ceph-volume: tolerate <=1% short-fall on requested db/wal size

When requested_size (e.g. 1 GiB) slightly exceeds abs_size (e.g.
1023.3 MiB lost to PE alignment), get_physical_fast_allocs() called
exit(1) and aborted the whole batch.

if the short-fall is within 1%, scale down to abs_size
with an info log instead of aborting. Anything larger still hits the
existing error path.

Needs review: confirm 1% is the right threshold (maybe a lower percentage is
sufficient) and that no caller assumes abs_size == requested_size after this branch.

Signed-off-by: Raimund Sacherer <rsachere@redhat.com>

diff --git a/src/ceph-volume/ceph_volume/devices/lvm/batch.py b/src/ceph-volume/ceph_volume/devices/lvm/batch.py
index 62083cba3154ebbe85128022692f7353de1921ff..062ec731359233f2c5d3af08cc027474a3bb3f11 100644 (file)
--- a/src/ceph-volume/ceph_volume/devices/lvm/batch.py
+++ b/src/ceph-volume/ceph_volume/devices/lvm/batch.py
@@ -90,6 +90,17 @@ def get_physical_fast_allocs(devices: List[device.Device], type_: str, fast_slot
                 if requested_size <= abs_size:
                     abs_size = requested_size
                     relative_size = int(abs_size) / dev_size
+                elif (int(requested_size) > 0 and
+                      (int(requested_size) - int(abs_size)) / int(requested_size) <= 0.01):
+                    # Tolerance: if the requested size overshoots what can be
+                    # fulfilled by <= 1% (e.g. 1GiB vs 1023.3MiB lost to PE
+                    # alignment), silently scale down to abs_size instead of
+                    # failing the whole batch.
+                    mlogger.info(
+                        '{} was requested for {}, fulfilling with {} (within 1 percent tolerance)'.format(
+                            requested_size, '{}_size'.format(type_), abs_size,
+                        ))
+                    relative_size = int(abs_size) / dev_size
                 else:
                     mlogger.error(
                         '{} was requested for {}, but only {} can be fulfilled'.format(

diff --git a/src/ceph-volume/ceph_volume/tests/devices/lvm/test_batch.py b/src/ceph-volume/ceph_volume/tests/devices/lvm/test_batch.py
index adc7c45cd9b733ad77330f8473f0220af6ffbe0b..a724b47410ad79483e9fcc5a02b0d9e20b14535b 100644 (file)
--- a/src/ceph-volume/ceph_volume/tests/devices/lvm/test_batch.py
+++ b/src/ceph-volume/ceph_volume/tests/devices/lvm/test_batch.py
@@ -395,6 +395,46 @@ class TestBatch(object):
         assert len(fast) == 1
         assert fast[0][0] == fast_dev.path
 
+    def test_get_physical_fast_allocs_tolerance_within_1_percent(self, factory,
+                                                                 conf_ceph_stub,
+                                                                 mock_device_generator):
+        # When requested_size overshoots the achievable abs_size by <=1%
+        # (e.g. PE alignment rounding 1 GiB down to ~1023.3 MiB), the
+        # allocator must scale down to abs_size silently instead of calling
+        # exit(1).
+        conf_ceph_stub('[global]\nfsid=asdf-lkjh')
+        # 20 GiB / 20 slots = 1 GiB abs_size; request 1 GiB + 100 KiB → ~0.01%
+        vg_size = 21474836480
+        fast_dev = mock_device_generator()
+        fast_dev.vg_size = [vg_size]
+        fast_dev.vg_free = [vg_size]
+        requested = disk.Size(b=int(vg_size / 20) + 100 * 1024)
+        args = factory(block_db_slots=20, block_db_size=requested,
+                       devices=['/dev/data'])
+        fast = batch.get_physical_fast_allocs([fast_dev], 'block_db',
+                                              20, 1, args)
+        assert len(fast) == 1
+        # abs_size is the achievable size, not the over-requested one
+        assert fast[0][2] == disk.Size(b=int(vg_size / 20))
+
+    def test_get_physical_fast_allocs_tolerance_over_1_percent(self, factory,
+                                                               conf_ceph_stub,
+                                                               mock_device_generator):
+        # Over the 1% threshold still aborts via exit(1).
+        conf_ceph_stub('[global]\nfsid=asdf-lkjh')
+        vg_size = 21474836480
+        fast_dev = mock_device_generator()
+        fast_dev.vg_size = [vg_size]
+        fast_dev.vg_free = [vg_size]
+        # Request 2 GiB on a 1 GiB slot — ~100% overshoot.
+        requested = disk.Size(b=int(vg_size / 20) * 2)
+        args = factory(block_db_slots=20, block_db_size=requested,
+                       devices=['/dev/data'])
+        with pytest.raises(SystemExit) as err:
+            batch.get_physical_fast_allocs([fast_dev], 'block_db',
+                                           20, 1, args)
+        assert err.value.code == 1
+
     def test_get_lvm_osds_return_len(self, factory,
                                      mock_lv_device_generator,
                                      conf_ceph_stub,