Fix: Spawn filesystem task on a blocking tokio thread

This patch changes the (possibly heavy) File reading from disk to be executed on
a blocking tokio thread.
This way, we ensure we do not block until the `read()` operation is finished and
can continue executing async tasks on the runtime.

Because IO might be expensive (think of a 5GB file that is read to memory), this
is a good optimization.

Signed-off-by: Matthias Beyer <matthias.beyer@atos.net>

2 files changed, 16 insertions, 10 deletions

diff --git a/Cargo.toml b/Cargo.toml
index ed3a4e4..8f3c7c5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -42,7 +42,7 @@ shiplift       = { git = "https://github.com/softprops/shiplift", rev = "03cc8c0
 syntect        = "4.4"
 tar            = "0.4"
 terminal_size  = "0.1"
-tokio          = { version = "0.2", features = ["macros", "fs", "process", "io-util"] }
+tokio          = { version = "0.2", features = ["macros", "fs", "process", "io-util", "blocking"] }
 toml           = "0.5"
 typed-builder  = "0.7"
 unindent       = "0.1"
diff --git a/src/source/mod.rs b/src/source/mod.rs
index c2a5bb0..20671bc 100644
--- a/src/source/mod.rs
+++ b/src/source/mod.rs
@@ -81,18 +81,24 @@ impl SourceEntry {
     }
 
     pub async fn verify_hash(&self) -> Result<()> {
-        use std::io::Read;
 
         let p = self.source_file_path();
-
         trace!("Reading to buffer: {}", p.display());
-        let mut buf = vec![];
-        std::fs::OpenOptions::new()
-            .create(false)
-            .create_new(false)
-            .read(true)
-            .open(&p)?
-            .read_to_end(&mut buf)?;
+
+        let path = p.clone();
+        let buf = tokio::task::spawn_blocking(move || {
+            use std::io::Read;
+
+            let mut buf = vec![];
+            std::fs::OpenOptions::new()
+                .create(false)
+                .create_new(false)
+                .read(true)
+                .open(path)?
+                .read_to_end(&mut buf)
+                .map(|_| buf)
+        })
+        .await??;
 
         trace!("Reading to buffer finished: {}", p.display());
         self.package_source