Extend status API with health checks for connected services (#314)

Signed-off-by: Marvin A. Ruder <[email protected]>

packages/backend/src/controllers/StatusController.live.test.ts

@@ -6,10 +6,10 @@ export const suiteName = "Status API";
 export const tests: LiveTestSuite = [];
 
 tests.push({
-  testName: "returns status “operational”",
+  testName: "returns status “healthy”",
   testFunction: async () => {
     const res = await supertest.get(`/api${statusEndpointPath}`);
     expect(res.status).toBe(200);
-    expect(res.body.status).toBe("operational");
+    expect(res.body.status).toBe("healthy");
   },
 });

packages/backend/src/controllers/StatusController.ts

@@ -1,6 +1,10 @@
 import { Request, Response } from "express";
 import { statusEndpointPath } from "@rating-tracker/commons";
 import Router from "../utils/router.js";
+import { redisIsReady } from "../redis/redis.js";
+import { prismaIsReady } from "../db/client.js";
+import { seleniumIsReady } from "../utils/webdriver.js";
+import { signalIsReadyOrUnused } from "../signal/signalBase.js";
 
 /**
  * This class is responsible for providing a trivial status response whenever the backend API is up and running.
@@ -18,6 +22,8 @@ export class StatusController {
     accessRights: 0,
   })
   get(_: Request, res: Response) {
-    res.status(200).json({ status: "operational" }).end();
+    Promise.all([redisIsReady(), prismaIsReady(), seleniumIsReady(), signalIsReadyOrUnused()])
+      .then(() => res.status(200).json({ status: "healthy" }).end())
+      .catch((e) => res.status(500).json({ status: "unhealthy", details: e.message }).end());
   }
 }

packages/backend/src/db/client.ts

@@ -5,4 +5,15 @@ import { PrismaClient } from "../../prisma/client";
  */
 const client = new PrismaClient();
 
+/**
+ * Checks if the database is reachable.
+ *
+ * @returns {Promise<void>} A promise that resolves when the database is reachable, or rejects with an error if it is
+ * not.
+ */
+export const prismaIsReady = (): Promise<void> =>
+  client.$executeRaw`SELECT null`
+    .then(() => Promise.resolve())
+    .catch((e) => Promise.reject(new Error("Database is not reachable: " + e.message)));
+
 export default client;

packages/backend/src/openapi/components.ts

@@ -387,5 +387,17 @@ export const components: OpenAPIV3.ComponentsObject = {
       },
       required: ["message"],
     },
+    Status: {
+      type: "object",
+      properties: {
+        status: {
+          type: "string",
+        },
+        details: {
+          type: "string",
+        },
+      },
+      required: ["status"],
+    },
   },
 };

packages/backend/src/openapi/paths/statusEndpoint.ts

@@ -1,16 +1,21 @@
 import { OpenAPIV3 } from "express-openapi-validator/dist/framework/types.js";
-import { okOperational } from "../responses/success.js";
+import { okHealthy } from "../responses/success.js";
+import { internalServerErrorServerUnhealthy } from "../responses/serverError.js";
 
 /**
- * Returns a JSON object with the status “operational” if online.
+ * Returns a JSON object with the status “healthy” if online and able to connect to all services, or “unhealthy”
+ * otherwise.
  */
 const get: OpenAPIV3.OperationObject = {
   tags: ["Status API"],
   operationId: "status",
   summary: "Status API",
-  description: "Returns a JSON object with the status “operational” if online.",
+  description:
+    "Returns a JSON object with the status “healthy” if online and able to connect to all services, or " +
+    "“unhealthy” otherwise.",
   responses: {
-    "200": okOperational,
+    "200": okHealthy,
+    "500": internalServerErrorServerUnhealthy,
   },
 };
 

packages/backend/src/openapi/responses/serverError.ts

@@ -14,6 +14,20 @@ export const internalServerError: OpenAPIV3.ResponseObject = {
   },
 };
 
+/**
+ * A response with a 500 Internal Server Error status code and a Status object body.
+ */
+export const internalServerErrorServerUnhealthy: OpenAPIV3.ResponseObject = {
+  description: "Internal Server Error – Server Unhealthy",
+  content: {
+    "application/json": {
+      schema: {
+        $ref: "#/components/schemas/Status",
+      },
+    },
+  },
+};
+
 /**
  * A response with a 501 Not Implemented status code and an Error object body.
  */

packages/backend/src/openapi/responses/success.ts

@@ -129,20 +129,14 @@ export const okWatchlistSummary: OpenAPIV3.ResponseObject = {
 };
 
 /**
- * A response with a 200 OK status code and an object containing a status string.
+ * A response with a 200 OK status code and a Status object body.
  */
-export const okOperational: OpenAPIV3.ResponseObject = {
+export const okHealthy: OpenAPIV3.ResponseObject = {
   description: "OK",
   content: {
     "application/json": {
       schema: {
-        type: "object",
-        properties: {
-          status: {
-            type: "string",
-          },
-        },
-        required: ["status"],
+        $ref: "#/components/schemas/Status",
       },
     },
   },

packages/backend/src/redis/redis.ts

@@ -22,4 +22,22 @@ redis.on(
 );
 await redis.connect();
 
