summaryrefslogtreecommitdiff
path: root/src/mongo/db/session_killer.h
blob: 3dde3893058507e9adb6432481db82fe969616c7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program 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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include <boost/optional.hpp>
#include <functional>
#include <memory>
#include <random>
#include <vector>

#include "mongo/base/status_with.h"
#include "mongo/db/kill_sessions.h"
#include "mongo/platform/mutex.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/thread.h"
#include "mongo/stdx/unordered_set.h"
#include "mongo/util/hierarchical_acquisition.h"
#include "mongo/util/net/hostandport.h"

namespace mongo {

/**
 * The SessionKiller enforces a single thread for session killing for any given ServiceContext.
 *
 * The killer owns a background thread which actually does the work, and callers batch their kills
 * together each round, before the killer starts its dispatching, after which they batch up for the
 * next round.
 *
 * The KillFunc's kill function is passed in to its constructor, and parameterizes its behavior
 * depending on context (mongod/mongos).
 */
class SessionKiller {
public:
    /**
     * The Result of a call is either:
     *
     * Status::OK(), empty vector - we killed everything
     * Status::OK(), filled vector - we killed something.  HostAndPort is filled with nodes we
     *                               failed to kill on.
     *
     * !Status::OK() - The kill function itself failed.  I.e. we may have killed nothing.
     *
     * This contract has a helper in kill_sessions_common.h which adapts results for command
     * implementations. (killSessionsCmdHelper)
     */
    using Result = StatusWith<std::vector<HostAndPort>>;
    using UniformRandomBitGenerator = std::minstd_rand;

    /**
     * For regular sessions, the Matcher will directly match an lsid pattern. For internal sessions,
     * the Matcher will return matches on the child sessions of a parent session as well.
     */
    class Matcher {
    public:
        Matcher(KillAllSessionsByPatternSet&& patterns);

        const KillAllSessionsByPatternSet& getPatterns() const;

        const KillAllSessionsByPattern* match(const LogicalSessionId& lsid) const;

    private:
        KillAllSessionsByPatternSet _patterns;
        LogicalSessionIdMap<const KillAllSessionsByPattern*> _lsids;
        stdx::unordered_map<SHA256Block, const KillAllSessionsByPattern*, SHA256Block::Hash> _uids;
        const KillAllSessionsByPattern* _killAll = nullptr;
    };

    /**
     * A process specific kill function (we have a different impl in mongos versus mongod).
     */
    using KillFunc =
        std::function<Result(OperationContext*, const Matcher&, UniformRandomBitGenerator* urbg)>;

    /**
     * The killer lives as a decoration on the service context.
     */
    static SessionKiller* get(ServiceContext* service);
    static SessionKiller* get(OperationContext* opCtx);

    /**
     * This method binds the SessionKiller to the ServiceContext.
     */
    static void set(ServiceContext* ctx, std::shared_ptr<SessionKiller> sk);

    static void shutdown(ServiceContext* ctx);

    explicit SessionKiller(ServiceContext* sc, KillFunc killer);
    ~SessionKiller();

    /**
     * This is the api for killSessions commands to invoke the killer.  It blocks until the kill is
     * finished, or until it fails (times out on all nodes in mongos).
     */
    std::shared_ptr<Result> kill(OperationContext* opCtx,
                                 const KillAllSessionsByPatternSet& toKill);

private:
    /**
     * This struct is a helper to default fill in the result, which is otherwise a little error
     * prone.
     */
    struct ReapResult {
        ReapResult();

        std::shared_ptr<boost::optional<Result>> result;
    };

    void _periodicKill(OperationContext* opCtx, stdx::unique_lock<Latch>& lk);

    KillFunc _killFunc;

    stdx::thread _thread;

    Mutex _mutex = MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(2), "SessionKiller::_mutex");
    stdx::condition_variable _callerCV;
    stdx::condition_variable _killerCV;

    UniformRandomBitGenerator _urbg;

    ReapResult _reapResults;
    KillAllSessionsByPatternSet _nextToReap;

    bool _inShutdown = false;
};

}  // namespace mongo