1
// Copyright (c) 2024 Cloudflare, Inc.
2
// Licensed under the Apache 2.0 license found in the LICENSE file or at:
3
//     https://opensource.org/licenses/Apache-2.0
4
 
5
#pragma once
6
 
7
#include "sqlite.h"
8
 
9
namespace workerd {
10
 
11
// Class which implements a simple metadata kv storage and cache on top of SQLite.  Currently used
12
// to store:
13
//
14
// * Durable Object alarm times (hardcoded as key = 1).
15
//
16
// * A local development bookmark used to simulate the getCurrentBookmark API used by D1 (hardcoded
17
//   as key = 2).  The local development bookmark is not used in production.
18
//
19
// The table is named `_cf_METADATA`. The naming is designed so that if the application is allowed to
20
// perform direct SQL queries, we can block it from accessing any table prefixed with `_cf_`.
21
class SqliteMetadata final: private SqliteDatabase::ResetListener {
22
 public:
23
  explicit SqliteMetadata(SqliteDatabase& db);
24
 
25
  // Return currently set alarm time, or none.
26
  kj::Maybe<kj::Date> getAlarm();
27
 
28
  // Sets current alarm time, or none. Returns true if the value changed, false if it was already
29
  // set to the same value.
30
  bool setAlarm(kj::Maybe<kj::Date> currentTime, bool allowUnconfirmed);
31
 
32
  // Return the current local development bookmark, or none if no bookmark has been set.
33
  kj::Maybe<uint64_t> getLocalDevelopmentBookmark();
34
 
35
  // Set the current ersatz bookmark.
36
  void setLocalDevelopmentBookmark(uint64_t);
37
 
38
 private:
39
  struct Uninitialized {};
40
  struct Initialized {
41
    SqliteDatabase& db;
42
 
43
    SqliteDatabase::Statement stmtGetAlarm = db.prepare(R"(
44
      SELECT value FROM _cf_METADATA WHERE key = 1
45
    )");
46
    SqliteDatabase::Statement stmtSetAlarm = db.prepare(R"(
47
      INSERT INTO _cf_METADATA VALUES(1, ?)
48
        ON CONFLICT DO UPDATE SET value = excluded.value;
49
    )");
50
 
51
    SqliteDatabase::Statement stmtGetLocalDevelopmentBookmark = db.prepare(R"(
52
      SELECT value FROM _cf_METADATA WHERE key = 2
53
    )");
54
    SqliteDatabase::Statement stmtSetLocalDevelopmentBookmark = db.prepare(R"(
55
      INSERT INTO _cf_METADATA VALUES(2, ?)
56
        ON CONFLICT DO UPDATE SET value = excluded.value;
57
    )");
58
 
59
    Initialized(SqliteDatabase& db): db(db) {}
60
  };
61
 
62
  bool tableCreated;
63
  kj::OneOf<Uninitialized, Initialized> dbState = Uninitialized{};
64
 
65
  struct Cache {
66
    kj::Maybe<kj::Date> alarmTime;
67
  };
68
  kj::Maybe<Cache> cacheState;
69
 
70
  kj::Maybe<kj::Date> getAlarmUncached();
71
  void setAlarmUncached(kj::Maybe<kj::Date> currentTime, bool allowUnconfirmed);
72
 
73
  Initialized& ensureInitialized(bool allowUnconfirmed);
74
  // Make sure the metadata table is created and prepared statements are ready. Not called until the
75
  // first write.
76
 
77
  // ResetListener interface:
78
  void beforeSqliteReset() override;
79
};
80
 
81
}  // namespace workerd