[Date Prev][Date Next] [Chronological] [Thread] [Top]

Re: Enforce serverID 0 is for single-master only

Howard Chu wrote:
Rein Tollevik wrote:

This would mean that slapd would refuse to start if syncrepl or syncprov
finds a contextCSN value with SID=0 in the database upon startup and
there is more than one contextCSN, or if MirrorMode is enabled. Syncrepl
should refuse to receive updates to contextCSN values under the same
conditions, and tear down the connection (and retry later) if one is seen.

The above check is going to be pretty annoying since there's no convenient offline tool to correct the situation. Note that the tool interface now provides a modify entry point, which is used by slapadd to update the contextCSN. If we provide a slapmodify offline tool, then this might be acceptable, but I still think it's going to be pretty annoying.

Yes, it will be annoying for those that have it misconfigured. That's why I suggest the slapd -c sid=xxx change to allow them easy access to fix their mistakes. But, being informed of a config error instead of having to track down the effects of it might not be so bad after all.

Just from a simple usage perspective, aside from adding a serverID to my config, I shouldn't have to do anything special to convert an existing single-master DB to a MM deployment.

You must also get rid of your old contextCSN with sid=0. Or you will be stuck with a value that no-one updates, and all the refresh phases will replay everthing that have happend since you switch to MM..

Syncprov should also refuse slapd to start if serverID is 0 and
MirrorMode is enabled

That sounds OK.

or any contextCSN with non-zero SIDs are found.

That's probably going too far.

Maybe, but then we will not be enforcing serverID 0 is for single master, and cannot assume that a csn with sid=0 was received from a mis-configured server.

This would require a non-zero serverID also on pure forwarding servers
that never changes anything by them self.

I don't think so. If they never change anything then their SID never propagates.

Their sid will not propagate, but the forwarding only servers would still barf seeing the serverID 0 it it was enforced as I outlined it.