IMO missing checkpoints should not be taken as the indicator of
first-time bootstrap - the invocation path for a node should be explicit
about that. I.e., a node should be started explicitly either in
first-time mode or not, and should thus only delete data if it was told
explicitly that it's in first-time mode.
On 11/29/17 2:52 PM, Murtadha Hubail wrote:
Just to clarify a couple of things.
If all existing checkpoints are corrupted, nothing is deleted and recovery is
performed from the beginning of the transactions log. In this case, most
likely your checkpoint file was completely missing. You can check the logs to
confirm if you still have them.
Regarding deleting storage on missing checkpoints, at one point many developers
were encountering issues during development or testing because
some test case is leaving some storage data and on the next run a failure is
encountered due to existing storage artifacts left behind. Hence, the
decision was made to delete existing storage on missing checkpoints since they
are our current indicator of a node’s first-time bootstrap or recovery
after restart.
Having said that, I agree that deleting all existing data isn’t the right thing
to do.
Cheers,
Murtadha
On 11/30/2017, 1:26 AM, "Chen Luo" <[email protected]> wrote:
I'm not sure how the checkpoint file was corrupted. For my experiments, I
have some versions of AsterixDB sharing the same storage dir (so that I can
evaluate the performance after making some changes). Recently I synced my
branch with master, and maybe this causes some problem with the checkpoint
file (e.g., different versions of codebase?).
However, I think cleaning up the entire data directory is dangerous. The
user (such as me) can backup the checkpoint file because it's small, but it
would be cumbersome to backup the entire data directory. When there indeed
is something wrong with the checkpoint file, it's better that the user can
be aware of this, and make decisions by himself.
Best regards,
Chen Luo
On Wed, Nov 29, 2017 at 2:11 PM, abdullah alamoudi <[email protected]>
wrote:
> I wonder how it got to that state.
>
> The first thing an instance does after initialization is create the
> snapshot file.
> This will only be deleted after a new (uncorrupted) snapshot file is
> created.
>
> I understand your point, but I wonder how it got to this state. Bug!?
>
> Cheers,
> Abdullah.
>
> > On Nov 29, 2017, at 1:54 PM, Chen Luo <[email protected]> wrote:
> >
> > Hi devs,
> >
> > Recently I was experiencing a very annoying issue about recovery. The
> > checkpoint file of my dataset was somehow corrupted (and I didn't know
> > why). However, when I was restarting AsterixDB, it fails to read the
> > checkpoint file, and starts recovering as a clean state. This is highly
> > undesirable in the sense that it clean up all of my experiment datasets
> > saliently, roughly 100GB. And it'll take me days to re-ingest these
data
> to
> > resume my experiments.
> >
> > I think the behavior of cleaning up all data when some small thing goes
> > wrong is undesirable and dangerous. When AsterixDB fails to restart,
and
> > finds the data directory non-empty, I think it should notify the user
and
> > let the user to make the decision. For example, it could fail to
restart
> at
> > this time, and user could clean up the directory manually, or try to
use
> a
> > backup checkpoint file, or add some flag to force restart. Anyway,
> blindly
> > cleaning up all files seem to be a dangerous solution.
> >
> > Any thoughts on this?
> >
> > Best regards,
> > Chen Luo
>
>
