My flink job loads several configuration files that contain job, operator and
business configuration. One of the operators is an AsyncOperator with
function like so:
class AsyncFun(config: T) extends RichAsyncFunction[X, Y] {
@transient private lazy val client = f(config, metricGroup, etc.)
@transient private lazy val metricGroup = ...
def asyncInvoke(....)
}
The variables are declared lazily as an alternative to implementing the open
method. This is un-avoidable as we're relying on flink's monitoring
libraries. Application resumes from checkpoint upon unexpected termination.
However, sometimes I want to change the parameter config that's passed as a
constructor argument but it doesn't work as Flink tries to restore from the
submittedJobGraph. This makes sense as Flink by itself doesn't know whether
its recovering from an abrupt termination and must therefore rely on old
config to build client or whether to start afresh. I want to know what
options do we have to allow for configuration changes (i.e. re-initializing
the operators):
1. Is there any way to restore from a checkpoint as well as recreate client
using newer configuration?
2. If we take a savepoint (drain and save) and then resume the job, then
will the configuration changes happen?
3. Will we have to move away from flink monitoring so as to initialize the
client inside the constructor?
4. One option is to remove the constructor argument entirely and load config
inside the open method. I want to know how this can be done without exposing
the entire application configuration. I could store the configuration inside
job parameters (by somehow converting this object to a map which I don't
want to) but how to load it back as this operator function is used by
multiple operators?
5. Any other option?
For functions that aren't AsyncFunction, is leveraging BroadcastState the
only way to dynamically update configuration?
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