[#175119536] Add health check

Info/__tests__/handler.test.ts

@@ -0,0 +1,30 @@
+import { fromLeft, taskEither } from "fp-ts/lib/TaskEither";
+import { HealthCheck, HealthProblem } from "../../utils/healthcheck";
+import { InfoHandler } from "../handler";
+
+afterEach(() => {
+  jest.clearAllMocks();
+});
+
+describe("InfoHandler", () => {
+  it("should return an internal error if the application is not healthy", async () => {
+    const healthCheck: HealthCheck = fromLeft([
+      "failure 1" as HealthProblem<"Config">,
+      "failure 2" as HealthProblem<"Config">
+    ]);
+    const handler = InfoHandler(healthCheck);
+
+    const response = await handler();
+
+    expect(response.kind).toBe("IResponseErrorInternal");
+  });
+
+  it("should return a success if the application is healthy", async () => {
+    const healthCheck: HealthCheck = taskEither.of(true);
+    const handler = InfoHandler(healthCheck);
+
+    const response = await handler();
+
+    expect(response.kind).toBe("IResponseSuccessJson");
+  });
+});

Info/handler.ts

@@ -1,27 +1,39 @@
 import * as express from "express";
 import { wrapRequestHandler } from "io-functions-commons/dist/src/utils/request_middleware";
 import {
+  IResponseErrorInternal,
   IResponseSuccessJson,
+  ResponseErrorInternal,
   ResponseSuccessJson
 } from "italia-ts-commons/lib/responses";
 import * as packageJson from "../package.json";
+import { checkApplicationHealth, HealthCheck } from "../utils/healthcheck";
 
 interface IInfo {
+  name: string;
   version: string;
 }
 
-type InfoHandler = () => Promise<IResponseSuccessJson<IInfo>>;
+type InfoHandler = () => Promise<
+  IResponseSuccessJson<IInfo> | IResponseErrorInternal
+>;
 
-export function InfoHandler(): InfoHandler {
-  return async () => {
-    return ResponseSuccessJson({
-      version: packageJson.version
-    });
-  };
+export function InfoHandler(healthCheck: HealthCheck): InfoHandler {
+  return () =>
+    healthCheck
+      .fold<IResponseSuccessJson<IInfo> | IResponseErrorInternal>(
+        problems => ResponseErrorInternal(problems.join("\n\n")),
+        _ =>
+          ResponseSuccessJson({
+            name: packageJson.name,
+            version: packageJson.version
+          })
+      )
+      .run();
 }
 
 export function Info(): express.RequestHandler {
-  const handler = InfoHandler();
+  const handler = InfoHandler(checkApplicationHealth());
 
