Confirm changes to a config file produce different has values

charms/kubernetes_snaps.py

@@ -6,7 +6,6 @@
 import os
 import re
 from base64 import b64encode
-from functools import lru_cache
 from pathlib import Path
 from socket import getfqdn, gethostname
 from subprocess import DEVNULL, CalledProcessError, call, check_call, check_output
@@ -479,17 +478,20 @@ def configure_scheduler(extra_args_config, kubeconfig):
     )
 
 
-@lru_cache
-def _sha256_file(config_file):
+def _sha256_file(config_file: str) -> hashlib.sha256:
     h = hashlib.sha256()
-    if Path(config_file).exists():
-        with open(config_file, "rb") as file:
+    h.update(config_file.encode())
+    config_file = Path(config_file)
+    if config_file.exists():
+        with config_file.open("rb") as file:
             while True:
                 # Reading is buffered, so we can read smaller chunks.
                 chunk = file.read(h.block_size)
                 if not chunk:
                     break
                 h.update(chunk)
+    else:
+        h.update(b"--empty--")
     return h
 
 
@@ -505,7 +507,7 @@ def _dict_compare(d1, d2):
 
 
 @contextlib.contextmanager
-def _calculate_config_difference(service, args, config_files):
+def _calculate_config_difference(service: str, args, config_files):
     args_hash = _snap_common_path(service) / "args-hash.txt"
 
     # gather existing config hash
@@ -524,18 +526,18 @@ def _calculate_config_difference(service, args, config_files):
     # discern differences
     added, removed, modified, _ = _dict_compare(updated, current)
     for key in added:
-        log.debug("New config value %s in test", key)
+        log.debug("%s: Added config value %s", service.capitalize(), key)
     for key in removed:
-        log.debug("Dropped config value %s in test", key)
+        log.debug("%s: Dropped config value %s", service.capitalize(), key)
     for key in modified:
-        log.debug("Updated config value %s in test", key)
+        log.debug("%s: Updated config value %s", service.capitalize(), key)
 
     different = added or removed or modified
     yield different
     if different:
         yaml.safe_dump(updated, args_hash.open("w"))
     else:
-        log.debug("No config changes detected for %s", service)
+        log.debug("%s: No config changes detected", service.capitalize())
 
 
 def configure_kubernetes_service(

tests/unit/test_kubernetes_snaps.py

@@ -247,7 +247,7 @@ def test_configure_apiserver(mock_path, configure_kubernetes_service, external_c
 @mock.patch("charms.kubernetes_snaps.service_restart")
 def test_configure_kubernetes_service_same_config(service_restart, check_call, caplog):
     caplog.set_level(logging.DEBUG)
-    log_message = "No config changes detected for test"
+    log_message = "Test: No config changes detected"
     base_args = {"arg1": "val1", "arg2": "val2"}
     extra_args = "arg2=val2-updated arg3=val3"
     hashed = {
@@ -272,14 +272,14 @@ def test_configure_kubernetes_service_same_config(service_restart, check_call, c
 @pytest.mark.parametrize(
     "extra_args, log_message",
     [
-        ("arg2=val2-updated", "Dropped config value arg3 in test"),
+        ("arg2=val2-updated", "Test: Dropped config value arg3"),
         (
             "arg2=val2-updated arg3=val3 arg4=val4",
-            "New config value arg4 in test",
+            "Test: Added config value arg4",
         ),
         (
             "arg2=val2-updated arg3=val3-updated",
-            "Updated config value arg3 in test",
+            "Test: Updated config value arg3",
         ),
     ],
     ids=["drop_key", "add_key", "update_key"],
@@ -305,3 +305,28 @@ def test_configure_kubernetes_service_difference(
     mock_open.assert_has_calls([mock.call(), mock.call("w")], any_order=True)
     safe_dump.assert_called_once()
     assert log_message in caplog.text
+
+
+@mock.patch("pathlib.Path.exists")
+def test_sha256_file(mock_exists):
+    # Non Existent file
+    mock_exists.return_value = False
+    hash = kubernetes_snaps._sha256_file("/path/to/file/1").hexdigest()
+    assert hash == "8054b8176bf428f030f0fb8b62ca2c26cf0b983196cfe97358cfb1e206aa9d75"
+
+    # Non Existent file with a different name
+    mock_exists.return_value = False
+    hash = kubernetes_snaps._sha256_file("/path/to/file/2").hexdigest()
+    assert hash == "f337cf841ac045041455bff9cc3f2e0b8a2a5bf5dfe44a0152be04e4fc2355b5"
+
+    # Existing file with same name but empty
+    mock_exists.return_value = True
+    with mock.patch("pathlib.Path.open", mock.mock_open(read_data=b"")):
+        hash = kubernetes_snaps._sha256_file("/path/to/file/2").hexdigest()
+    assert hash == "8d6fb329915afba8724a741f422894e127217854fe1934679e50d2115c2c3ca6"
+
+    # Existing file with same name with data
+    mock_exists.return_value = True
+    with mock.patch("pathlib.Path.open", mock.mock_open(read_data=b"data")):
+        hash = kubernetes_snaps._sha256_file("/path/to/file/2").hexdigest()
+    assert hash == "63699fd3e47d9eb242fe6763bc387a9f3f6d1ae3f08bf7a7c437cec51ce2d0c4"