fix(core) remove a memory leak introduced in the DB caching #3278
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Part of the fixes for #3277 for a regression introduced in de6390e. While the soft_to_hard error wrapper tries its best to be GC-friendly by not keeping references on the DB cache callbacks as they are used as keys to index their corresponding soft_to_hard_error wrappers. Unfortunately, because the created closure holds a reference to the callback itself, said callback cannot be garbage-collected. This is especially troublesome for callbacks that are generated on the fly, like so: local cache, err = cache:get("key", opts, function() return "cached value" end) The above anonymous function should be garbage-collected, but the soft_to_hard_error still holds a reference to it. This example could be observed prior to the parent commit, in which we replaced the cache callback to not create a function on the fly anymore. The drawback of this change is a larger memory footprint, the same cache callback will result in several copies of the same soft_to_hard_error function, if they are invoked with several caching keys.
This is part of the fixes for #3277 for a regression introduced in de6390e. Includes a port of the following mlcache commit: thibaultcha/lua-resty-mlcache/commit/4fdfbb976a9b4cda0f277ffc71294a14481a9c4d Supporting callback-returned errors allows us to get rid of the temporary workaround with a wrapper to throw errors on callback-returned errors.
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@thibaultcha fixes look great! I added a regression test to the PR. |
hishamhm
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Mar 9, 2018
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stable version 0.13 will release today or postponed？ |
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@kswen Given we had another rc this week, we will give some more time for the release candidate to do the rounds. |
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@kswen Glad you asked - we fixed the new date to March, 21st earlier today. Of course, you are welcome to try it and report any issue you may find (or else 0.13.0 will risk containing unreported bugs...). |
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This fixes a regression introduced in de6390e and released in 0.12.2 and 0.13.0rc1. It was reported in #3277 and investigated by @hishamhm and myself.
This PR takes a conservative approach at fixing the underlying issues: we introduce 3 commits from less to most disruptive, in an attempt to release a safe 0.12.3 hotfix:
soft_to_hard_errorwrapping closure that does not prevent the underlying callback from being GC'ed.soft_to_hard_errorwrapper workaround altogether (thibaultcha/lua-resty-mlcache@4fdfbb9)