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By hashing the config values and files, only restart services on differences #31

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By hashing the config values and files, only restart services on differences #31

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a97748f
By hashing the config values and files, only restart services when co…
addyess Aug 22, 2024
5c7fe83
Confirm changes to a config file produce different has values
addyess Aug 22, 2024
39d841e
check file existence with Path.is_file
addyess Aug 22, 2024
768eb06
improved set operations
addyess Aug 22, 2024
c1ebc5e
enable/disable cache calculation feature with env var
addyess Sep 6, 2024
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13 changes: 13 additions & 0 deletions charms/kubernetes_snaps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -478,6 +478,12 @@ def configure_scheduler(extra_args_config, kubeconfig):
)


def _enable_config_hashing() -> bool:
"""This is a debug option to enable config hashing."""
env = os.environ.get("JUJU_FEATURE_KUBERNETES_SNAP_CONFIG_HASHING") or ""
return env.lower() == "on"


Comment on lines +481 to +486
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This allows the charm at runtime (per hook even!!!) decide whether or not it wants to enable hashing.

Now an upgrade action could restart the service even if there aren't any config changes. We could even expose via charm config (though i think that'd be going too far).

def _sha256_file(config_file: str) -> hashlib.sha256:
h = hashlib.sha256()
h.update(config_file.encode())
Expand Down Expand Up @@ -510,6 +516,13 @@ def _dict_compare(d1, d2):
def _calculate_config_difference(service: str, args, config_files):
args_hash = _snap_common_path(service) / "args-hash.txt"

if not _enable_config_hashing():
log.debug("Config hashing disabled, skipping config change detection")
yield True
args_hash.unlink(missing_ok=True)
return
Comment on lines +519 to +523
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if hashing isn't enabled, this method declares there are changes, and we should reconfigure the service (as before this feature existed) and it also clears the cache file if one exists.


log.debug("Checking for config changes for %s", service)
# gather existing config hash
current, updated = {}, {}
if Path.is_file(args_hash):
Expand Down
34 changes: 32 additions & 2 deletions tests/unit/test_kubernetes_snaps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -245,7 +245,36 @@ def test_configure_apiserver(mock_path, configure_kubernetes_service, external_c
@mock.patch("pathlib.Path.is_file", mock.MagicMock(return_value=True))
@mock.patch("charms.kubernetes_snaps.check_call")
@mock.patch("charms.kubernetes_snaps.service_restart")
def test_configure_kubernetes_service_same_config(service_restart, check_call, caplog):
def test_configure_kubernetes_service_no_hashing(
service_restart, check_call, caplog, monkeypatch
):
monkeypatch.setenv("JUJU_FEATURE_KUBERNETES_SNAP_CONFIG_HASHING", "")
caplog.set_level(logging.DEBUG)
log_message = "Config hashing disabled, skipping config change detection"
base_args = {"arg1": "val1", "arg2": "val2"}
extra_args = "arg2=val2-updated arg3=val3"
with mock.patch("pathlib.Path.unlink") as mock_unlink:
kubernetes_snaps.configure_kubernetes_service("test", base_args, extra_args)
service_restart.assert_called_once_with("snap.test.daemon")
check_call.assert_called_once_with(
[
"snap",
"set",
"test",
'args=--arg1="val1" --arg2="val2-updated" --arg3="val3"',
]
)
mock_unlink.assert_called_once_with(missing_ok=True)
assert log_message in caplog.text


@mock.patch("pathlib.Path.is_file", mock.MagicMock(return_value=True))
@mock.patch("charms.kubernetes_snaps.check_call")
@mock.patch("charms.kubernetes_snaps.service_restart")
def test_configure_kubernetes_service_same_config(
service_restart, check_call, caplog, monkeypatch
):
monkeypatch.setenv("JUJU_FEATURE_KUBERNETES_SNAP_CONFIG_HASHING", "on")
caplog.set_level(logging.DEBUG)
log_message = "Test: No config changes detected"
base_args = {"arg1": "val1", "arg2": "val2"}
Expand Down Expand Up @@ -285,8 +314,9 @@ def test_configure_kubernetes_service_same_config(service_restart, check_call, c
ids=["drop_key", "add_key", "update_key"],
)
def test_configure_kubernetes_service_difference(
service_restart, check_call, extra_args, log_message, caplog
service_restart, check_call, extra_args, log_message, caplog, monkeypatch
):
monkeypatch.setenv("JUJU_FEATURE_KUBERNETES_SNAP_CONFIG_HASHING", "on")
caplog.set_level(logging.DEBUG)
base_args = {"arg1": "val1", "arg2": "val2"}
hashed = {
Expand Down