Disable memory swapping by default

[janko]

Thank you for maintaining this cookbook, it's been really helpful to us, and allowed us to remove a ton of manual configuration 😃

I just noticed that the cookbook doesn't seem to disable memory swapping, which according to the Elasticsearch documentation seems like it definitely should be the default. Specifically, I think the cookbook should add

bootstrap.memory_lock: true

for ES 5.x, and

bootstrap.mlockall: true

For ES 2.x and 1.x.

[martinb3]

Hi there -- the elasticsearch_configure resource has an option memlock_limit which sets the MAX_LOCKED_MEMORY environment variable for init scripts (the systemd scripts shipped with elasticsearch apparently have this commented out, but it's in there too). That environment variable, according to the current documentation, will automatically set bootstrap.memory_lock: true. Have you tried using that?

[janko]

@martinb3 I understood from the documentation that setting MAX_LOCKED_MEMORY=unlimited will allow Elasticsearch to set make the mlockall request once you set bootstrap.memory_lock: true, not that it will automatically make Elasticsearch prevent memory swapping. But I haven't tried checking the nodes whether swapping was prevented by deafult, and we already added bootstrap.mlockall: true (we're on 2.4).

[martinb3]

Just browsing through the issues filed on elastic/elasticsearch, it seems that a lot of folks have the same confusion that I did 😮

It seems that MAX_LOCKED_MEMORY is intended to affect the operating system, but bootstrap.memory_lock must still be paired with it. So it seems like the right thing to do would be to maybe change the default of bootstrap.memory_lock to be true. However, we're actually borrowing the defaults from elasticsearch's packaging.

We generally try to follow the defaults from Elasticsearch packaging -- I need to check and see what they do by default, and we'd likely follow that.