fix #1015 / linux: have swap_memory() rely on /proc fs instead of sys…

…info() syscall in order to be nice with Linux containers such as Docker and Heroku

.ci/travis/install.sh

@@ -51,4 +51,4 @@ elif [[ $TRAVIS_PYTHON_VERSION == '3.3' ]] || [[ $PYVER == 'py33' ]]; then
     pip install -U ipaddress
 fi
 
-pip install -U coverage coveralls flake8 pep8 setuptools
+pip install --upgrade coverage coveralls flake8 pep8 setuptools

.ci/travis/run.sh

@@ -24,10 +24,10 @@ else
     python psutil/tests/runner.py
 fi
 
-if [ "$PYVER" == "2.7" ] || [ "$PYVER" == "3.5" ]; then
-    # run mem leaks test
+# Run memory leak tests and linter only on Linux and latest major Python
+# versions.
+if [ "$PYVER" == "2.7" ] || [ "$PYVER" == "3.6" ]; then
     python psutil/tests/test_memory_leaks.py
-    # run linter (on Linux only)
     if [[ "$(uname -s)" != 'Darwin' ]]; then
         python -m flake8
     fi

.travis.yml

@@ -10,30 +10,18 @@ matrix:
         - python: 3.5
         - python: 3.6
         - "pypy"
-        # XXX - commented because OSX builds are deadly slow
-        # - language: generic
-        #   os: osx
-        #   env: PYVER=py26
         - language: generic
           os: osx
           env: PYVER=py27
-        # XXX - commented because OSX builds are deadly slow
-        # - language: generic
-        #   os: osx
-        #   env: PYVER=py33
         - language: generic
           os: osx
           env: PYVER=py34
-        # XXX - not supported yet
-        # - language: generic
-        #   os: osx
-        #   env: PYVER=py35
 install:
     - ./.ci/travis/install.sh
 script:
     - ./.ci/travis/run.sh
 after_success:
-    # upload reports to coveralls.io
+    # upload test reports to coveralls.io
     - |
         if [ "$(uname -s)" != 'Darwin' ]; then
             coveralls

HISTORY.rst

@@ -5,6 +5,12 @@
 5.2.3
 =====
 
+**Enhancements**
+
+- 1015_: swap_memory() now relies on /proc/meminfo instead of sysinfo() syscall
+  so that it can be used in conjunction with PROCFS_PATH in order to retrieve
+  memory info about Linux containers such as Docker and Heroku.
+
 **Bug fixes**
 
 - 1014_: Linux can mask legitimate ENOENT exceptions as NoSuchProcess.

docs/index.rst

@@ -302,6 +302,11 @@ Memory
     >>> psutil.swap_memory()
     sswap(total=2097147904L, used=886620160L, free=1210527744L, percent=42.3, sin=1050411008, sout=1906720768)
 
+  .. versionchanged:: 5.2.3 on Linux this function relies on /proc fs instead
+     of sysinfo() syscall so that it can be used in conjunction with
+     :const:`psutil.PROCFS_PATH` in order to retrieve memory info about
+     Linux containers such as Docker and Heroku.
+
 Disks
 -----
 
@@ -1979,9 +1984,18 @@ Constants
 .. _const-procfs_path:
 .. data:: PROCFS_PATH
 
-  The path of the /proc filesystem on Linux and Solaris (defaults to "/proc").
+  The path of the /proc filesystem on Linux and Solaris (defaults to
+  ``"/proc"``).
   You may want to re-set this constant right after importing psutil in case
-  your /proc filesystem is mounted elsewhere.
+  your /proc filesystem is mounted elsewhere or if you want to retrieve
+  information about Linux containers such as
+  `Docker <https://www.docker.io/>`__,
+  `Heroku <https://www.heroku.com/>`__ or
+  `LXC <https://linuxcontainers.org/>`__ (see
+  `here <https://fabiokung.com/2014/03/13/memory-inside-linux-containers/>`__
+  for more info).
+  It must be noted that this trick works only for APIs which rely on /proc
+  filesystem (e.g. `memory`_ APIs and most :class:`Process` class methods).
 
   Availability: Linux, Solaris
 

psutil/_pslinux.py

@@ -489,9 +489,23 @@ def virtual_memory():
 
 def swap_memory():
     """Return swap memory metrics."""
-    _, _, _, _, total, free, unit_multiplier = cext.linux_sysinfo()
-    total *= unit_multiplier
-    free *= unit_multiplier
+    mems = {}
+    with open_binary('%s/meminfo' % get_procfs_path()) as f:
+        for line in f:
+            fields = line.split()
+            mems[fields[0]] = int(fields[1]) * 1024
+    # We prefer /proc/meminfo over sysinfo() syscall so that
+    # psutil.PROCFS_PATH can be used in order to allow retrieval
+    # for linux containers, see:
+    # https://github.com/giampaolo/psutil/issues/1015
+    try:
+        total = mems['SwapTotal:']
+        free = mems['SwapFree:']
+    except KeyError:
+        _, _, _, _, total, free, unit_multiplier = cext.linux_sysinfo()
+        total *= unit_multiplier
+        free *= unit_multiplier
+
     used = total - free
     percent = usage_percent(used, total, _round=1)
     # get pgin/pgouts

psutil/tests/test_linux.py

@@ -421,8 +421,15 @@ def test_warnings_mocked(self):
 
     def test_no_vmstat_mocked(self):
         # see https://github.com/giampaolo/psutil/issues/722
-        with mock.patch('psutil._pslinux.open', create=True,
-                        side_effect=IOError) as m:
+        def open_mock(name, *args, **kwargs):
+            if name == "/proc/vmstat":
+                raise IOError(errno.ENOENT, 'no such file or directory')
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, create=True, side_effect=open_mock) as m:
             with warnings.catch_warnings(record=True) as ws:
                 warnings.simplefilter("always")
                 ret = psutil.swap_memory()
@@ -437,6 +444,17 @@ def test_no_vmstat_mocked(self):
                 self.assertEqual(ret.sin, 0)
                 self.assertEqual(ret.sout, 0)
 
+    def test_against_sysinfo(self):
+        with mock.patch('psutil._pslinux.cext.linux_sysinfo') as m:
+            swap = psutil.swap_memory()
+        assert not m.called
+        import psutil._psutil_linux as cext
+        _, _, _, _, total, free, unit_multiplier = cext.linux_sysinfo()
+        total *= unit_multiplier
+        free *= unit_multiplier
+        self.assertEqual(swap.total, total)
+        self.assertEqual(swap.free, free)
+
 
 # =====================================================================
 # --- system CPU