GeoMesa Cassandra Quick Start¶
This tutorial is the fastest and easiest way to get started with GeoMesa using Cassandra. It is a good stepping-stone on the path to the other tutorials, that present increasingly involved examples of how to use GeoMesa.
About this Tutorial¶
In the spirit of keeping things simple, the code in this tutorial only does a few small things:
- Establishes a new (static) SimpleFeatureType
- Prepares the Cassandra tables to store this type of data
- Creates a few thousand example SimpleFeatures
- Writes these SimpleFeatures to Cassandra
- Queries for a given geographic rectangle, time range, and attribute filter, writing out the entries in the result set
- Uses GeoServer to visualize the data (optional)
Prerequisites¶
Before you begin, you must have the following installed and configured:
Create A Cassandra Namespace¶
You will need a namespace in Cassandra to contain the tutorial tables. The easiest way to do
this is with the cqlsh
tool provided with Cassandra distributions. Start cqlsh
, then type:
cqlsh> CREATE KEYSPACE geomesa WITH REPLICATION = {'class': 'SimpleStrategy', 'replication_factor' : 3};
This creates a key space called “geomesa”. This is a top-level name space within Cassandra and it will provide a place for GeoMesa to put all of its data, including data for spatial features and associated metadata.
Download and Build the Tutorial¶
Pick a reasonable directory on your machine, and run:
$ git clone https://github.com/geomesa/geomesa-tutorials.git
$ cd geomesa-tutorials
Warning
Make sure that you download or checkout the version of the tutorials project that corresponds to your GeoMesa version. See About Tutorial Versions for more details.
To ensure that the quick start works with your environment, modify the pom.xml
to set the appropriate versions for Cassandra, etc.
For ease of use, the project builds a bundled artifact that contains all the required dependencies in a single JAR. To build, run:
$ mvn clean install -pl geomesa-tutorials-cassandra/geomesa-tutorials-cassandra-quickstart -am
Running the Tutorial¶
On the command line, run:
$ java -cp geomesa-tutorials-cassandra/geomesa-tutorials-cassandra-quickstart/target/geomesa-tutorials-cassandra-quickstart-$VERSION.jar \
org.geomesa.example.cassandra.CassandraQuickStart \
--cassandra.contact.point <host:port> \
--cassandra.keyspace <keyspace> \
--cassandra.catalog <table> \
--cassandra.username <user> \
--cassandra.password <password>
where you provide the following arguments:
<host:port>
the hostname and port your Cassandra instance is running on. For Cassandra standalone this will belocalhost:9042
. More information on how to find your connection is available here.<keyspace>
keyspace your table will be put into. If you followed the instructions above, this will begeomesa
. More information on how to setup keyspaces is available here.<table>
the name of the destination table that will accept these test records. This table should either not exist or should be empty<user>
(optional) the name of a Cassandra user that has permissions to create, read and write tables<password>
(optional) the password for the previously-mentioned Cassandra user
Optionally, you can also specify that the quick start should delete its data upon completion. Use the
--cleanup
flag when you run to enable this behavior.
Once run, you should see the following output:
Loading datastore
Creating schema: GLOBALEVENTID:String,Actor1Name:String,Actor1CountryCode:String,Actor2Name:String,Actor2CountryCode:String,EventCode:String,NumMentions:Integer,NumSources:Integer,NumArticles:Integer,ActionGeo_Type:Integer,ActionGeo_FullName:String,ActionGeo_CountryCode:String,dtg:Date,geom:Point
Generating test data
Writing test data
Wrote 2356 features
Running test queries
Running query BBOX(geom, -120.0,30.0,-75.0,55.0) AND dtg DURING 2017-12-31T00:00:00+00:00/2018-01-02T00:00:00+00:00
01 719024896=719024896|UNITED STATES|USA|SENATE||042|2|1|2|2|Texas, United States|US|2017-12-31T00:00:00.000Z|POINT (-97.6475 31.106)
02 719024888=719024888|SENATE||UNITED STATES|USA|043|2|1|2|2|Texas, United States|US|2017-12-31T00:00:00.000Z|POINT (-97.6475 31.106)
03 719024892=719024892|UNITED STATES|USA|DEPUTY||010|4|1|4|3|Abbeville, South Carolina, United States|US|2017-12-31T00:00:00.000Z|POINT (-82.379 34.1782)
04 719024891=719024891|UNITED STATES|USA|||010|2|1|2|3|Ninety Six, South Carolina, United States|US|2017-12-31T00:00:00.000Z|POINT (-82.024 34.1751)
