/// <summary>
/// Uses list func to fetch fresh data on the instances in the predicate.
/// Instances that fail the condition are enqueued for the next pass.
/// </summary>
/// <returns></returns>
internal async Task CallListAndProcessResults()
{
// extract the predicate that restricts the list call
string predicate = _odataFilterSB.ToString();
// clear the sb for the next batch
_odataFilterSB.Clear();
// early exit if there is no work to do
if (string.IsNullOrWhiteSpace(predicate))
{
return;
}
// update the detail level
_odataDetailLevel.FilterClause = predicate;
// get the enumerable to refresh the instances
IPagedEnumerable <T> tEnumberable = _listObjects();
// get the enumerator for asycn walk of the collection
IPagedEnumerator <T> tEnumerator = tEnumberable.GetPagedEnumerator();
// used to enumerate until out of data
bool thereIsMoreData;
do
{
// move to next instance, possibley make call to server to get next batch
Task <bool> asyncTask = tEnumerator.MoveNextAsync(this.CancellationToken);
thereIsMoreData = await asyncTask.ConfigureAwait(continueOnCapturedContext : false);
if (thereIsMoreData)
{
// get the current instance
T refreshedInstance = tEnumerator.Current;
// test it to see if it is done
if (!_condition(refreshedInstance))
{
// we will have to refresh it again so put in queue for next pass
// box it up
MonitorLastCall <T> mlc = new MonitorLastCall <T>(refreshedInstance, DateTime.UtcNow + _odataMonitorControl.DelayBetweenDataFetch);
// enqueue it for next pass
this.NextPassQueue.Enqueue(mlc);
}
}
}while (thereIsMoreData);
}
/// <summary>
/// Polls the collection of instances until each has passed the condition at least once.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="collectionToMonitor"></param>
/// <param name="condition"></param>
/// <param name="getName"></param>
/// <param name="listObjects"></param>
/// <param name="cancellationToken"></param>
/// <param name="detailLevel">Controls the detail level of the data returned by a call to the Azure Batch Service.</param>
/// <param name="control"></param>
/// <returns></returns>
public static async Task WhenAllAsync <T>(
IEnumerable <T> collectionToMonitor,
Func <T, bool> condition,
Func <T, string> getName,
ListDelegate <T> listObjects,
CancellationToken cancellationToken,
ODATADetailLevel detailLevel,
ODATAMonitorControl control) where T : IRefreshable
{
if (null == collectionToMonitor)
{
throw new ArgumentNullException("collectionToMonitor");
}
if (null == condition)
{
throw new ArgumentNullException("condition");
}
RefreshViaODATAFilterList <T> odataRefresher = new RefreshViaODATAFilterList <T>(cancellationToken, detailLevel, condition, listObjects, control);
// populate for first pass
foreach (T curT in collectionToMonitor)
{
// filter out the instances that already meet the condition
if (!condition(curT))
{
MonitorLastCall <T> box = new MonitorLastCall <T>(curT, /* flags each instance as available to refresh "now" */ DateTime.MinValue);
odataRefresher.CurrentPassQueue.Enqueue(box);
}
}
// process the instances in the current pass... swap queues to begin next pass
while (!odataRefresher.CancellationToken.IsCancellationRequested &&
odataRefresher.CurrentPassQueue.Count > 0)
{
// get next instance
MonitorLastCall <T> nextInstanceToProcess = odataRefresher.CurrentPassQueue.Dequeue();
// build an odata filter with as many names as the limit will allow and call refresh instances as needed
Task asyncProcessOneInstance = odataRefresher.ProcessOneInstance(nextInstanceToProcess, getName);
// a-wait for completion
await asyncProcessOneInstance.ConfigureAwait(continueOnCapturedContext : false);
// if the current pass queue is empty, swap the queues to begin next pass
if (0 == odataRefresher.CurrentPassQueue.Count)
{
odataRefresher.SwapQueues();
// if we appear to be done, the stringbuilder might have the last predicate in it so flush that
if (0 == odataRefresher.CurrentPassQueue.Count)
{
// start the call to process the last predicate
Task asyncListTask = odataRefresher.CallListAndProcessResults();
// a-wait for completion
await asyncListTask.ConfigureAwait(continueOnCapturedContext : false);
// if the last predicate created new work... the swap will bring it into a new pass
odataRefresher.SwapQueues();
}
}
}
//Were we cancelled?
odataRefresher.CancellationToken.ThrowIfCancellationRequested();
}
internal async Task ProcessOneInstance(MonitorLastCall <T> nextInstance, Func <T, string> getName)
{
// we will loop until this is null
MonitorLastCall <T> processThisInstance = nextInstance;
while (null != processThisInstance)
{
bool usePredicateToCallList = false;
DateTime utcNow = DateTime.UtcNow;
// if it is not too early, we can use this instance
if (utcNow >= nextInstance.DoNotRefreshUntilUTC)
{
// now check to see if it will fit
// remember the limit on the name is 64 and the limit on the predicate is 500
// the assumption is that even if these #s evolve at least one max-sized-name will fit.
StringBuilder possibleAdditionalExpression = new StringBuilder();
// if this is not the first name then we must "or" this name in
if (0 != _odataFilterSB.Length)
{
possibleAdditionalExpression.Append(OrOperator);
}
// add in the name prefix
possibleAdditionalExpression.Append(IdPrefix);
// get the name of the object
string name = getName(nextInstance.Instance);
// add in the name
possibleAdditionalExpression.Append(name);
// add the name postfix
possibleAdditionalExpression.Append(IdPostfix);
// if it will fit then append the clause to the predicate
if ((_odataFilterSB.Length + possibleAdditionalExpression.Length) < _odataMonitorControl.ODATAPredicateLimit)
{
// amend the predicate to refresh the object
_odataFilterSB.Append(possibleAdditionalExpression.ToString());
processThisInstance = null; // we are done
}
else
{
// it will not fit so we are done with this predicate
usePredicateToCallList = true;
}
}
else // if the next instance cannot be refreshed yet we may need to wait a bit
{
// if we have work to do... return to process that work and use up time
if (_odataFilterSB.Length > 0)
{
usePredicateToCallList = true;
}
else // if we have no work to do we should delay until the instance can be refreshed
{
TimeSpan delayThisMuch = processThisInstance.DoNotRefreshUntilUTC - utcNow;
if (delayThisMuch.Ticks > 0)
{
await System.Threading.Tasks.Task.Delay(delayThisMuch).ConfigureAwait(continueOnCapturedContext: false);
}
}
}
// should we call the server with the current predicate data?
if (usePredicateToCallList)
{
usePredicateToCallList = false;
// start the new list operation
Task asyncListTask = CallListAndProcessResults();
// wait for completion
await asyncListTask.ConfigureAwait(continueOnCapturedContext : false);
}
}
}