Chapter 12. Enabling Logshifter

In the example above, the standard pipe operator is used from a shell script to redirect logs from the cartridge process to logshifter. This works well for programs which are capable of managing a PID file internally. However, for cartridges which bootstrap a process and cannot manage a PID file by itself, using a simple pipe operator can be problematic. When piping programs using a shell, the programs are typically started in parallel, rendering the $! variable unreliable for determining the PID of the cartridge process. For these cases, setting up a named pipe can allow the cartridge to use logshifter and also manage the PID of the process. The following example demonstrates the setup of a named pipe used by a Java cartridge which preserves the reliability of $! so the cartridge script can manage the PID file manually: