https://github.com/mathieuprog/retry_on_stale

Elixir utility for retrying stale Ecto entry operations
https://github.com/mathieuprog/retry_on_stale

Last synced: about 2 months ago
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Elixir utility for retrying stale Ecto entry operations

• Host: GitHub
• URL: https://github.com/mathieuprog/retry_on_stale
• Owner: mathieuprog
• License: apache-2.0
• Created: 2023-07-22T03:28:16.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2023-07-22T04:37:20.000Z (over 1 year ago)
• Last Synced: 2024-10-20T10:20:27.581Z (3 months ago)
• Language: Elixir
• Size: 14.6 KB
• Stars: 2
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Funding: .github/FUNDING.yml
  • License: LICENSE

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README

        
# RetryOnStale

`retry_on_stale/2` performs an operation that might raise an `Ecto.StaleEntryError` and retries

it a specified number of times with a delay between each attempt.

## Example

The example features a wallet's `balance_amount`, protected by [optimistic locking](https://hexdocs.pm/ecto/Ecto.Changeset.html#optimistic_lock/3) to prevent race conditions. The `retry_on_stale/2` function handles `Ecto.StaleEntryError` from concurrent transactions, refetching the wallet and retrying the operation.

```elixir

import RetryOnStale, only: [retry_on_stale: 2]

def increase_wallet_balance(%Wallet{} = wallet, amount) do

  retry_on_stale(

    fn attempt ->

      # refetch the latest wallet data for subsequent attempts

      wallet = if attempt == 1, do: wallet, else: Repo.get!(Wallet, wallet.id)

      # this function could raise a StaleEntryError

      do_increase_wallet_balance(wallet, amount)

    end,

    max_attempts: 5, delay_ms: 100

  )

end

defp do_increase_wallet_balance(%Wallet{} = wallet, amount) do

  new_balance = Decimal.add(wallet.balance_amount, amount)

  wallet

  |> Ecto.Changeset.change(balance_amount: new_balance)

  |> Ecto.Changeset.optimistic_lock(:lock_version)

  |> Repo.update!()

end

```

## Options

`:max_attempts` - The maximum number of attempts to perform the operation

before giving up and re-raising the last Ecto.StaleEntryError.

`:delay_ms` - The delay in milliseconds between each attempt.

## Installation

Add `retry_on_stale` for Elixir as a dependency in your `mix.exs` file:

```elixir

def deps do

  [

    {:retry_on_stale, "~> 0.2.0"}

  ]

end

```

## HexDocs

HexDocs documentation can be found at [https://hexdocs.pm/retry_on_stale](https://hexdocs.pm/retry_on_stale).