Deprecate -no-exit and add -exit-on-errors. This essentially flips th…

…e default behavior as it always should have been for a long running HTTP server.

If you pass -no-exit a deprecation warning is printed and the app behaves as before.

CHANGELOG.md

@@ -1,5 +1,8 @@
 1.5
 ===
+* Deprecate `-no-exit`. Default behavior is not to exit on scrape errors as it should be for a long running HTTP server.
+  * This was design misstep. You will not get a deprecation warning if you pass `-no-exit` but the process behaves as before.
+  * New explicit `-exit-on-errors` has been added for users who want the old default behavior back.
 * Correctly export gauge and counter types from `varnishstat` output `type` property.
 * Add go module support.
 * Use `github.com/prometheus/client_golang` v1.0.0

main.go

@@ -42,10 +42,12 @@ type startParams struct {
 	Params                 *varnishstatParams
 
 	Verbose       bool
-	NoExit        bool
+	ExitOnErrors  bool
 	Test          bool
 	Raw           bool
 	WithGoMetrics bool
+
+	noExit bool // deprecated
 }
 
 type varnishstatParams struct {
@@ -86,12 +88,15 @@ func init() {
 	// modes
 	version := false
 	flag.BoolVar(&version, "version", version, "Print version and exit")
-	flag.BoolVar(&StartParams.NoExit, "no-exit", StartParams.NoExit, "Do not exit server on Varnish scrape errors.")
+	flag.BoolVar(&StartParams.ExitOnErrors, "exit-on-errors", StartParams.ExitOnErrors, "Exit process on scrape errors.")
 	flag.BoolVar(&StartParams.Verbose, "verbose", StartParams.Verbose, "Verbose logging.")
 	flag.BoolVar(&StartParams.Test, "test", StartParams.Test, "Test varnishstat availability, prints available metrics and exits.")
 	flag.BoolVar(&StartParams.Raw, "raw", StartParams.Test, "Raw stdout logging without timestamps.")
 	flag.BoolVar(&StartParams.WithGoMetrics, "with-go-metrics", StartParams.WithGoMetrics, "Export go runtime and http handler metrics")
 
+	// deprecated
+	flag.BoolVar(&StartParams.noExit, "no-exit", StartParams.noExit, "Deprecated: see -exit-on-errors")
+
 	flag.Parse()
 
 	if version {
@@ -111,10 +116,13 @@ func init() {
 		logFatal("-web.telemetry-path and -web.health-path cannot have same value")
 	}
 
-	// This looks weird, but we want the start param to have default value
-	// of the old behavior, not flip it with e.g. -exit. You have to
-	// explicitly turn on the changed behavior.
-	ExitHandler.exitOnError = StartParams.Test == true || StartParams.NoExit == false
+	// Don't log warning on !noExit as that would spam for the formed default value.
+	if StartParams.noExit {
+		logWarn("-no-exit is deprecated. As of v1.5 it is the default behavior not to exit process on scrape errors. You can remove this parameter.")
+	}
+
+	// Test run or user explicitly wants to exit on any scrape errors during runtime.
+	ExitHandler.exitOnError = StartParams.Test == true || StartParams.ExitOnErrors == true
 }
 
 func main() {