On 2017-12-07 14:41:31 +0100, Peter J. Holzer wrote: > We are testing bidirectional replication with pglogical: [...] > We have configured bidirectional replication on several tables. In > general that seems to work fine. When a row is inserted/updated/ > deleted on one node, it is replicated to the other. > > But now I seem to have triggered a replication loop: [...] > Subsequent selects randomly return one of three states for this row > (other rows are stable). The order above is the "logical order", i.e. > the row was first inserted with the first state, then updated to the > second, and finally to the third. > > I suspect that the updates are bounced between the two nodes eternally > overwriting each other and never reaching a stable state. > > Has anybody seen this? If so, is there a way to reliably avoid this? > (Maybe with a different pglogical.conflict_resolution setting, but if it > was a conflict, I should see something in the logs, right?) This paragraph from https://github.com/2ndQuadrant/pglogical/blob/master/README.md#subscription-management looks relevant: | * forward_origins - array of origin names to forward, currently only | supported values are empty array meaning don't forward any changes | that didn't originate on provider node (this is useful for two-way | replication between the nodes), or "{all}" which means replicate all | changes no matter what is their origin, default is "{all}" I didn't change the default, so that means that each change is replicated back to the originator. I guess that doesn't matter if it happens before the next change (then the change is essentially a noop and won't be replicated again), but it does trigger a loop if the row has changed (because then it is changed again, which means that the previous change will trigger another replication, and so on.) hp -- _ | Peter J. Holzer | we build much bigger, better disasters now |_|_) | | because we have much more sophisticated | | | hjp@xxxxxx | management tools. __/ | http://www.hjp.at/ | -- Ross Anderson <https://www.edge.org/>
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