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Buildfarm has been failing sporadically on the new test. I was able to reproduce this by adding a random 0-10 s delay in the walreceiver, just before it connects to the primary. There's a race condition where node_3 is promoted before it has fully caught up with node_1, leading to diverged timelines. When node_1 is later reconfigured as standby following node_3, it fails to catch up: LOG: primary server contains no more WAL on requested timeline 1 LOG: new timeline 2 forked off current database system timeline 1 before current recovery point 0/30000A0 That's the situation where you'd need to use pg_rewind, but in this case it happens already when we are just setting up the actual pg_rewind scenario we want to test, so change the test so that it waits until node_3 is connected and fully caught up before promoting it, so that you get a clean, controlled failover. Also rewrite some of the comments, for clarity. The existing comments detailed what each step in the test did, but didn't give a good overview of the situation the steps were trying to create. For reasons I don't understand, the test setup had to be written slightly differently in 9.6 and 9.5 than in later versions. The 9.5/9.6 version needed node 1 to be reinitialized from backup, whereas in later versions it could be shut down and reconfigured to be a standby. But even 9.5 should support "clean switchover", where primary makes sure that pending WAL is replicated to standby on shutdown. It would be nice to figure out what's going on there, but that's independent of pg_rewind and the scenario that this test tests. Discussion: https://www.postgresql.org/message-id/b0a3b95b-82d2-6089-6892-40570f8c5e60%40iki.fi |
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PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.