From fed2959658f541bebf03d264cfb60a63ce4418be Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Mon, 24 Feb 2020 21:14:22 +0200
Subject: [PATCH] lib/envflag: substitute dots with underscores in env var
 names if -envflag.enable is set

See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/311
---
 README.md              |  3 ++-
 lib/envflag/envflag.go | 12 ++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 90296c02c..dc63a5597 100644
--- a/README.md
+++ b/README.md
@@ -138,7 +138,8 @@ The following command-line flags are used the most:
 Pass `-help` to see all the available flags with description and default values.
 
 Default flag values may be read from environment variables if `-envflag.enable` command-line flag is set.
-See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/311) for more details.
+Substitute dots with underscores in env var names. Alternative syntax can be used for setting repeatable flags:
+`-arg=foo -arg=bar` can be written as `-arg=foo,bar`. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/311) for more details.
 
 It is recommended setting up [monitoring](#monitoring) for VictoriaMetrics.
 
diff --git a/lib/envflag/envflag.go b/lib/envflag/envflag.go
index 80f557917..4bf9d7447 100644
--- a/lib/envflag/envflag.go
+++ b/lib/envflag/envflag.go
@@ -4,6 +4,7 @@ import (
 	"flag"
 	"log"
 	"os"
+	"strings"
 )
 
 var enable = flag.Bool("envflag.enable", false, "Whether to enable reading flags from environment variables additionally to command line. "+
@@ -34,11 +35,18 @@ func Parse() {
 			return
 		}
 		// Get flag value from environment var.
-		if v, ok := os.LookupEnv(f.Name); ok {
+		fname := getEnvFlagName(f.Name)
+		if v, ok := os.LookupEnv(fname); ok {
 			if err := f.Value.Set(v); err != nil {
 				// Do not use lib/logger here, since it is uninitialized yet.
-				log.Fatalf("cannot set flag %s to %q, which is read from environment variable: %s", f.Name, v, err)
+				log.Fatalf("cannot set flag %s to %q, which is read from environment variable %q: %s", f.Name, v, fname, err)
 			}
 		}
 	})
 }
+
+func getEnvFlagName(s string) string {
+	// Substitute dots with underscores, since env var names cannot contain dots.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/311#issuecomment-586354129 for details.
+	return strings.ReplaceAll(s, ".", "_")
+}