Specify overwriting behavior in flag and add validation

Signed-off-by: haanhvu <haanh6594@gmail.com>

cmd/thanos/receive.go

@@ -818,7 +818,7 @@ func (rc *receiveConfig) registerFlag(cmd extkingpin.FlagClause) {
 	cmd.Flag("receive.hashrings", "Alternative to 'receive.hashrings-file' flag (lower priority). Content of file that contains the hashring configuration.").PlaceHolder("<content>").StringVar(&rc.hashringsFileContent)
 
 	hashringAlgorithmsHelptext := strings.Join([]string{string(receive.AlgorithmHashmod), string(receive.AlgorithmKetama)}, ", ")
-	cmd.Flag("receive.hashrings-algorithm", "The algorithm used when distributing series in the hashrings. Must be one of "+hashringAlgorithmsHelptext).
+	cmd.Flag("receive.hashrings-algorithm", "The algorithm used when distributing series in the hashrings. Must be one of "+hashringAlgorithmsHelptext+". Will be overwritten by the algorithm in the hashring config.").
 		Default(string(receive.AlgorithmHashmod)).
 		EnumVar(&rc.hashringsAlgorithm, string(receive.AlgorithmHashmod), string(receive.AlgorithmKetama))
 

pkg/receive/hashring.go

@@ -6,6 +6,7 @@ package receive
 import (
 	"context"
 	"fmt"
+	"log"
 	"sort"
 	"strconv"
 	"sync"
@@ -291,6 +292,10 @@ func HashringFromConfig(algorithm HashringAlgorithm, replicationFactor uint64, c
 	if len(config) == 0 {
 		return nil, errors.Wrapf(err, "failed to load configuration")
 	}
+
+	if (algorithm != "hashmod") && (algorithm != "ketama") {
+		log.Println("The specified algorithm is incorrect. Fall back to hashmod algorithm")
+	}
 
 	return newMultiHashring(algorithm, replicationFactor, config), err
 }