While testing n-way multi-provider with delta-syncrepl, I stumbled upon a sequence of events that leaves a consumer out of sync.
Assume two providers, provider-1, and provider-2, and a single consumer, consumer-1. They all initially have an attribute with the value 'A'. The following events cause the consumer to be out of sync:
1. Shut down provider-2, and immediately start it again. 2. Within the syncrepl retry window, modify the attribute to value 'B' on provider-2. 3. Within the syncrepl retry window, modify the attribute to value 'B' on provider-1, and then to value 'A' on provider-1. 4. Wait for provider-1 and consumer-1 to retry syncrepl against provider-2.
At this point provider-1 and provider-2 will be in sync, but consumer-2 will have the value 'B'. On retry, the modify from provider-2 is written to consumer-1, even though it is older than the modifications it received from provider-1.
Before I go too far down the rabbit hole (I've stopped at syncrepl.c:3271 in 2.6.13), I want to ask if n-way multi-provider with delta-syncrepl and a consumer that the providers are unaware of (no syncrepl directives to the consumer) is a valid config. Ideally I'd like to have a consumer with multimaster off to prevent writes completely, and I'd note that config has the same result. Normal syncrepl does not result in an out of sync consumer.
So, is this an invalid config, or should I submit an ITS?