Add helper to manually stop agent processes

In some specific contexts such as serverless functions, the execution is
stopped before the agent gets all the data to send it to AppSignal.

There's a new function that manually allows you to gracefully stop
AppSignal's agent processes so all the data is flushed before the
execution is closed.

.changesets/new-helper-to-manually-stop-all-agent-processes.md

@@ -0,0 +1,8 @@
+---
+bump: patch
+type: add
+---
+
+New helper to manually stop all agent processes.
+
+Some specific contexts as serverless functions require to ensure all the data is sent to AppSignal before finishing. To achieve this, a new method (`appsignal.stop_agent_processes()`) gracefully stops all AppSignal processes so the data is not lost when wrapping up the app or function execution.

src/appsignal/client.py

@@ -1,5 +1,9 @@
 from __future__ import annotations
 
+import os
+import signal
+import subprocess
+import time
 from typing import TYPE_CHECKING
 
 from . import internal_logger as logger
@@ -48,6 +52,21 @@ def start(self) -> None:
         else:
             logger.info("AppSignal not starting: no active config found")
 
+    def stop_agent_processes(self) -> None:
+        logger.info("Killing all AppSignal agent processes")
+
+        processes = subprocess.Popen(["ps", "-A"], stdout=subprocess.PIPE)
+        out, _ = processes.communicate()
+        processes_found = 0
+
+        for line in out.splitlines():
+            if b"appsignal-" in line:
+                pid = int(line.split(None, 1)[0])
+                os.kill(pid, signal.SIGTERM)
+                processes_found += 1
+
+        logger.info(f"AppSignal stopped {processes_found} agent processes")
+
     def _start_probes(self) -> None:
         if self._config.option("enable_minutely_probes"):
             start_probes()

tests/test_client.py

@@ -1,6 +1,8 @@
 from __future__ import annotations
 
 import os
+import signal
+from unittest.mock import call, patch
 
 from appsignal.agent import agent
 from appsignal.client import Client
@@ -98,3 +100,25 @@ def test_client_inactive():
         os.environ.get("OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST")
         is None
     )
+
+
+@patch("subprocess.Popen.communicate")
+@patch("os.kill")
+def test_client_stop(mock_kill, mock_communicate):
+    mock_communicate.return_value = (
+        b"123 ??        12:00.00 /bin/appsignal-agent\n124 ??        12:00.00 /foo/appsignal-agent\n",
+        None,
+    )
+    mock_kill.return_value = None
+
+    client = Client(active=True, name="MyApp", push_api_key="0000-0000-0000-0000")
+    client.start()
+
+    client.stop_agent_processes()
+
+    mock_kill.assert_has_calls(
+        [
+            call(123, signal.SIGTERM),
+            call(124, signal.SIGTERM),
+        ]
+    )