in-flight buffer credits

.github/workflows/ci.yml

@@ -55,7 +55,7 @@ jobs:
 
       - name: Install AsyncTCP (ESP32)
         if: ${{ matrix.core == 'esp32:esp32' }}
-        run: ARDUINO_LIBRARY_ENABLE_UNSAFE_INSTALL=true arduino-cli lib install --git-url https://github.com/mathieucarbou/AsyncTCP#v3.2.15
+        run: ARDUINO_LIBRARY_ENABLE_UNSAFE_INSTALL=true arduino-cli lib install --git-url https://github.com/mathieucarbou/AsyncTCP#v3.3.0
 
       - name: Install ESPAsyncTCP (ESP8266)
         if: ${{ matrix.core == 'esp8266:esp8266' }}

README.md

@@ -80,8 +80,8 @@ lib_deps = mathieucarbou/ESPAsyncWebServer @ 3.4.0
 
 **Dependencies:**
 
-- **ESP32 with AsyncTCP**: `mathieucarbou/AsyncTCP @ 3.2.15`
-  Arduino IDE: [https://github.com/mathieucarbou/AsyncTCP#v3.2.15](https://github.com/mathieucarbou/AsyncTCP/releases)
+- **ESP32 with AsyncTCP**: `mathieucarbou/AsyncTCP @ 3.3.0`
+  Arduino IDE: [https://github.com/mathieucarbou/AsyncTCP#v3.3.0](https://github.com/mathieucarbou/AsyncTCP/releases)
 
 - **ESP32 with AsyncTCPSock**: `https://github.com/mathieucarbou/AsyncTCPSock/archive/refs/tags/v1.0.3-dev.zip`
 
@@ -99,7 +99,7 @@ AsyncTCPSock can be used instead of AsyncTCP by excluding AsyncTCP from the libr
 lib_compat_mode = strict
 lib_ldf_mode = chain
 lib_deps =
-  ; mathieucarbou/AsyncTCP @ 3.2.15
+  ; mathieucarbou/AsyncTCP @ 3.3.0
   https://github.com/mathieucarbou/AsyncTCPSock/archive/refs/tags/v1.0.3-dev.zip
   mathieucarbou/ESPAsyncWebServer @ 3.4.0
 lib_ignore =
@@ -116,7 +116,7 @@ Performance of `mathieucarbou/ESPAsyncWebServer @ 3.4.0`:
 > autocannon -c 10 -w 10 -d 20 http://192.168.4.1
 ```
 
-With `mathieucarbou/AsyncTCP @ 3.2.15`
+With `mathieucarbou/AsyncTCP @ 3.3.0`
 
 [![](https://mathieu.carbou.me/ESPAsyncWebServer/perf-c10.png)](https://mathieu.carbou.me/ESPAsyncWebServer/perf-c10.png)
 

docs/index.md

@@ -80,8 +80,8 @@ lib_deps = mathieucarbou/ESPAsyncWebServer @ 3.4.0
 
 **Dependencies:**
 
-- **ESP32 with AsyncTCP**: `mathieucarbou/AsyncTCP @ 3.2.15`
-  Arduino IDE: [https://github.com/mathieucarbou/AsyncTCP#v3.2.15](https://github.com/mathieucarbou/AsyncTCP/releases)
+- **ESP32 with AsyncTCP**: `mathieucarbou/AsyncTCP @ 3.3.0`
+  Arduino IDE: [https://github.com/mathieucarbou/AsyncTCP#v3.3.0](https://github.com/mathieucarbou/AsyncTCP/releases)
 
 - **ESP32 with AsyncTCPSock**: `https://github.com/mathieucarbou/AsyncTCPSock/archive/refs/tags/v1.0.3-dev.zip`
 
@@ -99,7 +99,7 @@ AsyncTCPSock can be used instead of AsyncTCP by excluding AsyncTCP from the libr
 lib_compat_mode = strict
 lib_ldf_mode = chain
 lib_deps =
-  ; mathieucarbou/AsyncTCP @ 3.2.15
+  ; mathieucarbou/AsyncTCP @ 3.3.0
   https://github.com/mathieucarbou/AsyncTCPSock/archive/refs/tags/v1.0.3-dev.zip
   mathieucarbou/ESPAsyncWebServer @ 3.4.0
 lib_ignore =
@@ -116,7 +116,7 @@ Performance of `mathieucarbou/ESPAsyncWebServer @ 3.4.0`:
 > autocannon -c 10 -w 10 -d 20 http://192.168.4.1
 ```
 
