Added RetryAfter property for ratelimit errors, added parsing of rate limit return

CryptoExchange.Net/Clients/RestApiClient.cs

@@ -4,6 +4,7 @@ using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
@@ -344,8 +345,13 @@ namespace CryptoExchange.Net
                     _logger.Log(LogLevel.Warning, $"[{request.RequestId}] Error received in {sw.ElapsedMilliseconds}ms: {data}");
                     responseStream.Close();
                     response.Close();
-                    var parseResult = ValidateJson(data);
+
-                    var error = parseResult.Success ? ParseErrorResponse(parseResult.Data) : new ServerError(data)!;
+                    Error error;
+                    if (response.StatusCode == (HttpStatusCode)418 || response.StatusCode == (HttpStatusCode)429)
+                        error = ParseRateLimitResponse((int)response.StatusCode, response.ResponseHeaders, data);
+                    else
+                        error = ParseErrorResponse((int)response.StatusCode, response.ResponseHeaders, data);
+
                     if (error.Code == null || error.Code == 0)
                         error.Code = (int)response.StatusCode;
                     return new WebCallResult<T>(statusCode, headers, sw.Elapsed, data.Length, data, request.Uri.ToString(), request.Content, request.Method, request.GetHeaders(), default, error);
@@ -529,13 +535,39 @@ namespace CryptoExchange.Net
         }
 
         /// <summary>
-        /// Parse an error response from the server. Only used when server returns a status other than Success(200)
+        /// Parse an error response from the server. Only used when server returns a status other than Success(200) or ratelimit error (429 or 418)
         /// </summary>
-        /// <param name="error">The string the request returned</param>
+        /// <param name="httpStatusCode">The response status code</param>
+        /// <param name="responseHeaders">The response headers</param>
+        /// <param name="data">The response data</param>
         /// <returns></returns>
-        protected virtual Error ParseErrorResponse(JToken error)
+        protected virtual Error ParseErrorResponse(int httpStatusCode, IEnumerable<KeyValuePair<string, IEnumerable<string>>> responseHeaders, string data)
         {
-            return new ServerError(error.ToString());
+            return new ServerError(data);
+        }
+        
+        /// <summary>
+        /// Parse a rate limit error response from the server. Only used when server returns http status 429 or 418
+        /// </summary>
+        /// <param name="httpStatusCode">The response status code</param>
+        /// <param name="responseHeaders">The response headers</param>
+        /// <param name="data">The response data</param>
+        /// <returns></returns>
+        protected virtual Error ParseRateLimitResponse(int httpStatusCode, IEnumerable<KeyValuePair<string, IEnumerable<string>>> responseHeaders, string data)
+        {
+            // Handle retry after header
+            var retryAfterHeader = responseHeaders.SingleOrDefault(r => r.Key.Equals("Retry-After", StringComparison.InvariantCultureIgnoreCase));
+            if (!retryAfterHeader.Value.Any())
+                return new ServerRateLimitError(data);
+
+            var value = retryAfterHeader.Value.First();
+            if (int.TryParse(value, out var seconds))
+                return new ServerRateLimitError(data) { RetryAfter = DateTime.UtcNow.AddSeconds(seconds) };
+
+            if (DateTime.TryParse(value, out var datetime))
+                return new ServerRateLimitError(data) { RetryAfter = datetime };
+
+            return new ServerRateLimitError(data);
         }
 
         /// <summary>

CryptoExchange.Net/Objects/Error.cs

@@ -1,4 +1,6 @@
-namespace CryptoExchange.Net.Objects
+using System;
+
+namespace CryptoExchange.Net.Objects
 {
     /// <summary>
     /// Base class for errors
@@ -202,15 +204,14 @@
     }
 
     /// <summary>
-    /// Rate limit exceeded
+    /// Rate limit exceeded (client side)
     /// </summary>
-    public class RateLimitError : Error
+    public abstract class BaseRateLimitError : Error
     {
         /// <summary>
-        /// ctor
+        /// When the request can be retried
         /// </summary>
-        /// <param name="message"></param>
+        public DateTime? RetryAfter { get; set; }
-        public RateLimitError(string message) : base(null, "Rate limit exceeded: " + message, null) { }
 
         /// <summary>
         /// ctor
@@ -218,7 +219,47 @@
         /// <param name="code"></param>
         /// <param name="message"></param>
         /// <param name="data"></param>
-        protected RateLimitError(int? code, string message, object? data): base(code, message, data) { }
+        protected BaseRateLimitError(int? code, string message, object? data) : base(code, message, data) { }
+    }
+
+    /// <summary>
+    /// Rate limit exceeded (client side)
+    /// </summary>
+    public class ClientRateLimitError : BaseRateLimitError
+    {
+        /// <summary>
+        /// ctor
+        /// </summary>
+        /// <param name="message"></param>
+        public ClientRateLimitError(string message) : base(null, "Client rate limit exceeded: " + message, null) { }
+
+        /// <summary>
+        /// ctor
+        /// </summary>
+        /// <param name="code"></param>
+        /// <param name="message"></param>
+        /// <param name="data"></param>
+        protected ClientRateLimitError(int? code, string message, object? data): base(code, message, data) { }
+    }
+
+    /// <summary>
+    /// Rate limit exceeded (server side)
+    /// </summary>
+    public class ServerRateLimitError : BaseRateLimitError
+    {
+        /// <summary>
+        /// ctor
+        /// </summary>
+        /// <param name="message"></param>
+        public ServerRateLimitError(string message) : base(null, "Server rate limit exceeded: " + message, null) { }
+
+        /// <summary>
+        /// ctor
+        /// </summary>
+        /// <param name="code"></param>
+        /// <param name="message"></param>
+        /// <param name="data"></param>
+        protected ServerRateLimitError(int? code, string message, object? data) : base(code, message, data) { }
     }
 
     /// <summary>

CryptoExchange.Net/Objects/RateLimiter.cs

@@ -256,7 +256,7 @@ namespace CryptoExchange.Net.Objects
                             historyTopic.Semaphore.Release();
                             var msg = $"Request to {endpoint} failed because of rate limit `{historyTopic.Type}`. Current weight: {currentWeight}/{historyTopic.Limit}, request weight: {requestWeight}";
                             logger.Log(LogLevel.Warning, msg);
-                            return new CallResult<int>(new RateLimitError(msg));
+                            return new CallResult<int>(new ClientRateLimitError(msg) { RetryAfter = DateTime.UtcNow.AddSeconds(thisWaitTime) });
                         }
 
                         logger.Log(LogLevel.Information, $"Request to {endpoint} waiting {thisWaitTime}ms for rate limit `{historyTopic.Type}`. Current weight: {currentWeight}/{historyTopic.Limit}, request weight: {requestWeight}");