Class: Stream
The Stream class is the underlying class of the stream object. The stream instance represents the stream which is being processed at the time and is automatically available for access in any script-based Processor, e.g. the Javascript Processor. It provides a number of functions which can - and sometimes have to - be invoked to control stream processing. It is used to emit messages to output ports, request retries, rollbacks, and log messages, access the stream's metadata, and more.
Properties
id
readonlyid:string
The ID of the stream is represented as a v4 UUID string. It is unique for each stream and automatically generated by layline.io. The ID is used to identify the stream in the system. It is used in the Audit Trail and in the logs.
Example
const STREAM_ID = stream.id;
name
readonlyname:string
Returns the name of a stream.
For file-based processing, the stream name is the name of the file being processed. For other sources, you usually explicitly set the stream name in the respective Source Asset.
For example if your data stems from a Service Source Asset, then the stream name is defined in the configuration of that Asset like so:
${msg:IoT.StreamName}-${date:yyyy-MM-dd-HH-mm-ss} which will result in DeviceX-2022-10-10-21-45-33.
If your data source is a file, then this would be the file name, e.g. my_file_name.csv.
Same as getName.
Example
const STREAM_NAME = stream.name;
Methods
emit()
emit(
message,outputPort):void
Emit a message to the specified output port. Once emitted, the context of the message is lost. If you need to emit a message to another output port, you need to clone the original message first, and then emit the clone to that other output port.
Parameters
• message: Message
• outputPort: OutputPort
Returns
void
void
Example
OUTPUT_PORT = processor.getOutputPort('Output'); // Get the output port by the name given in the UI
stream.emit(message, OUTPUT_PORT); // Emits the message to the output port
getId()
getId():
string
Each Stream in layline.io has an ID which uniquely identifies a stream. Use this method to retrieve this unique ID.
Returns
string
Unique Stream ID
Example
const STREAM_ID = stream.getId();
getMetadata()
getMetadata():
Message
Retrieves metadata information from a stream. Returns the information in form of a Message. Depending on the type of stream, the message contains differing information. For example a file-based stream will return other data than a Kafka stream.
Returns
- Returns a message which contains the stream-type specific data.
Stream-type specific message return content:
File Stream:
| Property | Type | Description |
|---|---|---|
| Path | System.String | Directory path from which the file was read |
| Size | System.Long | File size in bytes |
| LastModified | System.DateTime | Last modified date and time |
| FolderSetup | System.String | Name of the directory path related folder configuration |
FTP Stream:
| Property | Type | Description |
|---|---|---|
| Path | System.String | Directory path from which the file was read |
| Size | System.Long | File size in bytes |
| LastModified | System.DateTime | Last modified date and time |
| FolderSetup | System.String | Name of the directory path related folder configuration |
HTTP Stream:
| Property | Type | Description |
|---|---|---|
| BindAddress | System.String | IP-Address |
| BindPort | System.Integer | IP-Port number |
Kafka (Exclusive Partition Stream):
| Property | Type | Description |
|---|---|---|
| GroupId | System.String | Consumer group id |
| Topics | System.String[] | Array of topics |
Kafka (Standard Stream):
| Property | Type | Description |
|---|---|---|
| GroupId | System.String | Consumer group id |
| Topic | System.String | Topic name of the exclusive partition |
| Partition | System.Integer | Partition number |
AWS S3 Service Source Stream:
| Property | Type | Description |
|---|---|---|
| Path | System.String | S3 path |
| Size | System.Long | S3 object size |
| StorageClass | System.String | S3 storage class |
| LastModified | System.DateTime | Last modified date and time |
AWS SQS Source Stream:
| Property | Type | Description |
|---|---|---|
| QueueUrl | System.String |
OneDrive Stream:
| Property | Type | Description |
|---|---|---|
| Path | System.String | OneDrive path from which the file was read |
| Size | System.Long | File size in bytes |
| LastModified | System.DateTime | Last modified date and time |
| FolderSetup | System.String | Name of the path related folder configuration |
SharePoint Stream:
| Property | Type | Description |
|---|---|---|
| Path | System.String | SharePoint path from which the file was read |
| Size | System.Long | File size in bytes |
| LastModified | System.DateTime | Last modified date and time |
| FolderSetup | System.String | Name of the path related folder configuration |
Serial Source Stream:
| Property | Type | Description |
|---|---|---|
| Port | System.String | Port name |
| BaudRate | System.Integer | Baud rate |
| DataBits | System.Integer | |
| StopBits | System.String | |
| Parity | System.String | |
| FlowControl | System.String |
Secondary Stream:
| Property | Type | Description |
|---|---|---|
| ParentStreamName | System.String | Name of the originating stream (parent) |
| ParentStreamId | System.String | Id of the originating stream (parent) |
Service Source Stream:
| Property | Type | Description |
|---|---|---|
| Service | System.String | Service name |
TCP Source Stream:
| Property | Type | Description |
|---|---|---|
| LocalAddress | System.String | |
| LocalPort | System.Integer | |
| RemoteAddress | System.String | |
| RemotePort | System.Integer |
Example
// Get the metadata for the stream (a Kafka stream in our example):
const msgMetadata = stream.getMetadata();
// Result:
// msgMetadata.data = {
// GroupId: "MyConsumerGroup",
// Topic: "mytopic",
// Partition: "0"
// }
}
getName()
getName():
string
Returns the name of a stream.
