Agentless Consul approach

[iconf...@gmail.com]

Hi there!

In a recent discussion about ways to deploy and use consul we got a proposal of using Consul without the distributed agents meaning that you could only deploy the server instances put a load balancer in front of the HTTP APIs of the instances and use this cluster as a service.

To register a service instead of using the local agent you will go directly to the Load Balanced HTTP interface and register, and then the server cluster will be in charge of executing remote Health Check calls to all the VMs which will need to provide a health check interface over HTTP.

Have someone test this kind of implementations? Does it provides any advantage to use this approach?

Thanks. 

[James Phillips]

Hi,

It would be possible to run Consul in an agentless setup like this,
but it's definitely not recommended.

The Consul agent is relatively lightweight and is pretty core to
Consul architecture. It does edge-triggered updates to the Consul
servers only when health check statuses change, so scales much better
than a centralized health checking approach. Also, the health of the
nodes running the agents are automatically checked by Consul's gossip
protocol, so if an agent goes offline the other agents will quickly
detect that and report it to the servers, which will mark all of its
services unhealthy via the automatic "serfHealth" check. Gossip also
allows the agents to find a healthy Consul server to talk to, so your
application doesn't need to discover the Consul servers (it can just
be hard-coded to talk to its local agent at 127.0.0.1).

This recent talk walks through this in more detail -
https://www.youtube.com/watch?v=tzk2HaOZ5nY.

Hope that helps!

-- James

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