image-download

#!/usr/bin/env python3

# This file is part of Cockpit.
#
# Copyright (C) 2013 Red Hat, Inc.
#
# Cockpit is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# Cockpit is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Cockpit; If not, see <http://www.gnu.org/licenses/>.

#
# Download images or other state
#
# Images usually have a name specific link committed to git. These
# are referred to as 'committed'
#
# Other state is simply referenced by name without a link in git
# This is referred to as 'state'
#
# The stores are places to look for images or other state
#

import argparse
import contextlib
import email
import fcntl
import io
import os
import shutil
import stat
import subprocess
import sys
import time
import urllib.parse

from lib import s3
from lib.constants import IMAGES_DIR
from lib.directories import get_images_data_dir
from lib.network import get_curl_ca_arg, redhat_network
from lib.stores import PUBLIC_STORES, REDHAT_STORES
from lib.testmap import get_test_image

EPOCH = "Thu, 1 Jan 1970 00:00:00 GMT"

if os.isatty(1):
    SYMBOLS = {'present': ' ✔', 'absent': ' ⨯', 'selected': '❯❯'}  # noqa: RUF001
else:
    SYMBOLS = {'present': ' >', 'absent': ' x', 'selected': '=>'}


def show_status(quiet, status, *args, prefix=''):
    if not quiet:
        message = ' '.join(args)
        sys.stderr.write(f'{prefix}{SYMBOLS[status]} {message}\n')


def curl_cmd(args):
    return ['curl', '--connect-timeout', '10', '--fail', *args]


def check_curl_args(args):
    head_args = ['--silent', '--head']  # only used for this check

    try:
        start = time.time()
        output = subprocess.check_output(curl_cmd(args + head_args), universal_newlines=True)
        duration = time.time() - start
        return output, duration
    except subprocess.CalledProcessError:
        return None


def find(name, stores, latest, quiet):
    found = []

    for store in stores:
        url = urllib.parse.urlparse(urllib.parse.urljoin(store, name))

        args = get_curl_ca_arg(url.netloc)

        # First, check if this is an S3 store for which we have a key
        if s3.is_key_present(url):
            result = check_curl_args(args + s3.sign_curl(url, method='HEAD'))
            if result:
                show_status(quiet, 'present', store, '(authenticated)')
                found.append((args + s3.sign_curl(url), result, store))  # GET
                continue
        else:
            # access the URL directly, without further authentication
            args.append(url.geturl())
            result = check_curl_args(args)
            if result:
                show_status(quiet, 'present', store)
                found.append((args, result, store))
                continue

        show_status(quiet, 'absent', store)

    # If we couldn't find the file, but it exists, we're good
    if not found:
        return None, None

    # Find the most recent version of this file
    def header_date(args):
        _, (output, duration), message = args
        try:
            reply_line, headers_alone = output.split('\n', 1)
            last_modified = email.message_from_file(io.StringIO(headers_alone)).get("Last-Modified", "")
            return time.mktime(time.strptime(last_modified, '%a, %d %b %Y %H:%M:%S %Z'))
        except ValueError:
            return ""

    if latest:
        # if we depend on getting the latest info, only download it from that one store
        found.sort(reverse=True, key=header_date)
    else:
        found.sort(reverse=False, key=lambda x: x[1][1])

    return found[0][0], found[0][2]


def download(dest, force, state, quiet, stores):
    name = os.path.basename(dest)

    if not stores:
        stores = PUBLIC_STORES
        if redhat_network():
            stores += REDHAT_STORES
        image_upload_store = os.environ.get('COCKPIT_IMAGE_UPLOAD_STORE')
        if image_upload_store:
            # NB: This is an *addition* to the built-in stores, used for
            # testing.  Compare with image-upload which *only* uploads to this
            # store, if it's present.
            stores += image_upload_store

    # The time condition for If-Modified-Since
    exists = not force and os.path.exists(dest)
    if exists:
        since = dest
    else:
        since = EPOCH

    args, message = find(name, stores, latest=state, quiet=quiet)

    # If we couldn't find the file, but it exists, we're good
    if not args:
        if exists:
            return
        raise RuntimeError(f"image-download: couldn't find file anywhere: {name}")

    show_status(quiet, 'selected', urllib.parse.urljoin(message, name))

    temp = dest + ".partial"

    # Adjust the arguments above that worked to make it visible and download real stuff
    args.append("--show-error")
    if not quiet and os.isatty(sys.stdout.fileno()):
        args.append("--progress-bar")
    else:
        args.append("--silent")
    args.append("--remote-time")
    args.append("--time-cond")
    args.append(since)
    args.append("--output")
    args.append(temp)
    if os.path.exists(temp):
        if force:
            os.remove(temp)
        else:
            args.append("-C")
            args.append("-")