-With `mathieucarbou/AsyncTCP @ 3.2.15`
+With `mathieucarbou/AsyncTCP @ 3.3.0`
 
 [![](https://mathieu.carbou.me/ESPAsyncWebServer/perf-c10.png)](https://mathieu.carbou.me/ESPAsyncWebServer/perf-c10.png)
 

library.json

@@ -28,7 +28,7 @@
     {
       "owner": "mathieucarbou",
       "name": "AsyncTCP",
-      "version": "^3.2.15",
+      "version": "^3.3.0",
       "platforms": "espressif32"
     },
     {

platformio.ini

@@ -31,7 +31,7 @@ lib_deps =
   ; bblanchon/ArduinoJson @ 5.13.4
   ; bblanchon/ArduinoJson @ 6.21.5
   bblanchon/ArduinoJson @ 7.2.1
-  mathieucarbou/AsyncTCP @ 3.2.15
+  mathieucarbou/AsyncTCP @ 3.3.0
 board = esp32dev
 board_build.partitions = partitions-4MB.csv
 board_build.filesystem = littlefs
@@ -49,7 +49,7 @@ platform = https://github.com/pioarduino/platform-espressif32/releases/download/
 ; board = esp32-s3-devkitc-1
 ; board = esp32-c6-devkitc-1
 lib_deps = 
-  mathieucarbou/AsyncTCP @ 3.2.15
+  mathieucarbou/AsyncTCP @ 3.3.0
 
 [env:arduino-310]
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/53.03.10-rc3/platform-espressif32.zip
@@ -102,7 +102,7 @@ board = ${sysenv.PIO_BOARD}
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.05/platform-espressif32.zip
 board = ${sysenv.PIO_BOARD}
 lib_deps = 
-  mathieucarbou/AsyncTCP @ 3.2.15
+  mathieucarbou/AsyncTCP @ 3.3.0
 
 [env:ci-arduino-310]
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/53.03.10-rc3/platform-espressif32.zip

src/WebResponseImpl.h

@@ -47,6 +47,10 @@ class AsyncBasicResponse : public AsyncWebServerResponse {
 
 class AsyncAbstractResponse : public AsyncWebServerResponse {
   private:
+    // amount of responce data in-flight, i.e. sent, but not acked yet
+    size_t _in_flight{0};
+    // in-flight queue credits
+    size_t _in_flight_credit{2};
     String _head;
     // Data is inserted into cache at begin().
     // This is inefficient with vector, but if we use some other container,

src/WebResponses.cpp

@@ -352,7 +352,21 @@ size_t AsyncAbstractResponse::_ack(AsyncWebServerRequest* request, size_t len, u
     request->client()->close();
     return 0;
   }
+  // return a credit for each chunk of acked data (polls does not give any credits)
+  if (len)
+    ++_in_flight_credit;
+
+  // for chunked responses ignore acks if there are no _in_flight_credits left
+  if (_chunked && !_in_flight_credit) {
+#ifdef ESP32
+    log_d("(chunk) out of in-flight credits");
+#endif
+    return 0;
+  }
+
   _ackedLength += len;
+  _in_flight -= (_in_flight > len) ? len : _in_flight;
+  // get the size of available sock space
   size_t space = request->client()->space();
 
   size_t headLen = _head.length();
@@ -364,16 +378,31 @@ size_t AsyncAbstractResponse::_ack(AsyncWebServerRequest* request, size_t len, u
       String out = _head.substring(0, space);
       _head = _head.substring(space);
       _writtenLength += request->client()->write(out.c_str(), out.length());
+      _in_flight += out.length();
+      --_in_flight_credit; // take a credit
       return out.length();
     }
   }
 
   if (_state == RESPONSE_CONTENT) {
+    // for response data we need to control the queue and in-flight fragmentation. Sending small chunks could give low latency,
+    // but flood asynctcp's queue and fragment socket buffer space for large responses.
+    // Let's ignore polled acks and acks in case when we have more in-flight data then the available socket buff space.
+    // That way we could balance on having half the buffer in-flight while another half is filling up, while minimizing events in asynctcp q
+    if (_in_flight > space) {
+      // log_d("defer user call %u/%u", _in_flight, space);
+      //  take the credit back since we are ignoring this ack and rely on other inflight data
+      if (len)
+        --_in_flight_credit;
+      return 0;
+    }
+
     size_t outLen;
     if (_chunked) {
       if (space <= 8) {
         return 0;
       }
+
       outLen = space;
     } else if (!_sendContentLength) {
       outLen = space;
@@ -422,6 +451,8 @@ size_t AsyncAbstractResponse::_ack(AsyncWebServerRequest* request, size_t len, u
 
     if (outLen) {
       _writtenLength += request->client()->write((const char*)buf, outLen);
+      _in_flight += outLen;
+      --_in_flight_credit; // take a credit
     }
 
     if (_chunked) {