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| 1 | +//! Resource pool implementation |
| 2 | +// TODO: fix tests |
| 3 | +use anyhow::anyhow; |
| 4 | +use std::{ |
| 5 | + collections::VecDeque, |
| 6 | + ops::{Deref, DerefMut}, |
| 7 | + sync::{Condvar, Mutex}, |
| 8 | + time::Duration, |
| 9 | +}; |
| 10 | + |
| 11 | +use crate::StdResult; |
| 12 | + |
| 13 | +/// Resource pool FIFO implementation |
| 14 | +pub struct ResourcePool<T: Send + Sync> { |
| 15 | + /// The size of the pool |
| 16 | + size: usize, |
| 17 | + |
| 18 | + /// Discriminant for the resource pool to check if a returned resource is stale |
| 19 | + discriminant: Mutex<u64>, |
| 20 | + |
| 21 | + /// Resources in the pool |
| 22 | + resources: Mutex<VecDeque<T>>, |
| 23 | + |
| 24 | + /// Condition variable to notify when a resource is available |
| 25 | + not_empty: Condvar, |
| 26 | +} |
| 27 | + |
| 28 | +impl<T: Send + Sync> ResourcePool<T> { |
| 29 | + /// Create a new resource pool |
| 30 | + pub fn new(pool_size: usize, resources: Vec<T>) -> Self { |
| 31 | + Self { |
| 32 | + size: pool_size, |
| 33 | + discriminant: Mutex::new(0), |
| 34 | + resources: Mutex::new(resources.into()), |
| 35 | + not_empty: Condvar::new(), |
| 36 | + } |
| 37 | + } |
| 38 | + |
| 39 | + /// Acquire a resource from the pool |
| 40 | + pub fn acquire_resource(&self) -> ResourcePoolItem<'_, T> { |
| 41 | + self.acquire_resource_with_timeout(Duration::MAX).unwrap() |
| 42 | + } |
| 43 | + |
| 44 | + /// Acquire a resource from the pool with a timeout |
| 45 | + pub fn acquire_resource_with_timeout( |
| 46 | + &self, |
| 47 | + duration: Duration, |
| 48 | + ) -> StdResult<ResourcePoolItem<'_, T>> { |
| 49 | + let mut resources = self.resources.lock().unwrap(); |
| 50 | + while resources.is_empty() { |
| 51 | + let (resources_locked, timeout) = |
| 52 | + self.not_empty.wait_timeout(resources, duration).unwrap(); |
| 53 | + if timeout.timed_out() { |
| 54 | + return Err(anyhow!("Acquire resource has timed out")); |
| 55 | + } |
| 56 | + resources = resources_locked; |
| 57 | + } |
| 58 | + |
| 59 | + Ok(ResourcePoolItem::new(self, resources.pop_front().unwrap())) |
| 60 | + } |
| 61 | + |
| 62 | + /// Return a resource to the pool |
| 63 | + /// A resource is returned to the pool only if the discriminant matches |
| 64 | + /// and if the pool is not already full |
| 65 | + pub fn return_resource(&self, resource: T, discriminant: u64) { |
| 66 | + if self.count() == self.size { |
| 67 | + return; |
| 68 | + } |
| 69 | + let mut resources = self.resources.lock().unwrap(); |
| 70 | + if self.discriminant() != discriminant { |
| 71 | + return; |
| 72 | + } |
| 73 | + resources.push_back(resource); |
| 74 | + self.not_empty.notify_one(); |
| 75 | + } |
| 76 | + |
| 77 | + /// Drain the pool |
| 78 | + pub fn drain(&self) { |
| 79 | + let mut resources = self.resources.lock().unwrap(); |
| 80 | + let _ = resources.drain(..).collect::<Vec<_>>(); |
| 81 | + } |
| 82 | + |
| 83 | + /// Get the discriminant of the resource pool item |
| 84 | + pub fn discriminant(&self) -> u64 { |
| 85 | + *self.discriminant.lock().unwrap() |
| 86 | + } |
| 87 | + |
| 88 | + /// Set the discriminant of the resource pool item |
| 89 | + pub fn set_discriminant(&self, discriminant: u64) { |
| 90 | + *self.discriminant.lock().unwrap() = discriminant; |
| 91 | + } |
| 92 | + |
| 93 | + /// Count the resources in the pool |
| 94 | + pub fn count(&self) -> usize { |
| 95 | + self.resources.lock().unwrap().len() |
| 96 | + } |
