Executing commands

Configuration

Every micro service is listening on two RabbitMQ queues, one for data ingestion and second for command execution.

Command execution

You could ask why do we need commands at all? As we may be running more than just one instance of the individual micro services, or we might want to control the flow of the data (like batch processing with "flush" commands), we need to make sure only one micro service executes the following command.

In order to execute your desired command, simply send a valid JSON command over micro service's RabbitMQ commands queue, specified in your configuration file, or via HTTP.

As an example you could take Billing micro service's invoice generation commands.

Develop your own

If you decide to implement your own command, first select which micro service should be executing it. Let's say you are designing an event processing command for your UDR micro service, then proceed by creating a new class that inherits from Commands parent class, has name that corresponds with _class JSON field, and Java class file is located in:

/core/udr/src/main/java/ch/icclab/cyclops/consume/command/model/

Now you can start developing your command and if you need to pass some arguments, simply register them in the Java class the same way as you would do it in a POJO class, where those object variables will be filled based on their corresponding JSON fields, or left as null/defaults.

Configuration

If you need to access some configuration properties just add new variables to the configuration file and map it to a POJO class (don't forget to include a public constructor), like this:

URLs urls = Loader.extractProperties(URLs.class);

InfluxDB

We will be providing couple of tools for you, one of which is standardised interface for time series data operations.

QueryBuilder

To access time series data you will need to create a query builder with measurement's name

QueryBuilder query = new QueryBuilder(name);

Because a builder pattern is utilised, you can continue and add another statements:

• select(String ... fields);
• where(String key, Object value);
• where(String key, String delimiter, Object value);
• and(String key, Object value);
• and(String key, String delimiter, Object value);
• timeFrom(Long time, TimeUnit unit);
• afterTime(Long time, TimeUnit unit);
• timeTo(Long time, TimeUnit unit);
• beforeTime(Long time, TimeUnit unit);
• groupBy(String ... keys);
• orderDesc();
• limit(Integer lmt);
• offset(Integer off);
• count(String field);
• sum(String field);

It is not necessary to specify select(*) as all fields are returned by default, only use select method to slice data, where the same applies to default ascending order.

This is just one of the possible examples:

QueryBuilder query = new QueryBuilder("OpenStackCeilometerCPU");
query.timeFrom(1451650521, TimeUnit.SECONDS);
query.timeTo(1467375357, TimeUnit.SECONDS);
query.where("account", "martin");
query.and("usage", ">", 15);

Executing and parsing

The next logical step is to execute prepared query and parse its result.

InfluxDBClient client = new InfluxDBClient();
InfluxDBResponse response = client.executeQuery(query);

InfluxDBResponse object offers you many ways how to access/parse retrieved response:

• String getTableAsJson();
• String getListOfObjectsAsJson();
• List getAsListOfType(Class clazz);
• List<Map> getListOfObjects();

You can also pass a list of query builders into client.executeQuery() if you know you will be doing multiple queries at the same time.

Creating databases

If you decide to persist data sets programatically, start with database creation

• createDatabases(String ... names);

Creating database points

In order to create Point.Builder object that will be used for DB point persistence, you can either create it manually or automatically via GenerateDBPoint class static methods:

• fromObject(Object o);
• fromObjectWithTime(Object o, String t, TimeUnit u);
• fromObjectWithTags(Object o, List<String> tg);
• fromObjectWithTimeAndTags(Object o, String t, TimeUnit u, List<String> tg);

Measurement name will be based on object's _class property.

Persisting data sets

There are two ways how to persist data points into underlying database, either point by point

• persistSinglePoint(Point.Builder builder);

or by using batch processing

• persistContainer(BatchPointsContainer container);

where adding points looks like this

• addPoint(Point.Builder builder);

Make sure tags and fields are never null.

RabbitMQ

In order to send messages to micro service's exchanges programatically use Messenger class, where you have these two methods available

• broadcast(Object content);
• publish(Object content, String routing);

Where the first one is connected to fanout and the second one to direct exchange. When passing object as argument, do it in a raw format and don't transform it to JSON as that will be done automatically for you.

However, if you are executing commands over RESTful API and not by using asynchronous RabbitMQ, simply return a serialisable object and the micro service will output it as JSON.