What is logspout?

Logspout is a tool for collecting and forwarding log output from Docker containers. Docker is a system for running applications in isolated containers, and each container produces its own stream of log messages. When you have many containers running on a server, gathering their logs and sending them somewhere central for storage or monitoring becomes a practical problem. Logspout solves this by attaching to all containers on a host and routing their output to a destination you specify. It runs as its own Docker container, which makes setup consistent with how other services are deployed in a container-based environment. You point it at a destination by passing a URL as a command argument, such as a remote syslog server address. Logspout then collects the standard output and error output from every other container on the host and forwards those logs in real time. You can control which containers Logspout pays attention to. Individual containers can be excluded by setting an environment variable or a label when they are started. Conversely, you can set filters so Logspout only forwards logs from containers whose names, IDs, or labels match a pattern. Multiple destinations are also supported by separating destination URLs with commas. An optional HTTP interface lets you inspect the live stream of all container logs in a terminal using a simple curl command, without configuring any remote destination. Routes can also be created and managed at runtime through this HTTP interface, and routes can be persisted to disk by mounting a volume. Logspout is designed to be stateless and lightweight. Its Docker image is about 15 megabytes. It focuses only on getting logs out of containers in real time, not on storing or searching them.