App-vNext/Polly · error · ArgumentOutOfRangeException

Value must be greater than zero.

Error message

Value must be greater than zero.

What it means

Thrown as ArgumentOutOfRangeException(nameof(maxParallelization)) when constructing a non-generic BulkheadPolicy via Policy.Bulkhead(...) with maxParallelization <= 0. The guard at BulkheadSyntax.cs:55–59 fires at policy construction time, before any semaphores are created. maxParallelization controls how many actions may execute concurrently through the bulkhead.

Source

Thrown at src/Polly/Bulkhead/BulkheadSyntax.cs:55

    public static BulkheadPolicy Bulkhead(int maxParallelization, int maxQueuingActions)
        => Bulkhead(maxParallelization, maxQueuingActions, EmptyAction);

    /// <summary>
    /// Builds a bulkhead isolation <see cref="Policy" />, which limits the maximum concurrency of actions executed through the policy.  Imposing a maximum concurrency limits the potential of governed actions, when faulting, to bring down the system.
    /// <para>When an execution would cause the number of actions executing concurrently through the policy to exceed <paramref name="maxParallelization" />, the policy allows a further <paramref name="maxQueuingActions" /> executions to queue, waiting for a concurrent execution slot.  When an execution would cause the number of queuing actions to exceed <paramref name="maxQueuingActions" />, a <see cref="BulkheadRejectedException" /> is thrown.</para>
    /// </summary>
    /// <param name="maxParallelization">The maximum number of concurrent actions that may be executing through the policy.</param>
    /// <param name="maxQueuingActions">The maximum number of actions that may be queuing, waiting for an execution slot.</param>
    /// <param name="onBulkheadRejected">An action to call, if the bulkhead rejects execution due to oversubscription.</param>
    /// <returns>The policy instance.</returns>
    /// <exception cref="ArgumentOutOfRangeException">maxParallelization;Value must be greater than zero.</exception>
    /// <exception cref="ArgumentOutOfRangeException">maxQueuingActions;Value must be greater than or equal to zero.</exception>
    /// <exception cref="ArgumentNullException">Thrown when <paramref name="onBulkheadRejected"/> is <see langword="null"/>.</exception>
    public static BulkheadPolicy Bulkhead(int maxParallelization, int maxQueuingActions, Action<Context> onBulkheadRejected)
    {
        if (maxParallelization <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(maxParallelization), "Value must be greater than zero.");
        }

        if (maxQueuingActions < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(maxQueuingActions), "Value must be greater than or equal to zero.");
        }

        if (onBulkheadRejected == null)
        {
            throw new ArgumentNullException(nameof(onBulkheadRejected));
        }

        return new BulkheadPolicy(
            maxParallelization,
            maxQueuingActions,
            onBulkheadRejected);
    }

View on GitHub (pinned to d0e46bdb1e)

Solutions

1. Ensure the configuration value for maxParallelization is at least 1
2. Add a fallback default when reading from configuration: config.GetValue("MaxParallel", 10)
3. Validate the value at application startup and fail fast with a clear message

Example fix

// before
var maxPar = config.GetValue<int>("Bulkhead:MaxParallelization"); // 0 if missing
var policy = Policy.Bulkhead(maxPar, 10, _ => { }); // throws

// after
var maxPar = config.GetValue<int>("Bulkhead:MaxParallelization");
if (maxPar <= 0) maxPar = Environment.ProcessorCount;
var policy = Policy.Bulkhead(maxPar, 10, _ => { });

if (maxParallelization <= 0)
{
    throw new InvalidOperationException($"Invalid maxParallelization: {maxParallelization}. Must be >= 1.");
}
var policy = Policy.Bulkhead(maxParallelization, maxQueuingActions, onReject);

public static bool IsValidParallelization(int value) => value > 0;

When it happens

Trigger: Calling Policy.Bulkhead(maxParallelization, ...) where maxParallelization is 0 or negative. Common when the value comes from configuration that defaults to 0 or is computed from a formula that yields a non-positive result.

Common situations: Reading maxParallelization from appsettings.json where the key is missing (binds to default int 0). Calculating parallelization as a percentage of processor count with rounding to zero. Environment variable not set, parsing to 0.

Related errors

• Value must be greater than or equal to zero.
• Value must be greater than zero.
• Value must be greater than or equal to zero.
• Value cannot be null.
• Value cannot be null.

AI-assisted analysis of App-vNext/Polly@d0e46bdb1e (2026-08-13). Data as JSON: /api/errors/6b77e5fb52030aea. Report an issue: GitHub.