Location Analytics - Real-Time Geofencing using Kafka

Guido Schmutz
Working at Trivadis for more than 22 years
Consultant, Trainer Software Architect for Java, Oracle, SOA and Big Data / Fast Data
Oracle Groundbreaker Ambassador & Oracle ACE Director
Head of Trivadis Architecture Board
Technology Manager @ Trivadis
More than 30 years of software development experience
Contact: guido.schmutz@trivadis.com
Blog: http://guidoschmutz.wordpress.com
Slideshare: http://www.slideshare.net/gschmutz
Twitter: gschmutz
167th edition

Agenda
1. Introduction & Motivation
2. Using KSQL
3. Using Kafka Streams
4. Using Tile38
5. Visualization using ArcadiaData
6. Summary

Guido Schmutz
Working at Trivadis for more than 22 years
Oracle Groundbreaker Ambassador & Oracle ACE Director
Consultant, Trainer, Software Architect for Java, AWS, Azure,
Oracle Cloud, SOA and Big Data / Fast Data
Platform Architect & Head of Trivadis Architecture Board
More than 30 years of software development experience
Contact: guido.schmutz@trivadis.com
Blog: http://guidoschmutz.wordpress.com
Slideshare: http://www.slideshare.net/gschmutz
Twitter: gschmutz
155th edition

Geofencing – What is it?
• the use of GPS or RFID technology to
create a virtual geographic boundary,
enabling software to trigger a response
when a object/device enters or leaves a
particular area
• Possible Events
• OUTSIDE
• lNSIDE
• ENTER
• EXIT
Source: https://tile38.com

Geofencing – What can we do with it?
• On-Demand and Delivery Services - assign
orders to an area's designated service
provider
• On-Demand Transportation - track Electronic
Transportation Devices and their distance
from charging stations
• Transportation Management - track flow of
people using public transport systems
• Commercial Real Estate - Identify how many
people drive or walk by a specific location
• Retail Shopper Guidance - Guide
customer to a specific product once they
are in your store
• Property Security - Open or lock doors as
individuals with designated devices
approach or leave a building or vehicle.
• Property Control - restrict vehicles to be
operational only inside a geofenced area –
like drones or construction equipment

Geo-Processing
• Well-known text (WKT) is a text markup language for
representing vector geometry objects on a map
• GeoTools is a free software GIS toolkit for developing standards
compliant solutions

Apache Kafka – A Streaming Platform
Source
Connector
Sink
Connector
trucking_
driver
KSQL Engine
Kafka Streams
Kafka Broker

Dash
board
High Level Overview of Use Case
geofence
Join Position
& Geofences
Vehicle
Position
object
position
pos &
geofences
Geo
fencing
geofence
status
key=10
{ "id" : "10", "latitude" : 38.35821, "longitude" : -90.15311}
key=3
{"id":3,"name":"Berlin, Germany","geometry_wkt":"POLYGON
((13.297920227050781 52.56195151687443,
…))","last_update":1560607149015}
Geofence
Mgmt
Vehicle
Position
Weather
Service

KSQL – Streams and Tabless
geofence
Table
vehicle
position
Stream
CREATE STREAM vehicle_position_s
(id VARCHAR,
latitude DOUBLE,
longitude DOUBLE)
WITH (KAFKA_TOPIC='vehicle_position',
VALUE_FORMAT='DELIMITED');
CREATE TABLE geo_fence_t
(id BIGINT,
name VARCHAR,
geometry_wkt VARCHAR)
WITH (KAFKA_TOPIC='geo_fence',
VALUE_FORMAT='JSON',
KEY = 'id');KSQL
Geofencing

How to determine "inside" or "outside" geofence?
Only one standard UDF for geo processing in KSQL: GEO_DISTANCE
Implement custom UDF using functionality from GeoTools Java library
public String geo_fence(final double latitude, final double longitude,
final String geometryWKT){ .. }
public List<String> geo_fence_bulk(final double latitude
, final double longitude, List<String> idGeometryListWKT) { .. }
ksql> SELECT geo_fence(latitude, longitude, ' POLYGON ((13.297920227050781
52.56195151687443, 13.2440185546875 52.530216577830124, ...))')
FROM test_geo_udf_s;
52.4497 | 13.3096 | OUTSIDE
52.4556 | 13.3178 | INSIDE

