feat: option to enable a graceful shutdown via cli

Closes: 1223
Signed-off-by: Travis Payne <travis.payne@accenture.com>

packages/cactus-cmd-api-server/README.md

@@ -15,6 +15,7 @@
 - [Prometheus Exporter](#prometheus-exporter)
   - [Usage Prometheus](#usage-prometheus)
   - [Prometheus Integration](#prometheus-integration)
+  - [Shutdown Hook](#shutdown-hook)
   - [Helper code](#helper-code)
         - [response.type.ts](#responsetypets)
         - [data-fetcher.ts](#data-fetcherts)
@@ -384,6 +385,18 @@ Here the `host:port` is where the prometheus exporter metrics are exposed. The t
 Once edited, you can start the prometheus service by referencing the above edited prometheus.yml file.
 On the prometheus graphical interface (defaulted to http://localhost:9090), choose **Graph** from the menu bar, then select the **Console** tab. From the **Insert metric at cursor** drop down, select **cactus_api_server_total_plugin_imports** and click **execute**
 
+### Shutdown Hook
+
+The API config contains a flag:
+```json
+    {
+      "enableShutdownHook": true
+    }
+```
+This allows for graceful shutdown of the API server after a SIGINT via cli CTRL + C. This hook can be disabled by passing in false either via the TypeScript constructor or the JSON config file.
+
+
+
 ### Helper code
 
 ###### response.type.ts

packages/cactus-cmd-api-server/package.json

@@ -85,6 +85,7 @@
     "convict": "6.0.0",
     "convict-format-with-validator": "6.2.0",
     "cors": "2.8.5",
+    "async-exit-hook": "2.0.1",
     "express": "4.17.1",
     "express-http-proxy": "1.6.2",
     "express-jwt": "6.0.0",

packages/cactus-cmd-api-server/src/main/typescript/api-server.ts

@@ -1,5 +1,6 @@
 import type { AddressInfo } from "net";
 import type { Server as SecureServer } from "https";
+import exitHook from "async-exit-hook";
 import os from "os";
 import path from "path";
 import tls from "tls";
@@ -37,7 +38,12 @@ import {
 import { PluginRegistry } from "@hyperledger/cactus-core";
 import { installOpenapiValidationMiddleware } from "@hyperledger/cactus-core";
 
-import { Logger, LoggerProvider, Servers } from "@hyperledger/cactus-common";
+import {
+  Bools,
+  Logger,
+  LoggerProvider,
+  Servers,
+} from "@hyperledger/cactus-common";
 
 import { ICactusApiServerOptions } from "./config/config-service";
 import OAS from "../json/openapi.json";
@@ -61,6 +67,7 @@ export interface IApiServerConstructorOptions {
   readonly httpServerCockpit?: Server | SecureServer;
   readonly config: ICactusApiServerOptions;
   readonly prometheusExporter?: PrometheusExporter;
+  readonly enableShutdownHook?: boolean;
 }
 
 export class ApiServer {
@@ -85,6 +92,8 @@ export class ApiServer {
   private readonly expressApi: Application;
   private readonly expressCockpit: Application;
   private readonly pluginsPath: string;
+  private readonly enableShutdownHook: boolean;
+
   public prometheusExporter: PrometheusExporter;
 
   public get className(): string {
@@ -99,6 +108,14 @@ export class ApiServer {
       throw new Error(`ApiServer#ctor options.config was falsy`);
     }
 
+    this.enableShutdownHook = Bools.isBooleanStrict(options.enableShutdownHook)
+      ? (options.enableShutdownHook as boolean)
+      : true;
+
+    if (this.enableShutdownHook) {
+      exitHook(() => this.shutdown());
+    }
+
     LoggerProvider.setLogLevel(options.config.logLevel);
 
     if (this.options.httpServerApi) {

packages/cactus-cmd-api-server/src/main/typescript/config/config-service.ts

@@ -58,6 +58,7 @@ export interface ICactusApiServerOptions {
   keyPairPem: string;
   keychainSuffixKeyPairPem: string;
   minNodeVersion: string;
+  enableShutdownHook: boolean;
 }
 
 export class ConfigService {
@@ -396,6 +397,16 @@ export class ConfigService {
         format: "*",
         default: "CACTUS_NODE_KEY_PAIR_PEM",
       },
+      enableShutdownHook: {
+        doc:
+          "It will cause the API server to listen to OS process signals and will attempt " +
+          "to gracefully shut itself down in response to these when the flag is enabled " +
+          "(which is the default behavior). You will want to turn this off if you are embedding " +
+          "the API server in your own application and would like to stop the API server from " +
+          "meddling in the OS process signal handling when you take care of it yourself in your own code.",
+        format: Boolean,
+        default: true,
+      },
     };
   }
 
@@ -465,6 +476,7 @@ export class ConfigService {
     const apiBaseUrl = `${apiProtocol}//${apiHost}:${apiPort}`;
     const grpcPort = (schema.grpcPort as SchemaObj).default;
     const grpcMtlsEnabled = (schema.grpcMtlsEnabled as SchemaObj).default;
+    const enableShutdownHook = (schema.enableShutdownHook as SchemaObj).default;
 
     const keyPair = JWK.generateSync("EC", "secp256k1", { use: "sig" }, true);
     const keyPairPem = keyPair.toPEM(true);
@@ -580,6 +592,7 @@ export class ConfigService {
       keychainSuffixKeyPairPem: (schema.keychainSuffixKeyPairPem as SchemaObj)
         .default,
       plugins,
+      enableShutdownHook,
     };
   }