feat: Add local server hostname to tags (#234)

* feat: Add local server hostname to tags
* move `srv.hostname` to metric only tag.

Closes #200 

Co-authored-by: Raphael Pierzina <raphael@hackebrot.de>

Cargo.toml

@@ -32,6 +32,7 @@ cloud-storage = { git = "https://github.com/mozilla-services/cloud-storage-rs",
 config = "0.11"
 dashmap = "4.0.2"
 futures = "0.3"
+gethostname = "0.2.1"
 hex = "0.4"
 hostname = "0.3"
 image = "0.23"

src/adm/tiles.rs

@@ -162,6 +162,15 @@ pub async fn get_tiles(
     .map_err(|e| HandlerError::internal(&e.to_string()))?;
     let adm_url = adm_url.as_str();
 
+    // To reduce cardinality, only add this tag when fetching data from
+    // the partner. (This tag is only for metrics.)
+    tags.add_metric(
+        "srv.hostname",
+        &gethostname::gethostname()
+            .into_string()
+            .unwrap_or_else(|_| "Unkwnown".to_owned()),
+    );
+
     info!("adm::get_tiles GET {}", adm_url);
     metrics.incr("tiles.adm.request");
     let response: AdmTileResponse = if state.settings.test_mode {

src/metrics.rs

@@ -179,6 +179,12 @@ impl Metrics {
                     tagged = tagged.with_tag(key, val.as_ref());
                 }
             }
+            // mix in the metric only tags.
+            for key in mtags.metric.keys().clone() {
+                if let Some(val) = mtags.metric.get(key) {
+                    tagged = tagged.with_tag(key, val.as_ref())
+                }
+            }
             // Include any "hard coded" tags.
             // incr = incr.with_tag("version", env!("CARGO_PKG_VERSION"));
             match tagged.try_send() {
@@ -235,7 +241,6 @@ mod tests {
     fn test_tags() {
         use actix_web::dev::RequestHead;
         use actix_web::http::{header, uri::Uri};
-        use std::collections::HashMap;
 
         let mut rh = RequestHead::default();
         let settings = Settings::default();
@@ -250,13 +255,10 @@ mod tests {
 
         let tags = Tags::from_head(&rh, &settings);
 
-        let mut result = HashMap::<String, String>::new();
-        result.insert("ua.os.ver".to_owned(), "NT 10.0".to_owned());
-        result.insert("ua.os.family".to_owned(), "Windows".to_owned());
-        result.insert("ua.browser.ver".to_owned(), "72.0".to_owned());
-        result.insert("uri.method".to_owned(), "GET".to_owned());
-
-        assert_eq!(tags.tags, result)
+        assert_eq!(tags.tags.get("ua.os.ver"), Some(&"NT 10.0".to_owned()));
+        assert_eq!(tags.tags.get("ua.os.family"), Some(&"Windows".to_owned()));
+        assert_eq!(tags.tags.get("ua.browser.ver"), Some(&"72.0".to_owned()));
+        assert_eq!(tags.tags.get("uri.method"), Some(&"GET".to_owned()));
     }
 
     #[test]

src/server/cache.rs

@@ -51,7 +51,7 @@ impl TilesCache {
         let metrics = Metrics::from(&metrics);
         actix_rt::spawn(async move {
             loop {
-                tiles_cache_periodic_reporter(&cache, &metrics).await;
+                tiles_cache_garbage_collect(&cache, &metrics).await;
                 actix_rt::time::delay_for(interval).await;
             }
         });
@@ -135,8 +135,8 @@ impl TilesContent {
     }
 }
 
-async fn tiles_cache_periodic_reporter(cache: &TilesCache, metrics: &Metrics) {
-    trace!("tiles_cache_periodic_reporter");
+async fn tiles_cache_garbage_collect(cache: &TilesCache, metrics: &Metrics) {
+    trace!("tiles_cache_garbage_collect");
     // calculate the size and GC (for seldomly used Tiles) while we're at it
     let mut cache_count = 0;
     let mut cache_size = 0;

src/tags.rs

@@ -78,15 +78,20 @@ pub fn parse_user_agent(agent: &str) -> (WootheeResult<'_>, &str) {
 /// `extra` are not searchable, but may not be sent to [crate::metrics::Metrics].
 #[derive(Clone, Debug)]
 pub struct Tags {
+    // All tags (both metric and sentry)
     pub tags: HashMap<String, String>,
+    // Sentry only "extra" data.
     pub extra: HashMap<String, String>,
+    // metric only supplemental tags.
+    pub metric: HashMap<String, String>,
 }
 
 impl Default for Tags {
     fn default() -> Tags {
         Tags {
             tags: HashMap::new(),
             extra: HashMap::new(),
+            metric: HashMap::new(),
         }
     }
 }
@@ -142,7 +147,11 @@ impl Tags {
         // `uri.path` causes too much cardinality for influx but keep it in
         // extra for sentry
         extra.insert("uri.path".to_owned(), req_head.uri.to_string());
-        Tags { tags, extra }
+        Tags {
+            tags,
+            extra,
+            metric: HashMap::new(),
+        }
     }
 }
 
@@ -166,6 +175,7 @@ impl Tags {
         Self {
             tags: HashMap::new(),
             extra,
+            metric: HashMap::new(),
         }
     }
 }
@@ -189,6 +199,7 @@ impl Tags {
         Tags {
             tags,
             extra: HashMap::new(),
+            metric: HashMap::new(),
         }
     }
 
@@ -213,6 +224,16 @@ impl Tags {
         }
     }
 
+    /// Add an element to the "extra" data.
+    ///
+    /// Extra data is non-key storage used by sentry. It is not
+    /// distributed to metrics.
+    pub fn add_metric(&mut self, key: &str, value: &str) {
+        if !value.is_empty() {
+            self.metric.insert(key.to_owned(), value.to_owned());
+        }
+    }
+
     /// Get a tag value.
     pub fn get(&self, label: &str) -> String {
         let none = "None".to_owned();
@@ -225,6 +246,7 @@ impl Tags {
     pub fn extend(&mut self, tags: Self) {
         self.tags.extend(tags.tags);
         self.extra.extend(tags.extra);
+        self.metric.extend(tags.metric);
     }
 
     /// Convert tag hash to a Binary Tree map (used by cadence and sentry)