Hello, my name is Ono and I'm a LINE engineer. In this blog post, I'd like to talk about "circuit breakers" which we use with our LINE servers.

What is a Circuit Breaker?​

The backend server systems for various web services and apps including LINE consist of networks that have several services connected with each other through APIs and RPCs.

What would happen if one of these networks suddenly failed to respond? The downed services would be blocked until they time-out, and all other services that rely on the blocked service would start a chain reaction of failures. If no one has been keeping an eye on the entire network, it will take a long time to figure out which service is the root cause.

Armeria is an asynchronous RPC/API client-server implementation built on top of Java 8 and Netty that went open-source last November under Apache License 2.0 by LINE Corporation. Its primary goal is to help engineers build high-performance asynchronous Thrift clients and servers that use HTTP/2 as a session layer protocol, although it is designed to be protocol-agnostic and highly extensible (for example, you can serve a directory of static files via HTTP/2 and run Java EE web applications).