gaborgsomogyi commented on code in PR #19372:
URL: https://github.com/apache/flink/pull/19372#discussion_r848157811
##########
flink-runtime/src/main/java/org/apache/flink/runtime/security/token/KerberosDelegationTokenManager.java:
##########
@@ -110,13 +126,84 @@ public void obtainDelegationTokens(Credentials
credentials) {
* task managers.
*/
@Override
- public void start() {
- LOG.info("Starting renewal task");
+ public void start() throws Exception {
+ checkState(renewalExecutor == null, "Manager is already started");
+
+ if (!isRenewalPossible()) {
+ LOG.info("Renewal is NOT possible, skipping to start renewal
task");
+ return;
+ }
+
+ ThreadFactory threadFactory =
+ new ThreadFactoryBuilder()
+ .setDaemon(true)
+ .setNameFormat("Credential Renewal Thread")
+ .build();
+ renewalExecutor = new ScheduledThreadPoolExecutor(1, threadFactory);
Review Comment:
After I've had a deep look I've found the following obstacles which blocks
us to use the mentioned executors:
* If you mean `ResourceManager.getMainThreadExecutor` to use in the first
bullet point then that's a `MainThreadExecutor` instance which doesn't support
`scheduleAtFixedRate`, please see
[here](https://github.com/apache/flink/blob/4034d3cd6d13e88e2e5ca101510bf333e94a53fa/flink-rpc/flink-rpc-core/src/main/java/org/apache/flink/runtime/rpc/RpcEndpoint.java#L537).
We can implement that from scratch but touching core threading can be super
dangerous, though I'm not against it to add such functionality.
* If we would rely on `ResourceManager.getMainThreadExecutor` then we must
modify the interface (`start` function) and we need to put implementation
details into the interface (the 2 executors) which would frustrate me a bit. I
think if we want to do dependency injection then the proper place would be the
constructor which is not touching the interface. Here if we decide to modify
the interface I can accept that but I would think the implementation would be
less clean.
* If we would add the new `scheduleAtFixedRate` functionality then
`ResourceManager` usage is covered but in
[MiniCluster](https://github.com/apache/flink/blob/f089a99ce73ad15531a4d1b72899d8367fab662a/flink-runtime/src/main/java/org/apache/flink/runtime/minicluster/MiniCluster.java#L431)
we must provide something too but there no such executor exists (at least I've
not found anything) so we need to come up w/ a new executor anyway.
All in all I've left the original code there for now until we make an
agreement.
Would like to hear your voice on this.
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