Adjust how librato source is calculated (#48)

This modification removes the regex crate and simplifies the way
we pull out the librato source. We add tests and correct an error
if source is at the found at the end of the tag list.

Signed-off-by: Brian L. Troutwine <blt@postmates.com>

Cargo.toml

@@ -12,7 +12,6 @@ mime = "0.2.0"
 rustc-serialize = "0.3.19"
 chrono = "0.2"
 url = "1.1.1"
-regex = "0.1"
 lalrpop-util = "0.11.0"
 string_cache = "0.2.21"
 clap = "2.9.2"

src/backend.rs

@@ -3,7 +3,6 @@ use metric::Metric;
 
 use config::Args;
 
-use regex::Regex;
 use std::sync::Arc;
 
 use std::sync::mpsc::{Receiver, Sender, channel};
@@ -34,6 +33,19 @@ pub trait Backend {
     }
 }
 
+pub fn librato_extract_source(tags: &str) -> &str {
+    for tag in tags.split(",") {
+        let mut tag_pieces = tag.split("=");
+        let name = tag_pieces.next();
+        let val = tag_pieces.next();
+
+        if name == Some("source") {
+            return val.unwrap()
+        }
+    }
+    "cernan"
+}
+
 /// Creates the collection of backends based on the paraemeters
 ///
 pub fn factory(args: Args) -> Vec<Sender<Arc<server::Event>>> {
@@ -69,9 +81,7 @@ pub fn factory(args: Args) -> Vec<Sender<Arc<server::Event>>> {
         // librato does not support arbitrary tags, only a 'source' tag. We have
         // to parse the source tag--if it exists--out and ship only that.
         thread::spawn(move || {
-            let re = Regex::new(r"(?x)(source=(?P<source>.*),+)?").unwrap();
-            let metric_source =
-                re.captures(&cp_args.tags).unwrap().name("source").unwrap_or("cernan");
+            let metric_source = librato_extract_source(&args.tags);
             librato::Librato::new(&cp_args.librato_username.unwrap(),
                                   &cp_args.librato_token.unwrap(),
                                   metric_source,
@@ -82,3 +92,16 @@ pub fn factory(args: Args) -> Vec<Sender<Arc<server::Event>>> {
     }
     backends
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_librato_source_extraction() {
+        assert_eq!("cernan", librato_extract_source("flkjsdf"));
+        assert_eq!("testsrc", librato_extract_source("host=hs,source=testsrc"));
+        assert_eq!("testsrc", librato_extract_source("source=testsrc,host=hs"));
+        assert_eq!("testsrc", librato_extract_source("source=testsrc"));
+    }
+}

src/main.rs

@@ -7,7 +7,6 @@ extern crate mime;
 extern crate rustc_serialize;
 extern crate chrono;
 extern crate url;
-extern crate regex;
 extern crate string_cache;
 extern crate fern;
 #[macro_use]