/*
 * Copyright (c) 2020, Red Hat Inc.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.internal.platform;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.System.Logger;
import java.lang.System.Logger.Level;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Consumer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Stream;

import jdk.internal.platform.cgroupv1.CgroupV1Subsystem;
import jdk.internal.platform.cgroupv2.CgroupV2Subsystem;

public class CgroupSubsystemFactory {

    private static final String CPU_CTRL = "cpu";
    private static final String CPUACCT_CTRL = "cpuacct";
    private static final String CPUSET_CTRL = "cpuset";
    private static final String BLKIO_CTRL = "blkio";
    private static final String MEMORY_CTRL = "memory";

    /*
     * From https://www.kernel.org/doc/Documentation/filesystems/proc.txt
     *
     *  36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
     *  (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
     *
     *  (1) mount ID:  unique identifier of the mount (may be reused after umount)
     *  (2) parent ID:  ID of parent (or of self for the top of the mount tree)
     *  (3) major:minor:  value of st_dev for files on filesystem
     *  (4) root:  root of the mount within the filesystem
     *  (5) mount point:  mount point relative to the process's root
     *  (6) mount options:  per mount options
     *  (7) optional fields:  zero or more fields of the form "tag[:value]"
     *  (8) separator:  marks the end of the optional fields
     *  (9) filesystem type:  name of filesystem of the form "type[.subtype]"
     *  (10) mount source:  filesystem specific information or "none"
     *  (11) super options:  per super block options
     */
    private static final Pattern MOUNTINFO_PATTERN = Pattern.compile(
        "^[^\\s]+\\s+[^\\s]+\\s+[^\\s]+\\s+" + // (1), (2), (3)
        "([^\\s]+)\\s+([^\\s]+)\\s+" +         // (4), (5)     - group 1, 2: root, mount point
        "[^-]+-\\s+" +                         // (6), (7), (8)
        "([^\\s]+)\\s+" +                      // (9)          - group 3: filesystem type
        ".*$");                                // (10), (11)

    static CgroupMetrics create() {
        Optional<CgroupTypeResult> optResult = null;
        try {
            optResult = determineType("/proc/self/mountinfo", "/proc/cgroups", "/proc/self/cgroup");
        } catch (IOException e) {
            return null;
        } catch (UncheckedIOException e) {
            return null;
        }

        if (optResult.isEmpty()) {
            return null;
        }
        CgroupTypeResult result = optResult.get();

        // If no controller is enabled, return no metrics.
        if (!result.isAnyControllersEnabled()) {
            return null;
        }

        // Warn about mixed cgroups v1 and cgroups v2 controllers. The code is
        // not ready to deal with that on a per-controller basis. Return no metrics
        // in that case
        if (result.isAnyCgroupV1Controllers() && result.isAnyCgroupV2Controllers()) {
            Logger logger = System.getLogger("jdk.internal.platform");
            logger.log(Level.DEBUG, "Mixed cgroupv1 and cgroupv2 not supported. Metrics disabled.");
            return null;
        }

        Map<String, CgroupInfo> infos = result.getInfos();
        if (result.isCgroupV2()) {
            // For unified it doesn't matter which controller we pick.
            CgroupInfo anyController = infos.get(MEMORY_CTRL);
            CgroupSubsystem subsystem = CgroupV2Subsystem.getInstance(anyController);
            return subsystem != null ? new CgroupMetrics(subsystem) : null;
        } else {
            CgroupV1Subsystem subsystem = CgroupV1Subsystem.getInstance(infos);
            return subsystem != null ? new CgroupV1MetricsImpl(subsystem) : null;
        }
    }

