/// <summary>
/// Gets the distributed context or creates a new one if the default tenant has changed.
/// </summary>
private async Task <DistributedContext> GetOrCreateDistributedContextAsync(ShellContext defaultContext)
{
// Check if the default tenant has changed.
if (_defaultContext != defaultContext)
{
_defaultContext = defaultContext;
var previousContext = _context;
// Create a new distributed context based on the default tenant settings.
_context = await CreateDistributedContextAsync(defaultContext.Settings);
// Release the previous one.
previousContext?.Release();
}
return(_context);
}
/// <summary>
/// Keep in sync tenants by sharing shell identifiers through an <see cref="IDistributedCache"/>.
/// </summary>
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
stoppingToken.Register(() =>
{
_logger.LogInformation("'{ServiceName}' is stopping.", nameof(DistributedShellHostedService));
});
// Init the idle time.
var idleTime = MinIdleTime;
while (!stoppingToken.IsCancellationRequested)
{
try
{
// Wait for the current idle time on each loop.
if (!await TryWaitAsync(idleTime, stoppingToken))
{
break;
}
// If there is no default tenant or it is not running, nothing to do.
if (!_shellHost.TryGetShellContext(ShellHelper.DefaultShellName, out var defaultContext) ||
defaultContext.Settings.State != TenantState.Running)
{
continue;
}
// Get or create a new distributed context if the default tenant has changed.
var context = await GetOrCreateDistributedContextAsync(defaultContext);
// If the required distributed features are not enabled, nothing to do.
var distributedCache = context?.DistributedCache;
if (distributedCache == null)
{
continue;
}
// Try to retrieve the tenant changed global identifier from the distributed cache.
string shellChangedId;
try
{
shellChangedId = await distributedCache.GetStringAsync(ShellChangedIdKey);
}
catch (Exception ex) when(!ex.IsFatal())
{
// Get the next idle time before retrying to read the distributed cache.
idleTime = NextIdleTimeBeforeRetry(idleTime, ex);
continue;
}
// Reset the idle time.
idleTime = MinIdleTime;
// Check if at least one tenant has changed.
if (shellChangedId == null || _shellChangedId == shellChangedId)
{
continue;
}
// Try to retrieve the tenant created global identifier from the distributed cache.
string shellCreatedId;
try
{
shellCreatedId = await distributedCache.GetStringAsync(ShellCreatedIdKey);
}
catch (Exception ex) when(!ex.IsFatal())
{
_logger.LogError(ex, "Unable to read the distributed cache before checking if a tenant has been created.");
continue;
}
// Retrieve all tenant settings that are already loaded.
var allSettings = _shellHost.GetAllSettings().ToList();
// Check if at least one tenant has been created.
if (shellCreatedId != null && _shellCreatedId != shellCreatedId)
{
// Retrieve all new created tenants that are not already loaded.
var names = (await _shellSettingsManager.LoadSettingsNamesAsync())
.Except(allSettings.Select(s => s.Name))
.ToArray();
// Load and enlist the settings of all new created tenant.
foreach (var name in names)
{
allSettings.Add(await _shellSettingsManager.LoadSettingsAsync(name));
}
}
// Init the busy start time.
var _busyStartTime = DateTime.UtcNow;
var syncingSuccess = true;
// Keep in sync all tenants by checking their specific identifiers.
foreach (var settings in allSettings)
{
// Wait for the min idle time after the max busy time.
if (!await TryWaitAfterBusyTime(stoppingToken))
{
break;
}
var semaphore = _semaphores.GetOrAdd(settings.Name, name => new SemaphoreSlim(1));
await semaphore.WaitAsync();
try
{
// Try to retrieve the release identifier of this tenant from the distributed cache.
var releaseId = await distributedCache.GetStringAsync(ReleaseIdKey(settings.Name));
if (releaseId != null)
{
// Check if the release identifier of this tenant has changed.
var identifier = _identifiers.GetOrAdd(settings.Name, name => new ShellIdentifier());
if (identifier.ReleaseId != releaseId)
{
// Upate the local identifier.
identifier.ReleaseId = releaseId;
// Keep in sync this tenant by releasing it locally.
await _shellHost.ReleaseShellContextAsync(settings, eventSource : false);
}
}
// Try to retrieve the reload identifier of this tenant from the distributed cache.
var reloadId = await distributedCache.GetStringAsync(ReloadIdKey(settings.Name));
if (reloadId != null)
{
// Check if the reload identifier of this tenant has changed.
var identifier = _identifiers.GetOrAdd(settings.Name, name => new ShellIdentifier());
if (identifier.ReloadId != reloadId)
{
// Upate the local identifier.
identifier.ReloadId = reloadId;
// Keep in sync this tenant by reloading it locally.
await _shellHost.ReloadShellContextAsync(settings, eventSource : false);
}
}
}
catch (Exception ex) when(!ex.IsFatal())
{
syncingSuccess = false;
_logger.LogError(ex, "Unable to read the distributed cache while syncing the tenant '{TenantName}'.", settings.Name);
break;
}
finally
{
semaphore.Release();
}
}
// Keep in sync the tenant global identifiers.
if (syncingSuccess)
{
_shellChangedId = shellChangedId;
_shellCreatedId = shellCreatedId;
}
}
catch (Exception ex) when(!ex.IsFatal())
{
_logger.LogError(ex, "Error while executing '{ServiceName}'", nameof(DistributedShellHostedService));
}
}
_terminated = true;
_context?.Release();
_defaultContext = null;
_context = null;
}
