Add metrics tracking DatabaseFileHandler usage

Author: Nemo157

src/web/file.rs

@@ -1,7 +1,7 @@
 //! Database based file handler
 
 use crate::storage::{Blob, Storage};
-use crate::{error::Result, Config};
+use crate::{error::Result, Config, Metrics};
 use iron::{status, Handler, IronResult, Request, Response};
 
 #[derive(Debug)]
@@ -60,6 +60,15 @@ impl Handler for DatabaseFileHandler {
         let storage = extension!(req, Storage);
         let config = extension!(req, Config);
         if let Ok(file) = File::from_path(&storage, &path, &config) {
+            let metrics = extension!(req, Metrics);
+
+            // Because all requests that don't hit another handler go through here, we will get all
+            // requests successful or not recorded by the RequestRecorder, so we inject an extra
+            // "database success" route to keep track of how often we succeed vs 404
+            metrics
+                .routes_visited
+                .with_label_values(&["database success"])
+                .inc();
             Ok(file.serve())
         } else {
             Err(super::error::Nope::CrateNotFound.into())

src/web/metrics.rs

@@ -133,6 +133,8 @@ mod tests {
             ("/-/sitemap.xml", "static resource"),
             ("/-/static/style.css", "static resource"),
             ("/-/static/vendored.css", "static resource"),
+            ("/rustdoc/rcc/0.0.0/rcc/index.html", "database"),
+            ("/rustdoc/gcc/0.0.0/gcc/index.html", "database"),
         ];
 
         wrapper(|env| {
@@ -179,6 +181,15 @@ mod tests {
                 );
             }
 
+            // extra metrics for the "database success" hack
+            assert_eq!(
+                metrics
+                    .routes_visited
+                    .with_label_values(&["database success"])
+                    .get(),
+                2
+            );
+
             Ok(())
         })
     }

src/web/mod.rs

@@ -103,6 +103,7 @@ use iron::{
     status::Status,
     Chain, Handler, Iron, IronError, IronResult, Listening, Request, Response, Url,
 };
+use metrics::RequestRecorder;
 use page::TemplateData;
 use postgres::Client;
 use router::NoRoute;
@@ -148,7 +149,7 @@ impl CratesfyiHandler {
             router_handler: Box::new(router_chain),
             database_file_handler: Box::new(routes::BlockBlacklistedPrefixes::new(
                 blacklisted_prefixes,
-                Box::new(file::DatabaseFileHandler),
+                Box::new(RequestRecorder::new(file::DatabaseFileHandler, "database")),
             )),
             inject_extensions,
         })