From f17987ac5554f035ab818508ae9ddb7b3f84d07c Mon Sep 17 00:00:00 2001
From: Konstantin Tsabolov <konstantin.tsabolov@spherity.com>
Date: Thu, 14 Dec 2023 15:18:05 +0100
Subject: [PATCH] feat(shared): add shared health module

---
 apps/shared/src/modules/health/constants.ts   |  1 +
 .../src/modules/health/health.controller.ts   | 20 ++++++++++++
 .../health/health.module-definition.ts        | 14 +++++++++
 .../src/modules/health/health.module.ts       | 14 +++++++++
 .../modules/health/indicators/nats.health.ts  | 31 +++++++++++++++++++
 5 files changed, 80 insertions(+)
 create mode 100644 apps/shared/src/modules/health/constants.ts
 create mode 100644 apps/shared/src/modules/health/health.controller.ts
 create mode 100644 apps/shared/src/modules/health/health.module-definition.ts
 create mode 100644 apps/shared/src/modules/health/health.module.ts
 create mode 100644 apps/shared/src/modules/health/indicators/nats.health.ts

diff --git a/apps/shared/src/modules/health/constants.ts b/apps/shared/src/modules/health/constants.ts
new file mode 100644
index 0000000..1978198
--- /dev/null
+++ b/apps/shared/src/modules/health/constants.ts
@@ -0,0 +1 @@
+export const NATS = 'NATS';
diff --git a/apps/shared/src/modules/health/health.controller.ts b/apps/shared/src/modules/health/health.controller.ts
new file mode 100644
index 0000000..fb6e94b
--- /dev/null
+++ b/apps/shared/src/modules/health/health.controller.ts
@@ -0,0 +1,20 @@
+import { Controller, Get, VERSION_NEUTRAL } from '@nestjs/common';
+import { ApiTags } from '@nestjs/swagger';
+import { HealthCheck, HealthCheckService } from '@nestjs/terminus';
+
+import { NATSHealthIndicator } from './indicators/nats.health.js';
+
+@Controller({ version: VERSION_NEUTRAL })
+@ApiTags('Health')
+export class HealthController {
+  public constructor(
+    private readonly natsHealthIndicator: NATSHealthIndicator,
+    private readonly health: HealthCheckService,
+  ) {}
+
+  @Get()
+  @HealthCheck()
+  public check() {
+    return this.health.check([() => this.natsHealthIndicator.isHealthy()]);
+  }
+}
diff --git a/apps/shared/src/modules/health/health.module-definition.ts b/apps/shared/src/modules/health/health.module-definition.ts
new file mode 100644
index 0000000..d548701
--- /dev/null
+++ b/apps/shared/src/modules/health/health.module-definition.ts
@@ -0,0 +1,14 @@
+import { ConfigurableModuleBuilder } from '@nestjs/common';
+
+export interface HealthModuleOptions {
+  nats?: {
+    monitoringUrl: string;
+  };
+}
+
+export const {
+  ConfigurableModuleClass,
+  MODULE_OPTIONS_TOKEN,
+  OPTIONS_TYPE,
+  ASYNC_OPTIONS_TYPE,
+} = new ConfigurableModuleBuilder<HealthModuleOptions>().build();
diff --git a/apps/shared/src/modules/health/health.module.ts b/apps/shared/src/modules/health/health.module.ts
new file mode 100644
index 0000000..c977650
--- /dev/null
+++ b/apps/shared/src/modules/health/health.module.ts
@@ -0,0 +1,14 @@
+import { HttpModule } from '@nestjs/axios';
+import { Module } from '@nestjs/common';
+import { TerminusModule } from '@nestjs/terminus';
+
+import { HealthController } from './health.controller.js';
+import { ConfigurableModuleClass } from './health.module-definition.js';
+import { NATSHealthIndicator } from './indicators/nats.health.js';
+
+@Module({
+  imports: [HttpModule, TerminusModule],
+  controllers: [HealthController],
+  providers: [NATSHealthIndicator],
+})
+export class HealthModule extends ConfigurableModuleClass {}
diff --git a/apps/shared/src/modules/health/indicators/nats.health.ts b/apps/shared/src/modules/health/indicators/nats.health.ts
new file mode 100644
index 0000000..b011cd8
--- /dev/null
+++ b/apps/shared/src/modules/health/indicators/nats.health.ts
@@ -0,0 +1,31 @@
+import type { HealthIndicatorResult } from '@nestjs/terminus';
+
+import { Inject, Injectable } from '@nestjs/common';
+import { HealthIndicator, HttpHealthIndicator } from '@nestjs/terminus';
+
+import { NATS } from '../constants.js';
+import {
+  HealthModuleOptions,
+  MODULE_OPTIONS_TOKEN,
+} from '../health.module-definition.js';
+
+@Injectable()
+export class NATSHealthIndicator extends HealthIndicator {
+  public constructor(
+    @Inject(MODULE_OPTIONS_TOKEN)
+    private readonly moduleOptions: HealthModuleOptions,
+    private readonly http: HttpHealthIndicator,
+  ) {
+    super();
+  }
+
+  public async isHealthy(): Promise<HealthIndicatorResult> {
+    if (this.moduleOptions.nats?.monitoringUrl) {
+      return this.http.pingCheck(NATS, this.moduleOptions.nats.monitoringUrl);
+    }
+
+    return this.getStatus(NATS, true, {
+      message: 'NATS server monitoring URL is not provided. Skipping check.',
+    });
+  }
+}
-- 
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