meta_srv/
selector.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
15pub mod common;
16pub mod lease_based;
17pub mod load_based;
18pub mod round_robin;
19#[cfg(test)]
20pub(crate) mod test_utils;
21pub mod weight_compute;
22pub mod weighted_choose;
23use std::collections::HashSet;
24
25use api::v1::meta::heartbeat_request::NodeWorkloads;
26use common_meta::affinity::AffinityRequirements;
27use serde::{Deserialize, Serialize};
28use store_api::storage::RegionId;
29use strum::AsRefStr;
30
31use crate::error;
32use crate::error::Result;
33
34#[async_trait::async_trait]
35pub trait Selector: Send + Sync {
36    type Context;
37    type Output;
38
39    async fn select(&self, ctx: &Self::Context, opts: SelectorOptions<'_>) -> Result<Self::Output>;
40}
41
42/// A selector that aware of region statistics
43///
44/// It selects the best destination peer for a list of regions.
45/// The selection is based on the region statistics, such as the region leader's write throughput.
46#[async_trait::async_trait]
47pub trait RegionStatAwareSelector: Send + Sync {
48    type Context;
49    type Output;
50
51    async fn select(
52        &self,
53        ctx: &Self::Context,
54        from_peer_id: u64,
55        region_ids: &[RegionId],
56        exclude_peer_ids: HashSet<u64>,
57        affinity: Option<&AffinityRequirements>,
58    ) -> Result<Self::Output>;
59}
60
61#[derive(Debug, Clone)]
62pub struct SelectorOptions<'a> {
63    /// Resolved requirements used to filter candidate nodes.
64    pub affinity: Option<&'a AffinityRequirements>,
65    /// Minimum number of selected results.
66    pub min_required_items: usize,
67    /// Whether duplicates are allowed in the selected result, default false.
68    pub allow_duplication: bool,
69    /// The peers to exclude from the selection.
70    pub exclude_peer_ids: HashSet<u64>,
71    /// The filter to select the peers based on their workloads.
72    pub workload_filter: Option<fn(&NodeWorkloads) -> bool>,
73}
74
75impl Default for SelectorOptions<'_> {
76    fn default() -> Self {
77        Self {
78            affinity: None,
79            min_required_items: 1,
80            allow_duplication: false,
81            exclude_peer_ids: HashSet::new(),
82            workload_filter: None,
83        }
84    }
85}
86
87/// [`SelectorType`] refers to the load balancer used when creating tables.
88#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Default, AsRefStr)]
89#[serde(try_from = "String")]
90pub enum SelectorType {
91    /// The current load balancing is based on the number of regions on each datanode node;
92    /// the more regions, the higher the load (it may be changed to Capacity Units(CU)
93    /// calculation in the future).
94    LoadBased,
95    /// This one randomly selects from all available (in lease) nodes. Its characteristic
96    /// is simplicity and fast.
97    LeaseBased,
98    /// This one selects the node in a round-robin way.
99    /// In most cases, it's recommended and is the default option. If you're unsure which
100    /// to choose, using it is usually correct.
101    #[default]
102    RoundRobin,
103}
104
105impl TryFrom<&str> for SelectorType {
106    type Error = error::Error;
107
108    fn try_from(value: &str) -> Result<Self> {
109        match value {
110            "load_based" | "LoadBased" => Ok(SelectorType::LoadBased),
111            "lease_based" | "LeaseBased" => Ok(SelectorType::LeaseBased),
112            "round_robin" | "RoundRobin" => Ok(SelectorType::RoundRobin),
113            other => error::UnsupportedSelectorTypeSnafu {
114                selector_type: other,
115            }
116            .fail(),
117        }
118    }
119}
120
121impl TryFrom<String> for SelectorType {
122    type Error = error::Error;
123
124    fn try_from(value: String) -> Result<Self> {
125        SelectorType::try_from(value.as_str())
126    }
127}
128
129#[cfg(test)]
130mod tests {
131    use super::SelectorType;
132    use crate::error::Result;
133
134    #[test]
135    fn test_default_selector_type() {
136        assert_eq!(SelectorType::RoundRobin, SelectorType::default());
137    }
138
139    #[test]
140    fn test_convert_str_to_selector_type() {
141        let lease_based = "lease_based";
142        let selector_type = lease_based.try_into().unwrap();
143        assert_eq!(SelectorType::LeaseBased, selector_type);
144        let lease_based = "LeaseBased";
145        let selector_type = lease_based.try_into().unwrap();
146        assert_eq!(SelectorType::LeaseBased, selector_type);
147
148        let load_based = "load_based";
149        let selector_type = load_based.try_into().unwrap();
150        assert_eq!(SelectorType::LoadBased, selector_type);
151        let load_based = "LoadBased";
152        let selector_type = load_based.try_into().unwrap();
153        assert_eq!(SelectorType::LoadBased, selector_type);
154
155        let unknown = "unknown";
156        let selector_type: Result<SelectorType> = unknown.try_into();
157        assert!(selector_type.is_err());
158    }
159}
meta_srv/selector.rs

meta_srv/
selector.rs
