Protocol

PAGE STATUS: early draft

Protocol message are not separately digitally signed due to the TLS transport and certificate authentication.

Protocol Extensions

Protocol extension negotiation is done on a transport-by-transport level. For WebSockets transport (the default) this is done with the X-Mosaic-Extensions header.

The following extensions have been defined:

Asynchronous

All client messages initiate an action, and all server messages are in response to client messages (NOTE: this may not apply to Mosaic extensions). Yet messaging is asychronous and both sides SHOULD be prepared to deal with a message sent at any time.

Servers SHOULD not send messages until they receive a message that requires a response.

If a server fails to receive a message from a client that does not have an open query or submission within a reasonable timeframe, it MAY close the connection.

If a client receives a server message that was not expected, it MUST ignore it and decide what to do next. In some cases, clients MAY close the connection because the service they were seeking failed. In other cases they MAY try something else. There is no provision for a client to alert a server of an error.

Messages

Every message starts with a one-byte type, shown below in the header of each type. Following this is the data of the message.

Initiator Message Type
Client Get 0x1
Client Query 0x2
Client Subscribe 0x3
Client Unsubscribe 0x4
Client Submission 0x5
Server Record 0x80
Server Locally Complete 0x81
Server Query Closed 0x82
Server Submission Result 0x83

Client Messages

Get

0x1

This is a query for specific records.

It has the following format:


    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x1 | 0x0 | QUERY_ID  |          0x0          |
 8  +-----------------------------------------------+
    | Mixed IDs or ADDRs ...                        |
    | ...                                           |
    +-----------------------------------------------+
  • [0:1] - The type 0x1
  • [1:2] - Zeroed
  • [2:4] - QUERY_ID, two bytes which should be made up by the client and used to associate returned Record responses to this request.
  • [4:8] - Zeroed
  • [*] - A sequence of mixed IDs and ADDRs. Note that ADDRs start with a 1 bit, whereas IDs start with a 0 bit, and both of them are 48 bytes long.

This is a client initiated message. Servers are expected to reply with:

  • A series of zero or more Record messages representing all the matched records on the server, followed by a Query Closed message.

Query

0x2

This is a query for records that closes once served.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x2 | 0x0 | QUERY_ID  |         LIMIT         |
 8  +-----------------------------------------------+
    | FILTER_LEN|              0x0                  |
16  +-----------------------------------------------+
    | FILTER ...                                    |
    | ...                                           |
    +-----------------------------------------------+
  • [0:1] - The type 0x2
  • [1:2] - Zeroed
  • [2:4] - QUERY_ID two bytes which should be made up by the client and used to associate returned Record responses to this request.
  • [4:8] - LIMIT, an unsigned integer in little-endian format, specifies the maximum number of responses that the client wishes to receive. A value of 0 indicates unlimited.
  • [8:10] - FILTER_LEN specifies the length of the FILTER in bytes.
  • [10:16] - Zeroed
  • [*] - The FILTER, see Filter.

This is a client initiated message. Servers are expected to reply with:

  • a series of zero or more Record messages representing all the matching records on the server initially, followed by a Query Closed message.

Queries MUST return results in anti-chronological order, from most recent backwards.

Subscribe

0x3

This is a query for records that is kept open after the initial records are served so that newly arriving records that match can be sent to the client immediately.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x3 | 0x0 | QUERY_ID  |         LIMIT         |
 8  +-----------------------------------------------+
    | FILTER_LEN|              0x0                  |
16  +-----------------------------------------------+
    | FILTER ...                                    |
    | ...                                           |
    +-----------------------------------------------+
  • [0:1] - The type 0x3
  • [1:2] - Zeroed
  • [2:4] - QUERY_ID, two bytes which should be made up by the client and used to associate returned Record responses to this request.
  • [4:8] - LIMIT, an unsigned integer in little-endian format, specifies the maximum number of responses that the client wishes to receive. A value of 0 indicates unlimited.
  • [8:10] - FILTER_LEN specifies the length of the FILTER in bytes.
  • [10:16] - Zeroed
  • [*] - The FILTER, see Filter.

This is a client initiated message. Servers are expected to reply with:

  • a series of zero or more Record messages representing all the matching records on the server initially, followed by a Locally Complete message, potentially followed by zero or more Record messages that flow in to the server after the initial response (so long as the query is still open), or
  • a Query Closed message if the query could not be served.

Queries MUST return results in anti-chronological order, from most recent backwards.

