feat: add load testing harness, coder loadtest command (#4853)

coderd/httpapi/json.go

@@ -0,0 +1,50 @@
+package httpapi
+
+import (
+	"encoding/json"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+// Duration wraps time.Duration and provides better JSON marshaling and
+// unmarshaling. The default time.Duration marshals as an integer and only
+// accepts integers when unmarshaling, which is not very user friendly as users
+// cannot write durations like "1h30m".
+//
+// This type marshals as a string like "1h30m", and unmarshals from either a
+// string or an integer.
+type Duration time.Duration
+
+var _ json.Marshaler = Duration(0)
+var _ json.Unmarshaler = (*Duration)(nil)
+
+// MarshalJSON implements json.Marshaler.
+func (d Duration) MarshalJSON() ([]byte, error) {
+	return json.Marshal(time.Duration(d).String())
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (d *Duration) UnmarshalJSON(b []byte) error {
+	var v interface{}
+	err := json.Unmarshal(b, &v)
+	if err != nil {
+		return xerrors.Errorf("unmarshal JSON value: %w", err)
+	}
+
+	switch value := v.(type) {
+	case float64:
+		*d = Duration(time.Duration(value))
+		return nil
+	case string:
+		tmp, err := time.ParseDuration(value)
+		if err != nil {
+			return xerrors.Errorf("parse duration %q: %w", value, err)
+		}
+
+		*d = Duration(tmp)
+		return nil
+	}
+
+	return xerrors.New("invalid duration")
+}