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TokenCredentialCache: Adds a fallback mechanism to AAD scope override. #5337

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TokenCredentialCache: Adds a fallback mechanism to AAD scope override. #5337

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352 changes: 190 additions & 162 deletions Microsoft.Azure.Cosmos/src/Authorization/TokenCredentialCache.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,9 @@ internal sealed class TokenCredentialCache : IDisposable
private readonly TimeSpan? userDefinedBackgroundTokenCredentialRefreshInterval;

private readonly SemaphoreSlim isTokenRefreshingLock = new SemaphoreSlim(1);
private readonly object backgroundRefreshLock = new object();
private readonly object backgroundRefreshLock = new object();
private readonly string defaultScope;
private readonly string? overrideScope;

private TimeSpan? systemBackgroundTokenCredentialRefreshInterval;
private Task<AccessToken>? currentRefreshOperation = null;
Expand All @@ -57,21 +59,21 @@ internal TokenCredentialCache(
TokenCredential tokenCredential,
Uri accountEndpoint,
TimeSpan? backgroundTokenCredentialRefreshInterval)
{
this.tokenCredential = tokenCredential ?? throw new ArgumentNullException(nameof(tokenCredential));

if (accountEndpoint == null)
{
throw new ArgumentNullException(nameof(accountEndpoint));
{
this.tokenCredential = tokenCredential ?? throw new ArgumentNullException(nameof(tokenCredential));
if (accountEndpoint == null)
{
throw new ArgumentNullException(nameof(accountEndpoint));
}

string? scopeOverride = ConfigurationManager.AADScopeOverrideValue(defaultValue: null);
this.defaultScope = string.Format(TokenCredentialCache.ScopeFormat, accountEndpoint.Host);
this.overrideScope = !string.IsNullOrEmpty(scopeOverride) ? scopeOverride : null;

this.tokenRequestContext = new TokenRequestContext(new string[]
{
!string.IsNullOrEmpty(scopeOverride)
? scopeOverride
: string.Format(TokenCredentialCache.ScopeFormat, accountEndpoint.Host)
{
this.overrideScope ?? this.defaultScope
});

if (backgroundTokenCredentialRefreshInterval.HasValue)
Expand Down Expand Up @@ -135,159 +137,185 @@ public void Dispose()

private async Task<AccessToken> GetNewTokenAsync(
ITrace trace)
{
// Use a local variable to avoid the possibility the task gets changed
// between the null check and the await operation.
Task<AccessToken>? currentTask = this.currentRefreshOperation;
if (currentTask != null)
{
// The refresh is already occurring wait on the existing task
return await currentTask;
}

try
{
await this.isTokenRefreshingLock.WaitAsync();

// avoid doing the await in the semaphore to unblock the parallel requests
if (this.currentRefreshOperation == null)
{
// ValueTask can not be awaited multiple times
currentTask = this.RefreshCachedTokenWithRetryHelperAsync(trace).AsTask();
this.currentRefreshOperation = currentTask;
}
else
{
currentTask = this.currentRefreshOperation;
}
}
finally
{
this.isTokenRefreshingLock.Release();
}

return await currentTask;
}

{
// Use a local variable to avoid the possibility the task gets changed
// between the null check and the await operation.
Task<AccessToken>? currentTask = this.currentRefreshOperation;
if (currentTask != null)
{
// The refresh is already occurring wait on the existing task
return await currentTask;
}
try
{
await this.isTokenRefreshingLock.WaitAsync();
// avoid doing the await in the semaphore to unblock the parallel requests
if (this.currentRefreshOperation == null)
{
// ValueTask can not be awaited multiple times
currentTask = this.RefreshCachedTokenWithRetryHelperAsync(trace).AsTask();
this.currentRefreshOperation = currentTask;
}
else
{
currentTask = this.currentRefreshOperation;
}
}
finally
{
this.isTokenRefreshingLock.Release();
}
return await currentTask;
}
private async ValueTask<AccessToken> RefreshCachedTokenWithRetryHelperAsync(
ITrace trace)
{
try
{
Exception? lastException = null;
const int totalRetryCount = 2;
for (int retry = 0; retry < totalRetryCount; retry++)
{
if (this.cancellationToken.IsCancellationRequested)
{
DefaultTrace.TraceInformation(
"Stop RefreshTokenWithIndefiniteRetries because cancellation is requested");

break;
}

using (ITrace getTokenTrace = trace.StartChild(
name: nameof(this.RefreshCachedTokenWithRetryHelperAsync),
component: TraceComponent.Authorization,
level: Tracing.TraceLevel.Info))
{
try
{
this.cachedAccessToken = await this.tokenCredential.GetTokenAsync(
requestContext: this.tokenRequestContext,
cancellationToken: this.cancellationToken);

if (!this.cachedAccessToken.HasValue)
{
throw new ArgumentNullException("TokenCredential.GetTokenAsync returned a null token.");
}

if (this.cachedAccessToken.Value.ExpiresOn < DateTimeOffset.UtcNow)
{
throw new ArgumentOutOfRangeException($"TokenCredential.GetTokenAsync returned a token that is already expired. Current Time:{DateTime.UtcNow:O}; Token expire time:{this.cachedAccessToken.Value.ExpiresOn:O}");
}

if (!this.userDefinedBackgroundTokenCredentialRefreshInterval.HasValue)
{
double refreshIntervalInSeconds = (this.cachedAccessToken.Value.ExpiresOn - DateTimeOffset.UtcNow).TotalSeconds * DefaultBackgroundTokenCredentialRefreshIntervalPercentage;

