Work with IPv6 in the new tracker.

include/xgboost/collective/socket.h

@@ -436,28 +436,38 @@ class TCPSocket {
    * \brief Accept new connection, returns a new TCP socket for the new connection.
    */
   TCPSocket Accept() {
-    HandleT newfd = accept(Handle(), nullptr, nullptr);
+    SockAddress addr;
+    TCPSocket newsock;
+    auto rc = this->Accept(&newsock, &addr);
+    SafeColl(rc);
+    return newsock;
+  }
+
+  [[nodiscard]] Result Accept(TCPSocket *out, SockAddress *addr) {
 #if defined(_WIN32)
     auto interrupt = WSAEINTR;
 #else
     auto interrupt = EINTR;
 #endif
-    if (newfd == InvalidSocket() && system::LastError() != interrupt) {
-      system::ThrowAtError("accept");
-    }
-    TCPSocket newsock{newfd};
-    return newsock;
-  }
-
-  [[nodiscard]] Result Accept(TCPSocket *out, SockAddrV4 *addr) {
-    struct sockaddr_in caddr;
-    socklen_t caddr_len = sizeof(caddr);
-    HandleT newfd = accept(Handle(), reinterpret_cast<sockaddr *>(&caddr), &caddr_len);
-    if (newfd == InvalidSocket()) {
-      return system::FailWithCode("Failed to accept.");
+    if (this->Domain() == SockDomain::kV4) {
+      struct sockaddr_in caddr;
+      socklen_t caddr_len = sizeof(caddr);
+      HandleT newfd = accept(Handle(), reinterpret_cast<sockaddr *>(&caddr), &caddr_len);
+      if (newfd == InvalidSocket() && system::LastError() != interrupt) {
+        return system::FailWithCode("Failed to accept.");
+      }
+      *addr = SockAddress{SockAddrV4{caddr}};
+      *out = TCPSocket{newfd};
+    } else {
+      struct sockaddr_in6 caddr;
+      socklen_t caddr_len = sizeof(caddr);
+      HandleT newfd = accept(Handle(), reinterpret_cast<sockaddr *>(&caddr), &caddr_len);
+      if (newfd == InvalidSocket() && system::LastError() != interrupt) {
+        return system::FailWithCode("Failed to accept.");
+      }
+      *addr = SockAddress{SockAddrV6{caddr}};
+      *out = TCPSocket{newfd};
     }
-    *addr = SockAddrV4{caddr};
-    *out = TCPSocket{newfd};
     return Success();
   }
 

python-package/xgboost/testing/__init__.py

@@ -429,8 +429,8 @@ def make_categorical(
     categories = np.arange(0, n_categories)
     for col in df.columns:
         if rng.binomial(1, cat_ratio, size=1)[0] == 1:
-            df[col] = df[col].astype("category")
-            df[col] = df[col].cat.set_categories(categories)
+            df.loc[:, col] = df[col].astype("category")
+            df.loc[:, col] = df[col].cat.set_categories(categories)
 
     if sparsity > 0.0:
         for i in range(n_features):

src/collective/coll.cc

@@ -1,12 +1,13 @@
 /**
- * Copyright 2023, XGBoost Contributors
+ * Copyright 2023-2024, XGBoost Contributors
  */
 #include "coll.h"
 
 #include <algorithm>    // for min, max, copy_n
 #include <cstddef>      // for size_t
 #include <cstdint>      // for int8_t, int64_t
 #include <functional>   // for bit_and, bit_or, bit_xor, plus
+#include <string>       // for string
 #include <type_traits>  // for is_floating_point_v, is_same_v
 #include <utility>      // for move
 
@@ -56,6 +57,8 @@ bool constexpr IsFloatingPointV() {
     return cpu_impl::RingAllreduce(comm, data, erased_fn, type);
   };
 
