pgespresso aborts running backups

[mhagander]

Running pgespresso_abort_backup() while a pg_basebackup based backup is running causes major breakage by throwing an assertion in the backend and restarting the whole cluster:

Console output:

pg_basebackup: could not read COPY data

Log output:

TRAP: FailedAssertion("!(XLogCtl->Insert.nonExclusiveBackups > 0)", File: "xlog.c", Line: 9795)
2014-05-28 13:10:11.775 CEST LOG:  server process (PID 18684) was terminated by signal 6: Aborted
2014-05-28 13:10:11.775 CEST LOG:  terminating any other active server processes

[mhagander]

This affects all supported PostgreSQL versions. Assert is obviously only thrown if it's an assert enabled build, but that just means that the breakage is silent on other builds.