public CircuitBreakerFactory(IMetricEvents metricEvents, IFailurePercentageCircuitBreakerConfig breakerConfig, IMjolnirLogFactory logFactory)
{
_metricEvents = metricEvents ?? throw new ArgumentNullException(nameof(metricEvents));
_breakerConfig = breakerConfig ?? throw new ArgumentNullException(nameof(breakerConfig));
_logFactory = logFactory ?? throw new ArgumentNullException(nameof(logFactory));
_log = logFactory.CreateLog <FailurePercentageCircuitBreaker>();
if (_log == null)
{
throw new InvalidOperationException($"{nameof(IMjolnirLogFactory)} implementation returned null from {nameof(IMjolnirLogFactory.CreateLog)} for type {typeof(CircuitBreakerFactory)}, please make sure the implementation returns a non-null log for all calls to {nameof(IMjolnirLogFactory.CreateLog)}");
}
_timer = new GaugeTimer(state =>
{
try
{
var keys = _circuitBreakers.Keys;
foreach (var key in keys)
{
if (_circuitBreakers.TryGetValue(key, out Lazy <FailurePercentageCircuitBreaker> lazy) && lazy.IsValueCreated)
{
var breaker = lazy.Value;
_metricEvents.BreakerGauge(
breaker.Name,
_breakerConfig.GetMinimumOperations(key),
_breakerConfig.GetWindowMillis(key),
_breakerConfig.GetThresholdPercentage(key),
_breakerConfig.GetTrippedDurationMillis(key),
_breakerConfig.GetForceTripped(key),
_breakerConfig.GetForceFixed(key),
breaker.IsTripped(),
breaker.Metrics.SuccessCount,
breaker.Metrics.FailureCount);
}
}
}
catch (Exception e)
{
_log.Error($"Error sending {nameof(IMetricEvents.BreakerGauge)} metric event", e);
}
});
}
/// <summary>
/// Checks to see if the breaker should trip, and trips if it should.
/// </summary>
/// <returns><code>true</code> if breaker is tripped</returns>
private bool CheckAndSetTripped()
{
if (_state == State.Tripped)
{
return(true);
}
if (!Monitor.TryEnter(_stateChangeLock))
{
return(_state == State.Tripped);
}
try
{
var snapshot = _metrics.GetSnapshot();
// If we haven't met the minimum number of operations needed to trip, don't trip.
if (snapshot.Total < _config.GetMinimumOperations(_key))
{
return(false);
}
// If we're within the error threshold, don't trip.
if (snapshot.ErrorPercentage < _config.GetThresholdPercentage(_key))
{
return(false);
}
_state = State.Tripped;
_lastTrippedTimestamp = _clock.GetMillisecondTimestamp();
_metricEvents.BreakerTripped(Name);
_log.Error($"Tripped Breaker={_key} Operations={snapshot.Total} ErrorPercentage={snapshot.ErrorPercentage} Wait={_config.GetTrippedDurationMillis(_key)}");
return(true);
}
finally
{
Monitor.Exit(_stateChangeLock);
}
}