Make polling apiclient update check frequency configurable

[jpmcb]

Frequency of polled updates

Currently, polling for a new update seem to be every 10 seconds:

bottlerocket-update-operator/agent/src/apiclient.rs

Lines 123 to 128 in c2e9504

	// Retry up to 5 times in case the Update API is busy; Waiting 10 seconds between each attempt.
	while attempts < MAX_ATTEMPTS {
	let output = Command::new(API_CLIENT_BIN)
	.args(&args)
	.output()
	.context(apiclient_error::ApiClientRawCommandSnafu { args: args.clone() })?;

It would be great if there was an brupop setting that made polling for updates configurable

        - name: POLLING_UPDATE_FREQUENCY
          value: 10

where the value is an expected length of seconds

Why?

Some users may not want egress traffic to the updates endpoint very frequently. Or maybe they want to poll for an update more frequently. This may be a network traffic restriction, the fact that nodes are deployed on edge (and polling for frequent updates are not ideal), etc.

[gthao313]

I don't think it's correct maybe I'm wrong.

Currently, pooling for a new update seem to be every 10 seconds:

The attempt logic here is to deal with 423 Locked response. The apiclient only sleep 10 sec if the update API return 423; otherwise if will return the output or error. Update API doesn't support frequent ask at short time, and it will return 423 busy if they are executing something.

bottlerocket-update-operator/agent/src/apiclient.rs

Lines 144 to 148 in c2e9504

	UPDATE_API_BUSY_STATUSCODE => {
	event!(Level::INFO, "API server busy, retrying later ...");
	// Retry after ten seconds if we get a 423 Locked response (update API busy)
	sleep(UPDATE_API_SLEEP_DURATION).await;
	attempts += 1;

Base on that, that setting you think we should introduce might not be related to this part. If I understand correct, we probably can look at agentclient which asks to invoke apiclient update check.

[jpmcb]

Good call - yeah I wasn't sure if that was exactly where we have the logic for frequency of polling. But somewhere, we should have a setting that we can make it configurable for users who need much less polling than we currently provide.

[cbgbt]

#524 reduces the default polling interval to 2 minutes, but I agree that we should make this configurable.