writetimetable

R2026b

Write timetable to event stream

Since R2022b

This function requires Streaming Data Framework for MATLAB^® Production Server™.

Syntax

writetimetable(stream,tt)

writetimetable(stream,tt,opts)

writetimetable(ks,tt,MissingTopic=action)

Description

writetimetable(stream,tt) writes the timetable tt to the end of the event stream stream.

writetimetable converts rows of a timetable into events in an event stream, where:

• The column names in the timetable become variable names in the event body.

• The values in each event row become the values of those variables.

• The row timestamp becomes the event timestamp.

You can append data to a stream but cannot modify data that is already written to a stream.

writetimetable(stream,tt,opts) additionally specifies an ExportOptions input.

You can use detectExportOptions to specify a value for opts.

writetimetable(ks,tt,MissingTopic=action) specifies whether to create a topic when writing a timetable to an event stream hosted by Kafka^® or fail the write operation when the topic is missing. If the Kafka cluster that you are writing to is configured to auto-create topics, specifying action has no effect.

Examples

Write Timetable to Event Stream

Load air quality data and weather measurements into a timetable.

load indoors

Create an InMemoryStream object to connect to an event stream hosted by MATLAB.

i = inMemoryStream;

Write the timetable to the event stream.

writetimetable(i,indoors)

Preview the data in the event stream.

preview(i)

ans =

  8×2 timetable

           Time            Humidity    AirQuality
    ___________________    ________    __________

    2015-11-15 00:00:24       36           80    
    2015-11-15 01:13:35       36           80    
    2015-11-15 02:26:47       37           79    
    2015-11-15 03:39:59       37           82    
    2015-11-15 04:53:11       36           80    
    2015-11-15 06:06:23       36           80    
    2015-11-15 07:19:35       36           80    
    2015-11-15 08:32:47       37           80    

Write Timetable to Stream Hosted by Kafka

Load air quality data and weather measurements into a timetable.

load indoors

Assume that you have a Kafka host running at network address kafka.host.com:9092. Create a KafkaStream object that processes 10 stream events at a time.

ks = kafkaStream("kafka.host.com",9092,"IndoorTemp",Rows=10);

Create the IndoorTemp topic and write the timetable to it.

writetimetable(ks,indoors)

Read the first 10 events from the stream.

tt1 = readtimetable(ks)

tt1 =

  10×3 timetable

         timestamp          Humidity    AirQuality    key
    ____________________    ________    __________    ___

    15-Nov-2015 00:00:24       36           80        "" 
    15-Nov-2015 01:13:35       36           80        "" 
    15-Nov-2015 02:26:47       37           79        "" 
    15-Nov-2015 03:39:59       37           82        "" 
    15-Nov-2015 04:53:11       36           80        "" 
    15-Nov-2015 06:06:23       36           80        "" 
    15-Nov-2015 07:19:35       36           80        "" 
    15-Nov-2015 08:32:47       37           80        "" 
    15-Nov-2015 09:45:59       37           79        "" 
    15-Nov-2015 10:59:11       36           80        "" 

Read the next 10 events from the stream.

tt2 = readtimetable(ks)

tt2 =

  10×3 timetable

         timestamp          Humidity    AirQuality    key
    ____________________    ________    __________    ___

    16-Nov-2015 00:24:22       36           81        "" 
    16-Nov-2015 01:37:34       37           80        "" 
    16-Nov-2015 02:50:46       36           79        "" 
    16-Nov-2015 04:03:58       37           80        "" 
    16-Nov-2015 05:17:09       37           81        "" 
    16-Nov-2015 06:30:21       36           79        "" 
    16-Nov-2015 07:43:33       37           79        "" 
    16-Nov-2015 08:56:45       37           79        "" 
    16-Nov-2015 10:09:57       37           85        "" 
    16-Nov-2015 11:23:09       37           80        ""  

Detect Data Export Options from Event Stream

Assume that you have a Kafka server running at the network address kafka.host.com:9092 that has a topic Triangles.

Create a KafkaStream object connected to the Triangles topic.

inKS = kafkaStream("kafka.host.com",9092,"Triangles");

Read events from the Triangles topic into a timetable. Preview the data by viewing the first row. The a, b, and c triangle side lengths are stored as strings.

tt = readtimetable(inKS);
row = tt(1,:)

row =

  1×3 timetable

     timestamp      a       b       c  
    ___________    ____    ____    ____

    03-Sep-2022    "15"    "31"    "36"

Use detectExportOptions to generate an ExportOptions object from the Kafka stream object. The function obtains the types used to export the variables from the first row of the timetable.

opts = detectExportOptions(inKS,row);

Use getvartype to confirm that the side length variables are currently exported to the stream as strings.

type = getvartype(opts,["a" "b" "c"]);

type = 

  1×3 string array

    "string"    "string"    "string"

Update the export options so that the side lengths are exported as double values. Confirm the updated options by using getvartype.

opts = setvartype(opts,["a","b","c"],"double");

[name,type] = getvartype(opts);
fprintf("%s: %s\n", [name; type])

a: double
b: double
c: double

Connect to the stream to export data to numericTriangles.

outKS = kafkaStream("kafka.host.com",9092,"numericTriangles")

outKS = 

  KafkaStream with properties:

                  Topic: "numericTriangles"
                  Group: "85c42e39-695d-467a-86f0-f0095792e7de"
                  Order: EventTime
                   Host: "kafka.host.com"
                   Port: 9092
      ConnectionTimeout: 30
         RequestTimeout: 61
          ImportOptions: "None"
          ExportOptions: "None"
          PublishSchema: "true"
             WindowSize: 50
            KeyVariable: "key"
            KeyEncoding: "utf16"
                KeyType: "text"
           KeyByteOrder: "BigEndian"
           BodyEncoding: "utf8"
             BodyFormat: "JSON"
              ReadLimit: "Size"
    TimestampResolution: "Milliseconds"

Export the timetable to the new stream. The triangle side lengths in this stream are of type double.

writetimetable(outKS,tt,opts);

Input Arguments

stream — Object connected to event stream

KafkaStream object | InMemoryStream object | TestStream object

Object connected to an event stream, specified as a KafkaStream, InMemoryStream, or TestStream object.

tt — Input timetable

timetable

Input timetable.

ks — Object connected to Kafka stream topic

KafkaStream object

Object connected to a Kafka stream topic, specified as a KafkaStream object.

action — Action to take if topic does not exist

"create" (default) | "fail"

Action to take if the topic to write the timetable to does not exist, specified as one of the following values:

• "create" — Creates new topic, if you have the required permissions on the Kafka host.

• "fail" — Does not create a new topic and the write operation fails.

Data Types: char | string

opts — Export options

ExportOptions object

Export options, specified as an ExportOptions object. You can use detectExportOptions to generate this.

Version History

Introduced in R2022b