Add workingDir parameter to DockerApp

Docker containers run by default under /. Additionally, when we ensure
and create a new user in the container, we run under /home/r ("r" is the
new user). Both of these options make it impossible to retrieve anything
from the working directory after execution finishes though, which is why
we need a new parameter that lets users specify under which directory
the container command will run (and thus they can also map it from the
host system).

This commit adds support for a new workingDir parameter in DockerApps.
Its value defaults to "/", and is only taken into account when the image
from which the container is started doesn't already contain a value for
its WorkingDir specification. We take care that this preference is
obeyed both when we internally create a new user, as well as when we
don't A new unit test checks that this is working as expected.

This work is part of LIU-53.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

daliuge-engine/dlg/apps/dockerapp.py

@@ -82,7 +82,9 @@ class DockerApp(BarrierAppDROP):
     `initialize` time, meaning that the docker images will become available at
     the time the physical graph (which this application is part of) is deployed.
     Docker containers also need a command to be run in them, which should be
-    an available program inside the image.
+    an available program inside the image. Optionally, users can provide a
+    working directory (in the container) under which the command will run
+    via the `workingDir` parameter.
 
     **Input and output**
 
@@ -247,6 +249,15 @@ def initialize(self, **kwargs):
             logger.debug("Took %.2f [s] to pull image '%s'", (end-start), self._image)
         else:
             logger.debug("Image '%s' found, no need to pull it", self._image)
+
+        # Check if the image specifies a working directory
+        # If it doesn't use the one provided by the user
+        inspection = c.api.inspect_image(self._image)
+        logger.debug("Docker Image inspection: %r", inspection)
+        self.workdir = inspection.get('ContainerConfig', {}).get('WorkingDir', None)
+        if not self.workdir:
+            self.workdir = self._getArg(kwargs, 'workingDir', '/')
+
         c.api.close()
 
         self._containerIp = None
@@ -327,7 +338,7 @@ def run(self):
             createUserAndGo = "id -u {0} &> /dev/null || adduser --uid {0} r; ".format(uid)
             for dirname in set([os.path.dirname(x.path) for x in dockerOutputs.values()]):
                 createUserAndGo += 'chown -R {0}.{0} "{1}"; '.format(uid, dirname)
-            createUserAndGo += "cd; su -l $(getent passwd {0} | cut -f1 -d:) -c /bin/bash -c '{1}'".format(uid, utils.escapeQuotes(cmd, doubleQuotes=False))
+            createUserAndGo += "su -l $(getent passwd {0} | cut -f1 -d:) -c /bin/bash -c 'cd {1}; {2}'".format(uid, self.workdir, utils.escapeQuotes(cmd, doubleQuotes=False))
 
             cmd = createUserAndGo
 
@@ -351,6 +362,7 @@ def rm(container):
                 volumes=binds,
                 user=user,
                 environment=env,
+                working_dir=self.workdir
         )
         self._containerId = cId = container.id
         logger.info("Created container %s for %r", cId, self)

daliuge-engine/test/apps/test_docker.py

@@ -201,3 +201,15 @@ def test_additional_bindings(self):
         # Cleanup
         os.unlink(tempFile)
         shutil.rmtree(tempDir)
+
+    def _test_working_dir(self, ensureUserAndSwitch):
+        a = DockerApp('a', 'a', workingDir='/mydir', image='ubuntu:14.04', command='pwd > %o0', ensureUserAndSwitch=ensureUserAndSwitch)
+        b = FileDROP('b', 'b')
+        a.addOutput(b)
+        with DROPWaiterCtx(self, b, 100):
+            a.execute()
+        self.assertEqual(b'/mydir', droputils.allDropContents(b).strip())
+
+    def test_working_dir(self):
+        self._test_working_dir(True)
+        self._test_working_dir(False)