kevy 6.4.0

kevy — a pure-Rust, zero-dependency, Redis-compatible KV server.
Documentation 
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//! `CLUSTER` — the read-only single-node cluster surface.
//!
//! With `[cluster] enabled`, kevy presents each shard as a virtual master
//! "node" at `ip:(port_base + i)` owning one contiguous slot range, so stock
//! cluster-aware clients (`redis-benchmark --cluster`, `redis-cli -c`,
//! client libraries) discover the topology and connect per shard. Disabled
//! (default), every subcommand keeps the standalone stub shape clients
//! expect from a non-cluster Redis.
//!
//! Single-machine scope: no failover, no MIGRATE/ASK, no gossip — the
//! topology is static and fully derived from the config.
//!
//! Stub semantics (by design, not an unfinished surface): in
//! standalone mode the read-only subcommands report the honest
//! single-node facts (`cluster_enabled:0`, one node owning all 16384
//! slots, empty SLOTS/SHARDS); mutating subcommands (RESET / SETSLOT
//! / FORGET / MEET …) answer `+OK` without effect, because there is
//! no dynamic membership to mutate — kevy's multi-node story is the
//! replication + scope planes, and membership changes are "push new
//! config, restart". Clients that probe CLUSTER defensively at
//! connect time therefore proceed instead of erroring out.

// CLUSTER NODES emits a multi-line description; the `push_str(&format!(...))`
// shape stays legible vs `write!` boilerplate, and it's not on a hot path.
#![allow(clippy::format_push_string)]

use kevy_config::Config;
use kevy_resp::{ArgvView, encode_array_len, encode_bulk, encode_integer, encode_simple_string};
use kevy_store::Store;

use super::wrong_args;
use crate::state::Ctx;

/// Deterministic 40-hex node id for shard `i` (stable across restarts;
/// `i + 1` so no id collides with the all-zero "unknown node" sentinel).
fn node_id(i: usize) -> String {
    format!("{:040x}", i + 1)
}

/// Advertised IPv4: the bind address, with `127.0.0.1` substituted for a
/// `0.0.0.0` wildcard (an unroutable advertise would strand every client).
fn advertised_ip(cfg: &Config) -> String {
    let [a, b, c, d] = cfg.server.bind;
    if [a, b, c, d] == [0, 0, 0, 0] { "127.0.0.1".into() } else { format!("{a}.{b}.{c}.{d}") }
}

// LOC-WAIVER: data-driven subcommand dispatch table — one reply-emitter arm per subcommand.
pub(crate) fn cmd_cluster<A: ArgvView + ?Sized>(
    ctx: &Ctx<'_>,
    store: &mut Store,
    args: &A,
    out: &mut Vec<u8>,
) {
    let cfg = &ctx.state.config();
    let sub = match args.get(1) {
        Some(s) => s.to_ascii_uppercase(),
        None => return wrong_args(out, "cluster"),
    };
    let n = cfg.server.threads.max(1);
    let enabled = cfg.cluster.enabled;
    match sub.as_slice() {
        b"INFO" => {
            // `cluster_known_nodes` is
            // peer count (self + every entry in `[cluster] peers`),
            // not shard count. `cluster_size` stays = shard count
            // (Redis semantics: number of masters serving slots).
            // Without `peers` we report 1 (this node only) when
            // cluster is enabled — clients see a real single-node
            // topology instead of 0.
            let known = if enabled { cfg.cluster.peers.len().max(1) } else { 1 };
            let body = format!(
                "cluster_enabled:{}\r\ncluster_state:ok\r\n\
                 cluster_slots_assigned:16384\r\ncluster_slots_ok:16384\r\n\
                 cluster_slots_pfail:0\r\ncluster_slots_fail:0\r\n\
                 cluster_known_nodes:{}\r\ncluster_size:{}\r\n\
                 cluster_current_epoch:0\r\ncluster_my_epoch:0\r\n",
                u8::from(enabled),
                known,
                if enabled { n } else { 1 },
            );
            encode_bulk(out, body.as_bytes());
        }
        b"NODES" if enabled => {
            encode_bulk(out, nodes_text(cfg, n, live_role(ctx), ctx.shard.shard_id()).as_bytes());
        }
        b"NODES" => {
            // Standalone stub. The role flag reflects live state
            // (the upstream slot is `Some` for a replica) — clients
            // that discover topology via NODES can therefore classify
            // the node correctly without a separate ROLE roundtrip.
            let role = live_role(ctx);
            let body = format!(
                "0000000000000000000000000000000000000000 :0@0 myself,{role} - 0 0 0 connected 0-16383\r\n",
            );
            encode_bulk(out, body.as_bytes());
        }
        b"SLOTS" if enabled => encode_slots(cfg, n, out),
        b"SHARDS" if enabled => encode_shards(cfg, n, out),
        b"SLOTS" | b"SHARDS" => encode_array_len(out, 0),
        b"MYID" if enabled => encode_bulk(out, node_id(ctx.shard.shard_id()).as_bytes()),
        b"MYID" => encode_bulk(out, b"0000000000000000000000000000000000000000"),
        b"KEYSLOT" => match args.get(2) {
            Some(key) => encode_integer(out, i64::from(kevy_hash::key_hash_slot(key))),
            None => wrong_args(out, "cluster|keyslot"),
        },
        b"COUNTKEYSINSLOT" => {
            let Some(slot) = args
                .get(2)
                .and_then(|s| std::str::from_utf8(s).ok())
                .and_then(|s| s.parse::<u16>().ok())
                .filter(|&s| s < 16384)
            else {
                return wrong_args(out, "cluster|countkeysinslot");
            };
            // Counts this shard's keyspace only (Redis semantics: the
            // answering node's view). O(keys of shard); diagnostic-only.
            let mut count = 0i64;
            store.snapshot_each(|key, _, _| {
                if kevy_hash::key_hash_slot(key) == slot {
                    count += 1;
                }
            });
            encode_integer(out, count);
        }
        // Mutating / gossip subcommands (RESET, SETSLOT, FORGET, MEET,
        // FAILOVER …): tolerated as no-op `+OK` — see the module doc's
        // stub-semantics declaration. There is no dynamic membership
        // to mutate; erroring here would break clients that probe
        // CLUSTER defensively at connect time.
        _ => encode_simple_string(out, "OK"),
    }
}