| 97 | + |
| 98 | + /// Size of the resource pool |
| 99 | + pub fn size(&self) -> usize { |
| 100 | + self.size |
| 101 | + } |
| 102 | +} |
| 103 | + |
| 104 | +impl<T: Send + Sync> Default for ResourcePool<T> { |
| 105 | + fn default() -> Self { |
| 106 | + Self::new(10, vec![]) |
| 107 | + } |
| 108 | +} |
| 109 | + |
| 110 | +/// Resource pool item which will return the resource to the pool when dropped |
| 111 | +pub struct ResourcePoolItem<'a, T: Send + Sync> { |
| 112 | + resource_pool: &'a ResourcePool<T>, |
| 113 | + discriminant: u64, |
| 114 | + resource: Option<T>, |
| 115 | +} |
| 116 | + |
| 117 | +impl<'a, T: Send + Sync> ResourcePoolItem<'a, T> { |
| 118 | + /// Create a new resource pool item |
| 119 | + pub fn new(resource_pool: &'a ResourcePool<T>, resource: T) -> Self { |
| 120 | + let discriminant = *resource_pool.discriminant.lock().unwrap(); |
| 121 | + Self { |
| 122 | + resource_pool, |
| 123 | + discriminant, |
| 124 | + resource: Some(resource), |
| 125 | + } |
| 126 | + } |
| 127 | + |
| 128 | + /// Get the discriminant of the resource pool item |
| 129 | + pub fn discriminant(&self) -> u64 { |
| 130 | + self.discriminant |
| 131 | + } |
| 132 | + |
| 133 | + /// Get a reference to the inner resource |
| 134 | + pub fn resource(&self) -> &T { |
| 135 | + self.resource.as_ref().unwrap() |
| 136 | + } |
| 137 | + |
| 138 | + /// Take the inner resource |
| 139 | + pub fn into_inner(&mut self) -> T { |
| 140 | + self.resource.take().unwrap() |
| 141 | + } |
| 142 | +} |
| 143 | + |
| 144 | +impl<T: Send + Sync> Deref for ResourcePoolItem<'_, T> { |
| 145 | + type Target = T; |
| 146 | + |
| 147 | + fn deref(&self) -> &T { |
| 148 | + self.resource.as_ref().unwrap() |
| 149 | + } |
| 150 | +} |
| 151 | + |
| 152 | +impl<T: Send + Sync> DerefMut for ResourcePoolItem<'_, T> { |
| 153 | + fn deref_mut(&mut self) -> &mut T { |
| 154 | + self.resource.as_mut().unwrap() |
| 155 | + } |
| 156 | +} |
| 157 | + |
| 158 | +impl<T: Send + Sync> Drop for ResourcePoolItem<'_, T> { |
| 159 | + fn drop(&mut self) { |
| 160 | + let resource = self.into_inner(); |
| 161 | + self.resource_pool |
| 162 | + .return_resource(resource, self.discriminant); |
| 163 | + } |
| 164 | +} |
| 165 | + |
| 166 | +#[cfg(test)] |
| 167 | +mod tests { |
| 168 | + use std::time::Duration; |
| 169 | + |
| 170 | + use super::*; |
| 171 | + |
| 172 | + #[test] |
| 173 | + fn test_resource_pool_acquire_returns_resource_when_available() { |
| 174 | + let pool_size = 10; |
| 175 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 176 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 177 | + |
| 178 | + let mut resources_items = vec![]; |
| 179 | + for _ in 0..pool_size { |
| 180 | + let resource_item = pool |
| 181 | + .acquire_resource_with_timeout(Duration::from_millis(1000)) |
| 182 | + .unwrap(); |
| 183 | + resources_items.push(resource_item); |
| 184 | + } |
| 185 | + let resources_result = resources_items |
| 186 | + .iter_mut() |
| 187 | + .map(|resource_item| resource_item.resource().to_owned()) |
| 188 | + .collect::<Vec<_>>(); |
| 189 | + |
| 190 | + assert_eq!(resources_expected, resources_result); |
| 191 | + assert_eq!(pool.count(), 0); |
| 192 | + } |
| 193 | + |
| 194 | + #[tokio::test] |
| 195 | + async fn test_resource_pool_acquire_locks_when_no_resource_available() { |
| 196 | + let pool_size = 10; |
| 197 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 198 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 199 | + |
