From b947e6afe5921808265ab6b804dc14ffecb04984 Mon Sep 17 00:00:00 2001
From: Chris Marsh <chris@discordapp.com>
Date: Tue, 18 Jul 2017 11:10:39 -0700
Subject: [PATCH] Back off on reconnect rate

---
 src/backoff.h       | 41 +++++++++++++++++++++++++++++++++++++++++
 src/discord-rpc.cpp | 19 ++++++++++++++++++-
 2 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 src/backoff.h

diff --git a/src/backoff.h b/src/backoff.h
new file mode 100644
index 0000000..ad14143
--- /dev/null
+++ b/src/backoff.h
@@ -0,0 +1,41 @@
+#pragma once
+
+#include <stdint.h>
+#include <algorithm>
+#include <random>
+
+struct Backoff
+{
+    int64_t minAmount;
+    int64_t maxAmount;
+    int64_t current;
+    int fails;
+    std::mt19937_64 randGenerator;
+    std::uniform_real_distribution<> randDistribution;
+
+    double rand01() {
+        return randDistribution(randGenerator);
+    }
+
+    Backoff(int64_t min, int64_t max)
+    : minAmount(min)
+    , maxAmount(max)
+    , current(min)
+    , fails(0)
+    {}
+
+    void reset()
+    {
+        fails = 0;
+        current = minAmount;
+    }
+
+    int64_t nextDelay()
+    {
+        ++fails;
+        int64_t delay = (int64_t)((double)current * 2.0 * rand01());
+        current = std::min(current + delay, maxAmount);
+        return current;
+    }
+};
+
diff --git a/src/discord-rpc.cpp b/src/discord-rpc.cpp
index a766c2f..0240580 100644
--- a/src/discord-rpc.cpp
+++ b/src/discord-rpc.cpp
@@ -2,13 +2,18 @@
 
 #include "rpc_connection.h"
 #include "yolojson.h"
+#include "backoff.h"
+
 #include "rapidjson/document.h"
 
 #include <stdio.h>
 #include <atomic>
 #include <chrono>
+
+#ifndef DISCORD_DISABLE_IO_THREAD
 #include <condition_variable>
 #include <thread>
+#endif
 
 constexpr size_t MaxMessageSize = 16 * 1024;
 constexpr size_t MessageQueueSize = 8;
@@ -29,6 +34,8 @@ static QueuedMessage SendQueue[MessageQueueSize]{};
 static std::atomic_uint SendQueueNextAdd{0};
 static std::atomic_uint SendQueueNextSend{0};
 static std::atomic_uint SendQueuePendingSends{0};
+static Backoff ReconnectTimeMs(500, 60 * 1000);
+static auto NextConnect{std::chrono::system_clock::now()};
 
 #ifndef DISCORD_DISABLE_IO_THREAD
 static std::atomic_bool KeepRunning{ true };
@@ -37,6 +44,11 @@ static std::condition_variable WaitForIOActivity;
 static std::thread IoThread;
 #endif // DISCORD_DISABLE_IO_THREAD
 
+static void UpdateReconnectTime()
+{
+    NextConnect = std::chrono::system_clock::now() + std::chrono::duration<int64_t, std::milli>{ReconnectTimeMs.nextDelay()};
+}
+
 static QueuedMessage* SendQueueGetNextAddMessage() {
     // if we are falling behind, bail
     if (SendQueuePendingSends.load() >= MessageQueueSize) {
@@ -56,7 +68,10 @@ static void SendQueueCommitMessage() {
 extern "C" void Discord_UpdateConnection()
 {
     if (!Connection->IsOpen()) {
-        Connection->Open();
+        if (std::chrono::system_clock::now() >= NextConnect) {
+            UpdateReconnectTime();
+            Connection->Open();
+        }
     }
     else {
         // reads
@@ -108,11 +123,13 @@ extern "C" void Discord_Initialize(const char* applicationId, DiscordEventHandle
     Connection = RpcConnection::Create(applicationId);
     Connection->onConnect = []() {
         WasJustConnected.exchange(true);
+        ReconnectTimeMs.reset();
     };
     Connection->onDisconnect = [](int err, const char* message) {
         LastErrorCode = err;
         StringCopy(LastErrorMessage, message, sizeof(LastErrorMessage));
         WasJustDisconnected.exchange(true);
+        UpdateReconnectTime();
     };
 
 #ifndef DISCORD_DISABLE_IO_THREAD