+/**
+ * Checks if the Redis server is reachable.
+ *
+ * @returns {Promise<void>} A promise that resolves when the Redis server is reachable, or rejects with an error if it
+ * is not.
+ */
+export const redisIsReady = (): Promise<void> =>
+  redis.isReady
+    ? redis
+        .ping()
+        .then((pong) =>
+          pong === "PONG"
+            ? Promise.resolve()
+            : /* c8 ignore next */ Promise.reject(new Error("Redis is not reachable: server responded with " + pong)),
+        )
+    : /* c8 ignore next */ Promise.reject(new Error("Redis is not ready"));
+// The errors only occurs when Redis server is not available, which is difficult to reproduce.
+
 export default redis;

packages/backend/src/signal/__mocks__/signalBase.ts

@@ -1,3 +1,10 @@
+/**
+ * A mock of the signalIsReadyOrUnused function. Always resolves to "No Signal URL provided".
+ *
+ * @returns {Promise<string | void>} A promise that resolves to "No Signal URL provided".
+ */
+export const signalIsReadyOrUnused = (): Promise<string | void> => Promise.resolve("No Signal URL provided");
+
 /**
  * A mock storage of sent Signal messages.
  */

packages/backend/src/signal/signalBase.ts

@@ -1,8 +1,22 @@
 // This file is not tested because tests must not depend on a running Signal Client instance
-import axios from "axios";
+import axios, { AxiosError } from "axios";
 import chalk from "chalk";
 import logger, { PREFIX_SIGNAL } from "../utils/logger.js";
 
+/**
+ * Checks if the Signal Client instance is reachable.
+ *
+ * @returns {Promise<string | void>} A promise that resolves when the Signal Client instance is reachable, or rejects
+ * with an error if it is not.
+ */
+export const signalIsReadyOrUnused = (): Promise<string | void> =>
+  process.env.SIGNAL_URL && process.env.SIGNAL_SENDER
+    ? axios
+        .get(`${process.env.SIGNAL_URL}/v1/health`, { timeout: 1000 })
+        .then((res) => (res.status === 204 ? Promise.resolve() : Promise.reject(new Error("Signal is not ready"))))
+        .catch((e: AxiosError) => Promise.reject(new Error("Signal is not reachable: " + e.message)))
+    : Promise.resolve("No Signal URL provided");
+
 /**
  * Send a message to a list of recipients.
  *

packages/backend/src/utils/__mocks__/webdriver.ts

@@ -0,0 +1,6 @@
+/**
+ * A mock of the seleniumIsReady function. Always resolves.
+ *
+ * @returns {Promise<void>} A promise that always resolves.
+ */
+export const seleniumIsReady = (): Promise<void> => Promise.resolve();

packages/backend/src/utils/cron.ts

@@ -123,7 +123,7 @@ export default (bypassAuthenticationForInternalRequestsToken: string, autoFetchS
       chalk.bgGrey.hex("#339933")("") +
       chalk.whiteBright.bgGrey(` Auto Fetch activated `) +
       chalk.grey("") +
-      chalk.green(" This instance will periodically fetch information from data providers for all known stocks."),
+      chalk.green(" This process will periodically fetch information from data providers for all known stocks."),
   );
   logger.info("");
 };

packages/backend/src/utils/webdriver.ts

@@ -6,13 +6,25 @@ import logger, { PREFIX_SELENIUM } from "./logger.js";
 import chalk from "chalk";
 import { Stock, resourceEndpointPath } from "@rating-tracker/commons";
 import { createResource } from "../redis/repositories/resourceRepository.js";
-import axios from "axios";
+import axios, { AxiosError } from "axios";
 
 /**
  * A page load strategy to use by the WebDriver.
  */
 type PageLoadStrategy = "normal" | "eager" | "none";
 
+/**
+ * Checks if the Selenium instance is reachable.
+ *
+ * @returns {Promise<void>} A promise that resolves when the Selenium instance is reachable, or rejects with an error if
+ * it is not.
+ */
+export const seleniumIsReady = (): Promise<void> =>
+  axios
+    .get(`${process.env.SELENIUM_URL}/status`, { timeout: 1000 })
+    .then((res) => (res.data.value.ready ? Promise.resolve() : Promise.reject(new Error("Selenium is not ready"))))
+    .catch((e: AxiosError) => Promise.reject(new Error("Selenium is not reachable: " + e.message)));
+
 /**
  * Creates and returns a new WebDriver instance.
  *

packages/backend/test/live.test.ts

@@ -13,6 +13,7 @@ import { sentMessages } from "../src/signal/__mocks__/signalBase";
 import * as signal from "../src/signal/signal";
 
 vi.mock("../src/utils/logger");
+vi.mock("../src/utils/webdriver");
 vi.mock("../src/signal/signalBase");
 vi.mock("@simplewebauthn/server", async () => await import("./moduleMocks/@simplewebauthn/server"));