private void CachePage(Page page, string subscriptionId)
{
if (IsCachingEnabled)
{
IReadOnlyList <Transaction> transactions = page.Transactions;
// Add to cache in reverse order to prevent other projectors seeing the first transactions on the cache before the entire page is there.
for (int index = transactions.Count - 1; index > 0; index--)
{
cachedTransactionsByPrecedingCheckpoint.Set(transactions[index - 1].Checkpoint, transactions[index]);
}
cachedTransactionsByPrecedingCheckpoint.Set(page.PrecedingCheckpoint, transactions[0]);
logDebug(() =>
$"Cached: (subscription: {subscriptionId}, precedingCheckpoint: {page.PrecedingCheckpoint}, transactions: {transactions.Count}, range: {transactions.First().Checkpoint}-{transactions.Last().Checkpoint}.");
}
}
private async Task <Page> TryLoadNextPage(long previousCheckpoint, string subscriptionId)
{
// Maybe it's just loaded to cache.
try
{
Page cachedPage = TryGetNextPageFromCache(previousCheckpoint, subscriptionId);
if (cachedPage.Transactions.Count > 0)
{
#if LIQUIDPROJECTIONS_DIAGNOSTICS
logger(() => $"Loader for subscription {subscriptionId} has found a page in the cache.");
#endif
return(cachedPage);
}
}
catch (Exception exception)
{
logger(() =>
$"Failed getting transactions after checkpoint {previousCheckpoint} from the cache: " + exception);
}
DateTime timeOfRequestUtc = getUtcNow();
List <Transaction> transactions;
try
{
transactions = await Task
.Run(() => eventStore
.GetFrom((previousCheckpoint == 0) ? (long?)null : previousCheckpoint)
.Take(maxPageSize)
.ToList())
.ConfigureAwait(false);
}
catch (Exception exception)
{
logger(() => $"Failed loading transactions after checkpoint {previousCheckpoint} from NEventStore: " +
exception);
throw;
}
if (transactions.Count > 0)
{
#if LIQUIDPROJECTIONS_DIAGNOSTICS
logger(() =>
$"Loader for subscription {subscriptionId ?? "without ID"} has loaded {transactions.Count} transactions " +
$"from checkpoint {transactions.First().Checkpoint} to checkpoint {transactions.Last().Checkpoint}.");
#endif
if (transactionCacheByPreviousCheckpoint != null)
{
/* Add to cache in reverse order to prevent other projectors
* from requesting already loaded transactions which are not added to cache yet. */
for (int index = transactions.Count - 1; index > 0; index--)
{
transactionCacheByPreviousCheckpoint.Set(transactions[index - 1].Checkpoint, transactions[index]);
}
transactionCacheByPreviousCheckpoint.Set(previousCheckpoint, transactions[0]);
#if LIQUIDPROJECTIONS_DIAGNOSTICS
logger(() =>
$"Loader for subscription {subscriptionId ?? "without ID"} has cached {transactions.Count} transactions " +
$"from checkpoint {transactions.First().Checkpoint} to checkpoint {transactions.Last().Checkpoint}.");
#endif
}
}
else
{
#if LIQUIDPROJECTIONS_DIAGNOSTICS
logger(() =>
$"Loader for subscription {subscriptionId} has discovered " +
$"that there are no new transactions yet. Next request for the new transactions will be delayed.");
#endif
Volatile.Write(
ref lastSuccessfulPollingRequestWithoutResults,
new CheckpointRequestTimestamp(previousCheckpoint, timeOfRequestUtc));
}
return(new Page(previousCheckpoint, transactions));
}