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Updated Filer Active Active cross cluster continuous synchronization (markdown)

Chris Lu 2022-01-11 00:36:54 -08:00
parent 90d1ce3348
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Filer-Active-Active-cross-cluster-continuous-synchronization.md

@ -37,9 +37,9 @@ If there are 3 or more clusters, you can choose fully connected setup or chained
In a sense, you can mix and match to setup filer synchronization as you wish. In a sense, you can mix and match to setup filer synchronization as you wish.
### Fully Connected Setup ### Fully Connected Setup?
Run one `weed filer.sync` for each pair of clusters. The fully connected topology provides redundancy in case of network failures. It is tempting to create a fully connected network topology. E.g., run one `weed filer.sync` for each pair of clusters. The fully connected topology may seem to be able to provide redundancy in case of network failures.
``` ```
cluster1 <-- filer.sync --> cluster2 cluster1 <-- filer.sync --> cluster2
@ -47,6 +47,14 @@ cluster2 <-- filer.sync --> cluster3
cluster3 <-- filer.sync --> cluster1 cluster3 <-- filer.sync --> cluster1
``` ```
However, this topology has a loop.
Every filer will leave a signature on each message. The `filer.sync` use the signatures to avoid processing the same message twice. But for any node within a loop, the same message can come from two difference neighbors. So this mechanism could not help to identify the duplicated the messages.
Because most metadata messages are idempotent, the network loop is not efficient but still works OK.
But for directory renaming, the execution order matters. So the loop should be avoided, or the directories will be inconsistent.
### Chained Setup ### Chained Setup
``` ```
cluster1 <-- filer.sync --> cluster2 <-- filer.sync --> cluster3 cluster1 <-- filer.sync --> cluster2 <-- filer.sync --> cluster3