Custom UDF to determine if Point is inside a geometry
@Udf(description = "determines if a lat/long is inside or outside the
geometry passed as the 3rd parameter as WKT encoded ...")
public String geo_fence(final double latitude, final double longitude,
final String geometryWKT) {
String status = "";
GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();
WKTReader reader = new WKTReader(geometryFactory);
Polygon polygon = (Polygon) reader.read(geometryWKT);
Coordinate coord = new Coordinate(longitude, latitude);
Point point = geometryFactory.createPoint(coord);
if (point.within(polygon)) {
status = "INSIDE";
} else {
status = "OUTSIDE";
}
return status;
}

1) Using Cross Join
geofence
Table
Join Position
& Geofences
vehicle
position
Stream
Stream
pos &
geofences
CREATE STREAM vp_join_gf_s
AS
SELECT vp.id, vp.latitude, vp.longitude,
gf.geometry_wkt
FROM vehicle_position_s AS vp
CROSS JOIN geo_fence_t AS gf
There is no Cross Join
in KSQL!

2) INNER Join
geofence
Stream
Join Position
& Geofences
vehicle
position
Stream
Stream
pos &
geofences
{ "group":1", "name":"St. Louis",
"geometry_wkt":"POLYGON ((13.297920227050781
52.56195151687443, …))",
"last_update":1560607149015}
{ "group":1", "name":"Berlin", "geometry_wkt":"POLYGON
((-90.23345947265625 38.484769753492536,…))",
"last_update":1560607149015}
Enrich Group
Table
geofences
by group 1
Enrich Group
Stream
postion by
group 1 Cannot insert into Table
from Stream
>INSERT INTO geo_fence_t
>SELECT '1' AS group_id, geof.id, …
>FROM geo_fence_s geof;
INSERT INTO can only be used to insert into
a stream. A02_GEO_FENCE_T is a table.
{ "group":"1", "id" : "10", "latitude" : 52.3924, "longitude" : 13.0514}

3) Geofences aggregated in one group
Join Position
& Geofences
Stream
geofence
status
Geofences
aggby group
Table
{ "group":1", "name":"St. Louis", "geometry_wkt":"POLYGON
((13.297920227050781 52.56195151687443, …))",
"last_update":1560607149015}
{"vehicle_id":10", "name":"Berlin",
"geometry_wkt":"POLYGON ((-90.23345947265625
38.484769753492536,…))", "last_update":1560607149015}
geo_fence_bulk
geofence
Stream
vehicle
position
Stream
{ "group":1", "name":"St. Louis",
52.56195151687443, …))",
"last_update":1560607149015}
{ "group":1", "name":"Berlin", "geometry_wkt":"POLYGON
((-90.23345947265625 38.484769753492536,…))",
"last_update":1560607149015}
Enrich With
Group-1
Stream
geofences
by group 1
Enrich With
Group-1
Stream
postion by
group 1
geofences
by group 1
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium
{ "group":"1", "id" : "10", "latitude" : 52.3924, "longitude" : 13.0514}

CREATE TABLE a03_geo_fence_aggby_group_t
AS
SELECT group_id
, collect_set(id + ':' + geometry_wkt) AS id_geometry_wkt_list
FROM a03_geo_fence_by_group_s geof
GROUP BY group_id;
CREATE STREAM a03_vehicle_position_by_group_s
AS
SELECT '1' group_id, vehp.id, vehp.latitude, vehp.longitude
FROM vehicle_position_s vehp
PARTITION BY group_id;

• CREATE STREAM a03_geo_fence_status_s
• AS
• SELECT vehp.id, vehp.latitude, vehp.longitude,
geo_fence_bulk(vehp.latitude, vehp.longitude,
geofaggid_geometry_wkt_list) AS geofence_status
• FROM a03_vehicle_position_by_group_s vehp
• LEFT JOIN a03_geo_fence_aggby_group_t geofagg
• ON vehp.group_id = geofagg.group_id;
ksql> SELECT * FROM a03_geo_fence_status_s;
46 | 52.47546 | 13.34851 | [1:OUTSIDE, 3:INSIDE]
46 | 52.47521 | 13.34881 | [1:OUTSIDE, 3:INSIDE]
...
As many as there are geo-fences