+  std::string msg{"Floating point is not supported for bit wise collective operations."};
+
   auto rc = DispatchDType(type, [&](auto t) {
     using T = decltype(t);
     switch (op) {
@@ -70,21 +73,21 @@ bool constexpr IsFloatingPointV() {
       }
       case Op::kBitwiseAND: {
         if constexpr (IsFloatingPointV<T>()) {
-          return Fail("Invalid type.");
+          return Fail(msg);
         } else {
           return fn(std::bit_and<>{}, t);
         }
       }
       case Op::kBitwiseOR: {
         if constexpr (IsFloatingPointV<T>()) {
-          return Fail("Invalid type.");
+          return Fail(msg);
         } else {
           return fn(std::bit_or<>{}, t);
         }
       }
       case Op::kBitwiseXOR: {
         if constexpr (IsFloatingPointV<T>()) {
-          return Fail("Invalid type.");
+          return Fail(msg);
         } else {
           return fn(std::bit_xor<>{}, t);
         }

src/collective/comm.cc

@@ -75,9 +75,11 @@ Result ConnectTrackerImpl(proto::PeerInfo info, std::chrono::seconds timeout, st
   } << [&] {
     return next->NonBlocking(true);
   } << [&] {
-    SockAddrV4 addr;
+    SockAddress addr;
     return listener->Accept(prev.get(), &addr);
-  } << [&] { return prev->NonBlocking(true); };
+  } << [&] {
+    return prev->NonBlocking(true);
+  };
   if (!rc.OK()) {
     return rc;
   }
@@ -157,10 +159,13 @@ Result ConnectTrackerImpl(proto::PeerInfo info, std::chrono::seconds timeout, st
   }
 
   for (std::int32_t r = 0; r < comm.Rank(); ++r) {
-    SockAddrV4 addr;
     auto peer = std::shared_ptr<TCPSocket>(TCPSocket::CreatePtr(comm.Domain()));
-    rc = std::move(rc) << [&] { return listener->Accept(peer.get(), &addr); }
-                       << [&] { return peer->RecvTimeout(timeout); };
+    rc = std::move(rc) << [&] {
+      SockAddress addr;
+      return listener->Accept(peer.get(), &addr);
+    } << [&] {
+      return peer->RecvTimeout(timeout);
+    };
     if (!rc.OK()) {
       return rc;
     }
@@ -187,7 +192,9 @@ RabitComm::RabitComm(std::string const& host, std::int32_t port, std::chrono::se
     : HostComm{std::move(host), port, timeout, retry, std::move(task_id)},
       nccl_path_{std::move(nccl_path)} {
   auto rc = this->Bootstrap(timeout_, retry_, task_id_);
-  CHECK(rc.OK()) << rc.Report();
+  if (!rc.OK()) {
+    SafeColl(Fail("Failed to bootstrap the communication group.", std::move(rc)));
+  }
 }
 
 #if !defined(XGBOOST_USE_NCCL)
@@ -247,18 +254,20 @@ Comm* RabitComm::MakeCUDAVar(Context const*, std::shared_ptr<Coll>) const {
   // get ring neighbors
   std::string snext;
   tracker.Recv(&snext);
+  if (!rc.OK()) {
+    return Fail("Failed to receive the rank for the next worker.", std::move(rc));
+  }
   auto jnext = Json::Load(StringView{snext});
 
   proto::PeerInfo ninfo{jnext};
-
   // get the rank of this worker
   this->rank_ = BootstrapPrev(ninfo.rank, world);
   this->tracker_.rank = rank_;
 
   std::vector<std::shared_ptr<TCPSocket>> workers;
   rc = ConnectWorkers(*this, &listener, lport, ninfo, timeout, retry, &workers);
   if (!rc.OK()) {
-    return rc;
+    return Fail("Failed to connect to other workers.", std::move(rc));
   }
 
   CHECK(this->channels_.empty());

src/collective/tracker.cc

@@ -1,5 +1,5 @@
 /**
- * Copyright 2023, XGBoost Contributors
+ * Copyright 2023-2024, XGBoost Contributors
  */
 #if defined(__unix__) || defined(__APPLE__)
 #include <netdb.h>       // gethostbyname
@@ -27,12 +27,14 @@
 #include "tracker.h"
 #include "xgboost/collective/result.h"  // for Result, Fail, Success
 #include "xgboost/collective/socket.h"  // for GetHostName, FailWithCode, MakeSockAddress, ...
-#include "xgboost/json.h"
+#include "xgboost/json.h"               // for Json
 