| 200 | + let mut resources_items = vec![]; |
| 201 | + for _ in 0..pool_size { |
| 202 | + let resource_item = pool |
| 203 | + .acquire_resource_with_timeout(Duration::from_millis(1000)) |
| 204 | + .unwrap(); |
| 205 | + resources_items.push(resource_item); |
| 206 | + } |
| 207 | + |
| 208 | + assert!(pool |
| 209 | + .acquire_resource_with_timeout(Duration::from_millis(1000)) |
| 210 | + .is_err()); |
| 211 | + } |
| 212 | + |
| 213 | + #[tokio::test] |
| 214 | + async fn test_resource_pool_drains_successfully() { |
| 215 | + let pool_size = 10; |
| 216 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 217 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 218 | + assert_eq!(pool.count(), pool_size); |
| 219 | + |
| 220 | + pool.drain(); |
| 221 | + |
| 222 | + assert_eq!(pool.count(), 0); |
| 223 | + } |
| 224 | + |
| 225 | + #[tokio::test] |
| 226 | + async fn test_resource_pool_returns_fresh_resource() { |
| 227 | + let pool_size = 10; |
| 228 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 229 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 230 | + assert_eq!(pool.count(), pool_size); |
| 231 | + |
| 232 | + let mut resource_item = pool |
| 233 | + .acquire_resource_with_timeout(Duration::from_millis(1000)) |
| 234 | + .unwrap(); |
| 235 | + assert_eq!(pool.count(), pool_size - 1); |
| 236 | + pool.return_resource(resource_item.into_inner(), pool.discriminant()); |
| 237 | + |
| 238 | + assert_eq!(pool.count(), pool_size); |
| 239 | + } |
| 240 | + |
| 241 | + #[tokio::test] |
| 242 | + async fn test_resource_pool_returns_automatically_resource() { |
| 243 | + let pool_size = 10; |
| 244 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 245 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 246 | + assert_eq!(pool.count(), pool_size); |
| 247 | + |
| 248 | + { |
| 249 | + let _resource_item = pool |
| 250 | + .acquire_resource_with_timeout(Duration::from_millis(1000)) |
| 251 | + .unwrap(); |
| 252 | + assert_eq!(pool.count(), pool_size - 1); |
| 253 | + } |
| 254 | + |
| 255 | + assert_eq!(pool.count(), pool_size); |
| 256 | + } |
| 257 | + |
| 258 | + #[tokio::test] |
| 259 | + async fn test_resource_pool_does_not_return_resource_when_pool_is_full() { |
| 260 | + let pool_size = 10; |
| 261 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 262 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 263 | + assert_eq!(pool.count(), pool_size); |
| 264 | + |
| 265 | + pool.return_resource("resource".to_string(), pool.discriminant()); |
| 266 | + |
| 267 | + assert_eq!(pool.count(), pool_size); |
| 268 | + } |
| 269 | + |
| 270 | + #[tokio::test] |
| 271 | + async fn test_resource_pool_does_not_return_stale_resource() { |
| 272 | + let pool_size = 10; |
| 273 | + let resources_expected: Vec<String> = (0..pool_size).map(|i| i.to_string()).collect(); |
| 274 | + let pool = ResourcePool::<String>::new(pool_size, resources_expected.clone()); |
| 275 | + assert_eq!(pool.count(), pool_size); |
| 276 | + |
| 277 | + let mut resource_item = pool |
| 278 | + .acquire_resource_with_timeout(Duration::from_millis(1000)) |
| 279 | + .unwrap(); |
| 280 | + assert_eq!(pool.count(), pool_size - 1); |
| 281 | + let discriminant_stale = pool.discriminant(); |
| 282 | + pool.set_discriminant(pool.discriminant() + 1); |
| 283 | + pool.return_resource(resource_item.into_inner(), discriminant_stale); |
| 284 | + |
| 285 | + assert_eq!(pool.count(), pool_size - 1); |
| 286 | + } |
| 287 | +} |
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