LVM Snapshot time limit during creation

gregor1 · July 18, 2021, 1:52pm

Hi,

sometimes I get the following error:

The external command failed to start. Error message: Duplicati.Library.Interface.UserInformationException: The external command failed to complete within the set time limit: /usr/lib/duplicati/lvm-scripts/create-lvm-snapshot.sh …

How long is the time limit and is it possible to increase the time limit?

regards
gregor

ts678 · July 20, 2021, 10:45pm

It appears to be 30 seconds (despite the comment on it), always has been, and isn’t user-configurable.

github.com

duplicati/duplicati/blob/184dfeae7860cd34019baf3d3ca635bf6b79dfbe/Duplicati/Library/Snapshots/Strings.cs#L3-L6


      
              internal static class LinuxSnapshot {
                  public static string ExternalProgramLaunchError(string message, string executable, string arguments) { return LC.L(@"The external command failed to start.
          Error message: {0}
          Command: {1} {2}", message, executable, arguments); }

github.com

duplicati/duplicati/blob/184dfeae7860cd34019baf3d3ca635bf6b79dfbe/Duplicati/Library/Snapshots/LinuxSnapshot.cs#L234-L242


      
          //Allow up 20 seconds for the execution

          if (!p.WaitForExit(30 * 1000))

          {

              //Attempt to close down semi-nicely

              p.Kill();

              p.WaitForExit(5 * 1000); //This should work, and if it does, prevents a race with any cleanup invocations

          

              throw new Interface.UserInformationException(Strings.LinuxSnapshot.ExternalProgramTimeoutError(program, commandline), "LvmScriptTimeout");

          }

Some sources say LVM snapshot creation is instantaneous (it just sets up to copy-on-write later, right?).
I suppose you could open an Issue to increase it, but it might help if you can provide supporting analysis.
The change itself looks easy enough, except perhaps for testing, which maybe you can do in a Canary?.