PDXPUG lab report – BDR

by gorthx

For the last PDXPUG lab of the year, we tried out BiDirectional Replication (BDR). Five of us just set up VMs on our laptops and followed the instructions on the wiki.

We only had about 90 minutes time for this lab, so the goal was to get a basic configuration up & running, understand the available configuration parameters, and then (time permitting) break it – because that’s how you learn to put it back together.

Alexander said it worked very well in his tests; Robert set about breaking it and found an interesting edge case involving updates to primary keys. (Advisable or not, we all have a customer who’s going to do it!)

Maher and I were doing pretty well with our setups until we tried configuring BDR between our two machines. After wrestling with VMWare’s network settings and getting absolutely nowhere, I realized this all felt very familiar … Oh right, CentOS’s pre-configured firewall1. Which does not allow Postgres ports, natch. Once we fixed that, our machines could at last communicate correctly with each other, but we ran out of time before we could get BDR working between them. (Which led to some jokes about “NDR”.)

Craig Ringer posted yesterday about the work that’s gone into this project thus far, and some of the side benefits. BDR is a particularly tricky problem to solve; kudos to the team for all the hard work.

The Quick Start guide is very easy to follow. I’m also very happy with the quality of the log messages available from BDR. I encourage you to check it out for yourself!

1 – Took me a bit of poking around to find it; it was moved from “System Administration” to “Sundry” in CentOS 7.

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