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

meta_srv/
selector.rs
