feat: improve the Docker backend. (#12)

* feat: improve the Docker backend.

* add support for specifying inputs by host file path.
* implement inputs as bind mounts rather than files uploaded to the container.
* implement mounts for tasks that use services rather than containers.
* make the Docker backend ensure the task execution's image exists locally
  before creating the container or service.
* use `alpine` for the examples as it is smaller than `ubuntu`.

* chore: update CHANGELOG.md.

crankshaft-docker/src/bin/docker-driver.rs

@@ -65,11 +65,9 @@ enum Command {
     /// existing).
     EnsureImage {
         /// The name of the image.
+        ///
+        /// If a tag is not specified, a default tag of `latest` is used.
         image: String,
-
-        #[arg(short, long, default_value = "latest")]
-        /// The tag for the image.
-        tag: String,
     },
 
     /// Lists all images.
@@ -156,8 +154,8 @@ async fn run(args: Args) -> Result<()> {
                 container.remove().await?;
             }
         }
-        Command::EnsureImage { image, tag } => {
-            docker.ensure_image(image, tag).await?;
+        Command::EnsureImage { image } => {
+            docker.ensure_image(image).await?;
         }
         Command::ListImages => {
             docker.list_images().await?;

crankshaft-docker/src/container/builder.rs

@@ -103,7 +103,7 @@ impl Builder {
     /// Sets multiple environment variables.
     pub fn envs(
         mut self,
-        variables: impl Iterator<Item = (impl Into<String>, impl Into<String>)>,
+        variables: impl IntoIterator<Item = (impl Into<String>, impl Into<String>)>,
     ) -> Self {
         self.env
             .extend(variables.into_iter().map(|(k, v)| (k.into(), v.into())));

crankshaft-docker/src/images.rs

@@ -56,23 +56,20 @@ pub(crate) async fn list_images(docker: &Docker) -> Result<Vec<ImageSummary>> {
 
 /// Ensures that an image exists in the Docker daemon.
 ///
+/// If the image does not specify a tag, a default tag of `latest` will be used.
+///
 /// It does this by:
 ///
 /// * Confirming that the image already exists there, or
 /// * Pulling the image from the remote repository.
-pub(crate) async fn ensure_image(
-    docker: &Docker,
-    name: impl AsRef<str>,
-    tag: impl AsRef<str>,
-) -> Result<()> {
-    let name = name.as_ref();
-    let tag = tag.as_ref();
-    debug!("ensuring image: `{name}:{tag}`");
+pub(crate) async fn ensure_image(docker: &Docker, image: impl AsRef<str>) -> Result<()> {
+    let image = image.as_ref();
+    debug!("ensuring image: `{image}`");
 
     let mut filters = HashMap::new();
-    filters.insert(String::from("reference"), vec![format!("{name}:{tag}")]);
+    filters.insert("reference", vec![image]);
 
-    debug!("checking if image exists locally: `{name}:{tag}`");
+    debug!("checking if image exists locally: `{image}`");
     let results = docker
         .inner()
         .list_images(Some(ListImagesOptions {
@@ -83,7 +80,7 @@ pub(crate) async fn ensure_image(
         .map_err(Error::Docker)?;
 
     if !results.is_empty() {
-        debug!("image `{name}:{tag}` exists locally");
+        debug!("image `{image}` exists locally");
 
         if enabled!(Level::TRACE) {
             trace!(
@@ -95,11 +92,11 @@ pub(crate) async fn ensure_image(
         return Ok(());
     }
 
-    debug!("image `{name}:{tag}` does not exist locally; attempting to pull from remote");
+    debug!("image `{image}` does not exist locally; attempting to pull from remote");
     let mut stream = docker.inner().create_image(
         Some(CreateImageOptions {
-            from_image: name,
-            tag,
+            from_image: image,
+            tag: if image.contains(':') { "" } else { "latest" },
             ..Default::default()
         }),
         None,

crankshaft-docker/src/lib.rs

@@ -75,12 +75,15 @@ impl Docker {
 
     /// Ensures that an image exists in the Docker daemon.
     ///
+    /// If the image does not specify a tag, a default tag of `latest` will be
+    /// used.
+    ///
     /// It does this by:
     ///
     /// * Confirming that the image already exists there, or
     /// * Pulling the image from the remote repository.
-    pub async fn ensure_image(&self, name: impl AsRef<str>, tag: impl AsRef<str>) -> Result<()> {
-        ensure_image(self, name, tag).await
+    pub async fn ensure_image(&self, image: impl AsRef<str>) -> Result<()> {
+        ensure_image(self, image).await
     }
 
