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Custom Metadata for Each Message

NuRaft provides an ability to ship custom metadata for each message and response that can be used for your own verification. When you set asio_options, there are a few options for it:

asio_service::options asio_opt;
asio_opt.write_req_meta_  = my_write_req_meta;
asio_opt.read_req_meta_   = my_read_req_meta;
asio_opt.write_resp_meta_ = my_write_resp_meta;
asio_opt.read_resp_meta_  = my_read_resp_meta;
  • write_req_meta_: return custom metadata to be shipped with the Raft message.
std::string my_write_req_meta(const asio_service::meta_cb_params& params) {
    return "my req metadata";
}
  • read_req_meta_: read the custom metadata shipped with each Raft message, and return a boolean flag to decide to accept the message.
bool my_read_req_meta(const asio_service::meta_cb_params& params,
                      const std::string& meta) {
    return (meta == "my req metadata");
}
  • write_resp_meta_: return custom metadata to be shipped with the Raft message response.
std::string my_write_resp_meta(const asio_service::meta_cb_params& params) {
    return "my resp metadata";
}
  • read_resp_meta_: read the custom metadata shipped with the Raft message response, and return a boolean flag to decide to accept the response.
bool my_read_resp_meta(const asio_service::meta_cb_params& params,
                       const std::string& meta) {
    return (meta == "my resp metadata");
}

If read_req_meta_ or read_resp_meta_ returns false, the message or response is discarded immediately; thus it behaves the same as if it is not received.