View Source 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 to prevent race conditions. The retry_on_stale/2
function handles Ecto.StaleEntryError
from concurrent transactions, refetching the wallet and retrying the operation.
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:
def deps do
[
{:retry_on_stale, "~> 0.2.0"}
]
end
HexDocs
HexDocs documentation can be found at https://hexdocs.pm/retry_on_stale.