Fix pool size, don't crash if we can't get a connection

When testing in staging, the runner started crashing on boot. This was
because we only set the connection pool size to 1 when we meant to set
it to 2 (one for the runner, one for the worker thread). So in each
loop, if all jobs took greater than 1 second to run, the runner would
crash.

This fixes the pool size, and also does not return an error if no
database connection could be retrieved from the pool.

Author: sgrif

src/background/runner.rs

@@ -57,9 +57,11 @@ impl<Env: RefUnwindSafe + Send + Sync + 'static> Runner<Env> {
     }
 
     pub fn run_all_pending_jobs(&self) -> CargoResult<()> {
-        let available_job_count = storage::available_job_count(&*self.connection()?)?;
-        for _ in 0..available_job_count {
-            self.run_single_job()
+        if let Some(conn) = self.try_connection() {
+            let available_job_count = storage::available_job_count(&conn)?;
+            for _ in 0..available_job_count {
+                self.run_single_job()
+            }
         }
         Ok(())
     }
@@ -112,6 +114,10 @@ impl<Env: RefUnwindSafe + Send + Sync + 'static> Runner<Env> {
         self.connection_pool.get().map_err(Into::into)
     }
 
+    fn try_connection(&self) -> Option<DieselPooledConn> {
+        self.connection_pool.try_get()
+    }
+
     pub fn assert_no_failed_jobs(&self) -> CargoResult<()> {
         self.wait_for_jobs();
         let failed_jobs = storage::failed_job_count(&*self.connection()?)?;

src/bin/background-worker.rs

@@ -19,7 +19,7 @@ fn main() {
     let config = cargo_registry::Config::default();
 
     // We're only using 1 thread, so we only need 2 connections
-    let db_config = r2d2::Pool::builder().max_size(1);
+    let db_config = r2d2::Pool::builder().max_size(2);
     let db_pool = db::diesel_pool(&config.db_url, config.env, db_config);
 
     let username = env::var("GIT_HTTP_USER");

src/db.rs

@@ -27,6 +27,13 @@ impl DieselPool {
         }
     }
 
+    pub fn try_get(&self) -> Option<DieselPooledConn> {
+        match self {
+            DieselPool::Pool(pool) => pool.try_get().map(DieselPooledConn::Pool),
+            DieselPool::Test(conn) => conn.try_lock().map(DieselPooledConn::Test),
+        }
+    }
+
     pub fn state(&self) -> r2d2::State {
         match self {
             DieselPool::Pool(pool) => pool.state(),