/// <summary>
/// Create a proxy for an interface of implementations of that interface using
/// the given
/// <see cref="FailoverProxyProvider{T}"/>
/// and the same retry policy for each
/// method in the interface.
/// </summary>
/// <param name="iface">the interface that the retry will implement</param>
/// <param name="proxyProvider">provides implementation instances whose methods should be retried
/// </param>
/// <param name="retryPolicy">the policy for retrying or failing over method call failures
/// </param>
/// <returns>the retry proxy</returns>
public static object Create <T>(FailoverProxyProvider <T> proxyProvider, RetryPolicy
retryPolicy)
{
System.Type iface = typeof(T);
return(Proxy.NewProxyInstance(proxyProvider.GetInterface().GetClassLoader(), new
Type[] { iface }, new RetryInvocationHandler <T>(proxyProvider, retryPolicy)));
}
/// <summary>
/// Create a proxy for an interface of implementations of that interface using
/// the given
/// <see cref="FailoverProxyProvider{T}"/>
/// and the a set of retry policies
/// specified by method name. If no retry policy is defined for a method then a
/// default of
/// <see cref="RetryPolicies.TryOnceThenFail"/>
/// is used.
/// </summary>
/// <param name="iface">the interface that the retry will implement</param>
/// <param name="proxyProvider">provides implementation instances whose methods should be retried
/// </param>
/// <param name="methodNameToPolicyMapa">map of method names to retry policies</param>
/// <returns>the retry proxy</returns>
public static object Create <T>(FailoverProxyProvider <T> proxyProvider, IDictionary
<string, RetryPolicy> methodNameToPolicyMap, RetryPolicy defaultPolicy)
{
System.Type iface = typeof(T);
return(Proxy.NewProxyInstance(proxyProvider.GetInterface().GetClassLoader(), new
Type[] { iface }, new RetryInvocationHandler <T>(proxyProvider, defaultPolicy, methodNameToPolicyMap
)));
}
/// <exception cref="System.Exception"/>
public virtual object Invoke(object proxy, MethodInfo method, object[] args)
{
RetryPolicy policy = methodNameToPolicyMap[method.Name];
if (policy == null)
{
policy = defaultPolicy;
}
// The number of times this method invocation has been failed over.
int invocationFailoverCount = 0;
bool isRpc = IsRpcInvocation(currentProxy.proxy);
int callId = isRpc ? Client.NextCallId() : RpcConstants.InvalidCallId;
int retries = 0;
while (true)
{
// The number of times this invocation handler has ever been failed over,
// before this method invocation attempt. Used to prevent concurrent
// failed method invocations from triggering multiple failover attempts.
long invocationAttemptFailoverCount;
lock (proxyProvider)
{
invocationAttemptFailoverCount = proxyProviderFailoverCount;
}
if (isRpc)
{
Client.SetCallIdAndRetryCount(callId, retries);
}
try
{
object ret = InvokeMethod(method, args);
hasMadeASuccessfulCall = true;
return(ret);
}
catch (Exception e)
{
if (Thread.CurrentThread().IsInterrupted())
{
// If interrupted, do not retry.
throw;
}
bool isIdempotentOrAtMostOnce = proxyProvider.GetInterface().GetMethod(method.Name
, Runtime.GetParameterTypes(method)).IsAnnotationPresent(typeof(Idempotent
));
if (!isIdempotentOrAtMostOnce)
{
isIdempotentOrAtMostOnce = proxyProvider.GetInterface().GetMethod(method.Name, Runtime.GetParameterTypes
(method)).IsAnnotationPresent(typeof(AtMostOnce));
}
RetryPolicy.RetryAction action = policy.ShouldRetry(e, retries++, invocationFailoverCount
, isIdempotentOrAtMostOnce);
if (action.action == RetryPolicy.RetryAction.RetryDecision.Fail)
{
if (action.reason != null)
{
Log.Warn("Exception while invoking " + currentProxy.proxy.GetType() + "." + method
.Name + " over " + currentProxy.proxyInfo + ". Not retrying because " + action.reason
, e);
}
throw;
}
else
{
// retry or failover
// avoid logging the failover if this is the first call on this
// proxy object, and we successfully achieve the failover without
// any flip-flopping
bool worthLogging = !(invocationFailoverCount == 0 && !hasMadeASuccessfulCall);
worthLogging |= Log.IsDebugEnabled();
if (action.action == RetryPolicy.RetryAction.RetryDecision.FailoverAndRetry && worthLogging)
{
string msg = "Exception while invoking " + method.Name + " of class " + currentProxy
.proxy.GetType().Name + " over " + currentProxy.proxyInfo;
if (invocationFailoverCount > 0)
{
msg += " after " + invocationFailoverCount + " fail over attempts";
}
msg += ". Trying to fail over " + FormatSleepMessage(action.delayMillis);
Log.Info(msg, e);
}
else
{
if (Log.IsDebugEnabled())
{
Log.Debug("Exception while invoking " + method.Name + " of class " + currentProxy
.proxy.GetType().Name + " over " + currentProxy.proxyInfo + ". Retrying " + FormatSleepMessage
(action.delayMillis), e);
}
}
if (action.delayMillis > 0)
{
Thread.Sleep(action.delayMillis);
}
if (action.action == RetryPolicy.RetryAction.RetryDecision.FailoverAndRetry)
{
// Make sure that concurrent failed method invocations only cause a
// single actual fail over.
lock (proxyProvider)
{
if (invocationAttemptFailoverCount == proxyProviderFailoverCount)
{
proxyProvider.PerformFailover(currentProxy.proxy);
proxyProviderFailoverCount++;
}
else
{
Log.Warn("A failover has occurred since the start of this method" + " invocation attempt."
);
}
currentProxy = proxyProvider.GetProxy();
}
invocationFailoverCount++;
}
}
}
}
}
