[PORT] [Authentication] Gov: Support temporary service unavailable results.

[tomlm]

Port this change from botbuilder-dotnet/master branch:
microsoft/botbuilder-dotnet#3734

Changed projects

• Microsoft.Bot.Connector
• Microsoft.Bot.Connector.Tests

[R9]

[tracyboehrer]

This needs more research. This has to do with retries to exceptions using Adal in C#. But Java uses MSAL and may (or may not) have the same abilities to provide the same functionality.

[tracyboehrer]

CredentialsAuthenticator.acquireToken might look something like this:

    public CompletableFuture<IAuthenticationResult> acquireToken() {
        return Retry.run(() -> app.acquireToken(parameters)
            .exceptionally(
                exception -> {
                    // wrapping whatever msal throws into our own exception
                    throw new AuthenticationException(exception);
                }
            ),
        (exception, count) -> {
            if (exception instanceof RetryException) {
                if (exception.getCause() instanceof MsalServiceException) {
                    MsalServiceException serviceException = (MsalServiceException) exception.getCause();
                    if (StringUtils.equals(
                        serviceException.errorCode(),
                        "temporarily_unavailable"
                    )) {
                        List<String> header = serviceException.headers().get("Retry-After");
                        if (header.isEmpty()) {
                            return RetryParams.defaultBackOff(count);
                        }

                        // need to parse Retry-After header value for Date or Delta and use
                        // that as the Retry backoff.
                        // For now, retry with default backoff.
                    }
                    return RetryParams.defaultBackOff(count);
                }
            }

            return RetryParams.stopRetrying();
        });
    }