Making streaming-only replication more robust

The first thing a slave has to do when connecting to a master is to play catch up. But can this always work? We have already seen that we can use a mixed setup consisting of a streaming-based and a file-based component. This gives us some extra security if streaming does not work.

In many real-world scenarios, two ways of transporting the XLOG might be too complicated. In many cases, it is enough to have just streaming. The point is that in a normal setup, as described already, the master can throw the XLOG away as soon as it is not needed to repair the master anymore. Depending on your checkpoint configuration, the XLOG might be around for quite a while or only a short time. The trouble is that if your slave connects to the master, it might happen that the desired XLOG is not around anymore. The slave cannot resync itself in this scenario. You might find this a little annoying, because it implicitly limits the maximum downtime of your slave to...