sneak
86436449c5
Handle never read the record's attributes, and WithAttrs and WithGroup returned the receiver unchanged. The JSON and webhook handlers also marshaled slog.Record itself, whose attributes are unexported. Each handler now carries a handlerAttrs value, copied rather than mutated, so sibling loggers cannot leak attributes into each other. JSON and webhook output nest groups as objects; the console appends key=value pairs with dotted group keys, quoted as slog.NewTextHandler quotes them, invalid UTF-8 included. Logged values are never written to. In JSON the record's own fields win a key collision, and a repeated key keeps its last value unless both are groups, which merge; the README documents both. Deviation: DEL is quoted on the console; the stdlib leaves it bare. Model: opus-5-5
110 lines
3.9 KiB
Markdown
110 lines
3.9 KiB
Markdown
# simplelog
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## Summary
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simplelog is an opinionated logging package designed to facilitate easy and
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structured logging in Go applications with an absolute minimum of
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boilerplate.
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The idea is that you can add a single import line which replaces the
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stdlib `log/slog` default handler, and solve the 90% case for logging.
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## Current Status
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Released v1.0.0 2024-06-14. Works as intended. No known bugs.
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## Features
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- if output is a tty, outputs pretty color logs
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- if output is not a tty, outputs json
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- supports delivering each log message via a webhook
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- emits every `slog` attribute: those passed to a log call, those
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accumulated with `WithAttrs`, and those qualified by `WithGroup`.
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`slog.Group` values nest, and `slog.LogValuer` values are resolved. In
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json output attributes are object fields (groups become nested objects);
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in console output they are appended as `key=value` pairs, with grouped
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keys written as `group.key=value`. See
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[Attribute output](#attribute-output) for the details worth knowing
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## Planned Features
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- supports delivering logs via tcp RELP (e.g. to remote rsyslog using imrelp)
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## Installation
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To use simplelog, first ensure your project is set up with Go modules:
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```bash
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go mod init your_project_name
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```
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Then, add SimpleLog to your project:
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```bash
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go get sneak.berlin/go/simplelog
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```
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## Usage
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Below is an example of how to use SimpleLog in a Go application. This
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example is provided in the form of a `main.go` file, which demonstrates
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logging at various levels using structured logging syntax.
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```go
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package main
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import (
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"log/slog"
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_ "sneak.berlin/go/simplelog"
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)
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func main() {
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// log structured data with slog as usual:
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slog.Info("User login attempt", slog.String("user", "JohnDoe"), slog.Int("attempt", 3))
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slog.Warn("Configuration mismatch", slog.String("expected", "config.json"), slog.String("found", "config.dev.json"))
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slog.Error("Failed to save data", slog.String("reason", "permission denied"))
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}
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```
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## Attribute output
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Attributes reach every handler: the ones passed to the log call, the ones
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accumulated with `WithAttrs`, and the ones qualified by the groups open at
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the time they were attached. `slog.Group` values nest, and
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`slog.LogValuer` values are resolved to the value they stand for. A few
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behaviours are worth knowing before you rely on them.
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**Your values are never modified.** Whatever you log is read and rendered,
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never written to. A map or a slice you pass to `slog.Any` comes back from
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the logger exactly as you handed it over, even when a group later uses the
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same key.
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**Durations are nanoseconds in json, and readable on the console.** The
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json and webhook payloads emit a `slog.Duration` as a number of
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nanoseconds, matching `slog.NewJSONHandler`, so a consumer can compare and
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aggregate the field without parsing it. The console line emits the same
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duration as `3s`, matching `slog.NewTextHandler`, because a person reads
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it.
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**The json payload is an object, with the consequences an object has.**
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The record's own fields are named `Time`, `Level`, `Message` and `PC`, and
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they own those names: an attribute keyed after one of them is dropped from
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the json and webhook output. A key logged more than once keeps its last
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value there for the same reason, with one exception: when both are
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`slog.Group` values sharing a key, the two groups are merged into one
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object holding the members of both, rather than the second replacing the
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first. Neither the collision nor the merge applies to the console output,
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which is a line of text: every pair appears, in order. If you need a field
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called `message`, pick a key that does not collide - the collision is
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silent.
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**Empty things follow the `slog.Handler` contract.** An empty `Attr` is
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ignored, an empty group is elided along with its key, a group with an
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empty key is inlined into its parent, and `WithGroup("")` returns the
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handler unchanged.
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## License
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[WTFPL](./LICENSE)
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