On 2014-14-10 21:17, Jeff McCune wrote:
On Tue, Oct 14, 2014 at 11:57 AM, Henrik Lindberg
<[email protected] <mailto:[email protected]>>
wrote:
On 2014-14-10 17:36, Ben Ford wrote:
I have to admit that this email made me feel a little bit dumb.
Could
you provide a TL;DR summary that at least provides a little
context for
this? Is this something that people writing types, functions, hiera
backends, or report processors need to concern themselves with?
Sorry about that - this is mostly if you are contributing to Puppet
itself, or if you find that your implementation in Ruby (of
whatever) leaks memory and you need to find the cause.
If you are following the well beaten path when writing types and
providers etc. you need not worry. If you are writing caching in any
form you are potentially causing memory leaks and the tips here apply.
Is my understanding that the way caching was implemented, by using a
full resource type object as the Hash key in a class variable, is what
caused the leak? Specifically, the resource type would never be cleaned
up by the garbage collector because it's a hash key in a class instance
variable, correct?
Here:
https://github.com/puppetlabs/puppet/pull/3188/files#diff-d8c96ce74a7f29debda40750462bd248L249
Yes, two problems;
1. The object used as the key does not provides hash and equals and thus
the cache would grow because of lack of cache hits unless the same
instance was again used as a key (which it isn't in a new instance of an
environment).
Had equals and hash been correctly implemented on type, we would
possibly see a slower leak since some environments would not introduce
new keys. (We would have other issues though).
2. The class level variable (@@nondeprecating_type) holds on to every
type seen and does not change when an environment expires. When an
environment expires, and the cache holds on to a type then a very large
set of objects are bound in memory since there are circular references
from that type binding to almost everything loaded in an environment
(via known_resource_types). Hence my analogy of "you think you are
holding on to a banana, but it comes with a Gorilla and its Jungle".
- henrik
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