Docs: HA logging

[voidspace]

A note on logging for HA. This should be part of the HA docs, when we have them.

Logging with HA

When running JuJu with HA (ensure-availability) logging is done to all state servers. "juju debug-log" connects to a random state server, but you'll still see logs from all the state servers and all units. This means that if your master (term?) state server dies, you'll still have logs on the other state servers and still see new logging.Essentially this means that logging works the same with HA as it does without HA. You can use "juju debug-log", or ssh into a state server and view the log file directly, to see all the logs.

Logging to a state server starts once a new state server comes online, i.e. after running ensure-availability. So if your master state server dies you will lose the logs from before new state servers were started.This will be fixed at some point, so new state servers will have all existing logs synced to them when they come online. This is not currently the case.

[evilnick]

thanks!

[pmatulis]

@voidspace

not clear (to me):

Logging to a state server starts once a new state server comes online [...]. So if your master state
server dies you will lose the logs from before new state servers were started.

1. does the logging to all state servers depend on the master?

I don't think so. Using rsyslog all units log to all of the state servers I believe.

1. for HA there are already multiple state servers so why say "before new state servers were started"?

Not entirely true. You always start with one state server and then you move to HA by starting new state servers. This is what is discussed (new state servers can be added, up to a maximum of 5 total, at any time).

1. i do, however, understand the point of a newly started state server not having cluster logs synced. has this been fixed?

I don't believe so.

1. has any of this been blogged/referenced anywhere else?

I don't believe so.

[pmatulis]

Reminder to talk about this here:

• juju-ha
• troubleshooting-debug-log

[pmatulis]

I removed label 'bug' because this feature (syncing past logs to new state servers) was never implemented and it's not important enough to prevent me from documenting HA logging.

I opened a bug on this now: LP #1484688.

[pmatulis]

How does the Juju master get associated with the Mongodb master? Is it random (among the ones which are about to be created) or is it always the initial single state server?

[evilnick]

i believe the latter, but i am sure someone on #juju could tell you

[pmatulis]

PR #604 merged. Closing.