 namespace xgboost::collective {
 Tracker::Tracker(Json const& config)
-    : n_workers_{static_cast<std::int32_t>(
-          RequiredArg<Integer const>(config, "n_workers", __func__))},
+    : sortby_{static_cast<SortBy>(
+          OptionalArg<Integer const>(config, "sortby", static_cast<Integer::Int>(SortBy::kHost)))},
+      n_workers_{
+          static_cast<std::int32_t>(RequiredArg<Integer const>(config, "n_workers", __func__))},
       port_{static_cast<std::int32_t>(OptionalArg<Integer const>(config, "port", Integer::Int{0}))},
       timeout_{std::chrono::seconds{OptionalArg<Integer const>(
           config, "timeout", static_cast<std::int64_t>(collective::DefaultTimeoutSec()))}} {}
@@ -56,13 +58,15 @@ Result Tracker::WaitUntilReady() const {
   return Success();
 }
 
-RabitTracker::WorkerProxy::WorkerProxy(std::int32_t world, TCPSocket sock, SockAddrV4 addr)
+RabitTracker::WorkerProxy::WorkerProxy(std::int32_t world, TCPSocket sock, SockAddress addr)
     : sock_{std::move(sock)} {
   std::int32_t rank{0};
   Json jcmd;
   std::int32_t port{0};
 
-  rc_ = Success() << [&] { return proto::Magic{}.Verify(&sock_); } << [&] {
+  rc_ = Success() << [&] {
+    return proto::Magic{}.Verify(&sock_);
+  } << [&] {
     return proto::Connect{}.TrackerRecv(&sock_, &world_, &rank, &task_id_);
   } << [&] {
     std::string cmd;
@@ -83,28 +87,33 @@ RabitTracker::WorkerProxy::WorkerProxy(std::int32_t world, TCPSocket sock, SockA
     }
     return Success();
   } << [&] {
-    auto host = addr.Addr();
-    info_ = proto::PeerInfo{host, port, rank};
+    if (addr.IsV4()) {
+      auto host = addr.V4().Addr();
+      info_ = proto::PeerInfo{host, port, rank};
+    } else {
+      auto host = addr.V6().Addr();
+      info_ = proto::PeerInfo{host, port, rank};
+    }
     return Success();
   };
 }
 
 RabitTracker::RabitTracker(Json const& config) : Tracker{config} {
   std::string self;
   auto rc = collective::GetHostAddress(&self);
-  auto host = OptionalArg<String>(config, "host", self);
+  host_ = OptionalArg<String>(config, "host", self);
 
-  host_ = host;
-  listener_ = TCPSocket::Create(SockDomain::kV4);
-  rc = listener_.Bind(host, &this->port_);
-  CHECK(rc.OK()) << rc.Report();
+  auto addr = MakeSockAddress(xgboost::StringView{host_}, 0);
+  listener_ = TCPSocket::Create(addr.IsV4() ? SockDomain::kV4 : SockDomain::kV6);
+  rc = listener_.Bind(host_, &this->port_);
+  SafeColl(rc);
   listener_.Listen();
 }
 
 Result RabitTracker::Bootstrap(std::vector<WorkerProxy>* p_workers) {
   auto& workers = *p_workers;
 
-  std::sort(workers.begin(), workers.end(), WorkerCmp{});
+  std::sort(workers.begin(), workers.end(), WorkerCmp{this->sortby_});
 
   std::vector<std::thread> bootstrap_threads;
   for (std::int32_t r = 0; r < n_workers_; ++r) {
@@ -224,7 +233,7 @@ Result RabitTracker::Bootstrap(std::vector<WorkerProxy>* p_workers) {
 
     while (state.ShouldContinue()) {
       TCPSocket sock;
-      SockAddrV4 addr;
+      SockAddress addr;
       this->ready_ = true;
       auto rc = listener_.Accept(&sock, &addr);
       if (!rc.OK()) {
@@ -291,7 +300,7 @@ Result RabitTracker::Bootstrap(std::vector<WorkerProxy>* p_workers) {
 
 [[nodiscard]] Json RabitTracker::WorkerArgs() const {
   auto rc = this->WaitUntilReady();
-  CHECK(rc.OK()) << rc.Report();
+  SafeColl(rc);
 
