tests: Add utilities for docker testing

docker.py is added with a number of useful subcommands to manager docker
images and instances for QEMU docker testing. Subcommands are:

run: A wrapper of "docker run" (or "sudo -n docker run" if necessary),
which takes care of killing and removing the running container at
SIGINT.

clean: Tear down all the containers including inactive ones that are
started by docker_run.

build: Compare an image from given dockerfile and rebuild it if they're
different.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1464755128-32490-2-git-send-email-famz@redhat.com

tests/docker/docker.py

@@ -0,0 +1,194 @@
+#!/usr/bin/env python2
+#
+# Docker controlling module
+#
+# Copyright (c) 2016 Red Hat Inc.
+#
+# Authors:
+#  Fam Zheng <famz@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2
+# or (at your option) any later version. See the COPYING file in
+# the top-level directory.
+
+import os
+import sys
+import subprocess
+import json
+import hashlib
+import atexit
+import uuid
+import argparse
+import tempfile
+from shutil import copy
+
+def _text_checksum(text):
+    """Calculate a digest string unique to the text content"""
+    return hashlib.sha1(text).hexdigest()
+
+def _guess_docker_command():
+    """ Guess a working docker command or raise exception if not found"""
+    commands = [["docker"], ["sudo", "-n", "docker"]]
+    for cmd in commands:
+        if subprocess.call(cmd + ["images"],
+                           stdout=subprocess.PIPE,
+                           stderr=subprocess.PIPE) == 0:
+            return cmd
+    commands_txt = "\n".join(["  " + " ".join(x) for x in commands])
+    raise Exception("Cannot find working docker command. Tried:\n%s" % \
+                    commands_txt)
+
+class Docker(object):
+    """ Running Docker commands """
+    def __init__(self):
+        self._command = _guess_docker_command()
+        self._instances = []
+        atexit.register(self._kill_instances)
+
+    def _do(self, cmd, quiet=True, **kwargs):
+        if quiet:
+            kwargs["stdout"] = subprocess.PIPE
+        return subprocess.call(self._command + cmd, **kwargs)
+
+    def _do_kill_instances(self, only_known, only_active=True):
+        cmd = ["ps", "-q"]
+        if not only_active:
+            cmd.append("-a")
+        for i in self._output(cmd).split():
+            resp = self._output(["inspect", i])
+            labels = json.loads(resp)[0]["Config"]["Labels"]
+            active = json.loads(resp)[0]["State"]["Running"]
+            if not labels:
+                continue
+            instance_uuid = labels.get("com.qemu.instance.uuid", None)
+            if not instance_uuid:
+                continue
+            if only_known and instance_uuid not in self._instances:
+                continue
+            print "Terminating", i
+            if active:
+                self._do(["kill", i])
+            self._do(["rm", i])
+
+    def clean(self):
+        self._do_kill_instances(False, False)
+        return 0
+
+    def _kill_instances(self):
+        return self._do_kill_instances(True)
+
+    def _output(self, cmd, **kwargs):
+        return subprocess.check_output(self._command + cmd,
+                                       stderr=subprocess.STDOUT,
+                                       **kwargs)
+
+    def get_image_dockerfile_checksum(self, tag):
+        resp = self._output(["inspect", tag])
+        labels = json.loads(resp)[0]["Config"].get("Labels", {})
+        return labels.get("com.qemu.dockerfile-checksum", "")
+
+    def build_image(self, tag, dockerfile, df_path, quiet=True, argv=None):
+        if argv == None:
+            argv = []
+        tmp_dir = tempfile.mkdtemp(prefix="docker_build")
+
+        tmp_df = tempfile.NamedTemporaryFile(dir=tmp_dir, suffix=".docker")
+        tmp_df.write(dockerfile)
+
+        tmp_df.write("\n")
+        tmp_df.write("LABEL com.qemu.dockerfile-checksum=%s" %
+                     _text_checksum(dockerfile))
+        tmp_df.flush()
+        self._do(["build", "-t", tag, "-f", tmp_df.name] + argv + \
+                 [tmp_dir],
+                 quiet=quiet)
+
+    def image_matches_dockerfile(self, tag, dockerfile):
+        try:
+            checksum = self.get_image_dockerfile_checksum(tag)
+        except Exception:
+            return False
+        return checksum == _text_checksum(dockerfile)
+
+    def run(self, cmd, keep, quiet):
+        label = uuid.uuid1().hex
+        if not keep:
+            self._instances.append(label)
+        ret = self._do(["run", "--label",
+                        "com.qemu.instance.uuid=" + label] + cmd,
+                       quiet=quiet)
+        if not keep:
+            self._instances.remove(label)
+        return ret
+
+class SubCommand(object):
+    """A SubCommand template base class"""
+    name = None # Subcommand name
+    def shared_args(self, parser):
+        parser.add_argument("--quiet", action="store_true",
+                            help="Run quietly unless an error occured")
+
+    def args(self, parser):
+        """Setup argument parser"""
+        pass
+    def run(self, args, argv):
+        """Run command.
+        args: parsed argument by argument parser.
+        argv: remaining arguments from sys.argv.
+        """
+        pass
+
+class RunCommand(SubCommand):
+    """Invoke docker run and take care of cleaning up"""
+    name = "run"
+    def args(self, parser):
+        parser.add_argument("--keep", action="store_true",
+                            help="Don't remove image when command completes")
+    def run(self, args, argv):
+        return Docker().run(argv, args.keep, quiet=args.quiet)
+
+class BuildCommand(SubCommand):
+    """ Build docker image out of a dockerfile. Arguments: <tag> <dockerfile>"""
+    name = "build"
+    def args(self, parser):
+        parser.add_argument("tag",
+                            help="Image Tag")
+        parser.add_argument("dockerfile",
+                            help="Dockerfile name")
+
+    def run(self, args, argv):
+        dockerfile = open(args.dockerfile, "rb").read()
+        tag = args.tag
+
+        dkr = Docker()
+        if dkr.image_matches_dockerfile(tag, dockerfile):
+            if not args.quiet:
+                print "Image is up to date."
+            return 0
+
+        dkr.build_image(tag, dockerfile, args.dockerfile,
+                        quiet=args.quiet, argv=argv)
+        return 0
+
+class CleanCommand(SubCommand):
+    """Clean up docker instances"""
+    name = "clean"
+    def run(self, args, argv):
+        Docker().clean()
+        return 0
+
+def main():
+    parser = argparse.ArgumentParser(description="A Docker helper",
+            usage="%s <subcommand> ..." % os.path.basename(sys.argv[0]))
+    subparsers = parser.add_subparsers(title="subcommands", help=None)
+    for cls in SubCommand.__subclasses__():
+        cmd = cls()
+        subp = subparsers.add_parser(cmd.name, help=cmd.__doc__)
+        cmd.shared_args(subp)
+        cmd.args(subp)
+        subp.set_defaults(cmdobj=cmd)
+    args, argv = parser.parse_known_args()
+    return args.cmdobj.run(args, argv)
+
+if __name__ == "__main__":
+    sys.exit(main())