I have a Glue script which is supposed to write its result in a Redshift table in a for loop.
After many hours of processing it raises this exception:
Py4JJavaError: An error occurred while calling o11362.pyWriteDynamicFrame.
: java.sql.SQLException: [Amazon](500150) Error setting/closing connection: Connection refused.
Why am I getting this exception?
It turns out that Redshift clusters have a maintenance window in which they are re-booted. This event of course causes the Glue Job to fail when attempting to write to a table of that cluster.
May be useful to reschedule the maintenance window https://docs.aws.amazon.com/redshift/latest/mgmt/managing-clusters-console.html
This error can occur for many reasons. I'm sure after a few google searches you've found that the most common cause of this is improper security group settings for your cluster (make sure your inbound settings are correct).
I would suggest that you make sure you're able to create a connection for even a short period of time before you try this longer process. If you are able to do so, then I bet the issue is that your connection is closing out after a timeout (since your process is so long). To solve this, you should look into connection pooling, which involves creating an instance of a connection and constantly checking to ensure it is still alive, thus allowing a process to continuously use the cluster connection.
Related
I have a bunch of tasks within a Cloud Composer Airflow DAG, one of which is a KubernetesPodOperator. This task seems to get stuck in the scheduled state forever and so the DAG runs continuously for 15 hours without finishing (it normally takes about an hour). I have to manually mark it failed for it to end.
I've set the DAG timeout to 2 hours but it does not make any difference.
The Cloud Composer logs show the following error:
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not connect to server:
Connection refused
Is the server running on host "airflow-sqlproxy-service.default.svc.cluster.local" (10.7.124.107)
and accepting TCP/IP connections on port 3306?
The error log also gives me a link to this documentation about that error type: https://docs.sqlalchemy.org/en/13/errors.html#operationalerror
When the DAG is next triggered on schedule, it works fine without any fix required. This issue happens intermittently, we've not been able to reproduce it.
Does anyone know the cause of this error and how to fix it?
The reason behind the issue is related to SQLAlchemy using a session by a thread and creating a callable session that can be used later in the Airflow Code. If there are some minimum delays between the queries and sessions, MySQL might close the connection. The connection timeout is set to approximately 10 minutes.
Solutions:
Use the airflow.utils.db.provide_session decorator. This decorator
provides a valid session to the Airflow database in the session
parameter and closes the session at the end of the function.
Do not use a single long-running function. Instead, move all database
queries to separate functions, so that there are multiple functions
with the airflow.utils.db.provide_session decorator. In this case,
sessions are automatically closed after retrieving query results.
So, this problem is happening randomly (it seems) and between different services.
For example we have a service A which needs to talk to service B, and some times we get this error, but after a while, the error goes away. And this error doesn't happen too often.
When this happens, we see the error log in service A throwing the “upstream connect error” message, but none in service B. So we think it might be related with the sidecars.
One thing we notice is that in service B, we get a lot of this error messages in the istio-proxy container:
[src/istio/mixerclient/report_batch.cc:109] Mixer Report failed with: UNAVAILABLE:upstream connect error or disconnect/reset before headers. reset reason: connection failure
And according to documentation when a request comes in, envoy asks Mixer if everything is good (authorization and other things), and if Mixer doesn’t reply, the request is not success. So that’s why exists an option called policyCheckFailOpen.
We have that in false, I guess is a sane default, we don’t want the request to go through if Mixer cannot be reached, but why can’t?
disablePolicyChecks: true
policyCheckFailOpen: false
controlPlaneSecurityEnabled: false
NOTE: istio-policy is running with the istio-proxy sidecar. Is that correct?
We don’t see that error in some other service which can also fail.
Another log that I can see a lot, and this one happens in all the services not running as root with fsGroup defined in the YAML files is:
watchFileEvents: "/etc/certs": MODIFY|ATTRIB
watchFileEvents: "/etc/certs/..2020_02_10_09_41_46.891624651": MODIFY|ATTRIB
watchFileEvents: notifying
One of the leads I'm chasing is about default circuitBreakers values. Could that be related with this?
Thanks
The error you are seeing is because of a failure to establish a connection to istio-policy
Based on this github issue
Community members add two answers here which could help you with your issue
If mTLS is enabled globally make sure you set controlPlaneSecurityEnabled: true
I was facing the same issue, then I read about protocol selection. I realised the name of the port in the service definition should start with for example http-. This fixed the issue for me. And . if you face the issue still you might need to look at the tls-check for the pods and resolve it using destinationrules and policies.
istio-policy is running with the istio-proxy sidecar. Is that correct?
