Hello! Let's suppose that a replication master is writting a WAL segment file into a directory. That directory is mounted on the replication slave. Is it possible that the slave will try to read a WAL segment file that is not yet fully flushed to disk? I did not find any requirement in the official documentation about this. How does it work? Do I have to copy segments to temp files, and rename them when they are fully flushed to disk? Or is it okay to have half complete files in the archive dir for a while? Actually I cannot mount the slave's archive directory on the mater, because the network is not reliable. The WAL files need to be copied from the master to the slave. The network can go down in the middle of a copy operation. I can write a program that detects this, and retries the copy when the network comes back. But what happens on the slave side? What will a replication slave do if it sees a half complete WAL file? Is there a utility that is widely used for WAL file shipping, and addresses these problems? I know that PostgreSQL itself does not care about how the log files are shipped, but I suspect that there are robust, proven methods for shipping WAL files over unreliable networks. And finally: if I also enable streaming replication, then it seems that log file shipping is not needed at all. If I omit archive_command and restore_command from the configs, and setup the replication slots and primary_conninfo only, then it seems to be working just fine. But when the network goes down for a while, then the slave goes out of sync and it cannot recover. It was not clear for me from the documentation, but am I right in that I can combine log file shipping with streaming replication, and achieve small replication delays plus the ability to recover after a longer period if network outage? Thanks, Laszlo
