feat: Reuse same HTTP Client Instance when possible (#340)

* reusing same http client instance

Signed-off-by: Deepanshu Agarwal <[email protected]>

* Fixing test

Signed-off-by: Deepanshu Agarwal <[email protected]>

* Update HTTPClient

Signed-off-by: Deepanshu Agarwal <[email protected]>

* if-else imorovement

Signed-off-by: Deepanshu Agarwal <[email protected]>

* Correct indentation

Signed-off-by: Deepanshu Agarwal <[email protected]>

Signed-off-by: Deepanshu Agarwal <[email protected]>

Author: DeepanshuA

src/implementation/Client/HTTPClient/HTTPClient.ts

@@ -25,15 +25,15 @@ import HTTPClientSidecar from "./sidecar";
 export default class HTTPClient implements IClient {
   private isInitialized: boolean;
 
-  private readonly client: typeof fetch;
+  private static client: typeof fetch;
   private readonly clientHost: string;
   private readonly clientPort: string;
   private readonly clientUrl: string;
   private readonly options: DaprClientOptions;
   private readonly logger: Logger;
 
-  private readonly httpAgent;
-  private readonly httpsAgent;
+  private static httpAgent: http.Agent;
+  private static httpsAgent: https.Agent;
 
   constructor(
     host = Settings.getDefaultHost()
@@ -45,7 +45,6 @@ export default class HTTPClient implements IClient {
     this.options = options;
     this.logger = new Logger("HTTPClient", "HTTPClient", this.options.logger);
     this.isInitialized = false;
-
     // fallback to default
     if (this.options.isKeepAlive === undefined) {
       this.options.isKeepAlive = true;
@@ -57,17 +56,21 @@ export default class HTTPClient implements IClient {
       this.clientUrl = `${this.clientHost}:${this.clientPort}/v1.0`;
     }
 
-    this.client = fetch;
+    if(!HTTPClient.client) {
+      HTTPClient.client = fetch;
+    }
 
     // Add a custom agent so we can decide if we want to reuse connections or not
     // we use an agent so we can reuse an open connection, limiting handshake requirements
     // Note: when using an agent, we will encounter TCPWRAP since the connection doesn't get destroyed
-    if (this.options.isKeepAlive) {
-      this.httpAgent = new http.Agent({ keepAlive: true, keepAliveMsecs: 30 * 1000 });
-      this.httpsAgent = new https.Agent({ keepAlive: true, keepAliveMsecs: 30 * 1000 });
-    } else {
-      this.httpAgent = new http.Agent();
-      this.httpsAgent = new https.Agent();
+    const keepAlive = this.options.isKeepAlive;
+    const keepAliveMsecs = 30 * 1000; // it is applicable only when keepAlive is set to true
+
+    if(!HTTPClient.httpAgent) {
+      HTTPClient.httpAgent = new http.Agent({ keepAlive: keepAlive, keepAliveMsecs: keepAliveMsecs });
+    }
+    if(!HTTPClient.httpsAgent) {
+      HTTPClient.httpsAgent = new https.Agent({ keepAlive: keepAlive, keepAliveMsecs: keepAliveMsecs });
     }
   }
 
@@ -78,7 +81,7 @@ export default class HTTPClient implements IClient {
       await this.start();
     }
 
-    return this.client;
+    return HTTPClient.client;
   }
 
   getClientHost(): string {
@@ -114,8 +117,8 @@ export default class HTTPClient implements IClient {
   }
 
   async stop(): Promise<void> {
-    this.httpAgent.destroy();
-    this.httpsAgent.destroy();
+    HTTPClient.httpAgent.destroy();
+    HTTPClient.httpsAgent.destroy();
   }
 
   async start(): Promise<void> {
@@ -171,7 +174,7 @@ export default class HTTPClient implements IClient {
     }
 
     const urlFull = url.startsWith("http") ? url : `${this.clientUrl}${url}`;
-    const agent = urlFull.startsWith("https") ? this.httpsAgent : this.httpAgent;
+    const agent = urlFull.startsWith("https") ? HTTPClient.httpsAgent : HTTPClient.httpAgent;
     params.agent = agent;
 
     this.logger.debug(`Fetching ${params.method} ${urlFull} with body: (${params.body})`);

test/unit/main/DaprClient.test.ts

@@ -31,4 +31,13 @@ describe('DaprClient', () => {
       expect(msg).toEqual("DAPR_INCORRECT_SIDECAR_PORT");
     }
   });
+
+  it('same http client should be returned for multiple DaprClient invocations', () => {
+    const daprClient1 = new DaprClient(host, port);
+    const daprClient2 = new DaprClient(host, port);
+    return Promise.all([daprClient1.getDaprClient().getClient(false), 
+      daprClient2.getDaprClient().getClient(false)]).then(function(values) {
+      expect(values[0]).toEqual(values[1]);
+    });
+  });
 });