Over the air updates

Over the air updates

Lots of maintainers run their needles on a bare metal machines. As long as this project is so frequently updated, it might be a good idea to let them update it without the hassle.

• [x] Enabled automatic time-based version check
• [x] Enabled application self-restart after it downloaded the update

Description

Support for the application self-update by downloading the latest release from the official repository.

Stay strong, be the first in line!

The version should be embedded in the binary during the build, see the build target in the Makefile.

Usage

Available flags

  -enable-self-update
        Enable the application automatic updates on the startup
  -restart-on-update
        Allows application to restart upon the successful update (ignored if auto-update is disabled) (default true)
  -self-update-check-frequency duration
        How often to run auto-update checks (default 24h0m0s)
  -skip-update-check-on-start
        Allows to skip the update check at the startup (usually set automatically by the previous version) (default false)

The default behavior if the self-update enabled:

* Check for the update
* If update is available - download it
   * If auto-restart is enabled
      * Notify the user that a newer version is available
      * Fork-Exec a new process (will have a different PID), add a flag to skip the version check upon startup
      * Stop the current process
   * If auto-restart is disabled - notify user that manual restart is required
* If update is NOT available - schedule the next check

Examples

To update your needle, start it with a flag -enable-self-update

./db1000n -enable-self-update

Advanced options

Start the needle with the self-update & self-restart

$ ./db1000n -enable-self-update
0000/00/00 00:00:00 main.go:82: DB1000n [Version: v0.6.4][PID=75259]
0000/00/00 00:00:00 main.go:166: Running a check for a newer version...
0000/00/00 00:00:00 main.go:176: Newer version of the application is found [0.7.0]
0000/00/00 00:00:00 main.go:177: What's new:
* Added some great improvements
* Added some spectacular bugs
0000/00/00 00:00:00 main.go:180: Auto restart is enabled, restarting the application to run a new version
0000/00/00 00:00:00 restart.go:45: new process has been started successfully [old_pid=75259,new_pid=75262]

# NOTE: Process 75259 exited, Process 75262 has started with a flag to skip version check on the startup

0000/00/00 00:00:00 main.go:82: DB1000n [Version: v0.7.0][PID=75262]
0000/00/00 00:00:00 main.go:155: Version update on startup is skipped, next update check is scheduled in 24h0m0s

Start the needle with the self-update but do not restart the process upon update (systemd friendly)

$ ./db1000n -enable-self-update -self-update-check-frequency=5m -restart-on-update=false
0000/00/00 00:00:00 main.go:82: DB1000n [Version: v0.6.4][PID=75320]
0000/00/00 00:00:00 main.go:166: Running a check for a newer version...
0000/00/00 00:00:00 main.go:176: Newer version of the application is found [0.7.0]
0000/00/00 00:00:00 main.go:177: What's new:
* Added some great improvements
* Added some spectacular bugs
0000/00/00 00:00:00 main.go:191: Auto restart is disabled, restart the application manually to apply changes!

References

1. Graceful restart with zero downtime for TCP connection - https://github.com/Scalingo/go-graceful-restart-example
2. Graceful restart with zero downtime for TCP connection (two variants) https://github.com/rcrowley/goagain
3. Graceful restart with zero downtime for TCP connection (alternative) https://grisha.org/blog/2014/06/03/graceful-restart-in-golang