Unsubscribe

0x4

This is a client request to close an open subscription query.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
     | 0x4 | 0x0 | QUERY_ID |         0x0           |
 8  +-----------------------------------------------+
  • [0:1] - The type 0x3
  • [1:2] - Zeroed
  • [2:4] - QUERY_ID, two bytes indicating which query should be closed.
  • [4:8] - Zeroed

This is a client initiated message. Servers are expected to reply with:

Submission

0x5

This is the submission of a record.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x5 |    LENGTH       |          0x0          |
 8  +-----------------------------------------------+
    | RECORD ...                                    |
    | ...                                           |
    +-----------------------------------------------+
  • [0:1] - The type 0x5
  • [1:4] - LENGTH is a 24-bit little-endian length, with a maximum value of the max length of a record (1024576 bytes) and representing the actual length of the subsequent record submitted.
  • [5:8] - Zeroed
  • [*] - RECORD is the record submitted

This is a client initiated message. Servers are expected to reply with:

Server Messages

Record

0x80

This is a record returned from a query.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x80| 0x0 | QUERY_ID  | 0x0 |     LENGTH      |
 8  +-----------------------------------------------+
    | RECORD ...                                    |
    | ...                                           |
    +-----------------------------------------------+
  • [0:1] - The type 0x80
  • [1:2] - Zeroed
  • [2:4] - QUERY_ID indicates the client query that this record matched.
  • [4:5] - Zeroed
  • [5:8] - LENGTH is a 24-bit little-endian length, with a maximum value of the max length of a record (1024576 bytes) and representing the actual length of the subsequent record supplied.
  • [*] - RECORD is the returned record.

This is a server response message in response to Get or Query or Subscribe.

Locally Complete

0x81

This is a message indicating that a query has served all matching local records, but remains open to serve matching records that subsequently arrive.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x81| 0x0 |  Query_ID |  0x0                  |
 8  +-----------------------------------------------+
  • [0:1] - The type 0x81
  • [1:2] - Zeroed
  • [2:4] - QUERY_ID indicates the client query that is now locally complete.
  • [4:8] - zeroed

This is a server response message in response to Subscribe.

Query Closed

0x82

This is a message indicating that a query has been closed.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x82| CODE|  Query_ID |  0x0                  |
 8  +-----------------------------------------------+
  • [0:1] - The type 0x82
  • [1:2] - CODE indicates the reason for closure from among the following defined reasons:
    • ON_REQUEST: 0x1 - In response to Unsubscribe
    • REJECTED_INVALID: 0x10 - Query was rejected due to being invalid
    • REJECTED_TOO_OPEN: 0x11 - Query was rejected due to being too open (scraping too many records)
    • REJECTED_TOO_FAST: 0x12 - Query was rejected due to too many queries (or messages of any type) being submitted recently by this client
    • REJECTED_TEMP_BANNED: 0x13 - Query was rejected due to the client being temporarily banned
    • REJECTED_PERM_BANNED: 0x14 - Query was rejected due to the client being permanently banned
    • SHUTTING_DOWN: 0x30 - The server is shutting down
    • INTERNAL_ERROR: 0xF0 - A server error occured
    • OTHER: 0xFF - Some other reason
  • [2:4] - QUERY_ID indicates the client query that is now closed.
  • [4:8] - zeroed

Submission Result

0x83

This is a message returning the result of a Submission.

It has the following format:

    0     1     2     3     4     5     6     7     8
 0  +-----------------------------------------------+
    | 0x83|CODE |   0x0                             |
 8  +-----------------------------------------------+
    | ID PREFIX bytes 0..8                          |
16  +-----------------------------------------------+
    | ID PREFIX bytes 8..16                         |
24  +-----------------------------------------------+
    | ID PREFIX bytes 16..24                        |
32  +-----------------------------------------------+
    | ID PREFIX bytes 24..32                        |
40  +-----------------------------------------------+
  • [0:1] - The type 0x83
  • [1:2] - CODE which indicates the result of the submission from among the following defined results:
    • OK: 0x1 - Record submission was accepted
    • DUPLICATE: 0x2 - Record is a duplicate. Servers may use this or they may optionally use OK in the same circumstance.
    • REJECTED_INVALID: 0x10 - Record is invalid
    • REJECTED_TOO_FAST: 0x12 - Record submission was rejected due to too many submissions (or messages of any type) being made recently by this client
    • REJECTED_TEMP_BANNED: 0x13 - Record submission was rejected due to the client being temporarily banned
    • REJECTED_PERM_BANNED: 0x14 - Record submission was rejected due to the client being permanently banned
    • REJECTED_REQUIRES_AUTHN: 0x15 - Record submission requires authentication but the client is connected anonymously.
    • REJECTED_REQUIRES_AUTHZ: 0x16 - Record submission requires authorization (e.g. an account with the server) which the client user does not have.
    • INTERNAL_ERROR: 0xF0 - A server error occured
    • OTHER: 0xFF - Some other reason
  • [2:8] - Zeroed
  • [8:40] - A 32-byte prefix of the 48-byte Id.