public async Task<HttpResponseMessage> Cas([FromUri] string key, [FromUri] string val, [FromUri] string prevValue)
{
JToken jVal;
try
{
jVal = JToken.Parse(val);
}
catch (JsonReaderException)
{
jVal = val;
}
JToken jPrevVal;
try
{
jPrevVal = JToken.Parse(prevValue);
}
catch (JsonReaderException)
{
jPrevVal = prevValue;
}
var taskCompletionSource = new TaskCompletionSource<object>();
var op = new CasCommand
{
Key = key,
Value = jVal,
PrevValue = jPrevVal,
Completion = taskCompletionSource
};
try
{
RaftEngine.AppendCommand(op);
}
catch (NotLeadingException e)
{
return this.RedirectToLeader(e.CurrentLeader, Request.RequestUri);
}
var newValueSet = await taskCompletionSource.Task;
return Request.CreateResponse(HttpStatusCode.OK, new
{
RaftEngine.State,
Key = key,
ValueChanged = newValueSet
});
}
public bool Cas(CasCommand op)
{
using (var tx = _storageEnvironment.NewTransaction(TransactionFlags.ReadWrite))
{
var items = tx.ReadTree("items");
var oldValue = items.Read(op.Key);
var ms = new MemoryStream();
var oldToken = oldValue == null ? JValue.CreateNull() : JToken.ReadFrom(new JsonTextReader(new StreamReader(oldValue.Reader.AsStream())));
if (!new JTokenEqualityComparer().Equals(oldToken, op.PrevValue))
{
return false;
}
ms.SetLength(0);
var writer = new StreamWriter(ms);
op.Value.WriteTo(new JsonTextWriter(writer));
writer.Flush();
ms.Position = 0;
items.Add(op.Key, ms);
tx.Commit();
return true;
}
}