Geo Hash for a better distribution
Geohash is a geocoding which
encodes a geographic location
into a short string of letters and
digits
Length Area width x height
1 5,009.4km x 4,992.6km
2 1,252.3km x 624.1km
3 156.5km x 156km
4 39.1km x 19.5km
12 3.7cm x 1.9cm
http://geohash.gofreerange.com/

Geo Hash Custom UDF
ksql> SELECT latitude, longitude, geo_hash(latitude, longitude, 3)
>FROM test_geo_udf_s;
38.484769753492536 | -90.23345947265625 | 9yz
public String geohash(final double latitude,
final double longitude, int length)
public List<String> neighbours(String geohash)
public String adjacentHash(String geohash, String directionString)
public List<String> coverBoundingBox(String geometryWKT, int length)
ksql> SELECT geometry_wkt, geo_hash(geometry_wkt, 5)
>FROM test_geo_udf_s;
POLYGON ((-90.23345947265625 38.484769753492536, -90.25886535644531
38.47455675836861, ...)) | [9yzf6, 9yzf7, 9yzfd, 9yzfe, 9yzff, 9yzfg, 9yzfk,
9yzfs, 9yzfu]

4) Geofences aggregated by GeoHash
Join Position
& Geofences
Stream
geofence
status
Geofences
gpby geohash
Table
{ "geohash":"u33", "name":"Postdam",
"geometry_wkt":"POLYGON
((13.297920227050781 52.56195151687443, …))",
"last_update":1560607149015}
{"geohash":"u33", "name":"Berlin",
38.484769753492536,…))",
"last_update":1560607149015}
geo_fence_bulk()
geofence
Table
vehicle
position
Stream
{ "geohash":"u33", "name":"Potsam",
52.56195151687443, …))",
"last_update":1560607149015}
{ "group":"u33", "name":"Berlin",
38.484769753492536,…))", "last_update":1560607149015}
Enrich with
GeoHash
Stream
geofences
& geohash
Enrich with
GeoHash
Stream
position &
geohash
geofences
by geohash
geo_hash()
geo_hash()
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium
{ "geohash":"u33", "id" : "10", "latitude" : 52.3924, "longitude" : 13.0514}

CREATE STREAM a04_geo_fence_by_geohash_s
AS
SELECT geo_hash(geometry_wkt, 3)[0] geo_hash, id, name, geometry_wkt
FROM a04_geo_fence_s
PARTITION by geo_hash;
INSERT INTO a04_geo_fence_by_geohash_s
SELECT geo_hash(geometry_wkt, 3)[1] geo_hash, id, name, geometry_wkt
FROM a04_geo_fence_s
WHERE geo_hash(geometry_wkt, 3)[1] IS NOT NULL
PARTITION BY geo_hash;s
INSERT INTO a04_geo_fence_by_geohash_s
SELECT ...
There is no explode()
functionality in KSQL! https://github.com/confluentinc/ksql/issues/527

CREATE TABLE a04_geo_fence_by_geohash_t
AS
SELECT geo_hash,
COLLECT_SET(id + ':' + geometry_wkt) AS id_geometry_wkt_list,
COLLECT_SET(id) id_list
FROM a04_geo_fence_by_geohash_s
GROUP BY geo_hash;
CREATE STREAM a04_vehicle_position_by_geohash_s
AS
SELECT vp.id, vp.latitude, vp.longitude,
geo_hash(vp.latitude, vp.longitude, 3) geo_hash
FROM vehicle_position_s vp
PARTITION BY geo_hash;

