proxy server: collapse low-priority push notifications

When a device is unreachable (deep doze, offline), FCM queues
non-collapsible messages individually, with a hard limit of 100
pending messages per device. A Jami device that is a member of a few
active swarms receives a sustained stream of connection-churn and
expiration notifications (observed: 27-44/min, ~12k/day), so a phone
suspended for a few tens of minutes is enough to overflow the queue.
Once full, FCM silently drops messages, including the high-priority
notification announcing an incoming call: the callee never wakes up
and the caller gets a timeout after the ICE window (observed in
production, with the call notification never delivered while pushes
sent after the device woke up arrived in under a second).

Mark Android notifications as collapsible (collapse_key) when they
are neither high-priority (calls, messages, invitations - as set by
the client through Value::priority) nor resubscribe requests. While
collapsed messages are pending, FCM only keeps the last one per key,
so routine sync noise can no longer evict actionable notifications.

A single constant key is used instead of one key per DHT listen key:
FCM only honors 4 distinct collapse keys per device, and the Android
client reacts to any low-priority notification the same way (wake up
and resynchronize against the proxy), so finer granularity would not
change client behavior.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/ccpp.yml

@@ -16,7 +16,7 @@ jobs:
     name: Ubuntu/GCC Meson build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
 
       - name: Install Dependencies
         run: |
@@ -40,7 +40,7 @@ jobs:
       matrix:
         cxx_standard: [17, 20, 23]
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
 
       - name: Install Minimal Dependencies
         run: |
@@ -78,7 +78,7 @@ jobs:
         DEBIAN_FRONTEND: noninteractive
 
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
 
       - name: Install Dependencies
         run: |
@@ -131,7 +131,7 @@ jobs:
       matrix:
         cxx_standard: [17, 20, 23]
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
 
       - name: Install Homebrew Dependencies
         run: brew install msgpack-cxx asio gnutls nettle readline fmt jsoncpp argon2 openssl cppunit

.github/workflows/clang-analyzer.yml

@@ -6,7 +6,7 @@ jobs:
     name: Clang Static Analysis
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
       - name: deps
         run: |
           sudo apt update && \

.github/workflows/codeql.yml

@@ -27,7 +27,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v7
+      uses: actions/checkout@v6
 
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v4

.github/workflows/python-wheels.yml

@@ -16,14 +16,14 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, ubuntu-24.04-arm, macos-15]
+        os: [ubuntu-latest, ubuntu-24.04-arm, macos-latest]
 
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
 
       # Run locally with: pipx run cibuildwheel --platform linux python
       - name: Build wheels
-        uses: pypa/cibuildwheel@v4.1.0
+        uses: pypa/cibuildwheel@v3.4.1
         with:
           package-dir: python
 
@@ -36,7 +36,7 @@ jobs:
     name: Build wheels on Windows
     runs-on: windows-latest
     env:
-      VCPKG_VERSION: "2026.06.01"
+      VCPKG_VERSION: "2025.07.25"
       VCPKG_INSTALLATION_ROOT: "C:\\vcpkg"
       VCPKG_DISABLE_METRICS: "1"
       VCPKG_DEFAULT_TRIPLET: x64-windows-release
@@ -44,11 +44,11 @@ jobs:
       VCPKG_DEFAULT_BINARY_CACHE: ${{ github.workspace }}\vcpkg_binary_cache
 
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6
 
       - name: Cache vcpkg installed packages
         id: cache-vcpkg
-        uses: actions/cache@v6
+        uses: actions/cache@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}

.github/workflows/release-package.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -66,7 +66,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -107,7 +107,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -148,7 +148,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -190,7 +190,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -231,7 +231,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -273,7 +273,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v4
@@ -309,7 +309,7 @@ jobs:
     name: Build Windows MSI Installer
     runs-on: windows-latest
     env:
-      VCPKG_VERSION: "2026.06.01"
+      VCPKG_VERSION: "2025.07.25"
       VCPKG_INSTALLATION_ROOT: "C:\\vcpkg"
       VCPKG_DISABLE_METRICS: "1"
       VCPKG_DEFAULT_TRIPLET: x64-windows
@@ -319,7 +319,7 @@ jobs:
       contents: read
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
         with:
           submodules: recursive
 
