Reads a continuous stream of GTFS Realtime (GTFS-RT) data with DIFFERENTIAL incrementality from NATS, converts it into a single FULL_DATASET GTFS-RT feed, and serves it via HTTP.
Note from gtfs-rt-differential-to-full-dataset, which is used for the conversion:
Right now, this package does not obey the draft
DIFFERENTIALspec exactly. See below and #1 for details.
npm install -g OpenDataVBB/nats-consuming-gtfs-rt-server# todoUsage:
serve-gtfs-rt-from-nats [options]
Options:
--port -p Port to serve the GTFS Realtime feed on.
Default: $PORT, otherwise 3000
--nats-servers NATS server(s) to connect to.
Default: $NATS_SERVERS
--nats-user User to use when authenticating with NATS server.
Default: $NATS_USER
--nats-client-name Name identifying the NATS client among others.
Default: vdv453-1-${randomHex(4)}
--nats-consumer-name Name of the NATS JetStream consumer on the
GTFS_RT_2 stream.
Default: $GTFS_RT_CONSUMER_NAME, otherwise `nats-
consuming-gtfs-rt-server`
--diff-entities-ttl Time to keep DIFFERENTIAL-mode GTFS-RT FeedEntities
in the combined FULL_DATASET-mode feed for, in seconds.
Default: 10 minutes
--t0 UNIX timestamp to use as now, for debugging purposes.
Default: current UNIX timestamp
Examples:
serve-gtfs-rt-from-nats --port 1234 --nats-user foo
Before running nats-consuming-gtfs-rt-server, you must create a NATS JetStream stream called GTFS_RT_2 holding the FeedEntity GTFS-RT messages. This can be done using the NATS CLI:
nats stream add \
# omit this if you want to configure more details
--defaults \
# collect all messages published to these subjects
--subjects='gtfsrt.>' \
# acknowledge publishes
--ack \
# with limited storage, discard the oldest limits first
--retention=limits --discard=old \
--description='GTFS-Realtime FeedEntity messages' \
# name of the stream
GTFS_RT_2On the GTFS_RT_2 stream, you must also create a durable consumer:
nats consumer add \
# omit this if you want to configure more details
--defaults \
# create a pull-based consumer (refer to the NATS JetStream docs)
--pull \
# let gtfs-rt-feed explicitly acknowledge all received messages
--ack=explicit \
# let the newly created consumer start with the latest messages in GTFS_RT_2 (not all)
--deliver=new \
# send gtfs-rt-feed at most 200 messages at once
--max-pending=500 \
# when & how often to re-deliver a message that hasn't been acknowledged (usually because it couldn't be processed)
--max-deliver=3 \
--backoff=linear \
--backoff-steps=2 \
--backoff-min=15s \
--backoff-max=1m \
--description 'OpenDataVBB/nats-consuming-gtfs-rt-server' \
# name of the stream
GTFS_RT_2 \
# name of the consumer
nats-consuming-gtfs-rt-servergtfs-rt-differential-to-full-dataset– Transform a differential GTFS Realtime feed into a full dataset/dump.gtfs-rt-bindings– Parse and serialize GTFS Realtime data encoded as protocol buffers. (third-party)gtfs-realtime-bindings– Javascript classes generated from the GTFS-realtime protocol buffer specification. (official)
If you have a question or need support using nats-consuming-gtfs-rt-server, please double-check your code and setup first. If you think you have found a bug or want to propose a feature, use the issues page.