CREATE STREAM a04_geo_fence_status_s
AS
SELECT vp.geo_hash, vp.id, vp.latitude, vp.longitude,
geo_fence_bulk (vp.latitude, vp.longitude, gf.id_geometry_wkt_list)
AS fence_status
FROM a04_vehicle_position_by_geohash_s vp
LEFT JOIN a04_geo_fence_by_geohash_t gf
ON (vp.geo_hash = gf.geo_hash);
ksql> SELECT * FROM a04_geo_fence_status_s;
u33 | 46 | 52.3906 | 13.1599 | [3:OUTSIDE]
u33 | 46 | 52.3906 | 13.1599 | [3:OUTSIDE]
9yz | 12 | 38.34409 | -90.15034 | [2:OUTSIDE, 1:OUTSIDE]
...
As many as there are geo-fences in
geohash

4a) Geofences aggregated by GeoHash
Join Position
& Geofences
Geofences
gpby geohash
Table
{ "group":"u33", "name":" Potsdam",
"geometry_wkt":"POLYGON ((5.668945 51.416016, …))",
"last_update":1560607149015}
38.484769753492536,…))", "last_update":1560607149015}
geo_fence_bulk()
geofence
Table
vehicle
position
Stream
{ "geohash":u33", "name":"Postsdam",
"last_update":1560607149015}
{ "geohash":"u33", "name":"Berlin",
38.484769753492536,…))", "last_update":1560607149015}
Enrich with
GeoHash
Stream
geofences
& geohash
Enrich with
GeoHash
Stream
position &
geohash
geofences
by geohash
geo_hash()
geo_hash()
Stream
udf
status
geofence
status
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium

4b) Geofences aggregated by GeoHash
Join Position
& Geofences
Geofences
gpby geohash
Table
{ "geohash":"u33", "name":"Potsdam",
"last_update":1560607149015}
{"vehicle_id":10", "name":"Berlin", "geometry_wkt":"POLYGON
((-90.23345947265625 38.484769753492536,…))",
"last_update":1560607149015}
geo_fence()
geofence
Table
vehicle
position
Stream
{ "geohash":"u33", "name":"Potsdam",
"last_update":1560607149015}
{ "group":"u33", "name":"Berlin",
38.484769753492536,…))", "last_update":1560607149015}
Enrich with
GeoHash
Stream
geofences
& geohash
Enrich with
GeoHash
Stream
position &
geohash
geofences by
geohash
geo_hash()
geo_hash()
Stream
position &
geofence
Explode
Geofendes
Stream
geofence
status
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium

4b) Geofences aggregated by GeoHash
CREATE STREAM a04b_geofence_udf_status_s
AS
SELECT id, latitude, longitude, id_list[0] AS geofence_id,
geo_fence(latitude, longitude, geometry_wkt_list[0]) AS geofence_status
ON (vp.geo_hash = gf.geo_hash);
INSERT INTO a04b_geofence_udf_status_s
SELECT id, latitude, longitude, id_list[1] geofence_id,
geo_fence(latitude, longitude, geometry_wkt_list[1]) AS geofence_status
ON (vp.geo_hash = gf.geo_hash)
WHERE id_list[1] IS NOT NULL;

Berne
Fribourg
It works …. but ….
• By re-partitioning by geohash
we lose the guaranteed order
for a given vehicle
• Can be problematic, if there is a
backlog in one of the
topics/partitions
u0m5
u0m4
u0m7
u0m6
Consumer 1 Consumer 2

Geo-Fencing with Kafka Streams and Global KTable
Enrich Position with GeoHash
& Join with Geofences
Global
KTable
{ "geohash":u33", "name":"Potsdam",
51.416016, …))",
"last_update":1560607149015}
"geometry_wkt":"POLYGON ((-
90.23345947265625
38.484769753492536,…))",
"last_update":1560607149015}
geofence
KTable
vehicle
position
{ "geohash":u33", "name":"Potsdam",
51.416016, …))",
"last_update":1560607149015}
{ "group":u33", "name":"Berlin",
"geometry_wkt":"POLYGON ((-
90.23345947265625
38.484769753492536,…))",
"last_update":1560607149015}
Enricht and Group
by GeoHash
matched
geofences
Detect Geo
Event
geofece_sa
tus
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium
geofence
by geohash
{"id":"10", "latitude" : 52.3924,
"longitude" : 13.0514, [
{"name":"Berlin"} ] }
{"id":"10", "status" : "ENTER", "geofenceName":"Berlin"} }
position &
geohash

