# GeoMesa Cassandra Quick Start¶

This tutorial is the fastest and easiest way to get started with GeoMesa. It is a good stepping-stone on the path to the other tutorials that present increasingly involved examples of how to use GeoMesa.

In the spirit of keeping things simple, the code in this tutorial only does a few small things:

1. establishes a new (static) SimpleFeatureType
2. prepares the Cassandra table to store this type of data
3. creates 1000 SimpleFeatures
4. writes these SimpleFeatures to the Cassandra table
5. queries for a given geographic rectangle, time range, and attribute filter, writing out the entries in the result set

The only dynamic element in the tutorial is the Cassandra destination; that is a property that you provide on the command-line when running the code.

## Prerequisites¶

Before you begin, you must have the following:

• an instance of Cassandra 3.x standalone or cluster,
• a Cassandra user that has both create-table and write permissions (not needed for Cassandra standalone versions),
• a local copy of the Java JDK 8,
• Apache Maven installed, and
• a GitHub client installed.

## Create A Cassandra Namespace¶

You will need a namespace in Cassandra for the tutorial to create tables in. The Easiest way to do this is with the cqlsh tool provided with Cassandra distributions. Start cqlsh, then type:

cqlsh>  CREATE KEYSPACE mykeyspace WITH REPLICATION = {'class': 'SimpleStrategy', 'replication_factor' : 3};


This creates a key space called “mykeyspace”. 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.

Pick a reasonable directory on your machine, and run:

$git clone https://github.com/geomesa/geomesa-tutorials.git$ cd geomesa-tutorials


Note

You may need to download a particular release of the tutorials project to target a particular GeoMesa release.

To build, run

$mvn clean install -pl geomesa-quickstart-cassandra  Note Ensure that the version of Cassandra, Hadoop, etc in the root pom.xml match your environment. Note Depending on the version, you may also need to build GeoMesa locally. Instructions can be found here. ## About this Tutorial¶ The QuickStart operates by inserting and then querying 1000 features. After the insertions are complete, a sequence of queries are run to demonstrate different types of queries possible via the GeoTools API. ## Run the Tutorial¶ On the command-line, run: $ java -cp geomesa-quickstart-cassandra/target/geomesa-quickstart-cassandra-${geomesa.version}.jar \ com.example.geomesa.cassandra.CassandraQuickStart \ -contact_point <host:port> \ -keyspace <keyspace> \ -catalog_table <catalog_table> \ -username <username> \ -password <password>  where you provide the following arguments: • <host:port> the hostname and port your Cassandra instance is running on. For Cassandra standalong this is localhost:9042.More info on how to find this information here • <keyspace> keyspace your table will be put into. More info on how to setup keyspaces here • <catalog_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 You should see output similar to the following (not including some of Maven’s output and log4j’s warnings): New Cassandra host /127.0.0.1:9042 added Creating feature-type (schema): CassandraQuickStart Creating new features Inserting new features Submitting query 1. Bierce|640|Sun Sep 14 15:48:25 EDT 2014|POINT (-77.36222958792739 -37.13013846773835)|null 2. Bierce|886|Tue Jul 22 14:12:36 EDT 2014|POINT (-76.59795732474399 -37.18420917493149)|null 3. Bierce|925|Sun Aug 17 23:28:33 EDT 2014|POINT (-76.5621106573523 -37.34321201566148)|null 4. Bierce|589|Sat Jul 05 02:02:15 EDT 2014|POINT (-76.88146600670152 -37.40156607152168)|null 5. Bierce|394|Fri Aug 01 19:55:05 EDT 2014|POINT (-77.42555615743139 -37.26710898726304)|null 6. Bierce|931|Fri Jul 04 18:25:38 EDT 2014|POINT (-76.51304097832912 -37.49406125975311)|null 7. Bierce|322|Tue Jul 15 17:09:42 EDT 2014|POINT (-77.01760098223343 -37.30933767159561)|null 8. Bierce|343|Wed Aug 06 04:59:22 EDT 2014|POINT (-76.66826220670282 -37.44503877750368)|null 9. Bierce|259|Thu Aug 28 15:59:30 EDT 2014|POINT (-76.90122194030118 -37.148525741002466)|null Submitting secondary index query Feature ID Observation.859 | Who: Bierce Feature ID Observation.355 | Who: Bierce Feature ID Observation.940 | Who: Bierce Feature ID Observation.631 | Who: Bierce Feature ID Observation.817 | Who: Bierce Submitting secondary index query with sorting (sorted by 'What' descending) Feature ID Observation.999 | Who: Addams | What: 999 Feature ID Observation.996 | Who: Addams | What: 996 Feature ID Observation.993 | Who: Addams | What: 993 Feature ID Observation.990 | Who: Addams | What: 990 Feature ID Observation.987 | Who: Addams | What: 987  The quick start code may also be run via Maven using the live-test profile: $ mvn -pl geomesa-quckstart-cassandra -Plive-test exec:exec -Dcontact_point=<host:port> -Dkeyspace=<keyspace> -Dcatalog_table=<catalog_table> -Dusername=<username> -Dpassword=<password>


