From: nobu@ruby-lang.org
To: ruby-core@ruby-lang.org
Subject: [ruby-core:69601] [Ruby trunk - Bug #11264] [Third Party's Issue] Memory leak in JSON stdlib ext (JSON generation)
Date: Tue, 16 Jun 2015 04:00:18 +0000 [thread overview]
Message-ID: <redmine.journal-52942.20150616040017.81c77407b0972ff1@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-11264.20150616025418@ruby-lang.org
Issue #11264 has been updated by Nobuyoshi Nakada.
Description updated
Status changed from Open to Third Party's Issue
Luke Gruber wrote:
> Once again, not sure if this is a bug or if we should never raise errors from custom to_json methods (ie: always wrap them in a begin... rescue block.
It doesn't work enough, as exceptions can raise even inside `cState_prepare_buffer()`.
----------------------------------------
Bug #11264: Memory leak in JSON stdlib ext (JSON generation)
https://bugs.ruby-lang.org/issues/11264#change-52942
* Author: Luke Gruber
* Status: Third Party's Issue
* Priority: Normal
* Assignee:
* ruby -v: 2.2-head
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
Hi,
I'm not sure if this is a bug, or just undocumented behaviour, but here's a script to reproduce the memory leak:
~~~ruby
require 'json'
class MyClass
def to_json(*)
"a" * 1048576 # 1 megabytes of chars
end
end
class MyOther
def to_json(*)
raise "OMG"
end
end
1000.times do |i| # will leak up to ~ 4 gigs
puts i
JSON.dump([MyClass.new, MyClass.new, MyClass.new, MyOther.new]) rescue nil
end
~~~
What's happening is that the C extension is iterating over the array to eventually dump it out to JSON. It's going through the array in order, appending to the `fbuffer` as needed. The problem is that that the API extension point of adding a `to_json` method to a class (or object), without wrapping the code in some sort of 'begin...rescue , free(buffer), re-raise' block results in the buffer never being freed. Normally this isn't too bad, except if a lot of data was appended to the buffer before the error got raised.
To test it against normal behaviour in the above script, take out the offending `MyOther.new` in the array. It should run much more smoothly this way :)
Note that since the `fbuffer`s aren't GC marked (not that they should be), it isn't possible to trace this leak using `GC.stat`.
Once again, not sure if this is a bug or if we should never raise errors from custom `to_json` methods (ie: always wrap them in a begin... rescue block.
Thanks,
I also reported this to the JSON gem maintainer here: https://github.com/flori/json/issues/251
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2015-06-16 3:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-11264.20150616025418@ruby-lang.org>
2015-06-16 2:54 ` [ruby-core:69599] [Ruby trunk - Bug #11264] [Open] Memory leak in JSON stdlib ext (JSON generation) luke.gru
2015-06-16 4:00 ` nobu [this message]
2015-06-16 23:33 ` [ruby-core:69622] [Ruby trunk - Bug #11264] " luke.gru
2015-06-17 0:53 ` [ruby-core:69623] " nobu
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