/// <summary>
/// Given a collection of server connections, query for the topic metadata.
/// </summary>
/// <param name="connections">The server connections to query. Will cycle through the collection, starting at zero until a response is received.</param>
/// <param name="topics">The collection of topics to get metadata for.</param>
/// <returns>MetadataResponse validated to be complete.</returns>
public MetadataResponse Get(IKafkaConnection[] connections, IEnumerable <string> topics)
{
var request = new MetadataRequest {
Topics = topics.ToList()
};
if (request.Topics.Count <= 0)
{
return(null);
}
var performRetry = false;
var retryAttempt = 0;
MetadataResponse metadataResponse = null;
do
{
performRetry = false;
metadataResponse = GetMetadataResponse(connections, request);
if (metadataResponse == null)
{
return(null);
}
foreach (var validation in ValidateResponse(metadataResponse))
{
switch (validation.Status)
{
case ValidationResult.Retry:
performRetry = true;
_log.WarnFormat(validation.Message);
break;
case ValidationResult.Error:
throw validation.Exception;
}
}
BackoffOnRetry(++retryAttempt, performRetry);
} while (_interrupted == false && performRetry);
return(metadataResponse);
}
private MetadataResponse GetMetadataResponse(IKafkaConnection[] connections, MetadataRequest request)
{
//try each default broker until we find one that is available
foreach (var conn in connections)
{
try
{
var response = conn.SendAsync(request).Result;
if (response != null && response.Count > 0)
{
return(response.FirstOrDefault());
}
}
catch (Exception ex)
{
_log.WarnFormat("Failed to contact Kafka server={0}. Trying next default server. Exception={1}", conn.Endpoint, ex);
}
}
throw new ServerUnreachableException(
"Unable to query for metadata from any of the default Kafka servers. At least one provided server must be available. Server list: {0}",
string.Join(", ", connections.Select(x => x.ToString())));
}