[Perf] Call Run() once before starting recording (#21162)

- Avoids capturing one-time setup like authorization requests
- Ported from Azure/azure-sdk-for-net#24263

tools/azure-devtools/src/azure_devtools/perfstress_tests/perf_stress_test.py

@@ -48,6 +48,12 @@ async def global_cleanup(self):
         return
 
     async def record_and_start_playback(self):
+        # Make one call to Run() before starting recording, to avoid capturing one-time setup like authorization requests
+        if self.args.sync:
+            self.run_sync()
+        else:
+            await self.run_async()
+
         await self._start_recording()
         self._test_proxy_policy.recording_id = self._recording_id
         self._test_proxy_policy.mode = "record"

tools/azure-devtools/src/azure_devtools/perfstress_tests/system_perfstress/pipeline_client_get_test.py

@@ -0,0 +1,60 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+# --------------------------------------------------------------------------------------------
+
+from azure.core import PipelineClient
+from azure.core import AsyncPipelineClient
+from azure.core.pipeline import PipelineResponse
+from azure.core.pipeline.transport import HttpResponse
+
+from azure_devtools.perfstress_tests import PerfStressTest
+
+
+class PipelineClientGetTest(PerfStressTest):
+    pipeline_client: PipelineClient = None
+    async_pipeline_client: AsyncPipelineClient = None
+    _first_run = True
+
+    def __init__(self, arguments):
+        super().__init__(arguments)
+        self.pipeline_client = PipelineClient(base_url=self.args.url, **self._client_kwargs)
+        self.async_pipeline_client = AsyncPipelineClient(base_url=self.args.url, **self._client_kwargs)
+
+    def run_sync(self):
+        if self._first_run:
+            for _ in range(self.args.first_run_extra_requests):
+                self._send_request_sync()
+            self._first_run = False
+        self._send_request_sync()
+
+    async def run_async(self):
+        if self._first_run:
+            for _ in range(self.args.first_run_extra_requests):
+                await self._send_request_async()
+            self._first_run = False
+        await self._send_request_async()
+
+    def _send_request_sync(self):
+        request = self.pipeline_client.get(self.args.url)
+        response: PipelineResponse = self.pipeline_client._pipeline.run(request)
+        # Consume response body
+        http_response: HttpResponse = response.http_response
+        data = http_response.body()
+
+    async def _send_request_async(self):
+        request = self.async_pipeline_client.get(self.args.url)
+        response: PipelineResponse = await self.async_pipeline_client._pipeline.run(request)
+        # Consume response body
+        http_response: HttpResponse = response.http_response
+        data = http_response.body()
+
+    async def close(self):
+        await self.async_pipeline_client.close()
+        await super().close()
+
+    @staticmethod
+    def add_arguments(parser):
+        parser.add_argument("--first-run-extra-requests", type=int, default=0, help='Extra requests to send on first run. ' +
+            'Simulates SDKs which require extra requests (like authentication) on first API call.')
+        parser.add_argument("-u", "--url", required=True)