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| 1 | +//! Kubernetes service discovery for groupcache. |
| 2 | +//! |
| 3 | +//! Discovers peers by listing pods matching a label selector via the |
| 4 | +//! Kubernetes API server. Requires the `kubernetes` feature. |
| 5 | +//! |
| 6 | +//! # Example |
| 7 | +//! |
| 8 | +//! ```no_run |
| 9 | +//! use groupcache::discovery::kubernetes::KubernetesDiscovery; |
| 10 | +//! |
| 11 | +//! # async fn example() -> Result<(), Box<dyn std::error::Error + Send + Sync>> { |
| 12 | +//! let client = kube::Client::try_default().await?; |
| 13 | +//! let discovery = KubernetesDiscovery::builder() |
| 14 | +//! .client(client) |
| 15 | +//! .label_selector("app=my-cache") |
| 16 | +//! .port(8080) |
| 17 | +//! .build()?; |
| 18 | +//! # Ok(()) |
| 19 | +//! # } |
| 20 | +//! ``` |
| 21 | +
|
| 22 | +use crate::groupcache::GroupcachePeer; |
| 23 | +use crate::service_discovery::ServiceDiscovery; |
| 24 | +use async_trait::async_trait; |
| 25 | +use k8s_openapi::api::core::v1::Pod; |
| 26 | +use kube::api::ListParams; |
| 27 | +use kube::{Api, Client}; |
| 28 | +use std::collections::HashSet; |
| 29 | +use std::error::Error; |
| 30 | +use std::net::SocketAddr; |
| 31 | +use std::time::Duration; |
| 32 | + |
| 33 | +/// Kubernetes-based service discovery for groupcache peers. |
| 34 | +/// |
| 35 | +/// Lists pods matching a label selector and extracts pod IPs to build |
| 36 | +/// the peer set. Uses the Kubernetes API server (via the `kube` crate). |
| 37 | +pub struct KubernetesDiscovery { |
| 38 | + api: Api<Pod>, |
| 39 | + label_selector: String, |
| 40 | + port: u16, |
| 41 | + poll_interval: Duration, |
| 42 | +} |
| 43 | + |
| 44 | +/// Builder for [`KubernetesDiscovery`]. |
| 45 | +pub struct KubernetesDiscoveryBuilder { |
| 46 | + client: Option<Client>, |
| 47 | + namespace: Option<String>, |
| 48 | + label_selector: Option<String>, |
| 49 | + port: Option<u16>, |
| 50 | + poll_interval: Option<Duration>, |
| 51 | +} |
| 52 | + |
| 53 | +impl KubernetesDiscoveryBuilder { |
| 54 | + /// Set the Kubernetes client. Required. |
| 55 | + pub fn client(mut self, client: Client) -> Self { |
| 56 | + self.client = Some(client); |
| 57 | + self |
| 58 | + } |
| 59 | + |
| 60 | + /// Set a specific namespace. Defaults to the pod's own namespace. |
| 61 | + pub fn namespace(mut self, namespace: impl Into<String>) -> Self { |
| 62 | + self.namespace = Some(namespace.into()); |
| 63 | + self |
| 64 | + } |
| 65 | + |
| 66 | + /// Set the label selector for discovering peer pods. Required. |
| 67 | + /// |
| 68 | + /// Example: `"app=my-groupcache-service"` |
| 69 | + pub fn label_selector(mut self, selector: impl Into<String>) -> Self { |
| 70 | + self.label_selector = Some(selector.into()); |
| 71 | + self |
| 72 | + } |
| 73 | + |
| 74 | + /// Set the port that groupcache peers listen on. Required. |
| 75 | + pub fn port(mut self, port: u16) -> Self { |
| 76 | + self.port = Some(port); |
| 77 | + self |
| 78 | + } |
| 79 | + |
| 80 | + /// Set the polling interval for service discovery. Default: 10 seconds. |
| 81 | + pub fn poll_interval(mut self, interval: Duration) -> Self { |
| 82 | + self.poll_interval = Some(interval); |
| 83 | + self |
| 84 | + } |
| 85 | + |
| 86 | + /// Build the [`KubernetesDiscovery`] instance. |
| 87 | + /// |
| 88 | + /// # Errors |
| 89 | + /// |
| 90 | + /// Returns an error if `client`, `label_selector`, or `port` were not set. |
| 91 | + pub fn build(self) -> Result<KubernetesDiscovery, Box<dyn Error + Send + Sync>> { |
| 92 | + let client = self |
| 93 | + .client |
| 94 | + .ok_or("KubernetesDiscovery requires a kube::Client")?; |
| 95 | + let label_selector = self |
| 96 | + .label_selector |
| 97 | + .ok_or("KubernetesDiscovery requires a label_selector")?; |
| 98 | + let port = self |
| 99 | + .port |
| 100 | + .ok_or("KubernetesDiscovery requires a port")?; |
| 101 | + |
| 102 | + let api = match self.namespace { |
| 103 | + Some(ns) => Api::namespaced(client, &ns), |
| 104 | + None => Api::default_namespaced(client), |
| 105 | + }; |
| 106 | + |
| 107 | + Ok(KubernetesDiscovery { |
| 108 | + api, |
| 109 | + label_selector, |
| 110 | + port, |
| 111 | + poll_interval: self.poll_interval.unwrap_or(Duration::from_secs(10)), |
| 112 | + }) |
| 113 | + } |
| 114 | +} |
| 115 | + |
| 116 | +impl KubernetesDiscovery { |
| 117 | + /// Create a new builder. |
| 118 | + pub fn builder() -> KubernetesDiscoveryBuilder { |
| 119 | + KubernetesDiscoveryBuilder { |
| 120 | + client: None, |
| 121 | + namespace: None, |
| 122 | + label_selector: None, |
| 123 | + port: None, |
| 124 | + poll_interval: None, |
| 125 | + } |
| 126 | + } |
| 127 | +} |
| 128 | + |
| 129 | +#[async_trait] |
| 130 | +impl ServiceDiscovery for KubernetesDiscovery { |
| 131 | + async fn pull_instances( |
| 132 | + &self, |
| 133 | + ) -> Result<HashSet<GroupcachePeer>, Box<dyn Error + Send + Sync + 'static>> { |
| 134 | + let params = ListParams::default().labels(&self.label_selector); |
| 135 | + let pods = self.api.list(¶ms).await?; |
| 136 | + |
| 137 | + let peers = pods |
| 138 | + .into_iter() |
| 139 | + .filter_map(|pod| { |
| 140 | + let pod_ip = pod.status?.pod_ip?; |
| 141 | + let ip = pod_ip.parse().ok()?; |
| 142 | + let addr = SocketAddr::new(ip, self.port); |
| 143 | + Some(GroupcachePeer::from_socket(addr)) |
| 144 | + }) |
| 145 | + .collect(); |
| 146 | + |
| 147 | + Ok(peers) |
| 148 | + } |
| 149 | + |
| 150 | + fn interval(&self) -> Duration { |
| 151 | + self.poll_interval |
| 152 | + } |
| 153 | +} |
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