feat(linstorvolumemanager): cache controller uri in a file #83

Millefeuille42 · 2025-03-05T09:46:06Z

No description provided.

Wescoeur · 2025-04-14T09:45:23Z

drivers/linstorvolumemanager.py

+    address = uri.removeprefix("linstor://")
+    session = util.timeout_call(10, util.get_localAPI_session)
+    for host_ref, host_record in session.xenapi.host.get_all():
+        if host_record.get('address', '') != address:
+            continue
+        return util.strtobool(
+            session.xenapi.host.call_plugin(host_ref, PLUGIN, PLUGIN_CMD, {})


I'm not sure that's necessary here. We can instead do a refactoring of the codebase:

We will assume that the cache is valid 99% of the time.

We can directly attempt to create a LINSTOR instance from the URI without checking anything using a plugin. This is the initial idea.

I think we can implement a new static function on LinstorVolumeManager that is used to create an instance of the class using the cached value directly without any checks. If it fails, we rebuild the local cache and try again. This allows us to improve several smapi functions.

There are a few edge cases left with this idea:

In some places we use the URI to create the journaler (linstor.KV) and to create a linstor object. We could try to use the cached URI without checks again and add a try/catch directly on these specific cases. In case of connection failure, we explicitly request the cache update.

I see one last edge case concerning the creation of a linstor instance using get_ips_from_xha_config_file, we could directly use the function to get the cached URI. In the worst can we can again fallback on the xha config file.

Edge cases are almost done. I pushed modification of the added functions 042014f and created the static method you suggested 0364eed. Could you please take a look at the current state of those functions to validate them before I start the refactor ?

Sounds good from my POV. Feel free to continue when you have time. :)

drivers/LinstorSR.py

drivers/linstorjournaler.py

drivers/linstorvolumemanager.py

drivers/LinstorSR.py

drivers/linstorvolumemanager.py

drivers/linstorjournaler.py

drivers/linstorvolumemanager.py

drivers/LinstorSR.py

drivers/linstorvolumemanager.py

Wescoeur · 2025-06-26T10:22:41Z

drivers/linstorvolumemanager.py

+def get_cached_controller_uri(ctx=None):
+    try:
+        with ctx if ctx else shared_reader(CONTROLLER_CACHE_PATH) as f:
+            return f.read().strip()
+    except FileNotFoundError:
+        pass
+    except Exception as e:
+        util.SMlog('Unable to read controller URI cache file at `{}` : {}'.format(CONTROLLER_CACHE_PATH,e))


Suggested change

def get_cached_controller_uri(ctx=None):

try:

with ctx if ctx else shared_reader(CONTROLLER_CACHE_PATH) as f:

return f.read().strip()

except FileNotFoundError:

pass

except Exception as e:

util.SMlog('Unable to read controller URI cache file at `{}` : {}'.format(CONTROLLER_CACHE_PATH,e))

def _read_controller_uri_from_file(f):

try:

return f.read().strip()

except Exception as e:

util.SMlog('Unable to read controller URI cache file at `{}`: {}'.format(CONTROLLER_CACHE_PATH, e))

def read_controller_uri_cache():

try:

with shared_reader(CONTROLLER_CACHE_PATH) as f:

return _read_controller_uri_from_file(f)

except FileNotFoundError:

pass

except Exception as e:

util.SMlog('Unable to read controller URI cache file at `{}`: {}'.format(CONTROLLER_CACHE_PATH, e))

done in 4f84f23

Wescoeur · 2025-06-26T10:23:15Z

drivers/linstorvolumemanager.py

+def delete_controller_uri_cache(ctx=None):
+    try:
+        with ctx if ctx else excl_writer(CONTROLLER_CACHE_PATH) as f:
+            f.seek(0)
+            f.truncate()
+    except FileNotFoundError:
+        pass
+    except Exception as e:
+        util.SMlog('Unable to delete uri cache file at `{}` : {}'.format(CONTROLLER_CACHE_PATH, e))