// Ensure the background refresh interval is a valid range.
refreshIntervalInSeconds = Math.Max(refreshIntervalInSeconds, TokenCredentialCache.MinimumTimeBetweenBackgroundRefreshInterval.TotalSeconds);
refreshIntervalInSeconds = Math.Min(refreshIntervalInSeconds, TokenCredentialCache.MaxBackgroundRefreshInterval.TotalSeconds);
this.systemBackgroundTokenCredentialRefreshInterval = TimeSpan.FromSeconds(refreshIntervalInSeconds);
}

return this.cachedAccessToken.Value;
}
catch (RequestFailedException requestFailedException)
{
lastException = requestFailedException;
getTokenTrace.AddDatum(
$"RequestFailedException at {DateTime.UtcNow.ToString(CultureInfo.InvariantCulture)}",
requestFailedException.Message);

DefaultTrace.TraceError($"TokenCredential.GetToken() failed with RequestFailedException. scope = {string.Join(";", this.tokenRequestContext.Scopes)}, retry = {retry}, Exception = {lastException.Message}");

// Don't retry on auth failures
if (requestFailedException.Status == (int)HttpStatusCode.Unauthorized ||
requestFailedException.Status == (int)HttpStatusCode.Forbidden)
{
this.cachedAccessToken = default;
throw;
}
}
catch (OperationCanceledException operationCancelled)
{
lastException = operationCancelled;
getTokenTrace.AddDatum(
$"OperationCanceledException at {DateTime.UtcNow.ToString(CultureInfo.InvariantCulture)}",
operationCancelled.Message);

DefaultTrace.TraceError(
$"TokenCredential.GetTokenAsync() failed. scope = {string.Join(";", this.tokenRequestContext.Scopes)}, retry = {retry}, Exception = {lastException.Message}");

throw CosmosExceptionFactory.CreateRequestTimeoutException(
message: ClientResources.FailedToGetAadToken,
headers: new Headers()
{
SubStatusCode = SubStatusCodes.FailedToGetAadToken,
},
innerException: lastException,
trace: getTokenTrace);
}
catch (Exception exception)
{
lastException = exception;
getTokenTrace.AddDatum(
$"Exception at {DateTime.UtcNow.ToString(CultureInfo.InvariantCulture)}",
exception.Message);

DefaultTrace.TraceError(
$"TokenCredential.GetTokenAsync() failed. scope = {string.Join(";", this.tokenRequestContext.Scopes)}, retry = {retry}, Exception = {lastException.Message}");
}
}
}

if (lastException == null)
{
throw new ArgumentException("Last exception is null.");
}

// The retries have been exhausted. Throw the last exception.
throw lastException;
}
finally
{
try
{
await this.isTokenRefreshingLock.WaitAsync();
this.currentRefreshOperation = null;
}
finally
{
this.isTokenRefreshingLock.Release();
}
}
{
try
{
Exception? lastException = null;
const int totalRetryCount = 2;
for (int retry = 0; retry < totalRetryCount; retry++)
{
if (this.cancellationToken.IsCancellationRequested)
{
DefaultTrace.TraceInformation(
"Stop RefreshTokenWithIndefiniteRetries because cancellation is requested");

break;
}

using (ITrace getTokenTrace = trace.StartChild(
name: nameof(this.RefreshCachedTokenWithRetryHelperAsync),
component: TraceComponent.Authorization,
level: Tracing.TraceLevel.Info))
{
try
{
if (this.overrideScope != null)
{
try
{
TokenRequestContext overrideContext = new TokenRequestContext(new string[] { this.overrideScope });
this.cachedAccessToken = await this.GetAndValidateTokenAsync(overrideContext);
}
catch (Exception ex)
{
DefaultTrace.TraceError($"TokenCredential.GetTokenAsync failed with override scope '{this.overrideScope}': {ex.Message}. Retrying with default scope '{this.defaultScope}'.");
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@kirankumarkolli kirankumarkolli Aug 15, 2025

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Wrapping it with our exception types gives us flexibility to include extra context like scopes.
With side-affect of mis-interpretting it as Cosmos issue. Thoughs?

