panic: Cannot allocate memory

[pjenvey]

As of the 0.5.8 deploy we're seeing nodes panic due to running out of memory:

https://sentry.prod.mozaws.net/operations/syncstorage-prod/issues/9483741/
https://sentry.prod.mozaws.net/operations/syncstorage-prod/issues/9537009/
https://sentry.prod.mozaws.net/operations/syncstorage-prod/issues/9488604/

Though there was one (edit: there's more than one case of this in 0.4.3 but their events may have not made it to sentry) previous case of this in 0.4.3:

https://sentry.prod.mozaws.net/operations/syncstorage-prod/issues/9449578/

Possibly related: one case of running out of file descriptors:

https://sentry.prod.mozaws.net/operations/syncstorage-prod/issues/9521360/

[jrconlin]

seeing a few machines spike past 80%.

https://earthangel-b40313e5.influxcloud.net/d/5kIPrfbWj/sync-rs-prod?viewPanel=52&orgId=1&refresh=1m&from=now-7d&to=now

https://sentry.prod.mozaws.net/operations/syncstorage-prod/?query=server_name%3A%22sync-prod-sync-app-1-785f6f46bc-v6xsm%22