I have a Zookeeper ensemble I'd like to upgrade from 3.3.X to 3.4.X branch. Can this be done on a live cluster? Requires downtime? Are there any instructions to be found on this somewhere?
From what I checked ,
What are the options/process for upgrading ZooKeeper?
There are two primary ways of doing this; 1) full restart or 2) rolling restart.
In the full restart case you can stage your updated code/configuration/etc..., stop all of the servers in the ensemble, switch code/configuration, and restart the ZooKeeper ensemble. If you do this programmatically (scripts typically, ie not by hand) the restart can be done on order of seconds. As a result the clients will lose connectivity to the ZooKeeper cluster during this time, however it looks to the clients just like a network partition. All existing client sessions are maintained and re-established as soon as the ZooKeeper ensemble comes back up. Obviously one drawback to this approach is that if you encounter any issues (it's always a good idea to test/stage these changes on a test harness) the cluster may be down for longer than expected.
The second option, preferable for many users, is to do a "rolling restart". In this case you upgrade one server in the ZooKeeper ensemble at a time; bring down the server, upgrade the code/configuration/etc..., then restart the server. The server will automatically rejoin the quorum, update it's internal state with the current ZK leader, and begin serving client sessions. As a result of doing a rolling restart, rather than a full restart, the administrator can monitor the ensemble as the upgrade progresses, perhaps rolling back if any issues are encountered
I am thinking you need to download the file and extract to a local folder and transfer the configuration file/settings into the new version and have the old server down and run the new version server
https://wiki.apache.org/hadoop/ZooKeeper/FAQ
Related
I am seeing various different issues while trying to start Kafka services on wsl2. Details/symptoms below:
Confluent Kafka (7.0.0) platform
wsl2 - ubuntu 20.04LTS
When I use the command:
confluent local services start
Typically the system will take a long time and then exit with service failed (e.g. zookeeper, as that is the first service to start).
If I check the logs, it is actually started. So I again type the command and sure enough it immediately says zookeeper up, then proceed to try start kafka, which again after a min will say failed to start (but it really has started).
I suspect after starting the service (which is quite fast), system is not able to communicate back/exit and thus times out, I am not sure where the logs related to this are.
Can see this in the screenshot below
This means to start the whole stack (zookeeper/kafka/schema-registry/kafka-rest/kafka-connect/etc), takes forever, and in between I start getting other errors (sometimes, schema-registry is not able to find the cluster id, sometimes its a log file related error), which means I need to destroy and start again.
I have tried this over a couple of days and cant get this to work. Is confluent kafka that unstable on windows or I am missing some config change.
In terms of setup, I have not done any change in the config and am using the default config/ports.
When I did the upgrade of concourse from 3.4.0 to 3.5.0, suddenly all running jobs changed their state from running to errored. I can see the string 'no workers' appearing at the start of their log now. Starting the jobs manually or triggered by the next changes didn't have any problem.
The upgrade of concourse itself was successful.
I was watching what bosh did at the time and I saw this change of job states took place all at once while either the web or the db VM was upgraded (I don't know which one). I am pretty sure that the worker VMs were not touched yet by bosh.
Is there a way to avoid this behavior?
We have one db, one web VM and six workers.
With only one web VM it's possible that it was out of service for long enough that all workers expired. Workers continuously heartbeat and if they miss two heartbeats (which takes 1 minute by default) they'll stall. They should come back after the deploy is finished but if scheduling happened before they heartbeats, that would cause those errors.
I'm using mesosphere on 3 host over Ubuntu 14.04 as follow:
one with mesos master
two with mesos slave
All work fine, but after restart all physical hosts all scheduled job was lost. It's normal? I'm expected that zookeeper will store the current jobs, then when the system will need restart it, all jobs will be rescheduled after the master boot.
Update:
I'm using marathon and mesos on a same node, and I'm run marathon with flag --zk
With marathon's --zk and --ha enabled, Marathon should be storing its state in ZK and recovering it on restart, as long as Mesos allows it to reregister with the same framework ID.
However, you'll also need to enable the Mesos registry (even for a single master), to ensure that Mesos persists information about what frameworkIds are registered in the event of master failover. This can be accomplished by setting the --registry=replicated_log (default), --quorum=1 (since you only have 1 master), and --work_dir=/path/to/registry (where to store the state).
I solved the problem following this installation instructions: How To Configure a Production-Ready Mesosphere Cluster on Ubuntu 14.04
Although you found a solution, I'd like to explain more to this issue:)
In official doc：http://mesos.apache.org/documentation/latest/slave-recovery/
Note that if the operating system on the slave is rebooted, all
executors and tasks running on the host are killed and are not
automatically restarted when the host comes back up.
So all frameworks on Mesos will be killed after reboot. One way to restart the frameworks is to run all frameworks on Marathon, which will manage other frameworks and restart them in need.
However, then you need to auto-restart Marathon when it's killed. In the digitialocean link you mentioned, the Marathon is installed with script in init.d, so it can be restarted after rebooted. Otherwise, if you installed the Marathon via source code, you can use tools like supervisord to monitor Marathon.
We are young team building an applicaiton using Storm and Kafka.
We have common Zookeeper ensemble of 3 nodes which is used by both Storm and Kafka.
I wrote a test case to test zooker Failovers
1) Check all the three nodes are running and confirm one is elected as a Leader.
2) Using Zookeeper unix client, created a znode and set a value. Verify the values are reflected on other nodes.
3) Modify the znode. set value in one node and verify other nodes have the change reflected.
4) Kill one of the worker nodes and make sure the master/leader is notified about the crash.
5) Kill the leader node. Verify out of other two nodes, one is elected as a leader.
Do i need i add any more test case? additional ideas/suggestion/pointers to add?
From the documentation
Verifying automatic failover
Once automatic failover has been set up, you should test its operation. To do so, first locate the active NameNode. You can tell which node is active by visiting the NameNode web interfaces -- each node reports its HA state at the top of the page.
Once you have located your active NameNode, you may cause a failure on that node. For example, you can use kill -9 to simulate a JVM crash. Or, you could power cycle the machine or unplug its network interface to simulate a different kind of outage. After triggering the outage you wish to test, the other NameNode should automatically become active within several seconds. The amount of time required to detect a failure and trigger a fail-over depends on the configuration of ha.zookeeper.session-timeout.ms, but defaults to 5 seconds.
If the test does not succeed, you may have a misconfiguration. Check the logs for the zkfc daemons as well as the NameNode daemons in order to further diagnose the issue.
more on setting up automatic failover
I never have my hands on coding. I got a doubt regarding mongodb replica sets
below is the situation
I have an alert monitoring application.
It is using mongodb with replica set with 3 nodes.
Applications Java code base keep connecting to the primary and doing some transactions.
Now my question is that,
if the primary server is down, how will it effect the application server.
I mean, would the app server writes error saying connection failed like errors.
OR
the replica set will pick one of the slaves automatically as master and provides the application server to do its activity. How will it happen...?
Thanks & Regards,
UDAY
The replica set will try to pick another server as the new primary. If you have three nodes, and one goes down, the other two will negotiate which one becomes the new master. If two go down, or somehow communication between the remaining breaks down, there will be no new master until the situation is recovered.
The official drivers support this automatic fail-over, as does the mongos routing server if you use it. So the application code does not need to do anything here.
I am not sure if there will be connection errors during the brief period of time this fail-over negotiation takes (you will probably get errors for a few seconds).