    # Always create the destination file (because --state)
    else:
        open(temp, 'a').close()

    curl = subprocess.Popen(curl_cmd(args))
    ret = curl.wait()
    if ret != 0:
        raise RuntimeError("curl: unable to download %s (returned: %s)" % (message, ret))

    os.chmod(temp, stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH)

    # Due to time-cond the file size may be zero
    # A new file downloaded, put it in place
    if not exists or os.path.getsize(temp) > 0:
        shutil.move(temp, dest)


# Calculate a place to put images where links are not committed in git
def state_target(path):
    data_dir = get_images_data_dir()
    os.makedirs(data_dir, mode=0o775, exist_ok=True)
    return os.path.join(data_dir, path)


# Calculate a place to put images where links are committed in git
def committed_target(image):
    link = os.path.join(IMAGES_DIR, image)
    if not os.path.islink(link):
        raise RuntimeError("image link does not exist: " + image)

    dest = os.readlink(link)
    relative_dir = os.path.dirname(os.path.abspath(link))
    full_dest = os.path.join(relative_dir, dest)
    while os.path.islink(full_dest):
        link = full_dest
        dest = os.readlink(link)
        relative_dir = os.path.dirname(os.path.abspath(link))
        full_dest = os.path.join(relative_dir, dest)

    dest = os.path.join(get_images_data_dir(), dest)

    # We have the file but there is not valid link
    if os.path.exists(dest):
        try:
            os.symlink(dest, os.path.join(IMAGES_DIR, os.readlink(link)))
        except FileExistsError:
            # can happen in unclean trees and deleting the image in the cache dir directly
            pass

    # The image file in the images directory, may be same as dest
    image_file = os.path.join(IMAGES_DIR, os.readlink(link))

    # Double check that symlink in place
    if os.path.abspath(dest) != os.path.abspath(image_file):
        try:
            os.symlink(os.path.abspath(dest), image_file)
        except FileExistsError:
            # .. but never make a cycle
            pass

    return dest


@contextlib.contextmanager
def wait_lock(target):
    lockfile = os.path.join(os.path.dirname(target), ".lock." + os.path.basename(target))

    # we need to keep the lock fd open throughout the entire runtime, so remember it in a global-scoped variable
    with open(lockfile, "w") as file:
        for retry in range(360):
            try:
                fcntl.flock(file, fcntl.LOCK_NB | fcntl.LOCK_EX)
                break
            except BlockingIOError:
                if retry == 0:
                    print("Waiting for concurrent image-download of %s..." % os.path.basename(target))
                time.sleep(10)
        else:
            raise TimeoutError("timed out waiting for concurrent downloads of %s\n" % target)

        yield

        # clean up lock file
        try:
            os.unlink(lockfile)
        except FileNotFoundError:
            # parallel runs may remove it already
            pass


def download_images(image_list, force, quiet, state, store):
    data_dir = get_images_data_dir()
    os.makedirs(data_dir, exist_ok=True)

    # A default set of images are all links in git.  These links have
    # no directory part.  Other links might exist, such as the
    # auxiliary links created by committed_target above, and we ignore
    # them.
    if not image_list:
        image_list = []
        if not state:
            for filename in os.listdir(IMAGES_DIR):
                link = os.path.join(IMAGES_DIR, filename)
                if os.path.islink(link) and os.path.dirname(os.readlink(link)) == "":
                    image_list.append(filename)

    success = True

    for image in image_list:
        image = get_test_image(image)
        try:
            if state:
                target = state_target(image)
            else:
                target = committed_target(image)

            # don't download the same thing multiple times in parallel
            with wait_lock(target):
                if force or state or not os.path.exists(target):
                    download(target, force, state, quiet, store)

        except Exception as ex:
            success = False
            sys.stderr.write(f"image-download: {ex!s}\n")

    return success


def main():
    parser = argparse.ArgumentParser(description='Download a bot state or images')
    parser.add_argument("--force", action="store_true", help="Force unnecessary downloads")
    parser.add_argument("--store", action="append", help="Where to find state or images")
    parser.add_argument("--quiet", action="store_true", help="Make downloading quieter")
    parser.add_argument("--state", action="store_true", help="Images or state not recorded in git")
    parser.add_argument('image', nargs='*')
    args = parser.parse_args()

    if not download_images(args.image, args.force, args.quiet, args.state, args.store):
        return 1

    return 0


if __name__ == '__main__':
    sys.exit(main())