@@ -334,7 +334,7 @@ jobs:
 
       - name: Cache vcpkg installed packages
         id: cache-vcpkg
-        uses: actions/cache@v6
+        uses: actions/cache@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}
@@ -413,7 +413,7 @@ jobs:
     name: Build Windows dhtnode
     runs-on: windows-latest
     env:
-      VCPKG_VERSION: "2026.06.01"
+      VCPKG_VERSION: "2025.07.25"
       VCPKG_INSTALLATION_ROOT: "C:\\vcpkg"
       VCPKG_DISABLE_METRICS: "1"
       VCPKG_DEFAULT_TRIPLET: x64-windows-static-release
@@ -423,7 +423,7 @@ jobs:
       contents: read
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
         with:
           submodules: recursive
 
@@ -432,7 +432,7 @@ jobs:
 
       - name: Cache vcpkg static installed packages
         id: cache-vcpkg-static
-        uses: actions/cache@v6
+        uses: actions/cache@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}
@@ -499,7 +499,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Download Windows MSI artifact
         uses: actions/download-artifact@v8

.github/workflows/windows-build.yml

@@ -9,7 +9,7 @@ on:
     branches: [ main, master ]
 
 env:
-  VCPKG_VERSION: "2026.06.01"
+  VCPKG_VERSION: "2026.01.16"
   VCPKG_INSTALLATION_ROOT: "C:\\vcpkg"
   VCPKG_DISABLE_METRICS: "1"
   VCPKG_INSTALLED_DIR: ${{ github.workspace }}\vcpkg_installed
@@ -27,7 +27,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up MSVC
         uses: microsoft/setup-msbuild@v3
@@ -41,7 +41,7 @@ jobs:
 
       - name: Cache vcpkg installed packages
         id: cache-vcpkg
-        uses: actions/cache@v6
+        uses: actions/cache@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}
@@ -75,7 +75,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up MSVC
         uses: microsoft/setup-msbuild@v3
@@ -89,7 +89,7 @@ jobs:
 
       - name: Cache vcpkg static installed packages
         id: cache-vcpkg-static
-        uses: actions/cache@v6
+        uses: actions/cache@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}
@@ -125,14 +125,14 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up MSVC
         uses: microsoft/setup-msbuild@v3
 
       - name: Restore vcpkg installed packages
         id: cache-vcpkg-restore
-        uses: actions/cache/restore@v6
+        uses: actions/cache/restore@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}
@@ -202,14 +202,14 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Set up MSVC
         uses: microsoft/setup-msbuild@v3
 
       - name: Restore vcpkg static installed packages
         id: cache-vcpkg-static-restore
-        uses: actions/cache/restore@v6
+        uses: actions/cache/restore@v5
         with:
           path: |
             ${{ env.VCPKG_INSTALLED_DIR }}
@@ -275,7 +275,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
 
       - name: Setup MinGW
         uses: msys2/setup-msys2@v2

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required (VERSION 3.21...4.4)
+cmake_minimum_required (VERSION 3.21...3.31)
 if(POLICY CMP0091)
     cmake_policy(SET CMP0091 NEW)
 endif()
@@ -10,7 +10,7 @@ if(POLICY CMP0167)
 endif()
 
 set (opendht_VERSION_MAJOR 4)
-set (opendht_VERSION_MINOR 1.1)
+set (opendht_VERSION_MINOR 0.0)
 set (opendht_VERSION ${opendht_VERSION_MAJOR}.${opendht_VERSION_MINOR})
 set (PACKAGE_VERSION ${opendht_VERSION})
 set (VERSION "${opendht_VERSION}")

include/opendht/thread_pool.h

@@ -10,9 +10,7 @@
 #include <future>
 #include <functional>
 
-#if __cplusplus < 202002L
-#include <ciso646>
-#endif
+#include <ciso646> // fix windows compiler bug
 
