add hashbrown and ahash as optional dependency

Author: lalitb

opentelemetry-sdk/Cargo.toml

@@ -12,12 +12,14 @@ rust-version = "1.65"
 [dependencies]
 opentelemetry = { version = "0.21", path = "../opentelemetry/" }
 opentelemetry-http = { version = "0.10", path = "../opentelemetry-http", optional = true }
+ahash = { version = "0.8", optional = true }
 async-std = { workspace = true, features = ["unstable"], optional = true }
 async-trait = { workspace = true, optional = true }
 crossbeam-channel = { version = "0.5", optional = true }
 futures-channel = "0.3"
 futures-executor = { workspace = true }
 futures-util = { workspace = true, features = ["std", "sink", "async-await-macro"] }
+hashbrown = { version = "0.14", optional = true }
 once_cell = { workspace = true }
 ordered-float = { workspace = true }
 percent-encoding = { version = "2.0", optional = true }
@@ -54,6 +56,7 @@ testing = ["opentelemetry/testing", "trace", "metrics", "logs", "rt-async-std",
 rt-tokio = ["tokio", "tokio-stream"]
 rt-tokio-current-thread = ["tokio", "tokio-stream"]
 rt-async-std = ["async-std"]
+use_hashbrown = ["hashbrown", "ahash"]
 
 [[bench]]
 name = "context"

opentelemetry-sdk/src/metrics/internal/sum.rs

@@ -1,16 +1,25 @@
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::{
-    collections::{hash_map::Entry, HashMap},
     sync::{Arc, Mutex},
     time::SystemTime,
 };
 
 use crate::attributes::AttributeSet;
 use crate::metrics::data::{self, Aggregation, DataPoint, Temporality};
 use opentelemetry::{global, metrics::MetricsError};
-use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};
 
+#[cfg(feature = "use_hashbrown")]
+use ahash::AHasher;
+#[cfg(feature = "use_hashbrown")]
+use hashbrown::{hash_map::Entry, HashMap};
+
+#[cfg(not(feature = "use_hashbrown"))]
+use std::collections::{
+    hash_map::{DefaultHasher, Entry},
+    HashMap,
+};
+
 use super::{
     aggregate::{is_under_cardinality_limit, STREAM_OVERFLOW_ATTRIBUTE_SET},
     AtomicTracker, Number,
@@ -48,7 +57,11 @@ impl<T: Number<T>> ValueMap<T> {
 
     // Hash function to determine the bucket
     fn hash_to_bucket(key: &AttributeSet) -> u8 {
+        #[cfg(not(feature = "use_hashbrown"))]
         let mut hasher = DefaultHasher::new();
+        #[cfg(feature = "use_hashbrown")]
+        let mut hasher = AHasher::default();
+
         key.hash(&mut hasher);
         // Use the 8 least significant bits directly, avoiding the modulus operation.
         hasher.finish() as u8

stress/Cargo.toml

@@ -24,7 +24,7 @@ ctrlc = "3.2.5"
 lazy_static = "1.4.0"
 num_cpus = "1.15.0"
 opentelemetry = { path = "../opentelemetry", features = ["metrics", "logs", "trace"] }
-opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["metrics", "logs", "trace"] }
+opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["metrics", "logs", "trace", "use_hashbrown"] }
 opentelemetry-appender-tracing = { path = "../opentelemetry-appender-tracing"}
 rand = { version = "0.8.4", features = ["small_rng"] }
 tracing = { workspace = true, features = ["std"]}