Re: [Bacula-users] FIFO Backup Questions

On 2/27/2015 6:53 PM, Heitor Faria wrote:

Dear Bacula Users,

1. Why FIFO isn't more popular for database dumps backups? Is there any drawback?

2. I inserted RedFifo=yes on FileSet Options and configured a simple RunBeforeJob script (below) to test FIFO backup, but the backup job stalls waitng for script termination. Am I missing something?

The FIFO special file created by mkfifo will block for read or write until both ends of the FIFO are opened. See man mkfifo(3).

Thanks Josh, I'm aware. I think that's why ReadFifo option exists on Bacula:

The last line of your script is attempting to write to the FIFIO. Bacula launches the script and waits for it to exit before continuing with the job. So, your script is waiting on Bacula to open the FIFO for read, but Bacula will never do so, because Bacula is waiting on the script to exit. You cannot write to the FIFO from the RunBeforeJob script. Instead, the script must launch a background process to write to the FIFO and the script must exit so that Bacula can continue the job and open the FIFO for reading.

"readfifo=yesnoIf enabled, tells the Client to read the data on a backup and write the data on a restore to any FIFO (pipe) that is explicitly mentioned in the FileSet. In this case, you must have a program already running that writes into the FIFO for a backup or reads from the FIFO on a restore. This can be accomplished with the RunBeforeJob directive. If this is not the case, Bacula will hang indefinitely on reading/writing the FIFO. When this is not enabled (default), the Client simply saves the directory entry for the FIFO.
Unfortunately, when Bacula runs a RunBeforeJob, it waits until that script terminates, and if the script accesses the FIFO to write into the it, the Bacula job will block and everything will stall. However, Vladimir Stavrinov as supplied tip that allows this feature to work correctly. He simply adds the following to the beginning of the RunBeforeJob script:
   exec > /dev/null"
Ps.: I tried the exec > /dev/null

[ -p /tmp/tubo ] ||mkfifo /tmp/tubo
ls -l > /tmp/tubo

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