    /*
     * Determine the type of the cgroup system (v1 - legacy or hybrid - or, v2 - unified)
     * based on three files:
     *
     *  (1) mountInfo  (i.e. /proc/self/mountinfo)
     *  (2) cgroups    (i.e. /proc/cgroups)
     *  (3) selfCgroup (i.e. /proc/self/cgroup)
     *
     * File 'cgroups' is inspected for the hierarchy ID of the mounted cgroup pseudo
     * filesystem. The hierarchy ID, in turn, helps us distinguish cgroups v2 and
     * cgroup v1. For a system with zero hierarchy ID, but with >= 1 relevant cgroup
     * controllers mounted in 'mountInfo' we can infer it's cgroups v2. Anything else
     * will be cgroup v1 (hybrid or legacy). File 'selfCgroup' is being used for
     * figuring out the mount path of the controller in the cgroup hierarchy.
     */
    public static Optional<CgroupTypeResult> determineType(String mountInfo,
                                                           String cgroups,
                                                           String selfCgroup) throws IOException {
        final Map<String, CgroupInfo> infos = new HashMap<>();
        List<String> lines = CgroupUtil.readAllLinesPrivileged(Paths.get(cgroups));
        for (String line : lines) {
            if (line.startsWith("#")) {
                continue;
            }
            CgroupInfo info = CgroupInfo.fromCgroupsLine(line);
            switch (info.getName()) {
            case CPU_CTRL:      infos.put(CPU_CTRL, info); break;
            case CPUACCT_CTRL:  infos.put(CPUACCT_CTRL, info); break;
            case CPUSET_CTRL:   infos.put(CPUSET_CTRL, info); break;
            case MEMORY_CTRL:   infos.put(MEMORY_CTRL, info); break;
            case BLKIO_CTRL:    infos.put(BLKIO_CTRL, info); break;
            }
        }

        // For cgroups v2 all controllers need to have zero hierarchy id
        // and /proc/self/mountinfo needs to have at least one cgroup filesystem
        // mounted. Note that hybrid hierarchy has controllers mounted via
        // cgroup v1. In that case hierarchy id's will be non-zero.
        boolean isCgroupsV2 = true;
        boolean anyControllersEnabled = false;
        boolean anyCgroupsV2Controller = false;
        boolean anyCgroupsV1Controller = false;
        for (CgroupInfo info: infos.values()) {
            anyCgroupsV1Controller = anyCgroupsV1Controller || info.getHierarchyId() != 0;
            anyCgroupsV2Controller = anyCgroupsV2Controller || info.getHierarchyId() == 0;
            isCgroupsV2 = isCgroupsV2 && info.getHierarchyId() == 0;
            anyControllersEnabled = anyControllersEnabled || info.isEnabled();
        }

        // If there are no mounted, relevant cgroup controllers in 'mountinfo' and only
        // 0 hierarchy IDs in file 'cgroups' have been seen, we are on a cgroups v1 system.
        // However, continuing in that case does not make sense as we'd need
        // information from mountinfo for the mounted controller paths which we wouldn't
        // find anyway in that case.
        lines = CgroupUtil.readAllLinesPrivileged(Paths.get(mountInfo));
        boolean anyCgroupMounted = false;
        for (String line: lines) {
            boolean cgroupsControllerFound = amendCgroupInfos(line, infos, isCgroupsV2);
            anyCgroupMounted = anyCgroupMounted || cgroupsControllerFound;
        }
        if (!anyCgroupMounted) {
            return Optional.empty();
        }

        // Map a cgroup version specific 'action' to a line in 'selfCgroup' (i.e.
        // /proc/self/cgroups) , split on the ':' token, so as to set the appropriate
        // path to the cgroup controller in cgroup data structures 'infos'.
        // See:
        //   setCgroupV1Path() for the action run for cgroups v1 systems
        //   setCgroupV2Path() for the action run for cgroups v2 systems
        try (Stream<String> selfCgroupLines =
             CgroupUtil.readFilePrivileged(Paths.get(selfCgroup))) {
            Consumer<String[]> action = (tokens -> setCgroupV1Path(infos, tokens));
            if (isCgroupsV2) {
                action = (tokens -> setCgroupV2Path(infos, tokens));
            }
            selfCgroupLines.map(line -> line.split(":"))
                     .filter(tokens -> (tokens.length >= 3))
                     .forEach(action);
        }

        CgroupTypeResult result = new CgroupTypeResult(isCgroupsV2,
                                                       anyControllersEnabled,
                                                       anyCgroupsV2Controller,
                                                       anyCgroupsV1Controller,
                                                       Collections.unmodifiableMap(infos));
        return Optional.of(result);
    }

