Add 3.8 Tests and force fork strategy (#42)

* add python 3.8 tests

* fix wheel link

* lint

* try

* add force

* lint

Co-authored-by: Kai Fricke <krfricke@users.noreply.github.com>

Author: amogkam

.github/workflows/test.yaml

@@ -6,7 +6,6 @@ jobs:
   test_lint:
     runs-on: ubuntu-latest
     timeout-minutes: 3
-
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python 3.7
@@ -25,18 +24,25 @@ jobs:
   test_linux_ray_master:
     runs-on: ubuntu-latest
     timeout-minutes: 12
-
+    strategy:
+      matrix:
+        python-version: [3.7, 3.8]
+        include:
+          - python-version: 3.7
+            ray-wheel: https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-1.2.0.dev0-cp37-cp37m-manylinux2014_x86_64.whl
+          - python-version: 3.8
+            ray-wheel: https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-1.2.0.dev0-cp38-cp38-manylinux2014_x86_64.whl
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.7
+    - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with:
-        python-version: 3.7
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
         python -m pip install codecov
-        python -m pip install -U https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-1.2.0.dev0-cp37-cp37m-manylinux2014_x86_64.whl
+        python -m pip install -U ${{ matrix.ray-wheel }}
         if [ -f requirements-test.txt ]; then python -m pip install -r requirements-test.txt; fi
     - name: Install package
       run: |
@@ -63,13 +69,15 @@ jobs:
   test_linux_ray_release:
     runs-on: ubuntu-latest
     timeout-minutes: 12
-
+    strategy:
+      matrix:
+        python-version: [3.7, 3.8]
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.7
+    - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with:
-        python-version: 3.7
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
@@ -103,13 +111,15 @@ jobs:
     # Test runs on latest ray release
     runs-on: ubuntu-latest
     timeout-minutes: 12
-
+    strategy:
+      matrix:
+        python-version: [3.7, 3.8]
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.7
+    - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v2
       with:
-        python-version: 3.7
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip

xgboost_ray/main.py

@@ -99,6 +99,12 @@ class _RabitTracker(xgb.RabitTracker):
     """
 
     def start(self, nslave):
+        # TODO: refactor RabitTracker to support spawn process creation.
+        # In python 3.8, spawn is used as default process creation on macOS.
+        # But spawn doesn't work because `run` is not pickleable.
+        # For now we force the start method to use fork.
+        multiprocessing.set_start_method("fork", force=True)
+
         def run():
             self.accept_slaves(nslave)