Reduce allocations

src/filter.rs

@@ -1,20 +1,13 @@
 use std::str;
 
-pub fn filter(block_list: &Vec<String>, buf: &[u8]) -> String {
+pub fn filter<'a>(block_list: &'a Vec<String>, buf: &'a [u8]) -> Vec<&'a str> {
     let statsd_str = unsafe { str::from_utf8_unchecked(&buf) };
 
-    let result_itr = statsd_str.split("\n").filter(|line| {
-        for prefix in block_list.iter() {
-            if line.starts_with(prefix) {
-                return false;
-            }
-        }
-        return true;
-    });
-
-    let result = result_itr.collect::<Vec<&str>>().join("\n");
-
-    return result;
+    statsd_str.split("\n")
+        .filter(|line| {
+            !block_list.iter().any(|prefix| line.starts_with(prefix))
+        })
+        .collect::<Vec<&str>>()
 }
 
 #[cfg(test)]
@@ -25,7 +18,7 @@ mod tests {
     fn test_should_not_block_multi_metric() {
         let block_list = vec![String::from("notfoo"), String::from("otherfoo")];
         let statsd_str_bytes = "foo:1|c\nfoo:2|c\nfoo:3|c".as_bytes();
-        let result = filter(&block_list, &statsd_str_bytes);
+        let result = filter(&block_list, &statsd_str_bytes).join("\n");
         assert_eq!("foo:1|c\nfoo:2|c\nfoo:3|c", result);
     }
 
@@ -34,31 +27,31 @@ mod tests {
     fn test_should_not_block_single_metric() {
         let block_list = vec![String::from("notfoo"), String::from("otherfoo")];
         let statsd_str_bytes = "foo:1|c".as_bytes();
-        let result = filter(&block_list, &statsd_str_bytes);
+        let result = filter(&block_list, &statsd_str_bytes).join("\n");
         assert_eq!("foo:1|c", result);
     }
 
     #[test]
     fn test_should_block_completely_single_metric() {
         let block_list = vec![String::from("foo"), String::from("otherfoo")];
         let statsd_str_bytes = "foo:1|c".as_bytes();
-        let result = filter(&block_list, &statsd_str_bytes);
+        let result = filter(&block_list, &statsd_str_bytes).join("\n");
         assert_eq!("", result);
     }
 
     #[test]
     fn test_should_block_completely_multi_metric() {
         let block_list = vec![String::from("foo"), String::from("otherfoo")];
         let statsd_str_bytes = "foo:1|c\nfoo:2|c\nfoo:3|c".as_bytes();
-        let result = filter(&block_list, &statsd_str_bytes);
+        let result = filter(&block_list, &statsd_str_bytes).join("\n");
         assert_eq!("", result);
     }
 
     #[test]
     fn test_should_block_partially_multi_metric() {
         let block_list = vec![String::from("foo"), String::from("otherfoo")];
         let statsd_str_bytes = "notfoo:1|c\nfoo:2|c\nnotfoo:3|c".as_bytes();
-        let result = filter(&block_list, &statsd_str_bytes);
+        let result = filter(&block_list, &statsd_str_bytes).join("\n");
         assert_eq!("notfoo:1|c\nnotfoo:3|c", result);
     }
 }

src/server.rs

@@ -44,8 +44,9 @@ pub async fn run_server(config: Config) -> io::Result<()> {
             let target_addr_clone = target_addr.clone();
             let blocklist_clone = blocklist.clone();
             tokio::spawn(async move {
-                let filtered_string = filter(&blocklist_clone, &buf[..len]);
-                if filtered_string.len() > 0 {
+                let filtered_string_parts = filter(&blocklist_clone, &buf[..len]);
+                if !filtered_string_parts.is_empty() {
+                    let filtered_string = filtered_string_parts.join("\n");
                     let len = sock_clone
                         .send_to(filtered_string.as_bytes(), &*target_addr_clone)
                         .await
@@ -60,8 +61,9 @@ pub async fn run_server(config: Config) -> io::Result<()> {
                 }
             });
         } else {
-            let filtered_string = filter(&blocklist, &buf[..len]);
-            if filtered_string.len() > 0 {
+            let filtered_string_parts = filter(&blocklist, &buf[..len]);
+            if !filtered_string_parts.is_empty() {
+                let filtered_string = filtered_string_parts.join("\n");
                 let len = sock
                     .send_to(filtered_string.as_bytes(), &*target_addr)
                     .await