mirror of
https://github.com/FairRootGroup/FairMQ.git
synced 2025-10-12 16:21:13 +00:00
53 lines
2.5 KiB
Markdown
53 lines
2.5 KiB
Markdown
← [Back](../README.md)
|
|
|
|
# 1. Device
|
|
|
|
The components encapsulating the tasks are called **devices** and derive from the common base class `FairMQDevice`. FairMQ provides ready to use devices to organize the dataflow between the components (without touching the contents of a message), providing functionality like merging and splitting of the data stream (see subdirectory `devices`).
|
|
|
|
## 1.1 Topology
|
|
|
|
Devices are arranged into **topologies** where each device has a defined number of data inputs and outputs.
|
|
|
|
Example of a simple FairMQ topology:
|
|
|
|
|
|
|
|
Within a topology each device needs a unique id (given to it via required command line option `--id`).
|
|
|
|
Topology configuration is currently happening via setup scripts. This is very rudimentary and a much more flexible system is now in development. For now, example setup scripts can be found in directory `FairRoot/example/Tutorial3/` along with some additional documentation.
|
|
|
|
## 1.2 Communication Patterns
|
|
|
|
FairMQ devices communicate via the communication patterns offered by ZeroMQ (or nanomsg): PUSH-PULL, PUB-SUB, REQ-REP, PAIR, [more info here](http://api.zeromq.org/4-0:zmq-socket). Each transport may provide further patterns.
|
|
|
|
## 1.3 State Machine
|
|
|
|
Each FairMQ device has an internal state machine:
|
|
|
|
|
|
|
|
The state machine can be querried and controlled via `GetCurrentStateName()` and `ChangeState("<state name>")` methods. Only legal state transitions are allowed (see image above). Illegal transitions will fail with an error.
|
|
|
|
If the device is running in interactive mode (default), states can be changed via keyboard input:
|
|
|
|
- `'h'` - help
|
|
- `'p'` - pause
|
|
- `'r'` - run
|
|
- `'s'` - stop
|
|
- `'t'` - reset task
|
|
- `'d'` - reset device
|
|
- `'q'` - end
|
|
- `'j'` - init task
|
|
- `'i'` - init device
|
|
|
|
Without the interactive mode, for example for a run in background, two other control mechanisms are available:
|
|
|
|
- static (`--control static`) - device goes through a simple init -> run -> reset -> exit chain.
|
|
- dds (`--control dds`) - device is controled by external command, in this case using dds commands (fairmq-dds-command-ui).
|
|
|
|
## 1.4 Multiple devices in the same process
|
|
|
|
Technically one can create two or more devices within the same process without any conflicts. However the configuration (FairMQProgOptions) currently assumes the supplied configuration values are for one device/process.
|
|
|
|
← [Back](../README.md)
|