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 serde::{Deserialize, Serialize};
26use store_api::storage::RegionId;
27use strum::AsRefStr;
28
29use crate::error;
30use crate::error::Result;
31
32#[async_trait::async_trait]
33pub trait Selector: Send + Sync {
34    type Context;
35    type Output;
36
37    async fn select(&self, ctx: &Self::Context, opts: SelectorOptions) -> Result<Self::Output>;
38}
39
40/// A selector that aware of region statistics
41///
42/// It selects the best destination peer for a list of regions.
43/// The selection is based on the region statistics, such as the region leader's write throughput.
44#[async_trait::async_trait]
45pub trait RegionStatAwareSelector: Send + Sync {
46    type Context;
47    type Output;
48
49    async fn select(
50        &self,
51        ctx: &Self::Context,
52        from_peer_id: u64,
53        region_ids: &[RegionId],
54        exclude_peer_ids: HashSet<u64>,
55    ) -> Result<Self::Output>;
56}
57
58#[derive(Debug)]
59pub struct SelectorOptions {
60    /// Minimum number of selected results.
61    pub min_required_items: usize,
62    /// Whether duplicates are allowed in the selected result, default false.
63    pub allow_duplication: bool,
64    /// The peers to exclude from the selection.
65    pub exclude_peer_ids: HashSet<u64>,
66}
67
68impl Default for SelectorOptions {
69    fn default() -> Self {
70        Self {
71            min_required_items: 1,
72            allow_duplication: false,
73            exclude_peer_ids: HashSet::new(),
74        }
75    }
76}
77
78/// [`SelectorType`] refers to the load balancer used when creating tables.
79#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Default, AsRefStr)]
80#[serde(try_from = "String")]
81pub enum SelectorType {
82    /// The current load balancing is based on the number of regions on each datanode node;
83    /// the more regions, the higher the load (it may be changed to Capacity Units(CU)
84    /// calculation in the future).
85    LoadBased,
86    /// This one randomly selects from all available (in lease) nodes. Its characteristic
87    /// is simplicity and fast.
88    LeaseBased,
89    /// This one selects the node in a round-robin way.
90    /// In most cases, it's recommended and is the default option. If you're unsure which
91    /// to choose, using it is usually correct.
92    #[default]
93    RoundRobin,
94}
95
96impl TryFrom<&str> for SelectorType {
97    type Error = error::Error;
98
99    fn try_from(value: &str) -> Result<Self> {
100        match value {
101            "load_based" | "LoadBased" => Ok(SelectorType::LoadBased),
102            "lease_based" | "LeaseBased" => Ok(SelectorType::LeaseBased),
103            "round_robin" | "RoundRobin" => Ok(SelectorType::RoundRobin),
104            other => error::UnsupportedSelectorTypeSnafu {
105                selector_type: other,
106            }
107            .fail(),
108        }
109    }
110}
111
112impl TryFrom<String> for SelectorType {
113    type Error = error::Error;
114
115    fn try_from(value: String) -> Result<Self> {
116        SelectorType::try_from(value.as_str())
117    }
118}
119
120#[cfg(test)]
121mod tests {
122    use super::SelectorType;
123    use crate::error::Result;
124
125    #[test]
126    fn test_default_selector_type() {
127        assert_eq!(SelectorType::RoundRobin, SelectorType::default());
128    }
129
130    #[test]
131    fn test_convert_str_to_selector_type() {
132        let lease_based = "lease_based";
133        let selector_type = lease_based.try_into().unwrap();
134        assert_eq!(SelectorType::LeaseBased, selector_type);
135        let lease_based = "LeaseBased";
136        let selector_type = lease_based.try_into().unwrap();
137        assert_eq!(SelectorType::LeaseBased, selector_type);
138
139        let load_based = "load_based";
140        let selector_type = load_based.try_into().unwrap();
141        assert_eq!(SelectorType::LoadBased, selector_type);
142        let load_based = "LoadBased";
143        let selector_type = load_based.try_into().unwrap();
144        assert_eq!(SelectorType::LoadBased, selector_type);
145
146        let unknown = "unknown";
147        let selector_type: Result<SelectorType> = unknown.try_into();
148        assert!(selector_type.is_err());
149    }
150}
meta_srv/selector.rs

meta_srv/
selector.rs
