Layer 3: Metadata Layer

Background

All database requests contain a header with a nonce and database uuid. The header is mirrored in the daemon replies to this request.

• The client must guarantee that no two requests have identical headers. This is the purpose of the nonce.

• The UUID should be a user-supplied string. (technically a v4 UUID, but this is not enforced)

• This layer should filter responses to match the nonce of the relevant request.

Specifications

• On outgoing messages:

  • Create a database_header message.

  • Fill in the uuid.

  • Generate a random 64-bit nonce.

    • Note that you may have to use a large-integer library or use bitwise arithmetic to fulfill all 64 bits.

  • Embed the header in the database_msg.

• On incoming messages:

  • Consider the nonce embedded within header.

  • Send this message to a handler specific to that nonce.

• All subsequent layers are interpreted as request-response. They assume that incoming messages are always replies to this particular request.

• Note that status_request's and status_responses do not implement headers and skip this layer.