 namespace dht {
 

meson.build

@@ -5,7 +5,7 @@ project(
     'cython',
     license: 'MIT',
     license_files: 'LICENSE',
-    version: '4.1.1',
+    version: '4.0.0',
     meson_version: '>=1.1.0',
     default_options: ['cpp_std=c++20', 'warning_level=3'],
 )
@@ -15,23 +15,10 @@ nettle = dependency('nettle')
 msgpack = dependency('msgpack-cxx', required: false)
 argon2 = dependency('libargon2')
 fmt = dependency('fmt')
-
-proxy_enabled = get_option('proxy_client').enabled() or get_option('proxy_server').enabled()
-
-openssl = dependency('openssl', required: proxy_enabled)
-jsoncpp = dependency('jsoncpp', required: proxy_enabled)
-llhttp = dependency('llhttp', 'libllhttp', required: proxy_enabled)
-simdutf = dependency('simdutf', required: proxy_enabled)
-
-# restinio is a header-only library that may not ship a pkg-config file
-restinio_dep = dependency('restinio', required: false)
-if not restinio_dep.found()
-    cpp = meson.get_compiler('cpp')
-    if cpp.has_header('restinio/all.hpp', required: proxy_enabled)
-        restinio_dep = declare_dependency()
-    endif
-endif
-
+openssl = dependency('openssl', required: get_option('proxy_client'))
+jsoncpp = dependency('jsoncpp', required: get_option('proxy_client'))
+llhttp = dependency('llhttp', 'libllhttp', required: get_option('proxy_client'))
+simdutf = dependency('simdutf', required: get_option('proxy_client'))
 io_uring = host_machine.system() == 'linux' ? dependency('liburing', required: false) : disabler()
 
 deps = [
@@ -46,10 +33,6 @@ deps = [
     llhttp,
 ]
 
-if restinio_dep.found()
-    deps += restinio_dep
-endif
-
 if host_machine.system() == 'linux' and io_uring.found()
     deps += io_uring
 endif
@@ -96,7 +79,7 @@ if get_option('indexation').enabled()
     opendht_src += 'src/indexation/pht.cpp'
     add_project_arguments('-DOPENDHT_INDEXATION', language: 'cpp')
 endif
-if jsoncpp.found() and simdutf.found()
+if jsoncpp.found()
     opendht_src += ['src/base64.cpp']
     add_project_arguments('-DOPENDHT_JSONCPP', language: 'cpp')
     conf_data.set('jsoncpp_lib', ', jsoncpp')

src/dht_proxy_server.cpp

@@ -1267,6 +1267,21 @@ DhtProxyServer::sendPushNotification(
                 Json::Value androidConfig(Json::objectValue);
                 androidConfig["priority"] = priority;
                 androidConfig["ttl"] = "86400s"; // time to live = 24 hours
+                // Make routine sync notifications (connection churn, value
+                // expirations) collapsible: FCM keeps only the last pending
+                // message per collapse key when the device is unreachable
+                // (dozing/offline), while non-collapsible messages pile up in
+                // a 100-message queue. When that queue overflows, FCM silently
+                // drops messages - including the high-priority ones that
+                // announce incoming calls. A single constant key is used
+                // because FCM only honors 4 distinct collapse keys per device
+                // and the Android client reacts to any of these notifications
+                // the same way: wake up and resynchronize against the proxy.
+                // High-priority notifications (calls, messages, invites - see
+                // Value::priority set by the client) and resubscribe requests
+                // remain non-collapsible so none of them can be overwritten.
+                if (!highPriority && !isResubscribe)
+                    androidConfig["collapse_key"] = "sync";
                 notification["android"] = std::move(androidConfig);
             } else {
                 notification["priority"] = priority;

