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Any plans on supporting Redis 3.0.7 version? It does not work if I change the configuration to 3.0.7. In application_manifest.rb:

configure(:redis => { :version => '3.0.7', :ruby_client => :latest }
recipe :redis

From http://redis.io/topics/faq

Background saving is failing with a fork() error under Linux even if I've a lot of free RAM!

Short answer: echo 1 > /proc/sys/vm/overcommit_memory :)

And now the long one:

Redis background saving schema relies on the copy-on-write semantic of fork in modern operating systems: Redis forks (creates a child process) that is an exact copy of the parent. The child process dumps the DB on disk and finally exits. In theory the child should use as much memory as the parent being a copy, but actually thanks to the copy-on-write semantic implemented by most modern operating systems the parent and child process will share the common memory pages. A page will be duplicated only when it changes in the child or in the parent. Since in theory all the pages may change while the child process is saving, Linux can't tell in advance how much memory the child will take, so if the overcommit_memory setting is set to zero fork will fail unless there is as much free RAM as required to really duplicate all the parent memory pages, with the result that if you have a Redis dataset of 3 GB and just 2 GB of free memory it will fail.

Setting overcommit_memory to 1 says Linux to relax and perform the fork in a more optimistic allocation fashion, and this is indeed what you want for Redis.

A good source to understand how Linux Virtual Memory work and other alternatives for overcommit_memory and overcommit_ratio is this classic from Red Hat Magazine, "Understanding Virtual Memory".

We already have moonshine_sysctl for managing this, so ideally it should just work when you install moonshine_redis. At the very least, the documentation should recommend it.

There were some recent modifications to moonshine_redis to allow for upgrades to happen. This exec will try to shutdown with redis-cli first before re-installing.

I'm not sure if this worked in the first place with new installs, or if it's something to do with the shadow_puppet version with 1.9 support.

I'm thinking these two things should be split off (shutdown redis if its installed and would be updated, then install it).