85 lines
3.7 KiB
Markdown
85 lines
3.7 KiB
Markdown
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godaemon
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========
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Daemonize Go applications with `exec()` instead of `fork()`. Read our [blog post](https://vividcortex.com/blog/2013/08/27/godaemon-a-library-to-daemonize-go-apps/) on the subject.
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You can't daemonize the usual way in Go. Daemonizing is a Unix concept that requires
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some [specific things](http://goo.gl/vTUsVy) you can't do
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easily in Go. But you can still accomplish the same goals
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if you don't mind that your program will start copies of itself
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several times, as opposed to using `fork()` the way many programmers are accustomed to doing.
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It is somewhat controversial whether it's even a good idea to make programs daemonize themselves,
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or how to do it correctly (and whether it's even possible to do correctly in Go).
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Read [here](https://code.google.com/p/go/issues/detail?id=227),
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[here](http://www.ryanday.net/2012/09/04/the-problem-with-a-golang-daemon/),
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and [here](http://stackoverflow.com/questions/14537045/how-i-should-run-my-golang-process-in-background)
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for more on this topic. However, at [VividCortex](https://vividcortex.com/) we do need to run one of our processes as a
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daemon with the usual attributes of a daemon, and we chose the approach implemented in this package.
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Because of the factors mentioned in the first link just given, you should take great care when
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using this package's approach. It works for us, because we don't do anything like starting up
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goroutines in our `init()` functions, or other things that are perfectly legal in Go in general.
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## Getting Started
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View the [package documentation](http://godoc.org/github.com/VividCortex/godaemon)
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for details about how it works. Briefly, to make your program into a daemon,
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do the following as soon as possible in your `main()` function:
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```go
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import (
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"github.com/VividCortex/godaemon"
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)
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func main() {
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godaemon.MakeDaemon(&godaemon.DaemonAttr{})
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}
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```
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Use the `CaptureOutput` attribute if you need to capture your program's
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standard output and standard error streams. In that case, the function returns
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two valid readers (`io.Reader`) that you can read from the program itself.
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That's particularly useful for functions that write error or diagnosis messages
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right to the error output, which are normally lost in a daemon.
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Use the `Files` attribute if you need to inherit open files into the daemon.
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This is primarily intended for avoiding race conditions when holding locks on
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those files (flocks). Releasing and re-acquiring locks between successive fork
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calls opens up the chance for another program to steal the lock. However, by
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declaring your file descriptors in the `Files` attribute, `MakeDaemon()` will
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guarantee that locks are not released throughout the whole process. Your daemon
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will inherit the file still holding the same locks, with no other process having
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intervened in between. See the
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[package documentation](http://godoc.org/github.com/VividCortex/godaemon) for
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more details and sample code. (Note that you shouldn't use this feature to
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inherit TTY descriptors; otherwise what you get is technically not a daemon.)
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## Contribute
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Contributions are welcome. Please open pull requests or issue reports!
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## License
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This repository is Copyright (c) 2013 VividCortex, Inc. All rights reserved.
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It is licensed under the MIT license. Please see the LICENSE file for applicable
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license terms.
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## Authors
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The primary author is [Gustavo Kristic](https://github.com/gkristic), with some
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documentation and other minor contributions by others at VividCortex.
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## History
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An earlier version of this concept with a slightly different interface was
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developed internally at VividCortex.
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## Cats
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A Go Daemon is a good thing, and so we present an angelic cat picture:
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