/cc: @FabianMeiswinkel


TokenRequestContext defaultContext = new TokenRequestContext(new string[] { this.defaultScope });
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@kirankumarkolli kirankumarkolli Aug 15, 2025

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Can you please share what's the behavior if multiple scopes are specified?

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@kirankumarkolli kirankumarkolli Aug 15, 2025

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Ex: What happens if both account and generic ones are included.

this.cachedAccessToken = await this.GetAndValidateTokenAsync(defaultContext);
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@kirankumarkolli kirankumarkolli Aug 15, 2025

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Orrides are final right?

}
}
else
{
TokenRequestContext defaultContext = new TokenRequestContext(new string[] { this.defaultScope });
this.cachedAccessToken = await this.GetAndValidateTokenAsync(defaultContext);
}

if (!this.userDefinedBackgroundTokenCredentialRefreshInterval.HasValue)
{
double refreshIntervalInSeconds = (this.cachedAccessToken.Value.ExpiresOn - DateTimeOffset.UtcNow).TotalSeconds * DefaultBackgroundTokenCredentialRefreshIntervalPercentage;

// Ensure the background refresh interval is a valid range.
refreshIntervalInSeconds = Math.Max(refreshIntervalInSeconds, TokenCredentialCache.MinimumTimeBetweenBackgroundRefreshInterval.TotalSeconds);
refreshIntervalInSeconds = Math.Min(refreshIntervalInSeconds, TokenCredentialCache.MaxBackgroundRefreshInterval.TotalSeconds);
this.systemBackgroundTokenCredentialRefreshInterval = TimeSpan.FromSeconds(refreshIntervalInSeconds);
}

return this.cachedAccessToken.Value;
}
catch (RequestFailedException requestFailedException)
{
lastException = requestFailedException;
getTokenTrace.AddDatum(
$"RequestFailedException at {DateTime.UtcNow.ToString(CultureInfo.InvariantCulture)}",
requestFailedException.Message);

DefaultTrace.TraceError($"TokenCredential.GetToken() failed with RequestFailedException. scope = {string.Join(";", this.overrideScope ?? this.defaultScope)}, retry = {retry}, Exception = {lastException.Message}");

// Don't retry on auth failures
if (requestFailedException.Status == (int)HttpStatusCode.Unauthorized ||
requestFailedException.Status == (int)HttpStatusCode.Forbidden)
{
this.cachedAccessToken = default;
throw;
}
}
catch (OperationCanceledException operationCancelled)
{
lastException = operationCancelled;
getTokenTrace.AddDatum(
$"OperationCanceledException at {DateTime.UtcNow.ToString(CultureInfo.InvariantCulture)}",
operationCancelled.Message);

DefaultTrace.TraceError(
$"TokenCredential.GetTokenAsync() failed. scope = {string.Join(";", this.overrideScope ?? this.defaultScope)}, retry = {retry}, Exception = {lastException.Message}");

throw CosmosExceptionFactory.CreateRequestTimeoutException(
message: ClientResources.FailedToGetAadToken,
headers: new Headers()
{
SubStatusCode = SubStatusCodes.FailedToGetAadToken,
},
innerException: lastException,
trace: getTokenTrace);
}
catch (Exception exception)
{
lastException = exception;
getTokenTrace.AddDatum(
$"Exception at {DateTime.UtcNow.ToString(CultureInfo.InvariantCulture)}",
exception.Message);

DefaultTrace.TraceError(
$"TokenCredential.GetTokenAsync() failed. scope = {string.Join(";", this.overrideScope ?? this.defaultScope)}, retry = {retry}, Exception = {lastException.Message}");
}
}
}

if (lastException == null)
{
throw new ArgumentException("Last exception is null.");
}

// The retries have been exhausted. Throw the last exception.
throw lastException;
}
finally
{
try
{
await this.isTokenRefreshingLock.WaitAsync();
this.currentRefreshOperation = null;
}
finally
{
this.isTokenRefreshingLock.Release();
}
}
}

private async Task<AccessToken> GetAndValidateTokenAsync(TokenRequestContext requestContext)
{
AccessToken? cachedAccessToken = await this.tokenCredential.GetTokenAsync(
requestContext: requestContext,
cancellationToken: this.cancellationToken);

if (!cachedAccessToken.HasValue)
{
throw new ArgumentNullException("TokenCredential.GetTokenAsync returned a null token.");
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@kirankumarkolli kirankumarkolli Aug 15, 2025 •
edited
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Include Scopes in all exception message.

}

if (cachedAccessToken.Value.ExpiresOn < DateTimeOffset.UtcNow)
{
throw new ArgumentOutOfRangeException($"TokenCredential.GetTokenAsync returned a token that is already expired. Current Time:{DateTime.UtcNow:O}; Token expire time:{cachedAccessToken.Value.ExpiresOn:O}");
}

return cachedAccessToken.Value;
}

#pragma warning disable VSTHRD100 // Avoid async void methods
Expand Down
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