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perf: periodic full GC to bound RSS (plexapi cyclic Element trees) (#802)

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measured the 'resource hungry' / lockup issue: browsing every page grows RSS ~300MB -> 1.8GB
and it stays. it's not a leak — it's deferred cyclic collection. plexapi parses Plex responses
into XML Element trees whose nodes reference each other in cycles; Python's generational GC
leaves them in gen2 and sweeps it rarely, so ~227k Element objects pile up. forcing gc.collect()
reclaimed ~700MB instantly (1.8GB -> 1.1GB live), confirming.

add a daemon that runs a full gc.collect() every 60s so the cyclic garbage is reclaimed on a
cadence instead of climbing into lock-up. full collect is ~tens of ms; once a minute is
negligible. this is the root of the reporter's 2GB + ramonskie's spike too.
This commit is contained in:
BoulderBadgeDad 2026-06-27 14:17:58 -07:00
parent de9e78cf95
commit f383a62c4f
1 changed files with 20 additions and 0 deletions
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20
web_server.py
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@ -38549,6 +38549,26 @@ def start_runtime_services():
# Initialize app start time for uptime tracking
app.start_time = time.time()
# Periodic full garbage collection (#802 / resource usage). plexapi builds large XML
# Element trees whose nodes reference each other in cycles; Python's generational GC
# parks those in gen2 and only sweeps it rarely, so they accumulate and RSS climbs
# (measured: ~300MB fresh -> 1.8GB after browsing every page, ~700MB of it reclaimable
# cyclic garbage that a full gc.collect() frees instantly). A scheduled full collect
# reclaims them on a cadence so RSS stays bounded instead of climbing into lock-up.
# A full collect on this heap is ~tens of ms; once a minute is negligible CPU.
def _periodic_gc(interval=60):
import gc
while True:
time.sleep(interval)
try:
n = gc.collect()
if n:
logger.debug("periodic gc.collect() reclaimed %d cyclic objects", n)
except Exception: # noqa: S110 — best-effort housekeeping, never crash the app
pass
threading.Thread(target=_periodic_gc, daemon=True, name='periodic-gc').start()
logger.info("Periodic GC sweeper started (full collect every 60s)")
# Register action handlers and start automation engine
_register_automation_handlers()
if automation_engine: