global19-atlassian-net / finagle-consul

Service discovery for Finagle cluster with Consul.

Finagle Consul

Service discovery for Finagle cluster with Consul. This project was originally developed by kachayev/finagle-consul, dmexe/finagle-consul and matteobanerjee/finagle-consul

About

Consul is a distributed, highly available and extremely scalable tool for service discovery and configuration.

This project provides two resolution/announcement strategies: one using Consul sessions and K/V, the other using Consul's native service registration mechanism (referred to as the "catalog" strategy here).

Catalog strategy

Usage:

Announce (the announcer requires an agent, usually running on localhost):

consul!localhost:8500!/serviceName

Resolve (doesn't require an agent):

consul!host1:port1,host2:port2,...!/serviceName

For Example:

val server = Http.serveAndAnnounce("consul!127.0.0.1:8500!/RandomNumber")
val client = Http.newService("consul!127.0.0.1:8500!/RandomNumber")

Pros:

• Integrates cleanly with native Consul Services

Cons:

• Requires a Consul Agent for server announcements
• Requires clean up of dead services in environments where server addresses are ephemeral, like Mesos

The catalog strategy uses Consul's built-in service discovery APIs. The main advantage of this is that it makes it easy to run Finagle services alongside non-finagle services. You can, for example, discover a Rails web service and MySQL database using this resolver.

The main downside is on the announcement side: The consul catalog does not support ephemeral nodes, so services will not be deregistered in case of an unclean shutdown, e.g. OOM errors or kill -9. They will instead only fail their health check and be put in a critical state. Though the resolver will filter these out, the Consul catalog will get polluted with dead nodes and will require clean up if running in an environment like Mesos. This is an issue with Consul itself that can be mitigated with a cron job.

Example

Server

val server = Http.server.serveAndAnnounce("consul!localhost:8500!/EchoServer?ttl=100", s":$serverPort", service)

// Ensure clean de-registration
sys.addShutdownHook {
  Await.result(server.close())
}
Await.ready(server)

Client

val client = Http.client.newService("consul!localhost:8500!/EchoServer")

D-Tab

Dentry.read("/account=>/$/gov.nih.nlm.ncbi.finagle.serverset/consul/consul.service.aws-prod.consul:80/account-version-2-2-build-73")))