KStream<String, GeoFence> geoFence = builder.stream(GEO_FENCE);
KStream<String, GeoFence> geoFenceByGeoHash =
geoFence.map((k,v) -> KeyValue.<GeoFence, List<String>> pair(v,
GeoHashUtil.coverBoundingBox(v.getWkt().toString(), 5)))
.flatMapValues(v -> v)
.map((k,v) -> KeyValue.<String,GeoFence>pair(v, createFrom(k, v)));
KTable<String, GeoFenceList> geofencesByGeohash =
geoFenceByGeoHash.groupByKey().aggregate(
() -> new GeoFenceList(new ArrayList<GeoFenceItem>()),
(aggKey, newValue, aggValue) -> {
GeoFenceItem geoFenceItem = new
GeoFenceItem(newValue.getId(), newValue.getName(),
newValue.getWkt(), "");
if (!aggValue.getGeoFences().contains(geoFenceItem))
aggValue.getGeoFences().add(geoFenceItem);
return aggValue;
},
Materialized.<String, GeoFenceList,
KeyValueStore<Bytes,byte[]>>as("geofences-by-geohash-store"));
geofencesByGeohash.toStream().to(GEO_FENCES_KEYEDBY_GEOHASH,
Produced.<String, GeoFenceList> keySerde(stringSerde));

final GlobalKTable<String, GeoFenceList> geofences =
builder.globalTable(GEO_FENCES_KEYEDBY_GEOHASH);
KStream<String, VehiclePositionWithMatchedGeoFences> positionWithMatchedGeoFences =
vehiclePositionsWithGeoHash.leftJoin(geofences,
(k, pos) -> pos.getGeohash().toString(),
(pos, geofenceList) -> {
List<MatchedGeoFence> matchedGeofences = new ArrayList<MatchedGeoFence>();
if(geofenceList != null) {
for (GeoFenceItem geoFenceItem : geofenceList.getGeoFences()) {
boolean geofenceStatus =
GeoFenceUtil.geofence(pos.getLatitude(), pos.getLongitude(),
geoFenceItem.getWkt().toString());
if(geofenceStatus)
matchedGeofences.add(new MatchedGeoFence(geoFenceItem.getId(),
geoFenceItem.getName(), null));
}
}
return new VehiclePositionWithMatchedGeoFences(pos.getVehicleId(), 0L,
pos.getLatitude(), pos.getLongitude(),
pos.getEventTime(), matchedGeofences);
});

final KStream<String, VehiclePositionWithMatchedGeoFences> positionWithMatchedGeoFences =
builder.stream(MATCHED_FENCE_STREAM);
final StoreBuilder<KeyValueStore<String, VehiclePositionWithMatchedGeoFences>>
vehicleGeoFenceStatusStore = Stores
.keyValueStoreBuilder(Stores.persistentKeyValueStore("GeoFenceSnapshotStore"),
Serdes.String(), positionWithMatchedGeoFencesSerde)
.withCachingEnabled();
builder.addStateStore(bargeGeoFenceStatusStore);
KStream<String, List<GeoEvent>> geoEvents = positionWithMatchedGeoFences.transformValues(
() -> new GeoEventEmitter (bargeGeoFenceStatusStore.name())
,vehicleGeoFenceStatusStore.name());
KStream<String, GeoEvent> geoEvent = geoEvents.flatMapValues(v -> v);
KStream<String, GeoEvent> geoEventByVehicleId =
geoEvent.selectKey((k, v) -> v.getVehicleId().toString());
geoEventByVechicleId.to(GEO_EVENT_STREAM);

Tile38
• https://tile38.com
• Open Source Geospatial Database & Geofencing Server
• Real Time Geofencing
• Roaming Geofencing
• Fast Spatial Indices
• Pluggable Event Notifications