    /*
     * Sets the path to the cgroup controller for cgroups v2 based on a line
     * in /proc/self/cgroup file (represented as the 'tokens' array).
     *
     * Example:
     *
     * 0::/
     *
     * => tokens = [ "0", "", "/" ]
     */
    private static void setCgroupV2Path(Map<String, CgroupInfo> infos,
                                        String[] tokens) {
        int hierarchyId = Integer.parseInt(tokens[0]);
        String cgroupPath = tokens[2];
        for (CgroupInfo info: infos.values()) {
            assert hierarchyId == info.getHierarchyId() && hierarchyId == 0;
            info.setCgroupPath(cgroupPath);
        }
    }

    /*
     * Sets the path to the cgroup controller for cgroups v1 based on a line
     * in /proc/self/cgroup file (represented as the 'tokens' array).
     *
     * Note that multiple controllers might be joined at a single path.
     *
     * Example:
     *
     * 7:cpu,cpuacct:/system.slice/docker-74ad896fb40bbefe0f181069e4417505fffa19052098f27edf7133f31423bc0b.scope
     *
     * => tokens = [ "7", "cpu,cpuacct", "/system.slice/docker-74ad896fb40bbefe0f181069e4417505fffa19052098f27edf7133f31423bc0b.scope" ]
     */
    private static void setCgroupV1Path(Map<String, CgroupInfo> infos,
                                        String[] tokens) {
        String controllerName = tokens[1];
        String cgroupPath = tokens[2];
        if (controllerName != null && cgroupPath != null) {
            for (String cName: controllerName.split(",")) {
                switch (cName) {
                    case MEMORY_CTRL: // fall through
                    case CPUSET_CTRL:
                    case CPUACCT_CTRL:
                    case CPU_CTRL:
                    case BLKIO_CTRL:
                        CgroupInfo info = infos.get(cName);
                        info.setCgroupPath(cgroupPath);
                        break;
                    // Ignore not recognized controllers
                    default:
                        break;
                }
            }
        }
    }