     /// Removes an image from the Docker daemon.

crankshaft-docker/src/service/builder.rs

@@ -1,6 +1,7 @@
 //! Builders for containers.
 
 use bollard::Docker;
+use bollard::secret::Mount;
 use bollard::secret::ServiceSpec;
 use bollard::secret::ServiceSpecMode;
 use bollard::secret::ServiceSpecModeReplicated;
@@ -16,7 +17,7 @@ use super::Service;
 use crate::Error;
 use crate::Result;
 
-/// A builder for a [`Container`].
+/// A builder for a [`Service`].
 pub struct Builder {
     /// A reference to the [`Docker`] client that will be used to create this
     /// container.
@@ -43,6 +44,9 @@ pub struct Builder {
     /// The working directory.
     work_dir: Option<String>,
 
+    /// The mounts for the service's task template.
+    mounts: Vec<Mount>,
+
     /// The task resources for the service.
     resources: Option<TaskSpecResources>,
 }
@@ -59,6 +63,7 @@ impl Builder {
             attach_stderr: false,
             env: Default::default(),
             work_dir: Default::default(),
+            mounts: Default::default(),
             resources: Default::default(),
         }
     }
@@ -96,7 +101,7 @@ impl Builder {
     /// Sets multiple environment variables.
     pub fn envs(
         mut self,
-        variables: impl Iterator<Item = (impl Into<String>, impl Into<String>)>,
+        variables: impl IntoIterator<Item = (impl Into<String>, impl Into<String>)>,
     ) -> Self {
         self.env
             .extend(variables.into_iter().map(|(k, v)| (k.into(), v.into())));
@@ -121,6 +126,18 @@ impl Builder {
         self
     }
 
+    /// Sets a mount for the service.
+    pub fn mount(mut self, mount: impl Into<Mount>) -> Self {
+        self.mounts.push(mount.into());
+        self
+    }
+
+    /// Sets multiple mounts for the service.
+    pub fn mounts(mut self, mounts: impl IntoIterator<Item = impl Into<Mount>>) -> Self {
+        self.mounts.extend(mounts.into_iter().map(Into::into));
+        self
+    }
+
     /// Sets the task resources.
     pub fn resources(mut self, resources: TaskSpecResources) -> Self {
         self.resources = Some(resources);
@@ -152,6 +169,7 @@ impl Builder {
                             args: Some(self.args),
                             dir: self.work_dir,
                             env: Some(self.env.iter().map(|(k, v)| format!("{k}={v}")).collect()),
+                            mounts: Some(self.mounts),
                             ..Default::default()
                         }),
                         resources: self.resources,

crankshaft-engine/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* Added support for bind mounting inputs to the Docker backend ([#12](https://github.com/stjude-rust-labs/crankshaft/pull/12)).
 * Added cancellation support to the engine and ctrl-c handling in the examples (#[11](https://github.com/stjude-rust-labs/crankshaft/pull/11)).
 * Added support for Docker Swarm in the docker backend (#[11](https://github.com/stjude-rust-labs/crankshaft/pull/11)).
 * Adds the initial version of the crate.
@@ -32,3 +33,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Swaps out most of the bespoke builders for `bon`.
 * Removes `#[builder(into)]` for numerical types
   ([#10](https://github.com/stjude-rust-labs/crankshaft/pull/10)).
+
+### Fixed
+
+* The Docker backend now ensures task execution images are present locally
+  before creating any containers ([#12](https://github.com/stjude-rust-labs/crankshaft/pull/12)).