dynomite/proto/redis/
verify.rs

1//! Redis request structural verifier.
2//!
3//! Reproduces `redis_verify_request` from the reference engine.
4//! Most commands have nothing to verify here; the only live check
5//! is that an `EVAL` request keeps every key it touches on the
6//! same shard. The verifier consults a caller-supplied dispatcher
7//! so the cluster-state coupling stays out of the protocol layer.
8
9use crate::msg::{Msg, MsgType};
10
11use super::fragment::FragmentDispatcher;
12
13/// Reserved metadata key prefixes the verifier ignores. These match
14/// the `_add-set` / `_rem-set` constants used by the read-repair
15/// engine.
16pub const ADD_SET_STR: &[u8] = b"._add-set";
17/// See [`ADD_SET_STR`].
18pub const REM_SET_STR: &[u8] = b"._rem-set";
19
20/// Run the parser-level structural checks against `r`.
21///
22/// Returns `Ok(())` when no rule was violated. Returns
23/// [`VerifyError::ScriptSpansNodes`] when an `EVAL` request touches
24/// keys belonging to more than one shard.
25///
26/// # Examples
27///
28/// ```
29/// use dynomite::msg::{KeyPos, Msg, MsgType};
30/// use dynomite::proto::redis::{redis_verify_request, FragmentDispatcher};
31///
32/// struct AllOnOne;
33/// impl FragmentDispatcher for AllOnOne {
34///     fn shard_for(&self, _key: &[u8]) -> u32 { 0 }
35///     fn shard_count(&self) -> u32 { 1 }
36/// }
37///
38/// let mut r = Msg::new(0, MsgType::ReqRedisEval, true);
39/// r.push_key(KeyPos::without_tag(b"a".to_vec()));
40/// r.push_key(KeyPos::without_tag(b"b".to_vec()));
41/// assert!(redis_verify_request(&r, &AllOnOne).is_ok());
42/// ```
43pub fn redis_verify_request<D: FragmentDispatcher + ?Sized>(
44    r: &Msg,
45    dispatcher: &D,
46) -> Result<(), VerifyError> {
47    if r.ty() != MsgType::ReqRedisEval {
48        return Ok(());
49    }
50    if r.keys().len() <= 1 {
51        return Ok(());
52    }
53    let mut prev_idx: Option<u32> = None;
54    for k in r.keys() {
55        let key = k.key();
56        if key.starts_with(ADD_SET_STR) || key.starts_with(REM_SET_STR) {
57            continue;
58        }
59        let idx = dispatcher.shard_for(k.tag_bytes());
60        match prev_idx {
61            None => prev_idx = Some(idx),
62            Some(prev) if prev == idx => {}
63            Some(_) => return Err(VerifyError::ScriptSpansNodes),
64        }
65    }
66    Ok(())
67}
68
69/// Errors [`redis_verify_request`] can produce.
70#[derive(Copy, Clone, Debug, Eq, PartialEq, thiserror::Error)]
71#[non_exhaustive]
72pub enum VerifyError {
73    /// `EVAL` request touches keys on more than one shard.
74    #[error("redis verify: script spans nodes")]
75    ScriptSpansNodes,
76}
77
78#[cfg(test)]
79mod tests {
80    use super::*;
81    use crate::msg::KeyPos;
82
83    struct OddEven;
84    impl FragmentDispatcher for OddEven {
85        fn shard_for(&self, key: &[u8]) -> u32 {
86            u32::from(*key.first().unwrap_or(&0)) % 2
87        }
88        fn shard_count(&self) -> u32 {
89            2
90        }
91    }
92
93    #[test]
94    fn non_eval_is_ok() {
95        let mut r = Msg::new(0, MsgType::ReqRedisGet, true);
96        r.push_key(KeyPos::without_tag(b"a".to_vec()));
97        r.push_key(KeyPos::without_tag(b"b".to_vec()));
98        assert!(redis_verify_request(&r, &OddEven).is_ok());
99    }
100
101    #[test]
102    fn eval_one_key_is_ok() {
103        let mut r = Msg::new(0, MsgType::ReqRedisEval, true);
104        r.push_key(KeyPos::without_tag(b"a".to_vec()));
105        assert!(redis_verify_request(&r, &OddEven).is_ok());
106    }
107
108    #[test]
109    fn eval_disjoint_shards_errors() {
110        let mut r = Msg::new(0, MsgType::ReqRedisEval, true);
111        r.push_key(KeyPos::without_tag(b"a".to_vec())); // 0x61 -> shard 1
112        r.push_key(KeyPos::without_tag(b"b".to_vec())); // 0x62 -> shard 0
113        assert_eq!(
114            redis_verify_request(&r, &OddEven),
115            Err(VerifyError::ScriptSpansNodes),
116        );
117    }
118
119    #[test]
120    fn eval_skips_metadata_keys() {
121        let mut r = Msg::new(0, MsgType::ReqRedisEval, true);
122        r.push_key(KeyPos::without_tag(b"a".to_vec()));
123        r.push_key(KeyPos::without_tag(b"._add-set".to_vec()));
124        assert!(redis_verify_request(&r, &OddEven).is_ok());
125    }
126}
dynomite/proto/redis/verify.rs

dynomite/proto/redis/
verify.rs
