public async Task SubscribeAsync(string key, Action <int, RedisMessage> onMessage)
{
_trace.TraceInformation("Subscribing to key: " + key);
var channel = await _redisSubscriber.SubscribeAsync(key);
channel.OnMessage(channelMessage =>
{
var message = RedisMessage.FromBytes(channelMessage.Message, _trace);
onMessage(0, message);
// Save the last message id in just in case redis shuts down
_latestMessageId = message.Id;
});
}
private void OnMessage(int streamIndex, RedisMessage message)
{
// locked to avoid overlapping calls (even though we have set the mode
// to preserve order on the subscription)
lock (_callbackLock)
{
if (lastId.HasValue && message.Id < lastId.Value)
{
_trace.TraceEvent(TraceEventType.Error, 0, $"ID regression occurred. The next message ID {message.Id} was less than the previous message {lastId.Value}");
}
lastId = message.Id;
OnReceived(streamIndex, message.Id, message.ScaleoutMessage);
}
}
public static RedisMessage FromBytes(byte[] data, TraceSource trace)
{
using (var stream = new MemoryStream(data))
{
var message = new RedisMessage();
// read message id from memory stream until SPACE character
var messageIdBuilder = new StringBuilder(20);
do
{
// it is safe to read digits as bytes because they encoded by single byte in UTF-8
int charCode = stream.ReadByte();
if (charCode == -1)
{
trace.TraceVerbose("Received Message could not be parsed.");
throw new EndOfStreamException(Resources.Error_EndOfStreamRedis);
}
char c = (char)charCode;
if (c == ' ')
{
message.Id = ulong.Parse(messageIdBuilder.ToString(), CultureInfo.InvariantCulture);
messageIdBuilder = null;
}
else
{
messageIdBuilder.Append(c);
}
}while (messageIdBuilder != null);
var binaryReader = new BinaryReader(stream);
int count = binaryReader.ReadInt32();
byte[] buffer = binaryReader.ReadBytes(count);
message.ScaleoutMessage = ScaleoutMessage.FromBytes(buffer);
return(message);
}
}
