Fix memory leak

[dougszumski]

Every time the collector is scraped, it makes a new connection. The connection is never cleaned up, even if you add a conn.close() after the scrape [1]. This is a likely bug.

This patch moves to using the instance connection, which works around the leak and is more efficient.

[1] https://docs.openstack.org/openstacksdk/latest/user/connection.html#openstack.connection.Connection.close

[dougszumski]

@cityofships reported it reaching ~30GB

[dougszumski]

Debug info:

Top 10 objects before patch, approx ~30 scrapes:

	/usr/lib/python3.12/json/decoder.py:353: size=581 KiB, count=9981, average=60 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/requests/structures.py:49: size=470 KiB, count=8331, average=58 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/response.py:654: size=143 KiB, count=191, average=768 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/response.py:271: size=142 KiB, count=382, average=380 B
	/usr/lib/python3.12/threading.py:293: size=131 KiB, count=352, average=380 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/openstack/proxy.py:161: size=89.7 KiB, count=116, average=792 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/_collections.py:323: size=88.8 KiB, count=2484, average=37 B
	/usr/lib/python3.12/email/message.py:516: size=85.9 KiB, count=1554, average=57 B
	/usr/lib/python3.12/email/_policybase.py:311: size=84.6 KiB, count=1380, average=63 B
	/usr/lib/python3.12/http/cookiejar.py:1263: size=75.5 KiB, count=804, average=96 B

Top 10 objects before patch, no scrapes:

	[ Top 10 ]
	/usr/lib/python3.12/json/decoder.py:353: size=277 KiB, count=4634, average=61 B
	<frozen abc>:123: size=44.7 KiB, count=477, average=96 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/requests/structures.py:49: size=27.9 KiB, count=494, average=58 B
	<frozen importlib._bootstrap_external>:753: size=23.4 KiB, count=196, average=122 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/prometheus_client/metrics.py:607: size=16.5 KiB, count=311, average=54 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/prometheus_client/values.py:16: size=14.6 KiB, count=340, average=44 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/keystoneauth1/access/service_catalog.py:99: size=11.2 KiB, count=98, average=11
	7 B
	/usr/lib/python3.12/threading.py:293: size=10.4 KiB, count=28, average=380 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/response.py:654: size=8448 B, count=11, average=768 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/response.py:271: size=8360 B, count=22, average=380 B

Note, no high count for structures.py and decoder.py

Top 10 objects with patch, approx 30 scrapes:

	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/requests/structures.py:49: size=44.8 KiB, count=800, average=57 B
	<frozen abc>:123: size=43.9 KiB, count=462, average=97 B
	/usr/lib/python3.12/email/message.py:491: size=41.6 KiB, count=761, average=56 B
	<frozen importlib._bootstrap_external>:753: size=23.4 KiB, count=196, average=122 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/keystoneauth1/_utils.py:29: size=17.7 KiB, count=362, average=50 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/requests/adapters.py:466: size=16.7 KiB, count=235, average=73 B
	<string>:1: size=16.5 KiB, count=255, average=66 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/prometheus_client/metrics.py:607: size=16.5 KiB, count=310, average=54 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/prometheus_client/values.py:16: size=14.6 KiB, count=340, average=44 B

Top 10 objects, closing the connection after each scrape, approx 30 scrapes:

	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/requests/structures.py:49: size=469 KiB, count=8328, average=58 B
	/usr/lib/python3.12/json/decoder.py:353: size=333 KiB, count=5876, average=58 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/response.py:654: size=143 KiB, count=191, average=768 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/response.py:271: size=142 KiB, count=382, average=380 B
	/usr/lib/python3.12/threading.py:293: size=131 KiB, count=352, average=380 B
	/usr/lib/python3.12/importlib/metadata/_collections.py:30: size=115 KiB, count=1560, average=75 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/openstack/proxy.py:161: size=89.7 KiB, count=116, average=792 B
	/home/ubuntu/src/os-capacity/osc/lib/python3.12/site-packages/urllib3/_collections.py:323: size=88.8 KiB, count=2484, average=37 B
	/usr/lib/python3.12/email/message.py:516: size=85.9 KiB, count=1554, average=57 B
	/usr/lib/python3.12/email/_policybase.py:311: size=84.6 KiB, count=1380, average=63 B

^ NOTE: this /should/ clean up, but it doesn't

[m-bull]

LGTM - the empirical evidence is nice too!

[dougszumski]

LGTM - the empirical evidence is nice too!

thanks for the review!