meta_srv/selector/
load_based.rs

1// Copyright 2023 Greptime Team
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::collections::HashMap;
16
17use common_meta::affinity::AffinityFallback;
18use common_meta::datanode::{DatanodeStatKey, DatanodeStatValue};
19use common_meta::peer::Peer;
20use common_telemetry::debug;
21
22use crate::cluster::MetaPeerClientRef;
23use crate::error::{self, Result};
24use crate::metasrv::SelectorContext;
25use crate::selector::common::{self, choose_items, filter_out_excluded_peers};
26use crate::selector::weight_compute::WeightCompute;
27use crate::selector::weighted_choose::RandomWeightedChoose;
28use crate::selector::{Selector, SelectorOptions};
29
30pub struct LoadBasedSelector<C> {
31    weight_compute: C,
32    meta_peer_client: MetaPeerClientRef,
33}
34
35impl<C> LoadBasedSelector<C> {
36    pub fn new(weight_compute: C, meta_peer_client: MetaPeerClientRef) -> Self {
37        Self {
38            weight_compute,
39            meta_peer_client,
40        }
41    }
42}
43
44impl<C> LoadBasedSelector<C>
45where
46    C: WeightCompute<Source = HashMap<DatanodeStatKey, DatanodeStatValue>>,
47{
48    async fn select_once(
49        &self,
50        ctx: &SelectorContext,
51        opts: &SelectorOptions<'_>,
52    ) -> Result<Vec<Peer>> {
53        // 1. get alive datanodes.
54        let alive_datanodes = common::active_schedulable_datanodes(ctx, opts.workload_filter)
55            .await?
56            .into_iter()
57            .filter(|node| {
58                opts.affinity
59                    .is_none_or(|requirements| ctx.affinity.matches(requirements, node))
60            })
61            .map(|node| node.peer)
62            .collect::<Vec<_>>();
63
64        // 2. get stat kvs and filter out expired datanodes.
65        let stat_keys = alive_datanodes
66            .iter()
67            .map(|k| DatanodeStatKey { node_id: k.id })
68            .collect();
69        let stat_kvs = filter_out_expired_datanode(
70            self.meta_peer_client.get_dn_stat_kvs(stat_keys).await?,
71            &alive_datanodes,
72        );
73
74        // 3. compute weight array.
75        let mut weight_array = self.weight_compute.compute(&stat_kvs);
76
77        // 4. filter out excluded peers.
78        filter_out_excluded_peers(&mut weight_array, &opts.exclude_peer_ids);
79        // 5. choose peers by weight_array.
80        let mut weighted_choose = RandomWeightedChoose::new(weight_array);
81        let selected = choose_items(opts, &mut weighted_choose)?;
82
83        debug!(
84            "LoadBasedSelector select peers: {:?}, opts: {:?}.",
85            selected, opts,
86        );
87
88        Ok(selected)
89    }
90}
91
92#[async_trait::async_trait]
93impl<C> Selector for LoadBasedSelector<C>
94where
95    C: WeightCompute<Source = HashMap<DatanodeStatKey, DatanodeStatValue>>,
96{
97    type Context = SelectorContext;
98    type Output = Vec<Peer>;
99
100    async fn select(
101        &self,
102        ctx: &Self::Context,
103        mut opts: SelectorOptions<'_>,
104    ) -> Result<Self::Output> {
105        match self.select_once(ctx, &opts).await {
106            Err(error::Error::NoEnoughAvailableNode {
107                required,
108                available,
109                ..
110            }) if opts.affinity.is_some()
111                && ctx.affinity_fallback == AffinityFallback::Unconstrained
112                && available < required =>
113            {
114                opts.affinity = None;
115                self.select_once(ctx, &opts).await
116            }
117            result => result,
118        }
119    }
120}
121
122fn filter_out_expired_datanode(
123    mut stat_kvs: HashMap<DatanodeStatKey, DatanodeStatValue>,
124    datanodes: &[Peer],
125) -> HashMap<DatanodeStatKey, DatanodeStatValue> {
126    datanodes
127        .iter()
128        .filter_map(|p| stat_kvs.remove_entry(&DatanodeStatKey { node_id: p.id }))
129        .collect()
130}
131
132#[cfg(test)]
133mod tests {
134    use std::collections::HashMap;
135
136    use common_meta::datanode::{DatanodeStatKey, DatanodeStatValue};
137    use common_meta::peer::Peer;
138
139    use crate::selector::load_based::filter_out_expired_datanode;
140
141    #[test]
142    fn test_filter_out_expired_datanode() {
143        let mut stat_kvs = HashMap::new();
144        stat_kvs.insert(
145            DatanodeStatKey { node_id: 0 },
146            DatanodeStatValue { stats: vec![] },
147        );
148        stat_kvs.insert(
149            DatanodeStatKey { node_id: 1 },
150            DatanodeStatValue { stats: vec![] },
151        );
152        stat_kvs.insert(
153            DatanodeStatKey { node_id: 2 },
154            DatanodeStatValue { stats: vec![] },
155        );
156
157        let lease_kvs = vec![Peer::new(1, "127.0.0.1:3002".to_string())];
158        let alive_stat_kvs = filter_out_expired_datanode(stat_kvs, &lease_kvs);
159
160        assert_eq!(1, alive_stat_kvs.len());
161        assert!(alive_stat_kvs.contains_key(&DatanodeStatKey { node_id: 1 }));
162    }
163}
meta_srv/selector/load_based.rs

meta_srv/selector/
load_based.rs