05 719024894=719024894|UNITED STATES|USA|DEPUTY||010|2|1|2|3|Abbeville County, South Carolina, United States|US|2017-12-31T00:00:00.000Z|POINT (-82.4665 34.2334)
06 719024887=719024887|DEPUTY||||010|4|1|4|3|Abbeville County, South Carolina, United States|US|2017-12-31T00:00:00.000Z|POINT (-82.4665 34.2334)
07 719024893=719024893|UNITED STATES|USA|DEPUTY||010|6|1|6|3|Abbeville County, South Carolina, United States|US|2017-12-31T00:00:00.000Z|POINT (-82.4665 34.2334)
08 719024895=719024895|UNITED STATES|USA|EMPLOYEE||010|2|1|2|3|Ninety Six, South Carolina, United States|US|2017-12-31T00:00:00.000Z|POINT (-82.024 34.1751)
09 719024889=719024889|SENATE||UNITED STATES|USA|043|2|1|2|3|Washington, District of Columbia, United States|US|2017-12-31T00:00:00.000Z|POINT (-77.0364 38.8951)
10 719024897=719024897|UNITED STATES|USA|SENATE||042|2|1|2|3|Washington, District of Columbia, United States|US|2017-12-31T00:00:00.000Z|POINT (-77.0364 38.8951)
Returned 669 total features
Running query BBOX(geom, -120.0,30.0,-75.0,55.0) AND dtg DURING 2017-12-31T00:00:00+00:00/2018-01-02T00:00:00+00:00
Returning attributes [GLOBALEVENTID, dtg, geom]
01 719024888=719024888|2017-12-31T00:00:00.000Z|POINT (-97.6475 31.106)
02 719024896=719024896|2017-12-31T00:00:00.000Z|POINT (-97.6475 31.106)
03 719024892=719024892|2017-12-31T00:00:00.000Z|POINT (-82.379 34.1782)
04 719024891=719024891|2017-12-31T00:00:00.000Z|POINT (-82.024 34.1751)
05 719024887=719024887|2017-12-31T00:00:00.000Z|POINT (-82.4665 34.2334)
06 719024893=719024893|2017-12-31T00:00:00.000Z|POINT (-82.4665 34.2334)
07 719024895=719024895|2017-12-31T00:00:00.000Z|POINT (-82.024 34.1751)
08 719024889=719024889|2017-12-31T00:00:00.000Z|POINT (-77.0364 38.8951)
09 719024897=719024897|2017-12-31T00:00:00.000Z|POINT (-77.0364 38.8951)
10 719024884=719024884|2017-12-31T00:00:00.000Z|POINT (-77.0364 38.8951)
Returned 669 total features
Running query EventCode = '051'
01 719024909=719024909|||MELBOURNE|AUS|051|10|1|10|4|Melbourne, Victoria, Australia|AS|2018-01-01T00:00:00.000Z|POINT (144.967 -37.8167)
02 719024963=719024963|||CITIZEN||051|6|2|6|4|City Of Sydney, New South Wales, Australia|AS|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
03 719025168=719025168|AUSTRALIAN|AUS|||051|18|1|10|4|Sydney, New South Wales, Australia|AS|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
04 719025178=719025178|AUSTRALIA|AUS|COMMUNITY||051|20|2|20|4|Sydney, New South Wales, Australia|AS|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
05 719025965=719025965|MIDWIFE||||051|10|1|10|4|Sydney, New South Wales, Australia|AS|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
06 719025248=719025248|BUSINESS||||051|10|1|10|1|Australia|AS|2018-01-01T00:00:00.000Z|POINT (135 -25)
07 719025509=719025509|COMMUNITY||AUSTRALIA|AUS|051|2|1|2|1|Australia|AS|2018-01-01T00:00:00.000Z|POINT (135 -25)
08 719025555=719025555|DENMARK|DNK|||051|2|1|2|1|Australia|AS|2018-01-01T00:00:00.000Z|POINT (135 -25)
09 719025634=719025634|FIJI|FJI|||051|2|1|2|1|Fiji|FJ|2018-01-01T00:00:00.000Z|POINT (178 -18)
10 719025742=719025742|KING||||051|22|3|22|3|San Diego, California, United States|US|2018-01-01T00:00:00.000Z|POINT (-117.157 32.7153)
Returned 138 total features
Running query EventCode = '051' AND dtg DURING 2017-12-31T00:00:00+00:00/2018-01-02T00:00:00+00:00
Returning attributes [GLOBALEVENTID, dtg, geom]
01 719024909=719024909|2018-01-01T00:00:00.000Z|POINT (144.967 -37.8167)
02 719024963=719024963|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
03 719025168=719025168|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
04 719025178=719025178|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
05 719025965=719025965|2018-01-01T00:00:00.000Z|POINT (151.217 -33.8833)
06 719025248=719025248|2018-01-01T00:00:00.000Z|POINT (135 -25)
07 719025509=719025509|2018-01-01T00:00:00.000Z|POINT (135 -25)
08 719025555=719025555|2018-01-01T00:00:00.000Z|POINT (135 -25)
09 719025634=719025634|2018-01-01T00:00:00.000Z|POINT (178 -18)
10 719025742=719025742|2018-01-01T00:00:00.000Z|POINT (-117.157 32.7153)
Returned 138 total features
Done
Looking at the Code¶
The source code is meant to be accessible for this tutorial. The main logic is contained in
the generic org.geomesa.example.quickstart.GeoMesaQuickStart
in the geomesa-tutorials-common
module,
which is datastore agnostic. Some relevant methods are:
createDataStore
get a datastore instance from the input configurationcreateSchema
create the schema in the datastore, as a pre-requisite to writing datawriteFeatures
use aFeatureWriter