   return wrapRequestHandler(handler);
 }

utils/healthcheck.ts

@@ -0,0 +1,146 @@
+import { CosmosClient } from "@azure/cosmos";
+import {
+  common as azurestorageCommon,
+  createBlobService,
+  createFileService,
+  createQueueService,
+  createTableService
+} from "azure-storage";
+import { sequenceT } from "fp-ts/lib/Apply";
+import { array } from "fp-ts/lib/Array";
+import { toError } from "fp-ts/lib/Either";
+import {
+  fromEither,
+  taskEither,
+  TaskEither,
+  tryCatch
+} from "fp-ts/lib/TaskEither";
+import { readableReport } from "italia-ts-commons/lib/reporters";
+import fetch from "node-fetch";
+import { getConfig, IConfig } from "./config";
+
+type ProblemSource = "AzureCosmosDB" | "AzureStorage" | "Config" | "Url";
+export type HealthProblem<S extends ProblemSource> = string & { __source: S };
+export type HealthCheck<
+  S extends ProblemSource = ProblemSource,
+  T = true
+> = TaskEither<ReadonlyArray<HealthProblem<S>>, T>;
+
+// format and cast a problem message with its source
+const formatProblem = <S extends ProblemSource>(
+  source: S,
+  message: string
+): HealthProblem<S> => `${source}|${message}` as HealthProblem<S>;
+
+// utility to format an unknown error to an arry of HealthProblem
+const toHealthProblems = <S extends ProblemSource>(source: S) => (
+  e: unknown
+): ReadonlyArray<HealthProblem<S>> => [
+  formatProblem(source, toError(e).message)
+];
+
+/**
+ * Check application's configuration is correct
+ *
+ * @returns either true or an array of error messages
+ */
+export const checkConfigHealth = (): HealthCheck<"Config", IConfig> =>
+  fromEither(getConfig()).mapLeft(errors =>
+    errors.map(e =>
+      // give each problem its own line
+      formatProblem("Config", readableReport([e]))
+    )
+  );
+
+/**
+ * Check the application can connect to an Azure CosmosDb instances
+ *
+ * @param dbUri uri of the database
+ * @param dbUri connection string for the storage
+ *
+ * @returns either true or an array of error messages
+ */
+export const checkAzureCosmosDbHealth = (
+  dbUri: string,
+  dbKey?: string
+): HealthCheck<"AzureCosmosDB", true> =>
+  tryCatch(() => {
+    const client = new CosmosClient({
+      endpoint: dbUri,
+      key: dbKey
+    });
+    return client.getDatabaseAccount();
+  }, toHealthProblems("AzureCosmosDB")).map(_ => true);
+
+/**
+ * Check the application can connect to an Azure Storage
+ *
+ * @param connStr connection string for the storage
+ *
+ * @returns either true or an array of error messages
+ */
+export const checkAzureStorageHealth = (
+  connStr: string
+): HealthCheck<"AzureStorage"> =>
+  array
+    .sequence(taskEither)(
+      // try to instantiate a client for each product of azure storage
+      [
+        createBlobService,
+        createFileService,
+        createQueueService,
+        createTableService
+      ]
+        // for each, create a task that wraps getServiceProperties
+        .map(createService =>
+          tryCatch(
+            () =>
+              new Promise<
+                azurestorageCommon.models.ServicePropertiesResult.ServiceProperties
+              >((resolve, reject) =>
+                createService(connStr).getServiceProperties((err, result) => {
+                  err
+                    ? reject(err.message.replace(/\n/gim, " ")) // avoid newlines
+                    : resolve(result);
+                })
+              ),
+            toHealthProblems("AzureStorage")
+          )
+        )
+    )
+    .map(_ => true);
+
+/**
+ * Check a url is reachable
+ *
+ * @param url url to connect with
+ *
+ * @returns either true or an array of error messages
+ */
+export const checkUrlHealth = (url: string): HealthCheck<"Url", true> =>
+  tryCatch(() => fetch(url, { method: "HEAD" }), toHealthProblems("Url")).map(
+    _ => true
+  );
+
+/**
+ * Execute all the health checks for the application
+ *
+ * @returns either true or an array of error messages
+ */
+export const checkApplicationHealth = (): HealthCheck<ProblemSource, true> =>
+  taskEither
+    .of<ReadonlyArray<HealthProblem<ProblemSource>>, void>(void 0)
+    .chain(_ => checkConfigHealth())
+    .chain(config =>
+      // TODO: once we upgrade to fp-ts >= 1.19 we can use Validation to collect all errors, not just the first to happen
+      sequenceT(taskEither)<
+        ReadonlyArray<HealthProblem<ProblemSource>>,
+        // tslint:disable readonly-array beacuse the following is actually mutable
+        Array<TaskEither<ReadonlyArray<HealthProblem<ProblemSource>>, true>>
+      >(
+        checkAzureCosmosDbHealth(config.COSMOSDB_URI, config.COSMOSDB_KEY),
+        checkAzureStorageHealth(config.QueueStorageConnection),
+        checkUrlHealth(config.WEBHOOK_CHANNEL_URL)
+      )
+    )
+    .map(_ => true);