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What is connection resiliency (retry on failure) in EF Core?

Entity Framework & EF Core Performance Advanced 3–5 Yrs5+ Yrs Conceptual 1 min read

Quick Answer

Connection resiliency automatically retries operations that fail with transient database errors (timeouts, Azure SQL throttling). Enable it with options.UseSqlServer(cs, o => o.EnableRetryOnFailure()). It's essential for Azure SQL, which briefly drops connections during failovers.

Connection resiliency makes EF Core automatically retry when it hits a transient error — a timeout, or Azure SQL throttling you or doing a failover. You turn it on with EnableRetryOnFailure, and for a cloud database it's basically mandatory because connections get dropped during failovers. The catch is transactions: if I open my own transaction and a retry happens, EF would only replay part of it, so I have to get the execution strategy and wrap the entire unit of work in strategy.ExecuteAsync so the whole thing retries as one.

  • Uses an execution strategy that catches a known list of transient error numbers and retries with backoff.
  • Gotcha: with retries enabled you can't start a user-initiated transaction (BeginTransaction) the normal way — a retry would replay only part of it. Wrap the whole unit of work in strategy.ExecuteAsync(async () => { ... }) so the entire block is retried atomically.
  • Also apply resilience to raw SqlConnection usage separately (it doesn't inherit EF's strategy).
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