simpledali 0.8.3

Datalink protocol in python

simpledali

Datalink in pure python.

Read the docs at readthedocs

Datalink is a protocol for near-realtime transfer of seismic data, usually in miniseed, but has flexibility to carry any payload such as JSON. The Protocol is defined at https://earthscope.github.io/libdali/datalink-protocol.html

See ringserver from IRIS for the most common datalink server instance. The public instance at rtserve.iris.washington.edu/ allows access to near-realtime streaming seismic data over web sockets at ws://rtserve.iris.washington.edu/datalink

For parsing for miniseed2 and miniseed3 see simplemseed, also in pure python.

Note starting with ringserver version 4, the stream ids have changed from the older NSLC, network_station_location_channel to the newer FDSN style source ids. See the FDSN documentation here. The protocol, dlproto, configures which of these are used. It can be set in the constructor, but it is preferrable to call id() immediately, before any other calls, so that the server's protocol is used.

Support for both regular sockets and websockets. For example:

import asyncio
import simpledali

async def main():
    host = "localhost"
    port = 16000
    uri = f"ws://{host}:{port}/datalink"
    verbose = True

    programname = "simpleDali"
    username = "dragrace"
    processid = 0
    architecture = "python"

    # for regular socket (DataLinkPort)
    async with simpledali.SocketDataLink(host, port, verbose=verbose) as dali:
        # very good idea to call id at start, both for logging on server
        # side and to get capabilities like packet size, dlproto or write ability
        serverId = await dali.id(programname, username, processid, architecture)
        print(f"Connect to {host}:{port} via regular socket")
        print(f"Socket Id: {serverId.message}")
    # for web socket (ListenPort)
    async with simpledali.WebSocketDataLink(uri, verbose=verbose) as dali:
        serverId = await dali.id(programname, username, processid, architecture)
        print(f"Connect to {uri} via websocket")
        print(f"WebSocket Id: {serverId.message}")

asyncio.run(main())

The dali2jsonl script will archive '/JSON' packets as JSON Lines. This is a similar function to the MSeedWrite configuration on ringserver, but in a separate process and saves JSON packets instead of miniseed. See jsonlines.org for the file format, basically one JSON value per line.

dali2jsonl --help
usage: dali2jsonl [-h] [-v] -c CONF

Archive JSON datalink packets as JSON Lines.

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         increase output verbosity
  -c CONF, --conf CONF  Configuration as TOML

The TOML configuration looks like:

[datalink]
# datalink host, defaults to localhost
host='localhost'
# datalink port, defaults to 18000
port=15004
# Match regular expression pattern on stream ids, ex '.*/JSON'
match='.*/JSON'

[jsonl]
# JSONL Write pattern, usage similar to MSeedWrite in ringserver
write='/data/scsn/www/jsonl/%n/%s/%Y/%j/%n.%s.%l.%c.%Y.%j.%H.jsonl'

Example

There are examples of sending and receiving Datalink packets in the example directory.