ZeroDivisionError: division by zero (osd_objs_acting)

[patrakov]

Another attempt of balancing the same half-broken cluster as in #35 after some CRUSH map cleanup yields this:

# ./placementoptimizer.py -v --osdsize device balance --osdused delta --max-pg-moves 100 --osdfrom fullest --only-crushclass hdd
[2024-03-15 16:03:45,878] gathering cluster state via ceph api...
Traceback (most recent call last):
  File "./placementoptimizer.py", line 5475, in <module>
    exit(main())
  File "./placementoptimizer.py", line 5431, in main
    state.preprocess()
  File "./placementoptimizer.py", line 2061, in preprocess
    metadata_estimate = int(meta_amount * pg_objects / osd_objs_acting)
ZeroDivisionError: division by zero

The debug archive will be sent via email, but note that this is a large cluster, so it exceeds your message size limit, so I will have to split the archive.

[patrakov]

An attempt to log the variables yields this:

meta_amount: 2188406858, pg_objects: 0, osd_objs_acting: 0

So, as a hack, I applied this change:

--- placementoptimizer.py.orig  2024-03-15 16:38:09.351499650 +0000
+++ placementoptimizer.py       2024-03-15 16:41:37.158122020 +0000
@@ -2058,7 +2058,9 @@
 
                 # calculated by weighting osd metadata sizes by pg object counts
                 pg_objects = self.pgs[pgid]['stat_sum']['num_objects']
-                metadata_estimate = int(meta_amount * pg_objects / osd_objs_acting)
+                if osd_objs_acting == 0:
+                    logging.info(f"meta_amount: {meta_amount}, pg_objects: {pg_objects}, osd_objs_acting: {osd_objs_acting}")
+                metadata_estimate = int(meta_amount * pg_objects / osd_objs_acting) if osd_objs_acting else 0
 
                 estimates = self.pgs[pgid]["metadata_estimates"]
                 estimates[osdid] = metadata_estimate

The first few upmaps that it generates make sense to me, but I don't think I actually need 100 pg moves.

The added logging line has triggered only once.

[TheJJ]

I think I already fixed this in 38e5d5f :)

[patrakov]

Fixed indeed!