From e1771fa7de1864727fcebf151e7cf81bdd0e5732 Mon Sep 17 00:00:00 2001
From: Andrea Cavalli <andrea@cavallium.it>
Date: Sun, 21 Mar 2021 00:27:18 +0100
Subject: [PATCH] Add an experimental option to delay get_channel_difference

---
 README.md                       |  2 ++
 td/telegram/MessagesManager.cpp | 21 ++++++++++++++++++++-
 td/telegram/MessagesManager.h   |  6 ++++--
 td/telegram/Td.cpp              |  5 +++++
 4 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 26a226abc..47e67aa9a 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,8 @@ We added some options:
 * **delete_file_reference_after_seconds** (positive number) During cleanup, free the memory of the files that have not been touched for more than X seconds
 * **experiment_enable_file_reference_cleanup** (**true**/false) During cleanup, free the memory of the file references
 * **experiment_enable_chat_access_hash_cleanup** (**true**/false) During cleanup, clean chats and channels access hash
+* **get_channel_difference_delay_milliseconds** (**0**) Delay get_channel_difference n milliseconds every ~3000pts (~300msg).
+    Don't modify this option unless you have a very large bot that struggles to keep up with start-up updates throughput.
 
 ## Custom API functions
 ### TdApi.OptimizeMemory
diff --git a/td/telegram/MessagesManager.cpp b/td/telegram/MessagesManager.cpp
index ac4b49f1a..7ea99f7bd 100644
--- a/td/telegram/MessagesManager.cpp
+++ b/td/telegram/MessagesManager.cpp
@@ -35641,6 +35641,23 @@ class MessagesManager::GetChannelDifferenceLogEvent {
   }
 };
 
+void MessagesManager::get_channel_difference_delayed(DialogId dialog_id, int32 pts,
+                                             bool force, double delay_seconds, const char *source) {
+  if (delay_seconds <= 0.0) {
+    // Execute get_channel_difference immediatly
+    get_channel_difference(dialog_id,pts, force, "on_get_channel_difference");
+  } else {
+    // Schedule get_channel_difference
+    create_actor<SleepActor>(
+        "GetChannelDifferenceDelayedActor", delay_seconds,
+        PromiseCreator::lambda([actor_id = actor_id(this), dialog_id, pts, force](Result<Unit> result) {
+          send_closure(actor_id, &MessagesManager::get_channel_difference, dialog_id, pts, force,
+                       "on_get_channel_difference");
+        }))
+        .release();
+  }
+}
+
 void MessagesManager::get_channel_difference(DialogId dialog_id, int32 pts, bool force, const char *source) {
   if (channel_get_difference_retry_timeout_.has_timeout(dialog_id.get())) {
     LOG(INFO) << "Skip running channels.getDifference for " << dialog_id << " from " << source
@@ -36057,7 +36074,9 @@ void MessagesManager::on_get_channel_difference(
 
   if (!is_final) {
     LOG_IF(ERROR, timeout > 0) << "Have timeout in not final ChannelDifference in " << dialog_id;
-    get_channel_difference(dialog_id, d->pts, true, "on_get_channel_difference");
+    auto delay_seconds = static_cast<double>(G()->shared_config()
+                                  .get_option_integer("get_channel_difference_delay_milliseconds", 0)) / 1000.0;
+    get_channel_difference_delayed(dialog_id, d->pts, true, delay_seconds, "on_get_channel_difference");
     return;
   }
 
diff --git a/td/telegram/MessagesManager.h b/td/telegram/MessagesManager.h
index a76aa53ce..b04aa62b2 100644
--- a/td/telegram/MessagesManager.h
+++ b/td/telegram/MessagesManager.h
@@ -1646,8 +1646,8 @@ class MessagesManager : public Actor {
   static constexpr int32 MAX_SEARCH_MESSAGES = 100;                // server side limit
   static constexpr int32 MIN_SEARCH_PUBLIC_DIALOG_PREFIX_LEN = 4;  // server side limit
   static constexpr int32 MIN_CHANNEL_DIFFERENCE = 10;
-  static constexpr int32 MAX_CHANNEL_DIFFERENCE = 100;
-  static constexpr int32 MAX_BOT_CHANNEL_DIFFERENCE = 100000;   // server side limit
+  static constexpr int32 MAX_BOT_CHANNEL_DIFFERENCE = 1000000;   // server side limit
+  static constexpr int32 MAX_CHANNEL_DIFFERENCE = MAX_BOT_CHANNEL_DIFFERENCE;
   static constexpr int32 MAX_RECENTLY_FOUND_DIALOGS = 30;       // some reasonable value
   static constexpr size_t MAX_TITLE_LENGTH = 128;               // server side limit for chat title
   static constexpr size_t MAX_DESCRIPTION_LENGTH = 255;         // server side limit for chat description
@@ -2774,6 +2774,8 @@ class MessagesManager : public Actor {
 
   void on_channel_get_difference_timeout(DialogId dialog_id);
 
+  void get_channel_difference_delayed(DialogId dialog_id, int32 pts, bool force, double timeout, const char *source);
+
   void get_channel_difference(DialogId dialog_id, int32 pts, bool force, const char *source);
 
   void do_get_channel_difference(DialogId dialog_id, int32 pts, bool force,
diff --git a/td/telegram/Td.cpp b/td/telegram/Td.cpp
index 0d32b3111..cb5fa9533 100644
--- a/td/telegram/Td.cpp
+++ b/td/telegram/Td.cpp
@@ -7462,6 +7462,11 @@ void Td::on_request(uint64 id, td_api::setOption &request) {
         return;
       }
       break;
+    case 'g':
+      if (set_integer_option("get_channel_difference_delay_milliseconds")) {
+        return;
+      }
+      break;
     case 'i':
       if (set_boolean_option("ignore_background_updates")) {
         return;