"prime" libpostal library when running in server mode (#16)

This allows us to respond to our first request immediately without loading a 2 GB perceptron model during the request.

Author: tomplex

src/geocoders/libpostal.rs

@@ -64,6 +64,20 @@ impl LibPostal {
             .collect::<Vec<_>>();
         LibPostal { column_names }
     }
+
+    pub async fn prime() {
+        // "Prime" libpostal by forcing it to load its language model and associated data
+        // into memory with a dummy call.
+        let libpostal = LibPostal::new();
+        let _ = libpostal
+            .geocode_addresses(&[Address {
+                street: "1 Main St".to_owned(),
+                city: Some("Anytown".to_owned()),
+                state: Some("VT".to_owned()),
+                zipcode: None,
+            }])
+            .await;
+    }
 }
 
 #[async_trait]

src/main.rs

@@ -279,6 +279,11 @@ async fn main() -> Result<()> {
     let result = match opt.cmd {
         // Run in server mode.
         Some(Command::Server { listen_address }) => {
+            // If we're running in server mode, then prime libpostal to load its
+            // model and data into memory. This can take 5-10 seconds,
+            // and we'd prefer that it happens as part of application startup,
+            // rather than at the time of the first request.
+            LibPostal::prime().await;
             run_server(&listen_address, geocoder).await
         }
         // Run in CLI pipeline mode.