Add LowCardinality host/measurement

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

.gitignore

@@ -1,21 +0,0 @@
-# If you prefer the allow list template instead of the deny list, see community template:
-# https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
-#
-# Binaries for programs and plugins
-*.exe
-*.exe~
-*.dll
-*.so
-*.dylib
-
-# Test binary, built with `go test -c`
-*.test
-
-# Output of the go coverage tool, specifically when used with LiteIDE
-*.out
-
-# Dependency directories (remove the comment below to include it)
-# vendor/
-
-# Go workspace file
-go.work

Makefile

@@ -1,7 +1,5 @@
 .PHONY: build
 
-COMMIT_HASH=$(shell git rev-parse --short HEAD)
-
 build:
-	CGOENABLED=false GOOS=linux GOARCH=amd64 go build -o clickhouse_${COMMIT_HASH}_amd64 cmd/main.go
+	CGOENABLED=false GOOS=linux GOARCH=amd64 go build -o telegraf-clickhouse-plugin-linux-amd64 cmd/main.go
-	CGOENABLED=false GOOS=linux GOARCH=arm64 go build -o clickhouse_${COMMIT_HASH}_arm64 cmd/main.go
+	CGOENABLED=false GOOS=linux GOARCH=arm64 go build -o telegraf-clickhouse-plugin-linux-arm64 cmd/main.go

README.md

@@ -4,6 +4,22 @@ The ClickHouse output plugin saves Telegraf metric data to a ClickHouse database
 
 The plugin uses Golang's generic "database/sql" interface and third party drivers.
 
+## Build
+
+Dependencies:
+
+* [Go](https://golang.org/doc/install)
+* [Make](https://www.gnu.org/software/make/)
+
+To build the plugin, run `make` in the root directory of the project.
+
+Alternatively, you can build the plugin using Docker:
+
+```bash
+docker run --rm -v $(pwd):/telegraf -w /telegraf -e CGOENABLED=false -e GOOS=linux -e GOARCH=amd64 golang go build -o telegraf-clickhouse-plugin-linux-amd64 cmd/main.go
+docker run --rm -v $(pwd):/telegraf -w /telegraf -e CGOENABLED=false -e GOOS=linux -e GOARCH=arm64 golang go build -o telegraf-clickhouse-plugin-linux-arm64 cmd/main.go
+```
+
 ## Getting started
 
 To use the plugin, set the data source name (DSN). The user account must have privileges to insert rows and create tables.

cmd/main.go

@@ -6,7 +6,7 @@ import (
 	"os"
 	"time"
 
-	_ "github.com/karaolidis/telegraf-clickhouse-plugin/plugins/outputs/clickhouse"
+	_ "git.karaolidis.com/karaolidis/telegraf-clickhouse-plugin/plugins/outputs/clickhouse"
 
 	"github.com/influxdata/telegraf/plugins/common/shim"
 )

go.mod

@@ -1,4 +1,4 @@
-module github.com/karaolidis/telegraf-clickhouse-plugin
+module git.karaolidis.com/karaolidis/telegraf-clickhouse-plugin
 
 go 1.20
 

plugins/outputs/clickhouse/clickhouse.go

@@ -158,11 +158,12 @@ func (ch *ClickHouse) toDatatype(value interface{}) string {
 	return datatype
 }
 
-func (ch *ClickHouse) toNullable(pair *orderedmap.Pair[string, string]) string {
+func (ch *ClickHouse) toNullableDatatype(key string, value interface{}) string {
-	if pair.Key != "host" && pair.Key != ch.TimestampColumn && pair.Key != "measurement" {
+	datatype := ch.toDatatype(value)
-		return fmt.Sprintf("Nullable(%s)", pair.Value)
+	if key == "host" || key == "measurement" {
+		return fmt.Sprintf("LowCardinality(%s)", datatype)
 	}
-	return pair.Value
+	return fmt.Sprintf("Nullable(%s)", datatype)
 }
 
 func (ch *ClickHouse) pepareMetrics(metrics []telegraf.Metric, metricsData map[string][]map[string]interface{}, columns map[string]*orderedmap.OrderedMap[string, string]) {
@@ -188,12 +189,12 @@ func (ch *ClickHouse) pepareMetrics(metrics []telegraf.Metric, metricsData map[s
 
 		for _, tag := range metric.TagList() {
 			metricEntry[tag.Key] = tag.Value
-			columns[tablename].Set(tag.Key, ch.toDatatype(tag.Value))
+			columns[tablename].Set(tag.Key, ch.toNullableDatatype(tag.Key, tag.Value))
 		}
 
 		for _, field := range metric.FieldList() {
 			metricEntry[field.Key] = field.Value
-			columns[tablename].Set(field.Key, ch.toDatatype(field.Value))
+			columns[tablename].Set(field.Key, ch.toNullableDatatype(field.Key, field.Value))
 		}
 
 		metricsData[tablename] = append(metricsData[tablename], metricEntry)
@@ -203,7 +204,7 @@ func (ch *ClickHouse) pepareMetrics(metrics []telegraf.Metric, metricsData map[s
 func (ch *ClickHouse) generateCreateTable(tablename string, columns *orderedmap.OrderedMap[string, string]) string {
 	columnDefs := make([]string, 0, columns.Len())
 	for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-		columnDefs = append(columnDefs, fmt.Sprintf("%s %s", quoteIdent(pair.Key), ch.toNullable(pair)))
+		columnDefs = append(columnDefs, fmt.Sprintf("%s %s", quoteIdent(pair.Key), pair.Value))
 	}
 
 	orderBy := make([]string, 0, 2)
@@ -230,15 +231,14 @@ func (ch *ClickHouse) generateAlterTable(tablename string, columns *orderedmap.O
 	modifyDefs := make([]string, 0, columns.Len())
 
 	for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-		columnType := ch.toNullable(pair)
 
 		alterDefs = append(alterDefs, fmt.Sprintf("ADD COLUMN IF NOT EXISTS %s %s",
 			quoteIdent(pair.Key),
-			columnType))
+			pair.Value))
 
 		modifyDefs = append(modifyDefs, fmt.Sprintf("MODIFY COLUMN IF EXISTS %s %s",
 			quoteIdent(pair.Key),
-			columnType))
+			pair.Value))
 	}
 
 	return fmt.Sprintf("ALTER TABLE %s %s, %s",
@@ -286,7 +286,7 @@ func (ch *ClickHouse) ensureTable(tablename string, columns *orderedmap.OrderedM
 	}
 
 	for pair := columns.Oldest(); pair != nil; pair = pair.Next() {
-		if _, ok := tableColumns[pair.Key]; !ok || tableColumns[pair.Key] != ch.toNullable(pair) {
+		if _, ok := tableColumns[pair.Key]; !ok || tableColumns[pair.Key] != pair.Value {
 			_, err = ch.db.Exec(ch.generateAlterTable(tablename, columns))
 			if err != nil {
 				return err