to write features to the datastorequeryFeatures
run several queries against the datastorecleanup
delete the sample data and dispose of the datastore instance
The quickstart uses a small subset of GDELT data. Code for parsing the data into GeoTools SimpleFeatures is
contained in org.geomesa.example.data.GDELTData
:
getSimpleFeatureType
creates theSimpleFeatureType
representing the datagetTestData
parses an embedded TSV file to createSimpleFeature
objectsgetTestQueries
illustrates several different query types, using CQL (GeoTools’ Contextual Query Language)
Visualize Data (optional)¶
There are two options to visual the data ingested by this quick start. The easiest option is to use the
export
command of the GeoMesa Cassandra tools distribution. For a more production ready example,
you can alternatively stand up a GeoServer and connect it to your Cassandra instance.
Visualize Data With Leaflet¶
Warning
To successfully run this command you must have a computer that is connected to the internet in order to access external leaflet resources.
The export
command is a part of the GeoMesa Cassandra command-line tools. In order to use the
command, ensure you have the command-line tools installed as described in
Setting up the Cassandra Command Line Tools. The export
command provides the leaflet
format which
will export the features to a leaflet map that you can open in your web browser. To produce the map,
run the following command from the GeoMesa Cassandra tools distribution directory:
bin/geomesa-cassandra export \
--output-format leaflet \
--contact-point <host:port> \
--key-space <keyspace> \
--catalog <table> \
--user <user> \
--password <password>
Where the connection parameters are the same you used above during the quickstart. To view the map simply open the url provided by the command in your web browser. If you click the menu in the upper right of the map you can enable and disable the heatmap and feature layers as well as the two provided base layers.
Visualize Data With GeoServer¶
You can use GeoServer to access and visualize the data stored in GeoMesa. In order to use GeoServer, download and install version 2.12.x. Then follow the instructions in Installing GeoMesa Cassandra in GeoServer to enable GeoMesa.
Register the GeoMesa Store with GeoServer¶
Log into GeoServer using your user and password credentials. Click
“Stores” and “Add new Store”. Select the Cassandra (GeoMesa)
vector data
source, and fill in the required parameters.
Basic store info:
workspace
this is dependent upon your GeoServer installationdata source name
pick a sensible name, such asgeomesa_quick_start
description
this is strictly decorative;GeoMesa quick start
Connection parameters:
- these are the same parameter values that you supplied on the command line when you ran the tutorial; they describe how to connect to the Cassandra instance where your data reside
Click “Save”, and GeoServer will search your Cassandra table for any GeoMesa-managed feature types.
Publish the Layer¶
GeoServer should recognize the gdelt-quickstart
feature type, and
should present that as a layer that can be published. Click on the
“Publish” link.
You will be taken to the “Edit Layer” screen. You will need to enter values for the data bounding boxes. In this case, you can click on the link to compute these values from the data.
Click on the “Save” button when you are done.
Take a Look¶
Click on the “Layer Preview” link in the left-hand gutter. If you don’t
see the quick-start layer on the first page of results, enter the name
of the layer you just created into the search box, and press
<Enter>
.
Once you see your layer, click on the “OpenLayers” link, which will open a new tab. You should see a collection of red dots similar to the following image:
Tweaking the display¶
Here are just a few simple ways you can play with the visualization:
- Click on one of the red points in the display, and GeoServer will report the detail records underneath the map area.
- Shift-click to highlight a region within the map that you would like to zoom into.
- Click on the “Toggle options toolbar” icon in the upper-left corner
of the preview window. The right-hand side of the screen will include
a “Filter” text box. Enter
EventCode = '051'
, and press on the “play” icon. The display will now show only those points matching your filter criterion. This is a CQL filter, which can be constructed in various ways to query your data. You can find more information about CQL from GeoServer’s CQL tutorial.