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Fallbacks in Ductape

Fallbacks in Ductape are composite resources that enable resilient workflows by orchestrating multiple providers or actions. If the primary provider fails, Ductape automatically attempts the next option in the sequence, ensuring high availability and graceful error handling.

What is a Fallback?​

A fallback is defined at the product level and includes:

  • A unique tag, name, and optional description.
  • An input schema describing the expected input fields and their types (using DataTypes).
  • An options array, where each option represents a provider or action to attempt, with its own event, input/output mapping, retries, and type.

Full Fallback Structure Example:

const paymentFallback = {
  tag: 'payments',
  name: 'Payments',
  description: 'Paystack and Flutterwave Fallback',
  input: {
    firstname: { type: DataTypes.STRING },
    lastname: { type: DataTypes.STRING },
    amount: { type: DataTypes.NUMBER_STRING },
    accountNumber: { type: DataTypes.NUMBER_STRING },
    bankCode: { type: DataTypes.NUMBER_STRING },
    narration: { type: DataTypes.STRING },
    paystack_type: { type: DataTypes.NOSPACES_STRING, maxlength: 3, minlength: 3 },
    currency: { type: DataTypes.NOSPACES_STRING, maxlength: 3, minlength: 3 },
    reference: { type: DataTypes.UUID }
  },
  options: [
    {
      event: 'paystack-funds-transfer',
      input: {
        firstname: '$Input{firstname}',
        lastname: '$Input{lastname}',
        accountNumber: '$Input{accountNumber}',
        bankCode: '$Input{bankCode}',
        currency: '$Uppercase($Input{currency})',
        type: '$Input{paystack_type}',
        amount: '$Input{amount}',
        narration: '$Input{narration}',
      },
      output: {
        provider: 'paystack',
        amount: '$Input{amount}',
        currency: '$Uppercase($Input{currency})',
        transactionId: '$Response{transfer_code}',
      },
      retries: 1,
      type: FeatureEventTypes.FEATURE
    },
    {
      app: 'ductape:flutterwave:ductape',
      type: FeatureEventTypes.ACTION,
      event: 'initiate_a_transfer',
      input: {
        params: {},
        body: {
          account_bank: '$Input{bankCode}',
          account_number: '$Input{accountNumber}',
          amount: '$Input{amount}',
          narration: '$Input{narration}',
          currency: '$Uppercase($Input{currency})',
          reference: '$Input{reference}',
          callback_url: '',
          debit_currency: '$Uppercase($Input{currency})',
        },
        query: {},
        headers: {
          'Content-Type': 'application/json',
          Authorization: '$Auth{bearer_token}{headers}{Authorization}'
        }
      },
      output: {
        provider: 'flutterwave',
        amount: '$Input{amount}',
        currency: '$Uppercase($Input{currency})',
        transactionId: '$Response{initiate_a_transfer}{data}{id}',
      },
      retries: 1
    }
  ]
};

How Fallbacks Are Used in Workflows​

  • You define the fallback in your product configuration as above.
  • In your event sequence, reference the fallback by its tag in a fallback event.
  • Ductape will attempt each option in order, using the input/output mappings and retry logic you define.

See Also​