I was speaking with Howard in person last week at LDAPCon about the problems I might hit if I wanted to run hundreds of replicas off a single master.  If I heard right, Howard told me that OpenLDAP uses a single thread for replication, and therefore processes each replica in a serial fashion, one at a time.  If any replica is going slowly (high network latency for example), it would have a knock-on effect to the time it takes to get changes replicated across the whole estate.

 

We have an aggressive target to meet - updates out in 5 minutes.  Updates are small, but alarm bells are now ringing in my head about OpenLDAP’s ability to deliver this.

 

This leads to a couple of questions:

 

1 - How easy would it be to patch OpenLDAP 2.4 to get the master to use multiple threads for replication?  Is that a reasonably straightforward fix, or is this quite a sizeable architectural change?

 

2 - If my master server has 40 cores, would there be mileage in setting up a number of slapd processes (say 10) on the same host, bound to different sockets, all acting as first-level replicas, and then all the replicas fanning out across the WAN synchronise from these processes rather than from the master process?  That would be a way, I suppose, of getting the master server to make better use of the available cores to get updates out quicker?

 

Thanks,

Mark.

 




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