github.com/cybozu-go/cmd

Go Command Framework

This is a framework to create well-behaving commands.

Features

• Context-based goroutine management.
• Signal handlers.
• Graceful stop/restart for any kind of network servers.
• Logging options.
• Enhanced http.Server.
• Ultra fast UUID-like ID generator.
• Activity tracking.
• Support for systemd socket activation.
• Support for github.com/spf13/cobra.

Requirements

Go 1.11 or later, though the code is expected to work with Go 1.7.

Specifications

Commands using this framework implement these external specifications:

Command-line options

• -logfile FILE

  Output logs to FILE instead of standard error.

• -loglevel LEVEL

  Change logging threshold to LEVEL. Default is info.
  LEVEL is one of critical, error, warning, info, or debug.

• -logformat FORMAT

  Change log formatter. Default is plain.
  FORMAT is one of plain, logfmt, or json.

Signal Handlers

• SIGUSR1

  If -logfile is specified, this signal make the program reopen the log file to cooperate with an external log rotation program.

  On Windows, this is not implemented.

• SIGINT and SIGTERM

  These signals cancel the context of the global environment, and hence goroutines registered with the environment. Usually this will result in graceful stop of network servers, if any.

  On Windows, only SIGINT is handled.

• SIGHUP

  This signal is used to restart network servers gracefully. Internally, the main (master) process restarts its child process. The PID of the master process thus will not change.

  There is one limitation: the location of log file cannot be changed by graceful restart. To change log file location, the server need to be (gracefully) stopped and started.

  On Windows, this is not implemented.

• SIGPIPE

  The framework changes the way Go handles SIGPIPE slightly. If a program using this framework receives SIGPIPE when writing to stdout or stderr, the program exits with status code 2. See #15 for details.

Environment variables

• REQUEST_ID_HEADER

  The value of this variable is used as HTTP header name. The HTTP header is used to track activities across services. The default header name is "X-Cybozu-Request-ID".

• CYBOZU_LISTEN_FDS

  This is used internally for graceful restart.

• CANCELLATION_DELAY_SECONDS

  After SIGINT or SIGTERM received, the signal handler waits for the seconds before cancelling the context. The default value is 5 sec.

Usage

Read Tutorial, the design notes and API documents.

A wiki page for cobra users is also available.

Real world examples

• github.com/cybozu-go/coil uses well with cobra.
• github.com/cybozu-go/aptutil
• github.com/cybozu-go/goma
• github.com/cybozu-go/transocks
• github.com/cybozu-go/usocksd

Pull requests are welcome to add your project to this list!