More info: The NoHostAvailable error is happening at random times on each
client host, so it's probably a client error. If the Cassandra cluster was
really offline then all client hosts would report the error at the same
time instead of different random times. The NoHostAvailable error occurs
about once every 30 minutes, so most request call Model.create() without
the error.
On Sun, Dec 31, 2017 at 1:07 AM, Alan Hamlett <alan.haml...@gmail.com>
wrote:
> I'm seeing tracebacks in my Python Flask app when creating rows:
>
> Traceback (most recent call last):
> File "/opt/app/current/app/api.py", line 1174, in consume_heartbeat
> Heartbeat.create(**form_data)
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/models.py",
> line 672, in create
> return cls.objects.create(**kwargs)
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/query.py",
> line 977, in create
> .using(connection=self._connection) \
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/models.py",
> line 738, in save
> if_exists=self._if_exists).save()
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/query.py",
> line 1476, in save
> self._execute(insert)
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/query.py",
> line 1351, in _execute
> results = _execute_statement(self.model, statement, self._consistency,
> self._timeout, connection=connection)
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/query.py",
> line 1505, in _execute_statement
> return conn.execute(s, params, timeout=timeout, connection=connection)
> File
> "/opt/app/current/venv/lib/python3.4/site-packages/cassandra/cqlengine/connection.py",
> line 341, in execute
> result = conn.session.execute(query, params, timeout=timeout)
> File "cassandra/cluster.py", line 2122, in cassandra.cluster.Session.execute
> File "cassandra/cluster.py", line 3982, in
> cassandra.cluster.ResponseFuture.result
> cassandra.cluster.NoHostAvailable: ('Unable to complete the operation against
> any hosts', {})
>
>
> I'm using the cassandra-driver client library 3.12.0 via Flask-CQLAlchemy
> 1.2.0 (https://github.com/thegeorgeous/flask-cqlalchemy) with uWSGI (
> https://github.com/unbit/uwsgi).
>
> cassandra.cqlengine.connection.setup is being passed lazy_connect=True
> and retry_connect=Truecassandra.cqlengine because lazy_connect=False
> causes requests to timeout to the Flask app for some reason.
>
> Also seeing these errors in my uWSGI log file:
>
> [control connection] Error connecting to 10.1.2.3: Traceback (most recent
> call last): File "cassandra/cluster.py", line 2781, in
> cassandra.cluster.ControlConnection._reconnect_internal File
> "cassandra/cluster.py", line 2803, in
> cassandra.cluster.ControlConnection._try_connect File "cassandra/cluster.py",
> line 1195, in cassandra.cluster.Cluster.connection_factory File
> "cassandra/connection.py", line 341, in
> cassandra.connection.Connection.factory cassandra.OperationTimedOut:
> errors=Timed out creating connection (5 seconds), last_host=None
>
>
> What's causing these connection and timeout errors? Something related to
> Flask-CQLAlchemy?
>
