69 lines
2.5 KiB
Python
69 lines
2.5 KiB
Python
"""Revision retention.
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Dedup already keeps growth low - a revision appears only when a setting really
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changed - so retention exists for the pathological case, not the normal one: a
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value that flaps (or two PCs alternately claiming one machine number) would
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otherwise append a revision every collection cycle forever.
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Two independent limits, both off by default at 0:
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retentioncount keep at most N revisions per asset per kind
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retentiondays additionally drop anything older than N days
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The NEWEST and the OLDEST revision are never pruned. The newest is the one a
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tech restores from; the oldest is the earliest known-good baseline, which is
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usually the most valuable row in the table and the one a naive "keep last N"
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would delete first.
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"""
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from datetime import datetime, timedelta
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from shopdb.api import db
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from ..models import BackupRevision
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def prune(assetid, backupkind, retentioncount=0, retentiondays=0):
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"""Delete surplus revisions for one asset+kind. Returns the number removed.
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Caller commits. Returns 0 when both limits are disabled.
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"""
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retentioncount = int(retentioncount or 0)
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retentiondays = int(retentiondays or 0)
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if retentioncount <= 0 and retentiondays <= 0:
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return 0
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revisions = (db.session.query(BackupRevision)
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.filter(BackupRevision.assetid == assetid,
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BackupRevision.backupkind == backupkind)
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.order_by(BackupRevision.backuprevisionid.desc())
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.all())
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if len(revisions) <= 2:
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return 0 # newest + oldest are both protected
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newest = revisions[0]
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oldest = revisions[-1]
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protected = {newest.backuprevisionid, oldest.backuprevisionid}
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doomed = []
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if retentioncount > 0 and len(revisions) > retentioncount:
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# Walk from the oldest END of the middle, so the surplus dropped is
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# always the least recent, never the newest.
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for revision in revisions[retentioncount:]:
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if revision.backuprevisionid not in protected:
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doomed.append(revision)
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if retentiondays > 0:
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cutoff = datetime.utcnow() - timedelta(days=retentiondays)
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for revision in revisions:
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if revision.backuprevisionid in protected:
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continue
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stamp = revision.collectedat or revision.createdat
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if stamp and stamp < cutoff and revision not in doomed:
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doomed.append(revision)
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for revision in doomed:
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db.session.delete(revision)
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return len(doomed)
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