Exception: ClientConnectorDNSError: Cannot connect to host www.maistra.com:443 ssl:default [Temporary failure in name resolution]

Anže Demšar,

Thanks for reaching out.

Could you please share me the error message screenshot to troubleshoot further.

Here is the error from the logs. Currently it is failing constantly no matter if we use custom DNS server configuration (Gooogle or Cloudflare).

Function app name is "maistra-proxy-prod-2"

Result: Failure
Exception: ClientConnectorDNSError: Cannot connect to host www.maistra.com:443 ssl:default [Temporary failure in name resolution]
Stack: File "/azure-functions-host/workers/python/3.9/LINUX/X64/azure_functions_worker/dispatcher.py", line 674, in _handle__invocation_request
await self._run_async_func(fi_context, fi.func, args)
File "/azure-functions-host/workers/python/3.9/LINUX/X64/azure_functions_worker/dispatcher.py", line 1012, in _run_async_func
return await ExtensionManager.get_async_invocation_wrapper(
File "/azure-functions-host/workers/python/3.9/LINUX/X64/azure_functions_worker/extension.py", line 143, in get_async_invocation_wrapper
result = await function(**args)
File "/home/site/wwwroot/SyncAvailabilityCalendar/__init__.py", line 41, in main
property_ids = await properties_to_sync(date)
File "/home/site/wwwroot/SyncAvailabilityCalendar/__init__.py", line 69, in properties_to_sync
cms_properties = json.loads(await cacheable_request_async('api/properties/index.json', 'en'))
File "/home/site/wwwroot/api.py", line 138, in cacheable_request_async
response = await request_async('GET', api_url)
File "/home/site/wwwroot/api.py", line 58, in request_async
async with session.request(method, url, data=data, headers=headers) as response:
File "/home/site/wwwroot/.python_packages/lib/site-packages/aiohttp/client.py", line 1425, in __aenter__
self._resp: _RetType = await self._coro
File "/home/site/wwwroot/.python_packages/lib/site-packages/aiohttp/client.py", line 703, in _request
conn = await self._connector.connect(
File "/home/site/wwwroot/.python_packages/lib/site-packages/aiohttp/connector.py", line 548, in connect
proto = await self._create_connection(req, traces, timeout)
File "/home/site/wwwroot/.python_packages/lib/site-packages/aiohttp/connector.py", line 1056, in _create_connection
_, proto = await self._create_direct_connection(req, traces, timeout)
File "/home/site/wwwroot/.python_packages/lib/site-packages/aiohttp/connector.py", line 1357, in _create_direct_connection
raise ClientConnectorDNSError(req.connection_key, exc) from exc

We also added a new diagnostics function app to the same datacenter, trying to connect and the error happens every ~10th run
https://maistra-proxy-diagnostics-py.azurewebsites.net/api/NetworkTest?dns_loops=20

Seems like there is no issue on a windows c# app though (same datacenter).

Any further response would be much appreciated.

Anže Demšar,

To avoid intermittent DNS failures please configure retry logic.

Also, please check If your function app is inside a VNet, check VNet DNS settings or try allowing outbound internet access.

Please confirm on your function plan.?

Anže Demšar,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.