For file-based processing, the stream name is the name of the file being processed. For other sources, you usually explicitly set the stream name in the respective Source Asset.
For example if your data stems from a Service Source Asset, then the stream name is defined in the configuration of that Asset like so:
${msg:IoT.StreamName}-${date:yyyy-MM-dd-HH-mm-ss} which will result in DeviceX-2022-10-10-21-45-33.
If your data source is a file, then this would be the file name, e.g. my_file_name.csv.
Same as Stream.name.
Returns
string
Stream name, e.g. my_file_name.csv
Example
const STREAM_NAME = stream.getName();
logError()
logError(
msg):void
Logs a message with Severity.ERROR to the stream log. You can view this both via the Audit Trail in the UI and output in the process terminal output.
Parameters
• msg: string
Information you want to log.
Returns
void
Example
stream.logError('Ran into the following problem: ' + problem);
logFatal()
logFatal(
msg):void
Logs a message with Severity.FATAL to the stream log. You can view this both via the Audit Trail in the UI and output in the process terminal output.
Parameters
• msg: string
Information you want to log.
Returns
void
Example
stream.logFatal('Ran into the following problem: ' + problem);
logInfo()
logInfo(
msg):void
Logs a message with Severity.INFO to the stream log. You can view this both via the Audit Trail in the UI and output in the process terminal output.
Parameters
• msg: string
Information you want to log.
Returns
void
Example
stream.logInfo('Here is some interesting information: ' + info);
logWarning()
logWarning(
msg):void
Logs a message with Severity.WARNING to the stream log. You can view this both via the Audit Trail in the UI and output in the process terminal output.
Parameters
• msg: string
Information you want to log.
Returns
void
Example
stream.logWarning('Here is a warning: ' + warning);
requestRetry()
requestRetry(
reason,ms?):void
In case you encounter an error in a stream and have caught it, then you can request for the stream to be retried after a defined number of milliseconds.
Parameters
• reason: Status
Status which should be attached to the retry signal. The Status should describe the reason for the retry.
• ms?: number
Retry timeout in milliseconds. Default is 60000 (60 seconds).
Returns
void
Example
// Request retry after 30 seconds
stream.requestRetry(Status.create(VENDOR, 'DB_NOT_AVAILABLE'), 30000);
requestRollback()
requestRollback(
status):void
Requests to roll back the currently processed stream.
To roll back a stream, you may issue a requestRollback to signal to layline.io that you want this stream rolled back and provide a Status which describes the reason for the rollback.
Parameters
• status: Status
Status which should be attached to the rollback signal. The Status should describe the reason for the rollback.
Returns
void
Example
// Request a rollback and add a status which (example) adds a Status of your type 'SEQ_NUMBER_UNKNOWN' and adds the file name
...
let fileInfo = {
sequence: message.data.IOT.SEQ_NO;
}
...
stream.requestRollback(Status.create(VENDOR, 'SEQ_NUMBER_UNKNOWN', fileInfo.sequence));
setDoneName()
setDoneName(
name):Stream
Set the name of a stream that is sent to the done path. In case your output is a file, this would then be the file's name.
// Set stream done name:
stream.setDoneName('New-Done-Stream-Name');
// Functions which return a Stream can be chained like this:
stream.setDoneName('New-Stream-Name').setDonePath('/my/specific/path')
Parameters
• name: string
New stream name
Returns
The manipulated stream.
setDonePath()
setDonePath(
path):Stream
Set the done path of a stream that is sent to the done path. In case your data is written to a file, this would then be the path to which the file is written.
