The New York City Taxi & Limousine Commission provides a public data set about taxi rides in New York City from 2009 to 2015. We use a modified subset of this data to generate streams of events about taxi rides.
1. Download the taxi data files
You can download the taxi data files by running the following commands
wget http://training.ververica.com/trainingData/nycTaxiRides.gz wget http://training.ververica.com/trainingData/nycTaxiFares.gz
It doesn’t matter if you use wget or something else to fetch these files, but however you get the data, do not decompress or rename the
2. Schema of Taxi Ride Events
Our taxi data set contains information about individual taxi rides in New York City. Each ride is represented by two events: a trip start, and a trip end event. Each event consists of eleven fields:
rideId : Long // a unique id for each ride taxiId : Long // a unique id for each taxi driverId : Long // a unique id for each driver isStart : Boolean // TRUE for ride start events, FALSE for ride end events startTime : DateTime // the start time of a ride endTime : DateTime // the end time of a ride, // "1970-01-01 00:00:00" for start events startLon : Float // the longitude of the ride start location startLat : Float // the latitude of the ride start location endLon : Float // the longitude of the ride end location endLat : Float // the latitude of the ride end location passengerCnt : Short // number of passengers on the ride
Note: The data set contains records with invalid or missing coordinate information (longitude and latitude are
There is also a related data set containing taxi ride fare data, with these fields:
rideId : Long // a unique id for each ride taxiId : Long // a unique id for each taxi driverId : Long // a unique id for each driver startTime : DateTime // the start time of a ride paymentType : String // CSH or CRD tip : Float // tip for this ride tolls : Float // tolls for this ride totalFare : Float // total fare collected
3. Generate a Taxi Ride Data Stream in a Flink program
Note: Many of the exercises already provide code for working with these taxi ride data streams.
We provide a Flink source function (
TaxiRideSource) that reads a
.gz file with taxi ride records and emits a stream of
TaxiRide events. The source operates in event-time. There’s an analogous source function (
In order to generate the stream as realistically as possible, events are emitted proportional to their timestamp. Two events that occurred ten minutes after each other in reality are also served ten minutes after each other. A speed-up factor can be specified to “fast-forward” the stream, i.e., given a speed-up factor of 60, events that happened within one minute are served in one second. Moreover, one can specify a maximum serving delay which causes each event to be randomly delayed within the specified bound. This yields an out-of-order stream as is common in many real-world applications.
For these exercises, a speed-up factor of 600 or more (i.e., 10 minutes of event time for every second of processing), and a maximum delay of 60 (seconds) will work well.
All exercises should be implemented using event-time characteristics. Event-time decouples the program semantics from serving speed and guarantees consistent results even in case of historic data or data which is delivered out-of-order.
Some of the exercises will expect you to use
CheckpointedTaxiFareSource instead. Unlike
TaxiFareSource, these variants are able to checkpoint their state.
Note also that there are
TaxiFareTableSource table sources available for use with the Table and SQL APIs.
How to use these sources
// get an ExecutionEnvironment StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment(); // configure event-time processing env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime); // get the taxi ride data stream DataStream<TaxiRide> rides = env.addSource( new TaxiRideSource("/path/to/nycTaxiRides.gz", maxDelay, servingSpeed));
// get an ExecutionEnvironment val env = StreamExecutionEnvironment.getExecutionEnvironment // configure event-time processing env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime) // get the taxi ride data stream val rides = env.addSource( new TaxiRideSource("/path/to/nycTaxiRides.gz", maxDelay, servingSpeed))
There is also a
TaxiFareSource that works in an analogous fashion, using the nycTaxiFares.gz file. This source creates a stream of
// get the taxi fare data stream DataStream<TaxiFare> fares = env.addSource( new TaxiFareSource("/path/to/nycTaxiFares.gz", maxDelay, servingSpeed));
// get the taxi fare data stream val fares = env.addSource( new TaxiFareSource("/path/to/nycTaxiFares.gz", maxDelay, servingSpeed))