httpmsgbus (HMB) functions as a messaging service which runs over HTTP. It facilitates the transfer of objects, such as SeisComP 3 data model items, but also other content, between a server and a client. Messages sent by one client can be received by multiple clients connected to the same bus. JSON and BSON formats are used for communication.
A bus may have multiple queues. Order of messages within a queue is preserved. A queue may have multiple topics; topic name is simply an attribute of a message. A receiving client subscribes to one or more queues and tells which topics it is interested in.
Each message within a queue has a sequence number, so it is possible to resume connection without data loss, provided that the needed messages are still in the queue. A client can also select messages based on start- and end-time, and filter messages using a subset of MongoDB query language.
HMB supports out-of-order messages by letting a sending client specify the sequence number when sending messages. Messages are received in order; a receiving client may ignore out-of-order messages or wait for missing messages until a timeout.
httpmsgbus can be used as a standalone program or as an add-on to SeisComP 3.
Note
httpmsgbus is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. For more information, see http://www.gnu.org/