VILLASnode/documentation/Configuration.md

# Configuration

The S2SS configuration is completly contained in a single file.
Take a look at the example configuration: `server/etc/example.conf`.

The configuration file consists of three sections:

## Global

The global section consists of some global configuration parameters:

#### `debug` *(integer)*

`debug` expects an integer number (0-10) which determines the verbosity of debug messages during the execution of the server.
Use this with care! Producing a lot of IO might decrease the performance of the server.
Omitting this setting or setting it to zero will disable debug messages completely.

#### `stats` *(float)*

`stats` specifies the rate in which statistics about the actives paths will be printed to the screen.
Setting this value to 5, will print 5 lines per second.
A line of includes information such as:
  - Source and Destination of path
  - Messages received
  - Messages sent
  - Messaged dropped

#### `affinity` *(integer)*

The `affinity` setting allows to restrict the exeuction of the daemon to certain CPU cores.
This technique, also called 'pinning', improves the determinism of the server by isolating the daemon processes on exclusive cores.

#### `priority` *(integer)*

The `priority` setting allows to adjust the scheduling priority of the deamon processes.
By default, the daemon uses a real-time optimized FIFO scheduling algorithm.

## Nodes

The node section is a **directory** of nodes (clients) which are connected to the S2SS instance.
The directory is indexed by the name of the node:

    nodes = {
        "sintef_node" = {
	    type = "socket"
	    ....
	}
    }

There are multiple diffrent type of nodes. But all types have the following settings in common:

#### `type` *("socket" | "gtfpga" | "file" | "ngsi")*

`type` sets the type of the node. This should be one of:
  - `socket` which refers to a [Socket](socket) node.
  - `gtfpga` which refers to a [GTFPGA](gtfpga) node.
  - `opal` which refers to a [OPAL Asynchronous Process](opal) node.
  - `file` which refers to a [File](file) node.

The remaining settings per node a depending on `type`.
Take a look a the specific pages for details.

## Paths

The path section consists of a **list** of paths:

    paths = [
        {
            in = "rtds",
            out = "broker",
            reverse = false,
            poolsize = 32,
            msgsize = 16,
            combine = 4,
            hook = [ "print", "ts" ]
        }
    ]

Every path is allowed to have the following settings:

##### `in` & `out` *(string)*

The `in` and `out` settings expect the name of the source and destination node.

The `out` setting itself is allowed to be list of nodes.
This enables 1-to-n distribution of simulation data.

##### `enabled` *(boolean)*

The optional `enabled` setting can be used to temporarily disable a path.
If omitted, the path is enabled by default.

##### `reverse` *(boolean)*

By default, the path is unidirectional. Meaning, that it only forwards samples from the source to the destination.
Sometimes a bidirectional path is needed.
This can be accomplished by setting `reverse` to `true`.

##### `combine` *(integer)*

This setting allows to send multiple samples in a single message to the destination nodes. Currently this is only supported by the `file` and `socket` node-types.

The value of this setting determines how many samples will be combined into one packet.

**Important:** Please make sure that the value of this setting is smaller or equal to the `poolsize` setting of this path.

##### `rate` *(float)*

A non-zero value for this setting will change this path to an asynchronous mode.
In this mode S2SS will send with a fixed rate to all destination nodes.
It will always send the latest value it received, possible skipping values which have been received in between.
If `combine` is larger than 1, it will send the last `combine` samples at once.

**Important:** Please note that there is no correlation between the time of arrival and time of departure in this mode. It might increase the latency of this path by up to `1 / rate` seconds!

##### `poolsize` *(integer)*

Every path manages a circular buffer to keep a history of past samples. This setting specifies the size of this circular buffer.

**Important:** There are some hook functions (or the `combine` setting) which require a minimum poolsize (for example the finite-impulse-response `fir` hook).

##### `hook` *(list of strings)*

A list of hook functions which will be executed for this path.

Please consult the hook chapter of this documentation for more details.