sharedstate 2.0.2

Sync heavily read state across many servers
Documentation 
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

use std::io;

use message_encoding::MessageEncoding;
use sharedstate::{
    protocol::messages::{SyncRequest, SyncResponse, PROTOCOL_VERSION},
    state::{
        deterministic_state::DeterministicState,
        recoverable_state::{RecoverableState, RecoverableStateAction, RecoverableStateDetails},
    },
};

#[derive(Clone, Debug, Default, PartialEq, Eq)]
struct CounterState(u64);

impl DeterministicState for CounterState {
    type Action = u64;
    type AuthorityAction = u64;

    fn accept_seq(&self) -> u64 {
        self.0
    }

    fn authority(&self, action: Self::Action) -> Self::AuthorityAction {
        action
    }

    fn update(&mut self, _action: &Self::AuthorityAction) {
        self.0 += 1;
    }
}

impl MessageEncoding for CounterState {
    const STATIC_SIZE: Option<usize> = u64::STATIC_SIZE;
    const MAX_SIZE: Option<usize> = u64::MAX_SIZE;

    fn write_to<T: io::Write>(&self, out: &mut T) -> io::Result<usize> {
        self.0.write_to(out)
    }

    fn read_from<T: io::Read>(read: &mut T) -> io::Result<Self> {
        Ok(Self(MessageEncoding::read_from(read)?))
    }
}

fn encoded<M: MessageEncoding>(message: &M) -> Vec<u8> {
    let mut bytes = Vec::new();
    let written = message.write_to(&mut bytes).unwrap();
    assert_eq!(written, bytes.len());
    bytes
}

fn sample_details() -> RecoverableStateDetails {
    let mut details = RecoverableStateDetails::new(0x0102_0304_0506_0708, 0x1112_1314_1516_1718);
    details.apply_generation_bump(0x2122_2324_2526_2728);
    details
}

#[test]
fn generation_history_retains_exactly_2048_boundaries() {
    let mut leader = RecoverableState::new(1000, CounterState::default());

    let just_beyond_retention = leader.details().clone();

    leader.update(&RecoverableStateAction::BumpGeneration { new_id: 1001 });
    let oldest_retained = leader.details().clone();

    for new_id in 1002..=3049 {
        leader.update(&RecoverableStateAction::BumpGeneration { new_id });
    }

    assert!(leader.details().can_recover_follower(&oldest_retained));
    assert!(!leader.details().can_recover_follower(&just_beyond_retention));
}

#[test]
fn protocol_version_marks_current_wire_format() {
    assert_eq!(PROTOCOL_VERSION, 2);
}

#[test]
fn recoverable_state_details_wire_snapshot() {
    let details = sample_details();

    assert_eq!(
        encoded(&details),
        vec![
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, // outer_state_next_seq
            0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, // id
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, // generation
            0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, // inner_state_next_seq
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, // history length
            0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, // history[0].old_id
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, // history[0].generation
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, // history[0].next_sequence
        ]
    );
}

#[test]
fn sync_request_subscribe_wire_snapshot() {
    let request = SyncRequest::<u64, CounterState>::Subscribe(sample_details());

    assert_eq!(
        encoded(&request),
        vec![
            0x00, 0x01, // SyncRequest::Subscribe
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, // outer_state_next_seq
            0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, // id
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, // generation
            0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, // inner_state_next_seq
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, // history length
            0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, // history[0].old_id
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, // history[0].generation
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, // history[0].next_sequence
        ]
    );
}

#[test]
fn sync_response_action_wire_snapshot() {
    let response = SyncResponse::<u64, CounterState>::Action {
        seq: 0x3132_3334_3536_3738,
        action: RecoverableStateAction::BumpGeneration {
            new_id: 0x4142_4344_4546_4748,
        },
    };

    assert_eq!(
        encoded(&response),
        vec![
            0x00, 0x03, // SyncResponse::Action
            0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, // seq
            0x00, 0x02, // RecoverableStateAction::BumpGeneration
            0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, // new_id
        ]
    );
}