   Json args{Object{}};
   args["DMLC_TRACKER_URI"] = String{host_};

src/collective/tracker.h

@@ -1,5 +1,5 @@
 /**
- * Copyright 2023, XGBoost Contributors
+ * Copyright 2023-2024, XGBoost Contributors
  */
 #pragma once
 #include <chrono>   // for seconds
@@ -36,6 +36,16 @@ namespace xgboost::collective {
  *     signal an error to the tracker and the tracker will notify other workers.
  */
 class Tracker {
+ protected:
+  // How to sort the workers, either by host name or by task ID. When using a multi-GPU
+  // setting, multiple workers can occupy the same host, in which case one should sort
+  // workers by task. Due to compatibility reason, the task ID is not always available, so
+  // we use host as the default.
+  enum class SortBy : std::int8_t {
+    kHost = 0,
+    kTask = 1,
+  } sortby_;
+
  protected:
   std::int32_t n_workers_{0};
   std::int32_t port_{-1};
@@ -76,7 +86,7 @@ class RabitTracker : public Tracker {
     Result rc_;
 
    public:
-    explicit WorkerProxy(std::int32_t world, TCPSocket sock, SockAddrV4 addr);
+    explicit WorkerProxy(std::int32_t world, TCPSocket sock, SockAddress addr);
     WorkerProxy(WorkerProxy const& that) = delete;
     WorkerProxy(WorkerProxy&& that) = default;
     WorkerProxy& operator=(WorkerProxy const&) = delete;
@@ -96,11 +106,14 @@ class RabitTracker : public Tracker {
 
     void Send(StringView value) { this->sock_.Send(value); }
   };
-  // provide an ordering for workers, this helps us get deterministic topology.
+  // Provide an ordering for workers, this helps us get deterministic topology.
   struct WorkerCmp {
+    SortBy sortby;
+    explicit WorkerCmp(SortBy sortby) : sortby{sortby} {}
+
     [[nodiscard]] bool operator()(WorkerProxy const& lhs, WorkerProxy const& rhs) {
-      auto const& lh = lhs.Host();
-      auto const& rh = rhs.Host();
+      auto const& lh = sortby == Tracker::SortBy::kHost ? lhs.Host() : lhs.TaskID();
+      auto const& rh = sortby == Tracker::SortBy::kHost ? rhs.Host() : rhs.TaskID();
 
       if (lh != rh) {
         return lh < rh;

src/learner.cc

@@ -18,7 +18,6 @@
 #include <cstdint>                        // for int32_t, uint32_t, int64_t, uint64_t
 #include <cstdlib>                        // for atoi
 #include <cstring>                        // for memcpy, size_t, memset
-#include <functional>                     // for less
 #include <iomanip>                        // for operator<<, setiosflags
 #include <iterator>                       // for back_insert_iterator, distance, back_inserter
 #include <limits>                         // for numeric_limits

tests/ci_build/Dockerfile.gpu

@@ -25,7 +25,7 @@ RUN \
     mamba create -n gpu_test -c rapidsai-nightly -c rapidsai -c nvidia -c conda-forge -c defaults \
         python=3.10 cudf=$RAPIDS_VERSION_ARG* rmm=$RAPIDS_VERSION_ARG* cudatoolkit=$CUDA_VERSION_ARG \
         nccl>=$(cut -d "-" -f 1 << $NCCL_VERSION_ARG) \
-        dask \
+        dask=2024.1.1 \
         dask-cuda=$RAPIDS_VERSION_ARG* dask-cudf=$RAPIDS_VERSION_ARG* cupy \
         numpy pytest pytest-timeout scipy scikit-learn pandas matplotlib wheel python-kubernetes urllib3 graphviz hypothesis \
         pyspark>=3.4.0 cloudpickle cuda-python && \

tests/test_distributed/test_gpu_with_dask/test_gpu_with_dask.py

@@ -252,7 +252,7 @@ def test_categorical(self, local_cuda_client: Client) -> None:
 
         X_onehot, _ = make_categorical(local_cuda_client, 10000, 30, 13, True)
         X_onehot = dask_cudf.from_dask_dataframe(X_onehot)
-        run_categorical(local_cuda_client, "gpu_hist", X, X_onehot, y)
+        run_categorical(local_cuda_client, "hist", "cuda", X, X_onehot, y)
 
     @given(
         params=hist_parameter_strategy,