// Set stream done path:
stream.setDonePath('New-Done-Stream-Path');
// Functions which return a Stream can be chained like this:
stream.setDoneName('New-Stream-Name').setDonePath('/my/specific/path')
Parameters
• path: string
New path name
Returns
Stream: The manipulated stream.
setErrorName()
setErrorName(
name):Stream
Set the name of a stream that is sent to the error path. In case your output is a file, this would then be the file's name.
// Set stream error name:
stream.setErrorName('New-Error-Stream-Name');
// Functions which return a Stream can be chained like this:
stream.setErrorName('New-Stream-Name').setErrorPath('/my/specific/path')
Parameters
• name: string
New stream name
Returns
The manipulated stream.
setErrorPath()
setErrorPath(
path):Stream
Set the error path of a stream that is sent to the done path. In case your data is written to a file, this would then be the path to which the file is written.
// Set stream error path:
stream.setErrorPath('New-Error-Stream-Path');
// Functions which return a Stream can be chained like this:
stream.setErrorName('New-Stream-Name').setErrorPath('/my/specific/path')
Parameters
• path: string
New path name
Returns
The manipulated stream.
setOutputName()
setOutputName(
name):Stream
Set the name of a stream that is sent to the output path. In case your output is a file, this would then be the file's name.
// Set stream output name:
stream.setOutputName('New-Output-Stream-Name');
// Functions which return a Stream can be chained like this:
stream.setOutputName('New-Stream-Name').setOutputPath('/my/specific/path')
Parameters
• name: string
New stream name
Returns
: The manipulated stream.
setOutputPath()
setOutputPath(
path):Stream
Set the output path of a stream that is sent to the normal output channel. In case your data is written to a file, this would then be the path to which the file is written.
// Set stream output path:
stream.setOutputPath('New-Output-Stream-Path');
// Functions which return a Stream can be chained like this:
stream.setOutputName('New-Stream-Name').setOutputPath('/my/specific/path')
Parameters
• path: string
New path name
Returns
: The manipulated stream.
setProcessorOutputName()
setProcessorOutputName(
outputProcessorName,streamName):Stream
Set the name of the output stream for a specific Processor. Use this for example, if you have a processor with multiple output ports, and need to send messages to either of these ports, but also determine what the name of the streams should be on either of these ports.
This is used to change the name of the output stream. E.g. if a file is written, this will be the filename in output.
Option 1:
// Set stream output names:
stream.setProcessorOutputName('NameOfOutputProcessor', 'MyNewStreamName');
// or Option 2:
const OUTPUT_PORT = getOutputPort('NameOfOutputPort');
stream.setProcessorOutputName(OUTPUT_PORT.getPeerProcessorName(), 'MyNewStreamName');
// Options 2 only works if the processor connected to OUTPUT_PORT is the actual Output-Processor.
// Functions which return a Stream can be chained like this:
stream.setProcessorOutputName('New-Stream-Name').setProcessorOutputPath('/my/specific/path')
Parameters
• outputProcessorName: string
Name of the output processor at the end of the workflow.
• streamName: string
New name the stream should have when data is sent out to the receiving processor.
Returns
The manipulated stream.
setProcessorOutputPath()
setProcessorOutputPath(
outputProcessorName,path):Stream
Set the path of the output stream for a specific Processor. Use this, for example, if you have a processor with multiple output ports, and need to send messages to either of these ports, but also determine what the path of the streams should be on either of these ports.
This is used to change the path of the output stream. E.g., if a file is written, this will be written to the specified path.
Parameters
• outputProcessorName: string
Name of the output processor at the end of the workflow.
• path: string
New name the stream should have when data is sent out to the receiving processor.
Returns
The manipulated stream.
Example
Option 1:
// Set stream path name:
stream.setProcessorPathName('NameOfOutputProcessor', '/my/specific/output/path');
// or Option 2:
const OUTPUT_PORT = getOutputPort('NameOfOutputPort');
stream.setProcessorOutputName(OUTPUT_PORT.getPeerProcessorName(), '/my/specific/output/path');
// Options 2 only works if the processor connected to OUTPUT_PORT is the actual Output-Processor.
// Functions which return a Stream can be chained like this:
stream.setProcessorOutputName('New-Stream-Name').setProcessorOutputPath('/my/specific/path')