Macros

Purpose

In some cases, when you configure your project, you run into the issue that you want to automatically have certain values filled in by variables.

Some example of variables:

• current date and time
• system environment variable
• layline.io environment variable
• layline.io message content
• etc.

As a quick example, let's assume that you are configuring a Amazon SQS Source. Within that configuration you must define a stream name to represent the stream which is being processed when reading from SQS. To provide a uniwue name, you could define the name like so:

When the source is accessed and creates a stream, the variable defined by ${date:yyyy-MM-dd-HH-mm-ss} will then be replaced by the current date/timestamp, e.g. like so: SQS-2023-01-01-12-23-45.

note

layline.io gives you the option to use macros within most fields. At this point in time, it's not fully documented where exactly. We are working on this!

Variable Structure

The structure of a variable within layline.io is compriesed like this:

${prefix:suffx}

Where prefix defines an group of variables, and the suffix defines either a format or a variable within that group. It will all make sense when we explain the different types of variables which are at you disposal.

Variable Types

lay:

The Prefix lay references an environment property which you have defined in a Environment Resource Asset. The suffix defines the value which you have defined for that property:

Example:

You can then access this variable like this: ${lay:DirBase}.

Environment Resource must be deployed

As this variable will be replaced at runtime, it is important that you include the Environment Resource as part of your deployment to the cluster. Otherwise, you will encounter an error when you try to start the deployment on the Reactive Cluster, as the cluster cannot find the referenced environment variable.

sec:

The Prefix sec references a secret property which you have defined in a Environment Secret Asset. The suffix defines the value which you have defined for that property:

Example:

You can then access this variable like this: ${sec:Secret1}.

Secret Resource must be deployed

As this variable will be replaced at runtime, it is important that you include the Secret Resource as part of your deployment to the cluster. Otherwise, you will encounter an error when you try to start the deployment on the Reactive Cluster, as the cluster cannot find the referenced environment variable.

As secrets are encrypted with a public/private key pair, you must make sure, that the secrets you deploy are encrypted with the same public key, for which the private key is available on the Reactive Cluster. Otherwise, the cluster will be unable to decrypt the secret at runtime.

msg:

The prefix msg allows you to access message content, as messages are being processed. This is useful when you want to replace content with a value from the stream which is being processed.

Example:

The Stream Boundary Controller Asset allows to split a long stream of data, into smaller individual streams based on configurable criteria. For each new stream created you need to define a stream name. You may want the stream name contain content from the message. In our example we want to include an ID from the message in the stream name, so we define it as Stream-${msg:Vehicle.Boat.Id}.

If the Id is 4711, then the complete expanded stream name would turn out to be Stream-4711. Note how we are using the Data Dictionary Accessor Path Vehicle.Boat.Id to access the field content.

tip

If you are not familiar with the message format and data dictionary then please take a look at the Data Dictionary concept.

build:

The prefix build provides access to some specific parameters which are available during Deployment to the Cluster.

You can use them within Deployment Assets (go to "Project -> Deployment" in the UI).

Variable	Description
timestamp	Current date and time
version	Project version (defined in Project Asset)

Example:

For an Engine Configuration Asset ("Project -> Deployment -> Engine Configurations"), we want to provide a deployment tag name which contains individual information about the deployment time and version. The tag name is how the individual deployment is identified on the cluster.

If we enter the tag name like so: dd-demo-${build-version}-${build:timestamp}:

Then the outcome could be dd-demo-1.2.21-20230808151420 (depending on version number and date/time of deployment to cluster).

mail:

The prefix mail provides access to some specific information available in conjunction with Email sources:

Variable	Description
folder	folder name from which email was read
from	email address of sender
subject	subject as read from the Email source
received	timestamp of receipt of email

Example:

Configuring the Email Settings within an Email Source you can use these macros for defining the stream name:

The outcome would look something like this subject: Test (from: test@layline.io, received: 2024-05-03T12:13:03Z)

Other Prefixes

layline.io utilizes the functionality of the Apache Commons Library for further macro support. Here is a list of what you can do:

Prefix	Variable	Example	Description
base64Decoder	A base64 encoded string	${base64Decoder:SGVsbG9Xb3JsZCE=}	Decode a base64 encoded string
base64Encoder	A string	${base64Encoder:HelloWorld!}	Encode a string in base64 format
const	A string	${const:java.awt.event.KeyEvent.VK_ESCAPE}	Java constant
env	Environment variable	${env:USERNAME}	A system environment variable
localhost	"canonical-name"	${localhost:canonical-name}	The canonical name of the host
urlDecoder	A url	${urlDecoder:Hello%20World%21}	Decoding a url to a string
urlEncoder	A string	${urlEncoder:Hello World!}	Encoding a string to a url

You can check out the full list here.

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Can't find what you are looking for?

Please note, that the creation of the online documentation is Work-In-Progress. It is constantly being updated. should you have questions or suggestions, please don't hesitate to contact us at support@layline.io .