Add Healthz support

config/default.yaml

@@ -106,3 +106,34 @@ commands:
   # as display names or prefixed with exclamation points.
   additionalPrefixes:
     - "mjolnir_bot"
+
+# Options for monitoring the health of the bot
+health:
+  # healthz options. These options are best for use in container environments
+  # like Kubernetes to detect how healthy the service is. The bot will report
+  # that it is unhealthy until it is able to process user requests. Typically
+  # this means that it'll flag itself as unhealthy for a number of minutes
+  # before saying "Now monitoring rooms" and flagging itself healthy.
+  #
+  # Health is flagged through HTTP status codes, defined below.
+  healthz:
+    # Whether the healthz integration should be enabled (default false)
+    enabled: false
+
+    # The port to expose the webserver on. Defaults to 8080.
+    port: 8080
+
+    # The address to listen for requests on. Defaults to all addresses.
+    address: "0.0.0.0"
+
+    # The path to expose the monitoring endpoint at. Defaults to `/healthz`
+    endpoint: "/healthz"
+
+    # The HTTP status code which reports that the bot is healthy/ready to
+    # process requests. Typically this should not be changed. Defaults to
+    # 200.
+    healthyStatus: 200
+
+    # The HTTP status code which reports that the bot is not healthy/ready.
+    # Defaults to 418.
+    unhealthyStatus: 418

src/Mjolnir.ts

@@ -26,6 +26,7 @@ import ErrorCache, { ERROR_KIND_FATAL, ERROR_KIND_PERMISSION } from "./ErrorCach
 import { IProtection } from "./protections/IProtection";
 import { PROTECTIONS } from "./protections/protections";
 import { AutomaticRedactionQueue } from "./queues/AutomaticRedactionQueue";
+import { Healthz } from "./health/healthz";
 
 export const STATE_NOT_STARTED = "not_started";
 export const STATE_CHECKING_PERMISSIONS = "checking_permissions";
@@ -169,7 +170,18 @@ export class Mjolnir {
             }
         }).then(async () => {
             this.currentState = STATE_RUNNING;
+            Healthz.isHealthy = true;
             await logMessage(LogLevel.INFO, "Mjolnir@startup", "Startup complete. Now monitoring rooms.");
+        }).catch(async err => {
+            try {
+                LogService.error("Mjolnir", "Error during startup:");
+                LogService.error("Mjolnir", err);
+                await logMessage(LogLevel.ERROR, "Mjolnir@startup", "Startup failed due to error - see console");
+            } catch (e) {
+                // If we failed to handle the error, just crash
+                console.error(e);
+                process.exit(1);
+            }
         });
     }
 

src/config.ts

@@ -43,6 +43,16 @@ interface IConfig {
         allowNoPrefix: boolean;
         additionalPrefixes: string[];
     };
+    health: {
+        healthz: {
+            enabled: boolean;
+            port: number;
+            address: string;
+            endpoint: string;
+            healthyStatus: number;
+            unhealthyStatus: number;
+        };
+    };
 
     /**
      * Config options only set at runtime. Try to avoid using the objects
@@ -79,6 +89,16 @@ const defaultConfig: IConfig = {
         allowNoPrefix: false,
         additionalPrefixes: [],
     },
+    health: {
+        healthz: {
+            enabled: false,
+            port: 8080,
+            address: "0.0.0.0",
+            endpoint: "/healthz",
+            healthyStatus: 200,
+            unhealthyStatus: 418,
+        },
+    },
 
     // Needed to make the interface happy.
     RUNTIME: {

src/health/healthz.ts

@@ -0,0 +1,41 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import config from "../config";
+import * as http from "http";
+import { LogService } from "matrix-bot-sdk";
+
+export class Healthz {
+    private static healthCode: number;
+
+    public static set isHealthy(val: boolean) {
+        Healthz.healthCode = val ? config.health.healthz.healthyStatus : config.health.healthz.unhealthyStatus;
+    }
+
+    public static get isHealthy(): boolean {
+        return Healthz.healthCode === config.health.healthz.healthyStatus;
+    }
+
+    public static listen() {
+        const server = http.createServer((req, res) => {
+            res.writeHead(Healthz.healthCode);
+            res.end(`health code: ${Healthz.healthCode}`);
+        });
+        server.listen(config.health.healthz.port, config.health.healthz.address, () => {
+            LogService.info("Healthz", `Listening for health requests on ${config.health.healthz.address}:${config.health.healthz.port}`);
+        });
+    }
+}

src/index.ts

@@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2019, 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -30,6 +30,7 @@ import { Mjolnir } from "./Mjolnir";
 import { logMessage } from "./LogProxy";
 import { MembershipEvent } from "matrix-bot-sdk/lib/models/events/MembershipEvent";
 import * as htmlEscape from "escape-html";
+import { Healthz } from "./health/healthz";
 
 config.RUNTIME = {client: null};
 
@@ -38,6 +39,11 @@ LogService.setLevel(LogLevel.fromString(config.logLevel, LogLevel.DEBUG));
 
 LogService.info("index", "Starting bot...");
 
+Healthz.isHealthy = false; // start off unhealthy
+if (config.health.healthz.enabled) {
+    Healthz.listen();
+}
+
 (async function () {
     const storage = new SimpleFsStorageProvider(path.join(config.dataPath, "bot.json"));