Similarly, the username and password are not required here and if you are using a Cassandra standalone instance with the example namespace setup in “Connecting to Cassandra” then you may simply run:

\$ mvn -pl geomesa-quckstart-cassandra -Plive-test exec:exec


## Looking at the Code¶

The source code is meant to be accessible for this tutorial, but here is a high-level breakdown of the methods in the CassandraQuickStart class that are relevant:

• getCommonRequiredOptions helper code to establish the command-line parser for Cassandra options
• getCassandraDataStoreConf create a HashMap of Cassandra parameters that will be used to fetch a DataStore
• createSimpleFeatureType defines the custom FeatureType used in the tutorial. There are five fields: Who, What, When, Where, and Why.
• createNewFeatures creates a collection of new features, each of which is initialized to some randomized set of values
• insertFeatures instructs the DataStore to write the collection of new features to the GeoMesa-managed Cassandra table
• createFilter given a set of geometric bounds, temporal bounds, and an optional attribute-only expression, construct a common query language (CQL) filter that embodies these constraints. This filter will be used to query data.
• queryFeatures query for records; for each, print out the five field (attribute) values
• secondaryIndexExample additional examples that build other CQL queries
• main this is the main entry point; it collects command-line parameters, builds the DataStore, creates and inserts new records, and then kicks off the queries

## Visualize Data With GeoServer¶

### Register the GeoMesa store with GeoServer¶

Log into GeoServer using your user and password credentials. Click “Stores” and “Add new Store”. If you do not see the Cassandra Feature Data Store listed under Vector Data Sources, ensure the plugin is in the right directory and restart GeoServer. For instructions on how to install the GeoMesa plugin for GeoServer see Installing GeoMesa Cassandra in GeoServer.

Select the Cassandra (GeoMesa) vector data source, and enter the following parameters:

Basic store info:

• workspace this is dependent upon your GeoServer installation
• data source name pick a sensible name, such as, geomesa_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.
• the geomesa.cassandra.username and geomesa.cassandra.password are required fields here. If you are using the Cassandra standalone, use the default value of cassandra for both.

Click “Save”, and GeoServer will search your Cassandra table for any GeoMesa-managed feature types.

### Publish the layer¶

GeoServer should recognize the CassandraQuickStart feature type, and should present that as a layer that could be published. Click on the “Publish” link.

You will be taken to the Edit Layer screen. Two of the tabs need to be updated: Data and Dimensions.

In the Data pane, enter values for the bounding boxes. In this case, you can click on the link to compute these values from the data.

In the Dimensions tab, check the “Enabled” checkbox under Time. Then select “When” in the Attribute and End Attribute dropdowns, and “Continuous Interval” in the Presentation dropdown.

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. By default, the display that opens will not show all the data, because we have enabled the time dimension for this layer, but the preview does not specify a time. In the URL bar for the visualization, add the following to the end:

&TIME=2014-01-01T00:00:00.000Z/2014-01-31T23:59:59.999Z

That tells GeoServer to display the records for the entire month of January 2014. You can find more information about the TIME parameter from GeoServer’s documentation.

Once you press <Enter>, the display will update, and 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.
• Alter the TIME= parameter in the URL to a different date range, and you can filter to see only the records that satisfy the temporal constraint.
• 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 Who = 'Bierce', 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 our data. You can find more information about CQL from GeoServer’s CQL tutorial.