in invoker/core/src/main/java/com/google/cloud/functions/invoker/gcf/ExecutionIdUtil.java [50:58]
private String getOrGenerateExecutionId(HttpServletRequest request) {
String executionId = request.getHeader(EXECUTION_ID_HTTP_HEADER);
if (executionId == null) {
byte[] array = new byte[EXECUTION_ID_LENGTH];
random.nextBytes(array);
executionId = Base64.getEncoder().encodeToString(array);
}
return executionId;
}