src/dhtrunner.cpp

@@ -99,11 +99,6 @@ DhtRunner::run(const Config& config, Context&& context)
         auto state_path = config.dht_config.node_config.persist_path;
         if (not state_path.empty())
             state_path += "_port.txt";
-        // Ports loaded from the persisted state are a best-effort hint to keep a
-        // stable identity across restarts; remember which ones we set so that we
-        // can fall back to random ports if they are already in use (e.g. a fast
-        // restart while the previous instance still holds them).
-        bool triedSavedPort = false;
         if (not state_path.empty() && (local4.getPort() == 0 || local6.getPort() == 0)) {
             std::ifstream inConfig(state_path);
             if (inConfig.is_open()) {
@@ -115,7 +110,6 @@ DhtRunner::run(const Config& config, Context&& context)
                                               fmt::ptr(this),
                                               port);
                         local4.setPort(port);
-                        triedSavedPort = true;
                     }
                 }
                 if (inConfig >> port) {
@@ -125,7 +119,6 @@ DhtRunner::run(const Config& config, Context&& context)
                                               fmt::ptr(this),
                                               port);
                         local6.setPort(port);
-                        triedSavedPort = true;
                     }
                 }
             }
@@ -143,20 +136,7 @@ DhtRunner::run(const Config& config, Context&& context)
 
         if (config.proxy_server.empty()) {
             if (not context.sock) {
-                try {
-                    context.sock.reset(new net::UdpSocket(local4, local6, context.logger));
-                } catch (const DhtException&) {
-                    if (not triedSavedPort)
-                        throw;
-                    // The saved ports are unavailable (typically still held by a
-                    // previous instance): fall back to OS-assigned ports.
-                    if (context.logger)
-                        context.logger->w("[runner %p] Saved ports unavailable, falling back to random ports",
-                                          fmt::ptr(this));
-                    local4.setPort(0);
-                    local6.setPort(0);
-                    context.sock.reset(new net::UdpSocket(local4, local6, context.logger));
-                }
+                context.sock.reset(new net::UdpSocket(local4, local6, context.logger));
             }
             context.sock->setOnReceive([&](net::PacketList&& pkts) {
                 net::PacketList ret;

src/op_cache.cpp

@@ -224,7 +224,7 @@ SearchCache::expire(const time_point& now, const std::function<void(size_t)>& on
     auto ret = nextExpiration_;
     for (auto it = ops.begin(); it != ops.end();) {
         auto expiration = it->second->getExpiration();
-        if (expiration <= now) {
+        if (expiration < now) {
             auto cache = std::move(it->second);
             it = ops.erase(it);
             onCancel(cache->searchToken);

src/thread_pool.cpp

@@ -6,10 +6,8 @@
 #include <atomic>
 #include <thread>
 #include <iostream>
-#include <cmath> // std::pow
-#if __cplusplus < 202002L
-#include <ciso646>
-#endif
+#include <ciso646> // fix windows compiler bug
+#include <cmath>   // std::pow
 
 namespace dht {
 

src/value.cpp

@@ -202,9 +202,6 @@ Value::Value(const Json::Value& json)
     const auto& jprio = json["prio"];
     if (jprio.isIntegral())
         priority = jprio.asUInt();
-    const auto& jpt = json[VALUE_KEY_PUSHTYPE];
-    if (jpt.isString())
-        pushType = jpt.asString();
 }
 
 Json::Value
@@ -231,8 +228,6 @@ Value::toJson() const
     }
     if (priority)
         val["prio"] = priority;
-    if (not pushType.empty())
-        val[VALUE_KEY_PUSHTYPE] = pushType;
     return val;
 }
 

tests/test_dhtrunner.cpp

@@ -9,8 +9,6 @@
 #include <future>
 #include <mutex>
 #include <condition_variable>
-#include <fstream>
-#include <cstdio>
 using namespace std::chrono_literals;
 using namespace std::literals;
 
@@ -542,34 +540,6 @@ DhtRunnerTester::testShutdownCompletesWithPendingPut()
     clientNode.join();
 }
 
-void
-DhtRunnerTester::testSavedPortFallback()
-{
-    // A saved port that is already taken by another process (e.g. fast
-    // application restart while the old instance still holds it) must not
-    // prevent the node from starting: it should fall back to a random port.
-    dht::DhtRunner::Config config;
-    config.dht_config.node_config.persist_path = "/tmp/opendht_test_port_fallback";
-    std::string portFile = config.dht_config.node_config.persist_path + "_port.txt";
-
-    // node1 (from setUp) holds a port; save it as our persisted port.
-    auto takenPort = node1.getBoundPort();
-    {
-        std::ofstream out(portFile);
-        out << takenPort << std::endl << takenPort << std::endl;
-    }
-
-    dht::DhtRunner testNode;
-    CPPUNIT_ASSERT_NO_THROW(testNode.run(0, config));
-    CPPUNIT_ASSERT(testNode.getBoundPort());
-    CPPUNIT_ASSERT(testNode.getBoundPort() != takenPort);
-
-    testNode.shutdown();
-    testNode.join();
-    std::remove(portFile.c_str());
-    std::remove((config.dht_config.node_config.persist_path + "_port.txt").c_str());
-}
-
 void
 DhtRunnerTester::testListen()
 {

