undefined method `dup_value!' with dalli 2.7.11 and rails 6.1

[roccoblues]

A simple Rails.cache.write with :dalli_store and Rails 6.1 leads to undefined method dup_value!'`.

I tracked it down to this commit in rails: rails/rails@9b09187#diff-ec46f57f15b817f91efebde97d0e74edfc656ada553296cecdf09a9611d95bf5

There was also an issue opened in rails reporting the same problem: rails/rails#40869

Is dalli 2.x supposed to support rails 6.1?

[petergoldstein]

@roccoblues So Dalli 2.x wasn't validated against Rails 6.1. Is there a reason you don't want to use MemCacheStore?

[roccoblues]

Hi @petergoldstein, we're using an internal gem that builds on DalliStore. We tried to switch that to MemCacheStore but had to rollback due to a huge increase (allocated bytes doubled) in allocations when we switched. We haven't investigated further but the theory is that that comes from the fact that MemCacheStore wraps every cache data into an additional ActiveSupport::Cache::Entry object.

[ssherman]

I am having this same problem. Switching to the mem_cache_store in the mean time.

[qrush]

Also running into this during a Rails 6.1 upgrade and didn't discover it until we got it out on our staging server.

@petergoldstein should there be a 2.7.12 released that is pinned to Rails < 6.1 ? And then maybe 2.8 can introduce 6.1 compat?

Relative stack trace here, coming from a Rails.cache.fetch block:

vendor/bundle/ruby/2.6.0/bundler/gems/rails-9f39d00ed29f/activesupport/lib/active_support/cache/strategy/local_cache.rb:68:in `write_entry': undefined method `dup_value!' for false:FalseClass (NoMethodError)
    from vendor/bundle/ruby/2.6.0/bundler/gems/rails-9f39d00ed29f/activesupport/lib/active_support/cache/strategy/local_cache.rb:162:in `write_entry'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:145:in `block (2 levels) in write'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/dalli/client.rb:266:in `with'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:83:in `with'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:143:in `block in write'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:386:in `block in instrument_with_log'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:395:in `block in instrument'
    from vendor/bundle/ruby/2.6.0/bundler/gems/rails-9f39d00ed29f/activesupport/lib/active_support/notifications.rb:205:in `instrument'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:394:in `instrument'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:386:in `instrument_with_log'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:142:in `write'
    from vendor/bundle/ruby/2.6.0/gems/dalli-2.7.9/lib/active_support/cache/dalli_store.rb:116:in `fetch'

[alexisraca]

Having the same problem with rails 6.1.3

EDIT: Can anyone elaborate on what's the plan for this bug? It is preventing us from upgrading to rails 6 and dalli_store is a cornerstone of our sytem.

I noticed that dalli 3.0 is going to deprecate dalli_store so is this bug even planned to be fixed in <= 2.X.X?

[alexisraca]

For anyone having this problem:

• we changed to mem_cache_store which solved the bug
• Then we found another bug about "undefined method get_multi_cas"

If you are using identity_cache on the latest tag, there is a bugfix in this commit mperham/connection_pool@97b2698 right above the top tag.

it is related to the connection_pool configuration.

[ghiculescu]

We had this issue happen after switching to the mem_cache_store if the value false was cached anywhere. For now we are rolling cache keys where this is likely, but have also proposed a fix in Rails: rails/rails#42559

[zhengpd]

undefined method `dup_value!' with dalli 2.7.11 and rails 6.1

Saw this when using :dalli_store. After switched to :mem_cache_store the error is gone.

[petergoldstein]

@ghiculescu Now that your fix in Rails is merged, is there anything additional to be fixed in Dalli to address this issue?

[ghiculescu]

My issue wasn’t exactly the same as OP’s, but no, my gut feel is this issue can be resolved. @byroot and I shipped a few rails PRs for backward compat around the local cache.

[petergoldstein]

@alexisraca Apologies for the late reply, but we're not planning to do any additional support work for :dalli_store.

Are all your post-switch issues resolved, or do you believe additional items need to be fixed in Dalli?

[alexisraca]

@petergoldstein Everything is cool now. The fixes posted in my last comment solved everything. There was a bug in our implementation with identity_cache which was solved by a commit above the top tag. Thank you!.

[petergoldstein]

Thanks @alexisraca .

Closing this issue.