Support configurable maxSockets for HTTP agents

lib/mixpanel-node.js

@@ -49,13 +49,14 @@ const create_client = function (token, config) {
     config: { ...DEFAULT_CONFIG },
   };
   const { keepAlive } = metrics.config;
+  const maxSockets = config && config.maxSockets;
 
   // mixpanel constants
   const MAX_BATCH_SIZE = 50;
   const REQUEST_LIBS = { http, https };
   const REQUEST_AGENTS = {
-    http: new http.Agent({ keepAlive }),
-    https: new https.Agent({ keepAlive }),
+    http: new http.Agent({ keepAlive, maxSockets }),
+    https: new https.Agent({ keepAlive, maxSockets }),
   };
   const proxyPath = process.env.HTTPS_PROXY || process.env.HTTP_PROXY;
   const proxyAgent = proxyPath

readme.md

@@ -28,6 +28,11 @@ var mixpanel = Mixpanel.init("<YOUR_TOKEN>", {
   keepAlive: false,
 });
 
+// limit the number of concurrent connections to Mixpanel
+var mixpanel = Mixpanel.init("<YOUR_TOKEN>", {
+  maxSockets: 10,
+});
+
 // pass the custom logger (default is console)
 var mixpanel = Mixpanel.init("<YOUR_TOKEN>", {
   debug: true,

test/send_request.js

@@ -182,6 +182,29 @@ describe("send_request", () => {
     expect(getConfig.agent).toBe(agent);
   });
 
+  it("uses custom maxSockets when configured", () => {
+    const agent = new https.Agent({ keepAlive: true });
+    const httpsStub = {
+      request: vi.fn().mockImplementation((_, cb) => {
+        cb(res);
+        return http_emitter;
+      }),
+      Agent: vi.fn().mockImplementation(function () {
+        return agent;
+      }),
+    };
+    delete process.env.HTTP_PROXY;
+    delete process.env.HTTPS_PROXY;
+    Mixpanel = proxyquire("../lib/mixpanel-node", {
+      https: httpsStub,
+    });
+    const proxyMixpanel = Mixpanel.init("token", { maxSockets: 10 });
+    proxyMixpanel.send_request({ endpoint: "", data: {} });
+
+    const agentOpts = httpsStub.Agent.mock.calls[0][0];
+    expect(agentOpts.maxSockets).toBe(10);
+  });
+
   it("uses correct hostname", () => {
     const host = "testhost.fakedomain";
     const customHostnameMixpanel = Mixpanel.init("token", { host: host });