const existing = register.getSingleMetric(config.name) as Histogram<T>;
+  return existing || new Histogram<T>(config);
+}