Yes, I just checked it and it's with sidecar.
Let me know if that help.
How have I written the code
createPool is used at the start of the app
then for every request I am using getConnection
I am using AWS RDS & it went into sudden recovery mode, due to which my db url was unchanged but instance IP must have changed as it was created in another AZ
So for such a scenario I am supposed to reinitialize my db connection so that new instance DNS is updated.
The issue is in such a scenario I did not received any timeout error or connection error. So how do I capture this type of error?
Kindly guide if possible.
Thanks
It is unclear from your description what exactly you have built, but it sounds like you've created a connection pool.
If you open a connection to the db, the first time you call getConnection you should validate that the connection is still active - obviously if the db fails over, the existing connection will get closed, and you will either need to create a new connection or re-open the existing one.
I have a worker role that uses an EventProcessorHost to ingest data from an EventHub. I frequently receive error messages of the following kind:
Microsoft.ServiceBus.Messaging.MessagingCommunicationException:
No connection handler was found for virtual host 'myservicebusnamespace.servicebus.windows.net:42777'. Remote container id is 'f37c72ee313c4d658588ad9855773e51'. TrackingId:1d200122575745cc89bb714ffd533b6d_B5_B5, SystemTracker:SharedConnectionListener, Timestamp:8/29/2016 6:13:45 AM
at Microsoft.ServiceBus.Common.ExceptionDispatcher.Throw(Exception exception)
at Microsoft.ServiceBus.Common.Parallel.TaskHelpers.EndAsyncResult(IAsyncResult asyncResult)
at Microsoft.ServiceBus.Messaging.IteratorAsyncResult`1.StepCallback(IAsyncResult result)
I can't seem to find a way to catch this exception. It seems I can just ignore the error because everything works as expected (I had previously mentioned here that it was dropping messages because of this error, but I have since found out that a bug in the software that sends the messages caused this problem), however I would like to know what causes these errors, since they are clogging up my logging now and then.
Can anyone shed some light on the cause?
The Event Hub partitions are distributed across multiple servers. They sometimes move due to load balancing, upgrade and other reasons. When this happens, the client connection is lost with this error. The connection will be reestablished very quickly so you should not see any issues with message processing. It is safe to ignore this communication error.
We have Clojure code which reads from a Rabbit queue. We would like to tolerate the case where the RabbitMQ server is down briefly, e.g. in the case of a restart (sudo service rabbitmq-server restart).
There appears to be some provision for reconnecting in Langohr. We adapted the example clojurewerkz.langohr.examples.recovery.example1 (Gist here). Slight differences vs. the published example include the connection parameters, and the removal of the lb/publish call (since we're filling the data with an external source).
We can successfully consume data from the queue and wait for more messages. However, when we restart RMQ (via the above sudo command on the VM hosting RabbitMQ), the following exception is thrown:
Caught an exception during connection recovery!
java.io.IOException
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:106)
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:102)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:378)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:516)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:545)
at com.novemberain.langohr.Connection.recoverConnection(Connection.java:166)
at com.novemberain.langohr.Connection.beginAutomaticRecovery(Connection.java:115)
at com.novemberain.langohr.Connection.access$000(Connection.java:18)
at com.novemberain.langohr.Connection$1.shutdownCompleted(Connection.java:93)
at com.rabbitmq.client.impl.ShutdownNotifierComponent.notifyListeners(ShutdownNotifierComponent.java:75)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:573)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error; reason: java.io.EOFException
at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:67)
at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:33)
at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:343)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:321)
... 8 more
Caused by: java.io.EOFException
at java.io.DataInputStream.readUnsignedByte(DataInputStream.java:273)
at com.rabbitmq.client.impl.Frame.readFrom(Frame.java:95)
at com.rabbitmq.client.impl.SocketFrameHandler.readFrame(SocketFrameHandler.java:131)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:533)
It seems likely that the intended restart mechanism provided by Langohr is breaking when it kicks in. Is there an alternative pattern which is preferred in the case of these "hard" restarts? Alternatively, I suppose we have to implement connection monitoring and retries ourselves. Any suggestions would be most welcome.
We used to see such stack traces, but we no longer see them with Langohr 2.9.0. After a restart, our clojure clients reconnect and messages start flowing again.
We are using the defaults, which have connection and topology coverage turned on, as shown by this:
(infof "Automatic recovery enabled? %s" (rmq/automatic-recovery-enabled? connection))
(infof "Topology recovery enabled? %s" (rmq/automatic-topology-recovery-enabled? connection))