Tile38 – How does it work?
> SETCHAN berlin WITHIN vehicle FENCE OBJECT
{"type":"Polygon","coordinates":[[[13.297920227050781,52.56195151687443],[1
3.2440185546875,52.530216577830124],[13.267364501953125,52.45998421679598],
[13.35113525390625,52.44826791583386],[13.405036926269531,52.44952338289473
],[13.501167297363281,52.47148826410652], ...]]}
> SUBSCRIBE berlin
{"ok":true,"command":"subscribe","channel":"berlin","num":1,"elapsed":"5.85
µs"}
.
.
.
{"command":"set","group":"5d07581689807d000193ac33","detect":"outside","hoo
k":"berlin","key":"vehicle","time":"2019-06-
17T09:06:30.624923584Z","id":"10","object":{"type":"Point","coordinates":[1
3.3096,52.4497]}}
SET vehicle 10 POINT 52.4497 13.3096

Tile38 – How does it work?
> SETHOOK berlin_hook kafka://broker-1:9092/tile38_geofence_status WITHIN
vehicle FENCE OBJECT
{"type":"Polygon","coordinates":[[[13.297920227050781,52.56195151687443],[1
3.2440185546875,52.530216577830124],[13.267364501953125,52.45998421679598],
[13.35113525390625,52.44826791583386],[13.405036926269531,52.44952338289473
],[13.501167297363281,52.47148826410652], ...]]}
bigdata@bigdata:~$ kafkacat -b localhost -t tile38_geofence_status
% Auto-selecting Consumer mode (use -P or -C to override)
{"command":"set","group":"5d07581689807d000193ac34","detect":"outside","hoo
k":"berlin_hook","key":"vehicle","time":"2019-06-
17T09:12:00.488599119Z","id":"10","object":{"type":"Point","coordinates":[1
3.3096,52.4497]}}
SET vehicle 10 POINT 52.4497 13.3096

1) Enrich with GeoFences – aggregated by geohash
geofence
Stream
vehicle
position
Stream
Invoke UDF
{"vehicle_id":10", "name":"St. Louis", "geometry_wkt":"POLYGON
((13.297920227050781 52.56195151687443, …))",
"last_update":1560607149015}
{"vehicle_id":10", "name":"Berlin", "geometry_wkt":"POLYGON ((-
90.23345947265625 38.484769753492536,…))", "last_update":1560607149015}
Invoke UDF
Geofence
Service
geofence
status
set_pos()
set_fence()
Stream
udf
status
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium

2) Using Custom Kafka Connector for Tile38
geofence
vehicle
position
{"vehicle_id":10", "name":"St. Louis", "geometry_wkt":"POLYGON
((13.297920227050781 52.56195151687443, …))",
"last_update":1560607149015}
{"vehicle_id":10", "name":"Berlin", "geometry_wkt":"POLYGON ((-
90.23345947265625 38.484769753492536,…))", "last_update":1560607149015}
Geofence
Service
kafka-to-
tile38
kafka-to-
tile38
geofence
status
high low
low high
low high
Scalable
Latency
"Code Smell"
medium
medium
medium

2) Using Custom Kafka Connector for Tile38
curl -X PUT
/api/kafka-connect-1/connectors/Tile38SinkConnector/config
-H 'Content-Type: application/json'
-H 'Accept: application/json'
-d '{
"connector.class":
"com.trivadis.geofence.kafka.connect.Tile38SinkConnector",
"topics": "vehicle_position",
"tasks.max": "1",
"tile38.key": "vehicle",
"tile38.operation": "SET",
"tile38.hosts": "tile38:9851"
}'
Currently only supports SET command

Visualization using Arcadia
Data

Arcadia Data https://www.arcadiadata.com/

Summary & Outlook
• Summary
• Geo Fencing is doable using Kafka and KSQL
• KSQL is similar to SQL, but don't think relational
• UDF and UDAF's is a powerful way to extend KSQL
• Use Geo Hashes to partition work
• Outlook
• Performance Tests
• Cleanup code of UDFs and UDAFs
• Implement Kafka Source Connector for Tile 38

Technology on its own won't help you.
You need to know how to use it properly.

Location Analytics - Real-Time Geofencing using Kafka

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