[COR-68] Add registry of loaded RPC clients and expose discovery metadata

.travis.yml

@@ -1,7 +1,7 @@
 language: node_js
 node_js:
-- '6'
-- lts/*
+  - "10"
+  - lts/*
 deploy:
   provider: npm
   email: [email protected]

index.js

@@ -12,17 +12,17 @@ const IPC_MANIFESTS_FOLDER = "ipc_manifests";
 const requestDuration = new Histogram({
   name: "http_rpc_client_request_duration_seconds",
   help: "Duration of rpc requests from the client",
-  labelNames: ["service", "method"]
+  labelNames: ["service", "method"],
 });
 const requestCount = new Counter({
   name: "http_rpc_client_requests_total",
   help: "The total number of rpc requests from the client",
-  labelNames: ["service", "method"]
+  labelNames: ["service", "method"],
 });
 const failureCount = new Counter({
   name: "http_rpc_client_failures_total",
   help: "The total number of rpc failures from the client",
-  labelNames: ["service", "method", "type", "status_code"]
+  labelNames: ["service", "method", "type", "status_code"],
 });
 
 class RpcResponseError {
@@ -31,7 +31,7 @@ class RpcResponseError {
       configurable: true,
       enumerable: false,
       value: this.constructor.name,
-      writable: true
+      writable: true,
     });
 
     Object.assign(this, responseBody);
@@ -46,9 +46,9 @@ class RpcResponseError {
         "\n" +
         [...this.source]
           .reverse()
-          .map(s => "    via " + s)
+          .map((s) => "    via " + s)
           .join("\n"),
-      writable: true
+      writable: true,
     });
   }
 
@@ -61,12 +61,36 @@ class RpcResponseError {
   }
 }
 
-exports.load = function(host, serviceName, options) {
-  const metaPath = getMetaPath(serviceName);
-  const client = new Client(host, options);
+class Registry {
+  constructor() {
+    this._registeredServices = {};
+  }
+
+  load(host, serviceName, options) {
+    const metaPath = getMetaPath(serviceName);
+    const client = new Client(host, options);
+
+    const loadClient = client.load(metaPath);
+    this._registeredServices[serviceName] = loadClient;
+
+    return loadClient;
+  }
+
+  createWellKnownHandler() {
+    return (req, res) => {
+      const services = Object.keys(this._registeredServices).map((s) => {
+        return { name: s };
+      });
+
+      res.json({
+        services,
+      });
+    };
+  }
+}
 
-  return client.load(metaPath);
-};
+exports.registry = new Registry();
+exports.Registry = Registry;
 
 // exports.createClient = function (host, options) {
 //   return new Client(host, options);
@@ -100,7 +124,7 @@ class Client {
     Object.assign(
       this,
       {
-        path: "/rpc"
+        path: "/rpc",
       },
       options
     );
@@ -128,21 +152,21 @@ class Client {
       .post(requestUrl, {
         body: JSON.stringify(params),
         headers: {
-          "Content-Type": "application/json"
+          "Content-Type": "application/json",
         },
         json: true,
         retries: 0,
-        timeout
+        timeout,
       })
-      .then(res => res.body)
-      .catch(err => {
+      .then((res) => res.body)
+      .catch((err) => {
         failureCount.inc(
           Object.assign(
             {
               type:
                 (err.response && err.response.body && err.response.body.type) ||
                 undefined,
-              status_code: err.statusCode
+              status_code: err.statusCode,
             },
             requestMeta
           )
@@ -160,16 +184,16 @@ class Client {
       protocol: this.protocol,
       host: this.host,
       port: this.port,
-      pathname: pathname
+      pathname: pathname,
     });
   }
 
   getMeta() {
     const requestUrl = this.formatUrl();
 
     return got(requestUrl, { json: true })
-      .then(res => res.body)
-      .catch(err => mapError(this.serviceName, "getMeta", err));
+      .then((res) => res.body)
+      .catch((err) => mapError(this.serviceName, "getMeta", err));
   }
 
   createInterface(meta) {
@@ -179,8 +203,8 @@ class Client {
     const multiArg = meta.multiArg || false;
     const self = this;
 
-    meta.interfaces.forEach(iface => {
-      rpcInterface[iface.methodName] = function() {
+    meta.interfaces.forEach((iface) => {
+      rpcInterface[iface.methodName] = function () {
         const args = Array.prototype.slice.call(arguments);
         const params = multiArg ? args : args[0];
         if (!multiArg && params && typeof params !== "object")