S3C-4618: backport HealthProbeServer

index.js

@@ -62,6 +62,8 @@ module.exports = {
         },
         probe: {
             ProbeServer: require('./lib/network/probe/ProbeServer'),
+            HealthProbeServer:
+                require('./lib/network/probe/HealthProbeServer'),
         },
         RoundRobin: require('./lib/network/RoundRobin'),
         kmip: require('./lib/network/kmip'),

lib/network/probe/HealthProbeServer.js

@@ -0,0 +1,97 @@
+const httpServer = require('../http/server');
+const werelogs = require('werelogs');
+const errors = require('../../errors');
+const ZenkoMetrics = require('../../metrics/ZenkoMetrics');
+
+function sendError(res, log, error, optMessage) {
+    res.writeHead(error.code);
+    let message;
+    if (optMessage) {
+        message = optMessage;
+    } else {
+        message = error.description || '';
+    }
+    log.debug('sending back error response', { httpCode: error.code,
+        errorType: error.message,
+        error: message });
+    res.end(`${JSON.stringify({ errorType: error.message,
+        errorMessage: message })}\n`);
+}
+
+function sendSuccess(res, log, msg) {
+    res.writeHead(200);
+    log.debug('replying with success');
+    const message = msg || 'OK';
+    res.end(message);
+}
+
+function checkStub(log) { // eslint-disable-line
+    return true;
+}
+
+class HealthProbeServer extends httpServer {
+    constructor(params) {
+        const logging = new werelogs.Logger('HealthProbeServer');
+        super(params.port, logging);
+        this.logging = logging;
+        this.setBindAddress(params.bindAddress || 'localhost');
+        // hooking our request processing function by calling the
+        // parent's method for that
+        this.onRequest(this._onRequest);
+        this._reqHandlers = {
+            '/_/health/liveness': this._onLiveness.bind(this),
+            '/_/health/readiness': this._onReadiness.bind(this),
+            '/_/monitoring/metrics': this._onMetrics.bind(this),
+        };
+        this._livenessCheck = params.livenessCheck || checkStub;
+        this._readinessCheck = params.readinessCheck || checkStub;
+    }
+
+    onLiveCheck(f) {
+        this._livenessCheck = f;
+    }
+
+    onReadyCheck(f) {
+        this._readinessCheck = f;
+    }
+
+    _onRequest(req, res) {
+        const log = this.logging.newRequestLogger();
+        log.debug('request received', { method: req.method,
+            url: req.url });
+        if (req.method !== 'GET') {
+            sendError(res, log, errors.MethodNotAllowed);
+        }
+        if (req.url in this._reqHandlers) {
+            this._reqHandlers[req.url](req, res, log);
+        } else {
+            sendError(res, log, errors.InvalidURI);
+        }
+    }
+
+    _onLiveness(req, res, log) {
+        if (this._livenessCheck(log)) {
+            sendSuccess(res, log);
+        } else {
+            sendError(res, log, errors.ServiceUnavailable);
+        }
+    }
+
+    _onReadiness(req, res, log) {
+        if (this._readinessCheck(log)) {
+            sendSuccess(res, log);
+        } else {
+            sendError(res, log, errors.ServiceUnavailable);
+        }
+    }
+
+    // expose metrics to Prometheus
+    _onMetrics(req, res) {
+        res.writeHead(200, {
+            'Content-Type': ZenkoMetrics.asPrometheusContentType(),
+        });
+        res.end(ZenkoMetrics.asPrometheus());
+    }
+}
+
+module.exports = HealthProbeServer;