From 0fdfc19fc5a91671d9d79ec9a1bf0c3707c852d4 Mon Sep 17 00:00:00 2001
From: Shulhan <ms@kilabit.info>
Date: Wed, 15 Mar 2023 23:09:50 +0700
Subject: lib/telemetry: add formatter for Influxdata Line Protocol

The IlpFormatter implement a formatter for Influxdata Line Protocol that
can be used for prepare raw metric for Influxdata or QuestDB.
---
 lib/telemetry/ilp_formatter.go      | 109 ++++++++++++++++++++++++++++++++++++
 lib/telemetry/ilp_formatter_test.go |  77 +++++++++++++++++++++++++
 2 files changed, 186 insertions(+)
 create mode 100644 lib/telemetry/ilp_formatter.go
 create mode 100644 lib/telemetry/ilp_formatter_test.go

diff --git a/lib/telemetry/ilp_formatter.go b/lib/telemetry/ilp_formatter.go
new file mode 100644
index 00000000..3a8f556b
--- /dev/null
+++ b/lib/telemetry/ilp_formatter.go
@@ -0,0 +1,109 @@
+// Copyright 2023, Shulhan <ms@kilabit.info>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package telemetry
+
+import (
+	"bytes"
+	"fmt"
+
+	libbytes "github.com/shuLhan/share/lib/bytes"
+)
+
+const (
+	ilpFormatterName = `ilp`
+)
+
+// IlpFormatter format the Metric using the Influxdata Line Protocol, [ILP].
+// Syntax,
+//
+//	ILP      = measurement [METADATA] " " METRIC [" " timestamp] LF
+//	METADATA = *("," key "=" value)
+//	METRIC   = key "=" value *("," METRIC)
+//
+// [ILP]: https://docs.influxdata.com/influxdb/cloud/reference/syntax/line-protocol/
+type IlpFormatter struct {
+	name        string
+	measurement string
+	mdRaw       []byte
+	mdVersion   int // Latest version of metadata.
+
+}
+
+// NewIlpFormatter create and initialize new IlpFormatter.
+func NewIlpFormatter(measurement string) (ilp *IlpFormatter) {
+	ilp = &IlpFormatter{
+		name:        ilpFormatterName,
+		measurement: measurement,
+	}
+	return ilp
+}
+
+// BulkFormat format list of Metric with metadata.
+func (ilp *IlpFormatter) BulkFormat(list []Metric, md *Metadata) []byte {
+	if len(list) == 0 {
+		return nil
+	}
+
+	ilp.generateMetadata(md)
+
+	var (
+		bb bytes.Buffer
+		m  Metric
+		x  int
+	)
+
+	bb.WriteString(ilp.measurement)
+	bb.Write(ilp.mdRaw)
+	bb.WriteByte(' ')
+
+	for _, m = range list {
+		if len(m.Name) == 0 {
+			continue
+		}
+		if x > 0 {
+			bb.WriteByte(',')
+		}
+		fmt.Fprintf(&bb, `%s=%f`, m.Name, m.Value)
+		x++
+	}
+
+	fmt.Fprintf(&bb, " %d\n", m.Timestamp)
+
+	return libbytes.Copy(bb.Bytes())
+}
+
+// Format single Metric.
+func (ilp *IlpFormatter) Format(m Metric, md *Metadata) []byte {
+	if len(m.Name) == 0 {
+		return nil
+	}
+	return ilp.BulkFormat([]Metric{m}, md)
+}
+
+func (ilp *IlpFormatter) generateMetadata(md *Metadata) {
+	var mdVersion = md.Version()
+	if ilp.mdVersion == mdVersion {
+		return
+	}
+
+	var (
+		keys, vals = md.KeysMap()
+
+		bb bytes.Buffer
+		k  string
+		v  string
+	)
+	for _, k = range keys {
+		v = vals[k]
+		fmt.Fprintf(&bb, `,%s=%s`, k, v)
+	}
+	ilp.mdRaw = libbytes.Copy(bb.Bytes())
+	ilp.mdVersion = mdVersion
+}
+
+// Name return the unique name of the formatter, "ilp".
+func (ilp *IlpFormatter) Name() string {
+	return ilp.name
+}
diff --git a/lib/telemetry/ilp_formatter_test.go b/lib/telemetry/ilp_formatter_test.go
new file mode 100644
index 00000000..4aca4b47
--- /dev/null
+++ b/lib/telemetry/ilp_formatter_test.go
@@ -0,0 +1,77 @@
+// Copyright 2023, Shulhan <ms@kilabit.info>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package telemetry
+
+import (
+	"testing"
+
+	"github.com/shuLhan/share/lib/test"
+)
+
+func TestIlpFormatter_Format(t *testing.T) {
+	var md = NewMetadata()
+	md.Set(`host`, `localhost`)
+	md.Set(`version`, `0.1.0`)
+
+	var ilp = NewIlpFormatter(`myapp`)
+
+	test.Assert(t, `Name`, `ilp`, ilp.Name())
+
+	var (
+		m   Metric
+		got []byte
+		exp string
+	)
+
+	got = ilp.Format(m, md)
+	test.Assert(t, `Format: empty`, exp, string(got))
+
+	m = Metric{
+		Timestamp: 1000,
+		Name:      `go_gc_total`,
+		Value:     0.004,
+	}
+	got = ilp.Format(m, md)
+
+	exp = `myapp,host=localhost,version=0.1.0 go_gc_total=0.004000 1000`
+
+	test.Assert(t, `Format`, string(exp), string(got))
+}
+
+func TestIlpFormatter_BulkFormat(t *testing.T) {
+	var md = NewMetadata()
+	md.Set(`host`, `localhost`)
+	md.Set(`version`, `0.1.0`)
+
+	var ilp = NewIlpFormatter(`myapp`)
+
+	test.Assert(t, `Name`, `ilp`, ilp.Name())
+
+	var (
+		list = []Metric{}
+		got  = ilp.BulkFormat(list, md)
+
+		exp string
+	)
+
+	test.Assert(t, `BulkFormat: empty`, exp, string(got))
+
+	list = append(list, Metric{
+		Timestamp: 1000,
+		Name:      `go_gc_total`,
+		Value:     0.004,
+	})
+	list = append(list, Metric{
+		Timestamp: 1000,
+		Name:      `go_gc_pause_seconds`,
+		Value:     0.00001,
+	})
+
+	got = ilp.BulkFormat(list, md)
+
+	exp = "myapp,host=localhost,version=0.1.0 go_gc_total=0.004000,go_gc_pause_seconds=0.000010 1000\n"
+
+	test.Assert(t, `BulkFormat`, string(exp), string(got))
+}
-- 
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