use the configured hostname in get_system_info (#689)

* use the configured hostname in get_system_info

fixes #688

* fix kubernetes tests and improve system_info test

Unfortunately, we can't use mock to "hardcode" the output
of socket.gethostname() anymore, as it is read when the
Config class is defined, which happens pretty early when
initializing the test suite. As such, we have to compare
the returned value dynamically with socket.gethostname()
in the test.

Author: beniwohli

elasticapm/base.py

@@ -35,7 +35,6 @@
 import logging
 import os
 import platform
-import socket
 import sys
 import time
 import warnings
@@ -330,7 +329,7 @@ def get_process_info(self):
 
     def get_system_info(self):
         system_data = {
-            "hostname": keyword_field(socket.gethostname()),
+            "hostname": keyword_field(self.config.hostname),
             "architecture": platform.machine(),
             "platform": platform.system().lower(),
         }

tests/client/client_tests.py

@@ -34,6 +34,7 @@
 
 import os
 import platform
+import socket
 import sys
 import time
 from collections import defaultdict
@@ -79,6 +80,14 @@ def test_system_info(elasticapm_client):
         mocked.return_value = {}
         system_info = elasticapm_client.get_system_info()
     assert {"hostname", "architecture", "platform"} == set(system_info.keys())
+    assert system_info["hostname"] == socket.gethostname()
+
+
+@pytest.mark.parametrize("elasticapm_client", [{"hostname": "my_custom_hostname"}], indirect=True)
+def test_system_info_hostname_configurable(elasticapm_client):
+    # mock docker/kubernetes data here to get consistent behavior if test is run in docker
+    system_info = elasticapm_client.get_system_info()
+    assert system_info["hostname"] == "my_custom_hostname"
 
 
 @pytest.mark.parametrize("elasticapm_client", [{"global_labels": "az=us-east-1,az.rack=8"}], indirect=True)
@@ -89,14 +98,11 @@ def test_global_labels(elasticapm_client):
 
 def test_docker_kubernetes_system_info(elasticapm_client):
     # mock docker/kubernetes data here to get consistent behavior if test is run in docker
-    with mock.patch("elasticapm.utils.cgroup.get_cgroup_container_metadata") as mock_metadata, mock.patch(
-        "socket.gethostname"
-    ) as mock_gethostname:
+    with mock.patch("elasticapm.utils.cgroup.get_cgroup_container_metadata") as mock_metadata:
         mock_metadata.return_value = {"container": {"id": "123"}, "kubernetes": {"pod": {"uid": "456"}}}
-        mock_gethostname.return_value = "foo"
         system_info = elasticapm_client.get_system_info()
     assert system_info["container"] == {"id": "123"}
-    assert system_info["kubernetes"] == {"pod": {"uid": "456", "name": "foo"}}
+    assert system_info["kubernetes"] == {"pod": {"uid": "456", "name": socket.gethostname()}}
 
 
 @mock.patch.dict(
@@ -164,7 +170,7 @@ def test_docker_kubernetes_system_info_except_hostname_from_environ():
         mock_gethostname.return_value = "foo"
         system_info = elasticapm_client.get_system_info()
     assert "kubernetes" in system_info
-    assert system_info["kubernetes"] == {"pod": {"name": "foo"}, "namespace": "namespace"}
+    assert system_info["kubernetes"] == {"pod": {"name": socket.gethostname()}, "namespace": "namespace"}
 
 
 def test_config_by_environment():