    
Amends cgroup infos with mount path and mount root. The passed in
'mntInfoLine' represents a single line in, for example,
/proc/self/mountinfo. Each line is matched with MOUNTINFO_PATTERN
(see above), so as to extract the relevant tokens from the line.
Host example cgroups v1:
44 30 0:41 / /sys/fs/cgroup/devices rw,nosuid,nodev,noexec,relatime shared:16 - cgroup cgroup rw,seclabel,devices
Container example cgroups v1:
1901 1894 0:37 /system.slice/docker-2291eeb92093f9d761aaf971782b575e9be56bd5930d4b5759b51017df3c1387.scope /sys/fs/cgroup/cpu,cpuacct ro,nosuid,nodev,noexec,relatime master:12 - cgroup cgroup rw,seclabel,cpu,cpuacct
Container example cgroups v2:
1043 1034 0:27 / /sys/fs/cgroup ro,nosuid,nodev,noexec,relatime - cgroup2 cgroup2 rw,seclabel,nsdelegate
Returns:
true iff a relevant controller has been found at the given line/**
     * Amends cgroup infos with mount path and mount root. The passed in
     * 'mntInfoLine' represents a single line in, for example,
     * /proc/self/mountinfo. Each line is matched with MOUNTINFO_PATTERN
     * (see above), so as to extract the relevant tokens from the line.
     *
     * Host example cgroups v1:
     *
     * 44 30 0:41 / /sys/fs/cgroup/devices rw,nosuid,nodev,noexec,relatime shared:16 - cgroup cgroup rw,seclabel,devices
     *
     * Container example cgroups v1:
     *
     * 1901 1894 0:37 /system.slice/docker-2291eeb92093f9d761aaf971782b575e9be56bd5930d4b5759b51017df3c1387.scope /sys/fs/cgroup/cpu,cpuacct ro,nosuid,nodev,noexec,relatime master:12 - cgroup cgroup rw,seclabel,cpu,cpuacct
     *
     * Container example cgroups v2:
     *
     * 1043 1034 0:27 / /sys/fs/cgroup ro,nosuid,nodev,noexec,relatime - cgroup2 cgroup2 rw,seclabel,nsdelegate
     *
     *
     * @return {@code true} iff a relevant controller has been found at the
     * given line
     */
    private static boolean amendCgroupInfos(String mntInfoLine,
                                            Map<String, CgroupInfo> infos,
                                            boolean isCgroupsV2) {
        Matcher lineMatcher = MOUNTINFO_PATTERN.matcher(mntInfoLine.trim());
        boolean cgroupv1ControllerFound = false;
        boolean cgroupv2ControllerFound = false;
        if (lineMatcher.matches()) {
            String mountRoot = lineMatcher.group(1);
            String mountPath = lineMatcher.group(2);
            String fsType = lineMatcher.group(3);
            if (fsType.equals("cgroup")) {
                Path p = Paths.get(mountPath);
                String[] controllerNames = p.getFileName().toString().split(",");
                for (String controllerName: controllerNames) {
                    switch (controllerName) {
                        case MEMORY_CTRL: // fall-through
                        case CPU_CTRL:
                        case CPUACCT_CTRL:
                        case BLKIO_CTRL: {
                            CgroupInfo info = infos.get(controllerName);
                            assert info.getMountPoint() == null;
                            assert info.getMountRoot() == null;
                            info.setMountPoint(mountPath);
                            info.setMountRoot(mountRoot);
                            cgroupv1ControllerFound = true;
                            break;
                        }
                        case CPUSET_CTRL: {
                            CgroupInfo info = infos.get(controllerName);
                            if (info.getMountPoint() != null) {
                                // On some systems duplicate cpuset controllers get mounted in addition to
                                // the main cgroup controllers most likely under /sys/fs/cgroup. In that
                                // case pick the one under /sys/fs/cgroup and discard others.
                                if (!info.getMountPoint().startsWith("/sys/fs/cgroup")) {
                                    info.setMountPoint(mountPath);
                                    info.setMountRoot(mountRoot);
                                }
                            } else {
                                info.setMountPoint(mountPath);
                                info.setMountRoot(mountRoot);
                            }
                            cgroupv1ControllerFound = true;
                            break;
                        }
                        default:
                            // Ignore controllers which we don't recognize
                            break;
                    }
                }
            } else if (fsType.equals("cgroup2")) {
                if (isCgroupsV2) { // will be false for hybrid
                    // All controllers have the same mount point and root mount
                    // for unified hierarchy.
                    for (CgroupInfo info: infos.values()) {
                        assert info.getMountPoint() == null;
                        assert info.getMountRoot() == null;
                        info.setMountPoint(mountPath);
                        info.setMountRoot(mountRoot);
                    }
                }
                cgroupv2ControllerFound = true;
            }
        }
        return cgroupv1ControllerFound || cgroupv2ControllerFound;
    }

    public static final class CgroupTypeResult {
        private final boolean isCgroupV2;
        private final boolean anyControllersEnabled;
        private final boolean anyCgroupV2Controllers;
        private final boolean anyCgroupV1Controllers;
        private final Map<String, CgroupInfo> infos;

        private CgroupTypeResult(boolean isCgroupV2,
                                 boolean anyControllersEnabled,
                                 boolean anyCgroupV2Controllers,
                                 boolean anyCgroupV1Controllers,
                                 Map<String, CgroupInfo> infos) {
            this.isCgroupV2 = isCgroupV2;
            this.anyControllersEnabled = anyControllersEnabled;
            this.anyCgroupV1Controllers = anyCgroupV1Controllers;
            this.anyCgroupV2Controllers = anyCgroupV2Controllers;
            this.infos = infos;
        }

        public boolean isCgroupV2() {
            return isCgroupV2;
        }

        public boolean isAnyControllersEnabled() {
            return anyControllersEnabled;
        }

        public boolean isAnyCgroupV2Controllers() {
            return anyCgroupV2Controllers;
        }

        public boolean isAnyCgroupV1Controllers() {
            return anyCgroupV1Controllers;
        }

        public Map<String, CgroupInfo> getInfos() {
            return infos;
        }
    }
}