server : Add k6 Load Testing Script (#3175)

* add load testing script and update README for k6 integration

examples/server/bench.js

@@ -0,0 +1,29 @@
+import http from 'k6/http'
+import { check } from 'k6'
+
+export let options = {
+  vus: parseInt(__ENV.CONCURRENCY) || 4,
+  iterations: parseInt(__ENV.CONCURRENCY) || 4,
+}
+
+const filePath        = __ENV.FILE_PATH
+const baseURL         = __ENV.BASE_URL        || 'http://127.0.0.1:8080'
+const endpoint        = __ENV.ENDPOINT        || '/inference'
+const temperature     = __ENV.TEMPERATURE     || '0.0'
+const temperatureInc  = __ENV.TEMPERATURE_INC || '0.2'
+const responseFormat  = __ENV.RESPONSE_FORMAT || 'json'
+
+// Read the file ONCE at init time
+const fileBin = open(filePath, 'b')
+
+export default function () {
+  const payload = {
+    file:           http.file(fileBin, filePath),
+    temperature:    temperature,
+    temperature_inc: temperatureInc,
+    response_format: responseFormat,
+  }
+
+  const res = http.post(`${baseURL}${endpoint}`, payload)
+  check(res, { 'status is 200': r => r.status === 200 })
+}