[ruby-core:100952] [Ruby master Bug#17334] Marshal cannot dump instance of Monitor

Issue #17334 has been updated by chrisseaton (Chris Seaton).


I'm not sure what a dumped instance of `Monitor` would look like though? Its state implicitly includes the current stack trace of threads using it. What do you imagine an undumped `Monitor` with blocked threads would look like?

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Bug #17334: Marshal cannot dump instance of Monitor
https://bugs.ruby-lang.org/issues/17334#change-88606

* Author: Littlejd1997 (Jon David Schober)
* Status: Rejected
* Priority: Normal
* ruby -v: 2.7.2
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
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I'm not really sure why, but I hope someone else know whats going on.

I was digging into an error I had with Rails caching. Long story short, I was caching a HTTP::CookieJar object which has an instance variable of type Monitor.

The rails cache uses Marshaling, which fails on Monitor instances
``` ruby
2.7.2 :005 > Marshal.dump(Monitor.new)
Traceback (most recent call last):
        6: from /Users/jondavid.schober/.rvm/rubies/ruby-2.7.2/bin/irb:23:in `<main>'
        5: from /Users/jondavid.schober/.rvm/rubies/ruby-2.7.2/bin/irb:23:in `load'
        4: from /Users/jondavid.schober/.rvm/rubies/ruby-2.7.2/lib/ruby/gems/2.7.0/gems/irb-1.2.6/exe/irb:11:in `<top (required)>'
        3: from (irb):4
        2: from (irb):5:in `rescue in irb_binding'
        1: from (irb):5:in `dump'
TypeError (no _dump_data is defined for class Monitor)
2.7.2 :006 > 
```




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