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75 lines
2.7 KiB
Markdown
75 lines
2.7 KiB
Markdown
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# go-debug
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Conditional debug logging for Go libraries.
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View the [docs](http://godoc.org/github.com/tj/go-debug).
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## Installation
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```
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$ go get github.com/tj/go-debug
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```
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## Example
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```go
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package main
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import . "github.com/tj/go-debug"
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import "time"
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var debug = Debug("single")
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func main() {
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for {
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debug("sending mail")
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debug("send email to %s", "tobi@segment.io")
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debug("send email to %s", "loki@segment.io")
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debug("send email to %s", "jane@segment.io")
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time.Sleep(500 * time.Millisecond)
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}
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}
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```
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If you run the program with the `DEBUG=*` environment variable you will see:
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```
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15:58:15.115 34us 33us single - sending mail
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15:58:15.116 3us 3us single - send email to tobi@segment.io
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15:58:15.116 1us 1us single - send email to loki@segment.io
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15:58:15.116 1us 1us single - send email to jane@segment.io
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15:58:15.620 504ms 504ms single - sending mail
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15:58:15.620 6us 6us single - send email to tobi@segment.io
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15:58:15.620 4us 4us single - send email to loki@segment.io
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15:58:15.620 4us 4us single - send email to jane@segment.io
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15:58:16.123 503ms 503ms single - sending mail
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15:58:16.123 7us 7us single - send email to tobi@segment.io
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15:58:16.123 4us 4us single - send email to loki@segment.io
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15:58:16.123 4us 4us single - send email to jane@segment.io
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15:58:16.625 501ms 501ms single - sending mail
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15:58:16.625 4us 4us single - send email to tobi@segment.io
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15:58:16.625 4us 4us single - send email to loki@segment.io
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15:58:16.625 5us 5us single - send email to jane@segment.io
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```
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A timestamp and two deltas are displayed. The timestamp consists of hour, minute, second and microseconds. The left-most delta is relative to the previous debug call of any name, followed by a delta specific to that debug function. These may be useful to identify timing issues and potential bottlenecks.
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## The DEBUG environment variable
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Executables often support `--verbose` flags for conditional logging, however
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libraries typically either require altering your code to enable logging,
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or simply omit logging all together. go-debug allows conditional logging
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to be enabled via the __DEBUG__ environment variable, where one or more
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patterns may be specified.
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For example suppose your application has several models and you want
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to output logs for users only, you might use `DEBUG=models:user`. In contrast
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if you wanted to see what all database activity was you might use `DEBUG=models:*`,
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or if you're love being swamped with logs: `DEBUG=*`. You may also specify a list of names delimited by a comma, for example `DEBUG=mongo,redis:*`.
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The name given _should_ be the package name, however you can use whatever you like.
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# License
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MIT
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