aos/configuration.fbs

include "reflection/reflection.fbs";

namespace aos;

enum LoggerConfig : ubyte {
  // This data should be logged on this node.
  LOCAL_LOGGER,
  // This data should be logged on a remote node.
  REMOTE_LOGGER,
  // This data should not be logged.
  NOT_LOGGED,
  // This data should be logged both on this node and on the remote node.
  // This is useful where you want to log a message on both the sender and
  // receiver to create self-contained log files.
  LOCAL_AND_REMOTE_LOGGER
}

table Connection {
  // Node name to forward to.
  name:string;

  // How the delivery timestamps for this connection should be logged.  Do we
  // log them with the local logger (i.e. the logger running on the node that
  // this message is delivered to)?  Do we log them on another node (a central
  // logging node)?  Do we log them in both places redundantly?
  timestamp_logger:LoggerConfig = LOCAL_LOGGER;

  // If the corresponding delivery timestamps for this channel are logged
  // remotely, which node should be responsible for logging the data.  Note:
  // for now, this can only be the source node.  Empty implies the node this
  // connection is connecting to (i.e. name).
  timestamp_logger_node:string;

  // Priority to forward data with.
  priority:ushort = 100;

  // Time to live in nanoseconds before the message is dropped.
  // A value of 0 means no timeout, i.e. reliable.  When a client connects, the
  // latest message from this channel will be sent regardless.
  // TODO(austin): We can retry more than just the last message on reconnect
  //   if we want.  This is an unlikely scenario though.
  time_to_live:uint = 0;
}

// Table representing a channel.  Channels are where data is published and
// subscribed from.  The tuple of name, type is the identifying information.
table Channel {
  // Name of the channel.
  name:string;
  // Type name of the flatbuffer.
  type:string;
  // Max frequency in messages/sec of the data published on this channel.
  frequency:int = 100;
  // Max size of the data being published.  (This will hopefully be
  // automatically computed in the future.)
  max_size:int = 1000;

  // Sets the maximum number of senders on a channel.
  num_senders:int = 10;
  // Sets the maximum number of watchers on a channel.
  num_watchers:int = 10;

  // The schema for the data sent on this channel.
  schema:reflection.Schema;

  // The source node name for the data sent on this channel.
  // If nodes is populated below, this needs to also be populated.
  source_node:string;

  // The destination nodes for data sent on this channel.
  // This only needs to be populated if this message is getting forwarded.
  destination_nodes:[Connection];

  // What service is responsible for logging this channel:
  logger:LoggerConfig = LOCAL_LOGGER;
  // If the channel is logged remotely, which node should be responsible for
  // logging the data.  Note: this requires that the data is forwarded to the
  // node responsible for logging it.  Empty implies the node this connection
  // is connecting to (i.e. name).
  logger_node:string;
}

// Table to support renaming channel names.
table Map {
  // Channel to match with.  If the name in here matches, the name is replaced
  // with the name in rename.
  // Node specific matches are also supported.
  match:Channel;
  // The channel to merge in.
  rename:Channel;
}

// Application specific information.
table Application {
  // Name of the application.
  name:string;
  // List of maps to apply for this specific application.  Application specific
  // maps are applied in reverse order, and before the global maps.
  // For example
  //   "maps": [ { "match": { "name": "/foo" }, "rename": { "name": "/bar" } } ]
  // will make it so any channels named "/foo" actually go to "/bar" for just
  // this application.  This is super handy for running an application twice
  // publishing to different channels, or for injecting a little application
  // to modify messages live for testing.
  //
  //   "maps": [
  //     { "match": { "name": "/foo" }, "rename": { "name": "/bar" } },
  //     { "match": { "name": "/foo" }, "rename": { "name": "/baz" } }
  //   ]
  //
  // will map "/foo" to "/baz", even if there is a global list of maps.
  maps:[Map];

  // The node that this application will be started on.
  // TODO(austin): Teach starter how to use this for starting applications.
  node:string;
}

// Per node data and connection information.
table Node {
  // Short name for the node.  This provides a short hand to make it easy to
  // setup forwarding rules as part of the channel setup.
  name:string;

  // Hostname used to identify and connect to the node.
  hostname:string;
  // Port to serve forwarded data from.
  port:ushort = 9971;
}

// Overall configuration datastructure for the pubsub.
table Configuration {
  // List of channels.
  channels:[Channel] (id: 0);
  // List of global maps.  These are applied in reverse order.
  maps:[Map] (id: 1);

  // If present, this is the list of nodes in the system.  If this is not
  // present, AOS will be running in a single node configuration.
  nodes:[Node] (id: 4);

  // List of applications.
  applications:[Application] (id: 2);
  // List of imports.  Imports are loaded first, and then this configuration
  // is merged into them.
  imports:[string] (id: 3);

  // Length of the channels in nanoseconds.  Every channel will have enough
  // data allocated so that if data is published at the configured frequency,
  // this many seconds of messages will be available for fetchers.
  channel_storage_duration:long = 2000000000 (id: 5);
}

root_type Configuration;