add config option check logging (#3722)

config/options_check.go

@@ -0,0 +1,82 @@
+package config
+
+import (
+	"regexp"
+)
+
+// KeyAction defines the Pomerium behavior when it encounters a deprecated config field
+type KeyAction string
+
+// FieldCheckMsg is a log message to print for a config option
+type FieldCheckMsg string
+
+const (
+	// KeyActionWarn would result in warning to log
+	KeyActionWarn = KeyAction("warn")
+	// KeyActionError would result in error in log and possibly program stop
+	KeyActionError = KeyAction("error")
+	// UnknownFieldAction default behavior when observing an unknown field is to warn
+	UnknownFieldAction = KeyActionWarn
+	// FieldCheckMsgRemoved log message when field was removed
+	FieldCheckMsgRemoved = FieldCheckMsg("config option was removed")
+	// FieldCheckMsgUnknown log message for unrecognized / unhandled config option
+	FieldCheckMsgUnknown = FieldCheckMsg("unknown config option")
+)
+
+var reKeyPath = regexp.MustCompile(`\[\d+\]`)
+
+var (
+	// options that were deprecated in the config
+	removedConfigFields = map[string]string{
+		"idp_service_account":            "https://docs.pomerium.com/docs/overview/upgrading#idp-directory-sync",
+		"idp_refresh_directory_timeout":  "https://docs.pomerium.com/docs/overview/upgrading#idp-directory-sync",
+		"idp_refresh_directory_interval": "https://docs.pomerium.com/docs/overview/upgrading#idp-directory-sync",
+		"idp_qps":                        "https://docs.pomerium.com/docs/overview/upgrading#idp-directory-sync",
+		"routes.allowed_groups":          "https://docs.pomerium.com/docs/overview/upgrading#idp-groups-policy",
+	}
+
+	// mapstructure has issues with embedded protobuf structs that we should ignore
+	ignoreConfigFields = map[string]struct{}{
+		"routes.outlier_detection": {},
+		"routes.health_checks":     {},
+	}
+)
+
+// FieldMsg returns information
+type FieldMsg struct {
+	Key     string
+	DocsURL string
+	FieldCheckMsg
+	KeyAction
+}
+
+// CheckUnknownConfigFields returns list of messages to be emitted about unrecognized fields
+func CheckUnknownConfigFields(fields []string) []FieldMsg {
+	out := make([]FieldMsg, 0, len(fields))
+
+	for _, key := range fields {
+		path := reKeyPath.ReplaceAllString(key, "")
+
+		if docsURL, ok := removedConfigFields[path]; ok {
+			out = append(out, FieldMsg{
+				Key:           path,
+				DocsURL:       docsURL,
+				KeyAction:     KeyActionError,
+				FieldCheckMsg: FieldCheckMsgRemoved,
+			})
+			continue
+		}
+
+		if _, ok := ignoreConfigFields[path]; ok {
+			continue
+		}
+
+		out = append(out, FieldMsg{
+			Key:           path,
+			KeyAction:     KeyActionWarn,
+			FieldCheckMsg: FieldCheckMsgUnknown,
+		})
+	}
+
+	return out
+}