/// Walk the advertised topology — the single derivation (advertised IP,
/// per-shard port, slot range) all three emitters (`NODES` / `SLOTS` /
/// `SHARDS`) format from: `f(i, ip, port, start, end)` per virtual node.
fn for_each_node(cfg: &Config, n: usize, mut f: impl FnMut(usize, &str, i64, u16, u16)) {
    let ip = advertised_ip(cfg);
    let base = i64::from(crate::cluster_port_base(cfg));
    for i in 0..n {
        let (start, end) = kevy_rt::shard_slot_range(i, n);
        f(i, &ip, base + i as i64, start, end);
    }
}

/// The answering node's role from live replication state — the OTHER
/// shards within this same process share the same role (they're
/// sibling shards in one process), so callers apply it to every entry.
fn live_role(ctx: &Ctx<'_>) -> &'static str {
    if ctx.state.replication.current_upstream().is_some() { "slave" } else { "master" }
}

/// `CLUSTER NODES` text: one line per virtual node. The answering
/// shard (`me`) is flagged `myself`. No cluster bus — `@cport` mirrors
/// the data port.
fn nodes_text(cfg: &Config, n: usize, role: &str, me: usize) -> String {
    let mut body = String::new();
    for_each_node(cfg, n, |i, ip, port, start, end| {
        let flags = if i == me { format!("myself,{role}") } else { role.to_string() };
        body.push_str(&format!(
            "{} {ip}:{port}@{port} {flags} - 0 0 {} connected {start}-{end}\r\n",
            node_id(i),
            i + 1,
        ));
    });
    body
}

/// `CLUSTER SLOTS`: `[[start, end, [ip, port, id, []]], …]` — the 4th node
/// element (metadata map, RESP2-encoded as an empty array) matches the
/// Redis 7 / valkey shape clients are parsed against.
fn encode_slots(cfg: &Config, n: usize, out: &mut Vec<u8>) {
    encode_array_len(out, n as i64);
    for_each_node(cfg, n, |i, ip, port, start, end| {
        encode_array_len(out, 3);
        encode_integer(out, i64::from(start));
        encode_integer(out, i64::from(end));
        encode_array_len(out, 4);
        encode_bulk(out, ip.as_bytes());
        encode_integer(out, port);
        encode_bulk(out, node_id(i).as_bytes());
        encode_array_len(out, 0);
    });
}

/// `CLUSTER SHARDS` (Redis 7 shape): per shard a 2-pair map-as-array of
/// `slots` `[start, end]` and `nodes` `[node-detail-map]`.
fn encode_shards(cfg: &Config, n: usize, out: &mut Vec<u8>) {
    encode_array_len(out, n as i64);
    for_each_node(cfg, n, |i, ip, port, start, end| {
        encode_array_len(out, 4); // 2 k/v pairs flattened
        encode_bulk(out, b"slots");
        encode_array_len(out, 2);
        encode_integer(out, i64::from(start));
        encode_integer(out, i64::from(end));
        encode_bulk(out, b"nodes");
        encode_array_len(out, 1);
        encode_array_len(out, 12); // 6 k/v pairs flattened
        encode_bulk(out, b"id");
        encode_bulk(out, node_id(i).as_bytes());
        encode_bulk(out, b"port");
        encode_integer(out, port);
        encode_bulk(out, b"ip");
        encode_bulk(out, ip.as_bytes());
        encode_bulk(out, b"endpoint");
        encode_bulk(out, ip.as_bytes());
        encode_bulk(out, b"role");
        encode_bulk(out, b"master");
        encode_bulk(out, b"health");
        encode_bulk(out, b"online");
    });
}