feat: Add PromService and some decorators

Add PromService to be able to create metric on the fly
Add new decorators to auto generate metric for class instance and method
call

lib/common/prom.decorators.ts

@@ -1,10 +1,46 @@
 import { Inject } from '@nestjs/common';
-import { getMetricToken } from './prom.utils';
+import { getMetricToken, findOrCreateCounter } from './prom.utils';
+import * as client from 'prom-client';
 
 export const InjectCounterMetric = (name: string) => Inject(getMetricToken(`Counter`, name));
 export const InjectGaugeMetric = (name: string) => Inject(getMetricToken(`Gauge`, name));
 export const InjectHistogramMetric = (name: string) => Inject(getMetricToken(`Histogram`, name));
 export const InjectSummaryMetric = (name: string) => Inject(getMetricToken(`Summary`, name));
 
-// export const InjectRegistry = (name?: string) =>
-//   Inject(name ? getRegistryName(name) : '');
+/**
+ * Create and increment a counter when the method is called
+ * 
+ * @param param0 
+ */
+export const PromMethodCounter = () => {
+    return (target: Object, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<Function>) => {
+        const className = target.constructor.name;
+        const counterMetric = findOrCreateCounter({
+            name: `${className}_${propertyKey.toString()}_method_counter`,
+            help: `${className}#${propertyKey.toString()} called counter`,
+        });
+        const methodFunc = descriptor.value;
+        descriptor.value = function (...args) {
+            counterMetric.inc(1);
+            return methodFunc.apply(this, args);
+        }
+    };
+}
+
+/**
+ * Create and increment a counter when a new instance is created
+ * 
+ * @param ctor 
+ */
+export const PromInstanceCounter = <T extends { new(...args: any[]): {} }>(ctor: T) => {
+    const counterMetric = findOrCreateCounter({
+        name: `${ctor.name}_instance_counter`,
+        help: `${ctor.name} object instances counter`,
+    });
+    return class extends ctor {
+        constructor(...args) {
+            counterMetric.inc(1);
+            super(...args);
+        }
+    }
+};

lib/common/prom.utils.ts

@@ -1,4 +1,6 @@
 
+import * as client from 'prom-client';
+
 export function getMetricToken(type: string, name: string) {
   return `${name}${type}`;
 }
@@ -10,3 +12,87 @@ export function getRegistryName(name: string) {
 export function getOptionsName(name: string) {
   return `${name}PromOptions`;
 }
+
+export const findOrCreateMetric = ({
+  name,
+  type,
+  help,
+}: {
+  name: string;
+  type: string;
+  help?: string;
+}): client.Metric => {
+
+  let metric: client.Metric = client.register.getSingleMetric(name);
+  if (!metric) {
+    return new client.Counter({
+      name: name,
+      help: help || `${name} ${type}`,
+    });
+  }
+
+  if (metric instanceof client.Counter === false) {
+    return new client.Counter({
+      name: getMetricToken(type, name),
+      help: help || `${name} ${type}`,
+    });
+  }
+
+  return metric;  
+}
+
+export const findOrCreateCounter = ({
+  name,
+  help,
+}: {
+  name: string,
+  help?: string,
+}): client.Counter => {
+  return findOrCreateMetric({
+    name,
+    help,
+    type: `Counter`,
+  }) as client.Counter;
+}
+
+export const findOrCreateGauge = ({
+  name,
+  help,
+}: {
+  name: string,
+  help?: string,
+}): client.Gauge => {
+  return findOrCreateMetric({
+    name,
+    help,
+    type: `Gauge`,
+  }) as client.Gauge;
+}
+
+export const findOrCreateHistogram = ({
+  name,
+  help,
+}: {
+  name: string,
+  help?: string,
+}): client.Histogram => {
+  return findOrCreateMetric({
+    name,
+    help,
+    type: `Histogram`,
+  }) as client.Histogram;
+}
+
+export const findOrCreateSummary = ({
+  name,
+  help,
+}: {
+  name: string,
+  help?: string,
+}): client.Summary => {
+  return findOrCreateMetric({
+    name,
+    help,
+    type: `Summary`,
+  }) as client.Summary;
+}

lib/prom.constants.ts

@@ -2,3 +2,5 @@
 export const DEFAULT_PROM_REGISTRY = 'PromRegistry';
 export const DEFAULT_PROM_OPTIONS = 'PromOptions';
 export const PROM_REGISTRY_NAME = 'PromRegistryName';
+
+export const PROM_COUNTER_METRIC_AUTO_INC = 'PROM_COUNTER_METRIC_AUTO_INC';

lib/prom.module.ts

@@ -6,6 +6,7 @@ import * as client from 'prom-client';
 import { PromController } from './prom.controller';
 import { InboundMiddleware } from './middleware/inbound.middleware';
 import { DEFAULT_PROM_OPTIONS } from './prom.constants';
+import { PromService } from './prom.service';
 
 @Module({})
 export class PromModule {
@@ -24,8 +25,12 @@ export class PromModule {
       module: PromModule,
       imports: [PromCoreModule.forRoot(options)],
       controllers: [],
-      exports: [],
-      providers: [],
+      exports: [
+        PromService,
+      ],
+      providers: [
+        PromService,
+      ],
     };
 
     // default push default controller

lib/prom.service.ts

@@ -0,0 +1,21 @@
+import { Injectable } from '@nestjs/common';
+import { findOrCreateCounter, findOrCreateGauge, findOrCreateHistogram } from './common/prom.utils';
+
+@Injectable()
+export class PromService {
+  getCounterMetric(name: string) {
+    return findOrCreateCounter({ name });
+  }
+
+  getGaugeMetric(name: string) {
+    return findOrCreateGauge({ name });
+  }
+
+  getHistogramMetric(name: string) {
+    return findOrCreateHistogram({ name });
+  }
+
+  getSummaryMetric(name: string) {
+    return findOrCreateHistogram({ name });
+  }
+}

tsconfig.json

@@ -20,4 +20,4 @@
     "node_modules",
     "**/*.spec.ts"
   ]
-}
+}