Delay

Unstable API 0.7.0 @project-lakechain/delay

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The Delay middleware allows to insert a user-defined delay between 2 middlewares. This can either allow to insert a fixed delay between processing of documents, or resume the processing of a pipeline at a given arbitrary time.

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⏰ Delaying Processing

To use this middleware, you import it in your CDK stack and instantiate it as part of a pipeline.

💁 In this example, we specify a fixed duration to the .withTime method, during which the Delay middleware will wait before passing the document to the next middleware in the pipeline.

import * as cdk from 'aws-cdk-lib';
import { Delay } from '@project-lakechain/delay';
import { CacheStorage } from '@project-lakechain/core';

class Stack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string) {
    // The cache storage.
    const cache = new CacheStorage(this, 'Cache');

    // The delay middleware.
    const delay = new Delay.Builder()
      .withScope(this)
      .withIdentifier('Delay')
      .withCacheStorage(cache)
      .withSource(source) // 👈 Specify a data source
      .withTime(cdk.Duration.seconds(30))
      .build();
  }
}

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Using Date Objects

It is also possible to specify an arbitrary Date object to the .withTime method, specifying when to resume the processing of a pipeline.

import * as cdk from 'aws-cdk-lib';
import { Delay } from '@project-lakechain/delay';

// Now + 24 hours.
const date = new Date();
date.setHours(date.getHours() + 24);

const delay = new Delay.Builder()
  .withScope(this)
  .withIdentifier('Delay')
  .withCacheStorage(cache)
  .withSource(source)
  .withTime(date)
  .build();

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🏗️ Architecture

The Delay middleware uses AWS Step Functions to orchestrate the delay using a state machine. The Step Function is configured to wait for a given duration before passing the document to the next middleware in the pipeline.

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🏷️ Properties

Supported Inputs

Mime Type	Description
*/*	The delay middleware can consume any type of document.

Supported Outputs

Mime Type	Description
*/*	The delay middleware can produce any type of document.

Supported Compute Types

Type	Description
CPU	This middleware only supports CPU compute.

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📖 Examples

• Delay Pipeline - An example showcasing how to delay a pipeline execution.