0

Referring to https://github.com/newrelic/newrelic_api for the New Relic API, I was wondering what was the difference between hosts and instances.

Basically, I get what an application is and what a server is (obviously). I would assume instances are instances of the application, i.e. if my app were running on Heroku, each instance would correspond to a dyno running my app. But then what is a host? And what's the difference between host and instance?

Thanks,

-Billy

UPDATE

Thanks for the answer!

So if I got this right, in the general case, the mapping between applications and instances is 1-to-n, i.e. each app can have 1 or more instances. Also, the mapping between instances and hosts is n-to-m, i.e. each instance can be running on at most one host (at any given time), but instances are distributed among available hosts. Similarly, hosts are distributed among servers (say, m-to-s). Is that it? (Apologies if this sound like I'm saying very obvious stuff, but I'm unfamiliar with the terminology they are using over at New Relic)

If the above is correct, how can I get the instances - hosts and hosts - servers mappings from the API? I can see how to get the applications - instances and applications - hosts, but what about the other two?

Thanks again for your help!

S.L. Barth is on codidact.com
  • 8,198
  • 71
  • 51
  • 66
user510159
  • 1,379
  • 14
  • 26
  • If my answer was helpful, please accept it. The more good answers you accept, the more likely it is your future questions will be answered on StackOverflow. Of course, perhaps my answer isn't quite right =) – rkb May 08 '12 at 14:17

1 Answers1

5

A host (server) can run many instances of an application. Each process that responds to requests (e.g., a Unicorn worker) is an instance from the New Relic perspective. The host/instance distinction is roughly equivalent to the difference between an IP address and a port.

If you're using Heroku, New Relic treats the entire dyno grid as a single host/server, and each dyno as an instance.

Re: the updated question

A host is a machine or VM that applications run on, and each one can run N instances of the application.

A "server", for the purposes of the NR API, is an OS+hardware that's monitored by New Relic Server Monitoring. The NR application monitoring agent can also be running on a server monitored by the Server Monitoring agent. In that case, both the host and the server should report the same name to New Relic ("server01.example.com").

There isn't a way to get the instance-host or host-server mappings explicitly from the New Relic API. But in the case of server-host, the mapping is that they share the same name. You can probably infer the instance-host mapping from the instance names, too, since they will almost always contain the host name (and possibly also the port number).

rkb
  • 3,442
  • 19
  • 25