tests/test_dhtrunner.h

@@ -27,7 +27,6 @@ class DhtRunnerTester : public CppUnit::TestFixture
     CPPUNIT_TEST(testBootstrapThenPutNoRace);
     CPPUNIT_TEST(testBootstrapMissingNodeThenPutFails);
     CPPUNIT_TEST(testShutdownCompletesWithPendingPut);
-    CPPUNIT_TEST(testSavedPortFallback);
     CPPUNIT_TEST_SUITE_END();
 
     dht::DhtRunner node1 {};
@@ -73,7 +72,6 @@ public:
     void testBootstrapThenPutNoRace();
     void testBootstrapMissingNodeThenPutFails();
     void testShutdownCompletesWithPendingPut();
-    void testSavedPortFallback();
     /**
      * Test listen method with lot of datas
      */

tests/test_value.cpp

@@ -137,29 +137,4 @@ ValueTester::testPushTypePreservedAfterEncrypt()
     CPPUNIT_ASSERT(encrypted.isEncrypted());
 }
 
-void
-ValueTester::testPushTypeJsonRoundTrip()
-{
-#ifdef OPENDHT_JSONCPP
-    dht::Value original {(const uint8_t*) "hello", 5};
-    original.id = 42;
-    original.priority = 1;
-    original.pushType = "videoCall";
-
-    dht::Value restored(original.toJson());
-
-    CPPUNIT_ASSERT_EQUAL(original.id, restored.id);
-    CPPUNIT_ASSERT_EQUAL(original.priority, restored.priority);
-    CPPUNIT_ASSERT_EQUAL(original.pushType, restored.pushType);
-
-    // No pushType: the field must stay absent from the JSON and empty after parse.
-    dht::Value plain {(const uint8_t*) "data", 4};
-    plain.id = 7;
-    auto json = plain.toJson();
-    CPPUNIT_ASSERT(!json.isMember("pt"));
-    dht::Value plainRestored(json);
-    CPPUNIT_ASSERT_EQUAL(std::string(), plainRestored.pushType);
-#endif
-}
-
 } // namespace test

tests/test_value.h

@@ -16,7 +16,6 @@ class ValueTester : public CppUnit::TestFixture
     CPPUNIT_TEST(testPushTypeMsgpackRoundTrip);
     CPPUNIT_TEST(testPushTypeAbsentAfterUnpack);
     CPPUNIT_TEST(testPushTypePreservedAfterEncrypt);
-    CPPUNIT_TEST(testPushTypeJsonRoundTrip);
     CPPUNIT_TEST_SUITE_END();
 
 public:
@@ -39,7 +38,6 @@ public:
     void testPushTypeMsgpackRoundTrip();
     void testPushTypeAbsentAfterUnpack();
     void testPushTypePreservedAfterEncrypt();
-    void testPushTypeJsonRoundTrip();
 };
 
 } // namespace test

vcpkg-configuration.json

@@ -1,7 +1,7 @@
 {
   "default-registry": {
     "kind": "git",
-    "baseline": "f3e10653cc27d62a37a3763cd84b38bca07c6075",
+    "baseline": "66c0373dc7fca549e5803087b9487edfe3aca0a1",
     "repository": "https://github.com/microsoft/vcpkg"
   },
   "registries": [

vcpkg.json

@@ -1,6 +1,6 @@
 {
   "name": "opendht",
-  "version-string": "4.1.1",
+  "version-string": "4.0.0",
   "port-version": 1,
   "description": "OpenDHT: A lightweight C++17 Distributed Hash Table library.",
   "homepage": "https://opendht.net",