Suggested change

def delete_controller_uri_cache(ctx=None):

try:

with ctx if ctx else excl_writer(CONTROLLER_CACHE_PATH) as f:

f.seek(0)

f.truncate()

except FileNotFoundError:

pass

except Exception as e:

util.SMlog('Unable to delete uri cache file at `{}` : {}'.format(CONTROLLER_CACHE_PATH, e))

def delete_controller_uri_cache():

try:

with excl_writer(CONTROLLER_CACHE_PATH) as f:

f.seek(0)

f.truncate()

except FileNotFoundError:

pass

except Exception as e:

util.SMlog('Unable to delete URI cache file at `{}`: {}'.format(CONTROLLER_CACHE_PATH, e))

done in 4f84f23

Wescoeur · 2025-06-26T10:26:50Z

drivers/linstorvolumemanager.py

+def write_controller_uri_cache(uri, ctx=None):
+    try:
+        if not os.path.exists(CONTROLLER_CACHE_DIRECTORY):
+            os.makedirs(CONTROLLER_CACHE_DIRECTORY)
+            os.chmod(CONTROLLER_CACHE_DIRECTORY, 0o700)
+        with ctx if ctx else excl_writer(CONTROLLER_CACHE_PATH) as f:
+            f.seek(0)
+            f.write(uri)
+            f.truncate()
+    except FileNotFoundError:
+        pass
+    except Exception as e:
+        util.SMlog('Unable to write URI cache file at `{}` : {}'.format(CONTROLLER_CACHE_PATH, e))
+
+
+def build_controller_uri_cache():
+    with excl_writer(CONTROLLER_CACHE_PATH) as f:
+        uri = get_cached_controller_uri(contextlib.nullcontext(f))
        if uri:
            return uri
+        uri = _get_controller_uri()
+        if not uri:
+            for retries in range(9):
+                time.sleep(1)
+                uri = _get_controller_uri()
+                if uri:
+                    break

-        retries += 1
-        if retries >= 10:
-            break
-        time.sleep(1)
+        if uri:
+            write_controller_uri_cache(uri, contextlib.nullcontext(f))
+        return uri


Cannot add suggestion due to github limitation but:

def build_controller_uri_cache(): uri = '' try: with excl_writer(CONTROLLER_CACHE_PATH) as f: uri = _read_controller_uri_from_file(f) if uri: return uri uri = _get_controller_uri() if not uri: for retries in range(9): time.sleep(1) uri = _get_controller_uri() if uri: break if uri: f.seek(0) f.write(uri) f.truncate() except FileNotFoundError: if os.path.exists(CONTROLLER_CACHE_DIRECTORY): raise os.makedirs(CONTROLLER_CACHE_DIRECTORY) os.chmod(CONTROLLER_CACHE_DIRECTORY, 0o700) return build_controller_uri_cache() except Exception as e: util.SMlog('Unable to write URI cache file at `{}` : {}'.format(CONTROLLER_CACHE_PATH, e)) return uri

done in 1f6ffbb

Wescoeur · 2025-06-26T10:27:29Z

drivers/linstorvolumemanager.py

+def get_controller_uri():
+    uri = get_cached_controller_uri()
+    if not uri:
+        uri = build_controller_uri_cache()
+    return uri


Suggested change

def get_controller_uri():

uri = get_cached_controller_uri()

if not uri:

uri = build_controller_uri_cache()

return uri

def get_controller_uri():

uri = read_controller_uri_cache()

if not uri:

uri = build_controller_uri_cache()

return uri

done in 4f84f23

Wescoeur · 2025-06-26T10:28:21Z

drivers/linstorvolumemanager.py

+        :param function logger: Function to log messages.
+        :param int attempt_count: Number of attempts to join the controller.
+        """
+        uri = get_cached_controller_uri()


Suggested change

uri = get_cached_controller_uri()

uri = read_controller_uri_cache()

done in 4f84f23

Co-authored-by: Ronan Abhamon <[email protected]> Co-authored-by: Damien Thenot <[email protected]> Signed-off-by: Mathieu Labourier <[email protected]>

Millefeuille42 requested review from Wescoeur and Nambrok March 5, 2025 09:46

Millefeuille42 self-assigned this Mar 5, 2025

Wescoeur changed the base branch from 3.2.3-8.3 to 3.2.12-8.3 March 20, 2025 14:33

Millefeuille42 force-pushed the mlr-533-cache-controller-uri-in-a-file branch 2 times, most recently from 958caec to 42b42bc Compare March 20, 2025 14:53

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feat: add caching functions for controller_uri

3579d92

Co-authored-by: Ronan Abhamon <[email protected]> Co-authored-by: Damien Thenot <[email protected]> Signed-off-by: Mathieu Labourier <[email protected]>

Millefeuille42 force-pushed the mlr-533-cache-controller-uri-in-a-file branch from 6cdeb37 to 3579d92 Compare September 4, 2025 14:12

	uri = get_cached_controller_uri()
	uri = read_controller_uri_cache()

feat(linstorvolumemanager): cache controller uri in a file #83

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feat(linstorvolumemanager): cache controller uri in a file #83

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Millefeuille42 commented Mar 5, 2025

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Millefeuille42 Apr 28, 2025 •

edited

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