perf: Cap RANDOM_STRING_N to 8182 (#1193)

Author: TwiN

README.md

@@ -295,7 +295,7 @@ You may use the following placeholders in the body (`endpoints[].body`):
 - `[ENDPOINT_GROUP]` (resolved from `endpoints[].group`)
 - `[ENDPOINT_URL]` (resolved from `endpoints[].url`)
 - `[LOCAL_ADDRESS]` (resolves to the local IP and port like `192.0.2.1:25` or `[2001:db8::1]:80`)
-- `[RANDOM_STRING_N]` (resolves to a random string of numbers and letters of length N)
+- `[RANDOM_STRING_N]` (resolves to a random string of numbers and letters of length N (max: 8192))
 
 
 ### External Endpoints

config/endpoint/endpoint.go

@@ -344,6 +344,9 @@ func (e *Endpoint) getParsedBody() string {
 	if err == nil {
 		body = randRegex.ReplaceAllStringFunc(body, func(match string) string {
 			n, _ := strconv.Atoi(match[15 : len(match)-1])
+			if n > 8192 {
+				n = 8192 // Limit the length of the random string to 8192 bytes to avoid excessive memory usage
+			}
 			const availableCharacterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
 			b := make([]byte, n)
 			for i := range b {