packagr-io-beta
77 lines
2.7 KiB
Markdown
77 lines
2.7 KiB
Markdown
logstreamer [![Build Status][BuildStatusIMGURL]][BuildStatusURL]
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===============
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[![Flattr][FlattrIMGURL]][FlattrURL]
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[BuildStatusIMGURL]: https://secure.travis-ci.org/kvz/logstreamer.png?branch=master
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[BuildStatusURL]: //travis-ci.org/kvz/logstreamer "Build Status"
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[FlattrIMGURL]: http://api.flattr.com/button/flattr-badge-large.png
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[FlattrURL]: https://flattr.com/submit/auto?user_id=kvz&url=github.com/kvz/logstreamer&title=logstreamer&language=&tags=github&category=software
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Prefixes streams (e.g. stdout or stderr) in Go.
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If you are executing a lot of (remote) commands, you may want to indent all of their
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output, prefix the loglines with hostnames, or mark anything that was thrown to stderr
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red, so you can spot errors more easily.
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For this purpose, Logstreamer was written.
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You pass 3 arguments to `NewLogstreamer()`:
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- Your `*log.Logger`
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- Your desired prefix (`"stdout"` and `"stderr"` prefixed have special meaning)
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- If the lines should be recorded `true` or `false`. This is useful if you want to retrieve any errors.
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This returns an interface that you can point `exec.Command`'s `cmd.Stderr` and `cmd.Stdout` to.
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All bytes that are written to it are split by newline and then prefixed to your specification.
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**Don't forget to call `Flush()` or `Close()` if the last line of the log
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might not end with a newline character!**
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A typical usage pattern looks like this:
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```go
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// Create a logger (your app probably already has one)
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logger := log.New(os.Stdout, "--> ", log.Ldate|log.Ltime)
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// Setup a streamer that we'll pipe cmd.Stdout to
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logStreamerOut := NewLogstreamer(logger, "stdout", false)
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defer logStreamerOut.Close()
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// Setup a streamer that we'll pipe cmd.Stderr to.
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// We want to record/buffer anything that's written to this (3rd argument true)
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logStreamerErr := NewLogstreamer(logger, "stderr", true)
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defer logStreamerErr.Close()
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// Execute something that succeeds
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cmd := exec.Command(
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"ls",
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"-al",
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)
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cmd.Stderr = logStreamerErr
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cmd.Stdout = logStreamerOut
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// Reset any error we recorded
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logStreamerErr.FlushRecord()
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// Execute command
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err := cmd.Start()
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```
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## Test
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```bash
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$ cd src/pkg/logstreamer/
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$ go test
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```
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Here I issue two local commands, `ls -al` and `ls nonexisting`:
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Over at [Transloadit](http://transloadit.com) we use it for streaming remote commands.
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Servers stream command output over SSH back to me, and every line is prefixed with a date, their hostname & marked red in case they
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wrote to stderr.
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## License
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This project is licensed under the MIT license, see `LICENSE.txt`.
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