Merge pull request 'feat: persist a build artifact cache between builds' (#7) from liw/cache into main

Reviewed-on: https://codeberg.org/ambient/ambient-run/pulls/7

4 files changed, 84 insertions, 3 deletions

diff --git a/ambient-run.md b/ambient-run.md
index 76fca3f..db16dfb 100644
--- a/ambient-run.md
+++ b/ambient-run.md
@@ -168,6 +168,7 @@ image: /my/image.qcow2
 artifact: null
 artifact_max_size: null
 dependencies: null
+cache: null
 ~~~
 
 ### Show per-build configuration
@@ -346,6 +347,47 @@ dependencies: foo-deps
 ~~~
 
 ### Cache is persistent between builds
+
+_Requirement:_ The build can persist files between builds in a cache
+device.
+
+_Justification:_ This allows incremental builds and caching of build
+artifacts.
+
+_Stakeholder:_ Lars.
+
+~~~scenario
+given an installed ambient-run
+given file cache-project.yaml
+given file foo/README.md from cache-project.yaml
+given a directory foo-cache
+given image file image.qcow2 specified for test suite
+then file foo-cache/cached.file does not exist
+when I run ambient-run build cache-project.yaml --log foo.log
+then file foo.log contains "creating cached file"
+then file foo-cache/cached.file exists
+when I run ambient-run build cache-project.yaml --log foo2.log
+then file foo2.log contains "cache has file"
+~~~
+
+
+~~~{#cache-project.yaml .file .yaml}
+source: foo
+shell: |
+  #!/bin/bash
+  set -xeuo pipefail
+  find /workspace -ls
+  file="/workspace/cache/cached.file"
+  if [ -e "$file" ]; then
+    echo "cache has file"
+  else
+    echo "creating cached file"
+    touch "$file"
+  fi
+image: image.qcow2
+cache: foo-cache
+~~~
+
 ### Build gets the resources is demands
 
 ## Utility functionality
diff --git a/src/bin/ambient-run.rs b/src/bin/ambient-run.rs
index dbe7bfa..8157de7 100644
--- a/src/bin/ambient-run.rs
+++ b/src/bin/ambient-run.rs
@@ -218,7 +218,8 @@ impl BuildCommand {
             .with_source(&project.source())
             .with_artifact(project.artifact())
             .with_artifact_max_size(project.artifact_max_size())
-            .with_dependencies(project.dependencies());
+            .with_dependencies(project.dependencies())
+            .with_cache(project.cache());
         if let Some(log) = &self.log {
             qemu = qemu.with_log(log);
         }
diff --git a/src/project.rs b/src/project.rs
index c9b2c38..19ca947 100644
--- a/src/project.rs
+++ b/src/project.rs
@@ -15,6 +15,7 @@ pub struct Project {
     artifact: Option<PathBuf>,
     artifact_max_size: Option<u64>,
     dependencies: Option<PathBuf>,
+    cache: Option<PathBuf>,
 }
 
 impl Project {
@@ -74,6 +75,7 @@ impl Project {
         self.artifact = snippet.artifact;
         self.artifact_max_size = snippet.artifact_max_size;
         self.dependencies = snippet.dependencies;
+        self.cache = snippet.cache;
         Ok(())
     }
 
@@ -111,6 +113,11 @@ impl Project {
     pub fn dependencies(&self) -> &Option<PathBuf> {
         &self.dependencies
     }
+
+    /// Cache directory.
+    pub fn cache(&self) -> &Option<PathBuf> {
+        &self.cache
+    }
 }
 
 #[derive(Debug, Deserialize)]
@@ -122,6 +129,7 @@ struct ProjectSnippet {
     artifact: Option<PathBuf>,
     artifact_max_size: Option<u64>,
     dependencies: Option<PathBuf>,
+    cache: Option<PathBuf>,
 }
 
 /// Possible errors from configuration file handling.
diff --git a/src/qemu.rs b/src/qemu.rs
index 2853e52..2a7a6b6 100644
--- a/src/qemu.rs
+++ b/src/qemu.rs
@@ -21,6 +21,7 @@ pub struct Qemu {
     artifact: Option<PathBuf>,
     artifact_max_xize: u64,
     dependencies: Option<PathBuf>,
+    cache: Option<PathBuf>,
 }
 
 impl Qemu {
@@ -70,6 +71,12 @@ impl Qemu {
         self
     }
 
+    /// Set directory where project build cache is.
+    pub fn with_cache(mut self, dirname: &Option<PathBuf>) -> Self {
+        self.cache = dirname.clone();
+        self
+    }
+
     /// Run QEMU in the specified way.
     pub fn run(&self) -> Result<(), QemuError> {
         eprintln!("qemu run");
@@ -97,8 +104,13 @@ impl Qemu {
         };
 
         eprintln!("cache drive");
-        let cache_drive =
-            Self::create_tar_with_size(tmp.path().join("cache"), empty.path(), MAX_OUTPUT_SIZE)?;
+        let cache_drive = if let Some(dirname) = &self.cache {
+            eprintln!("cache {}", dirname.display());
+            Self::create_tar_with_size(tmp.path().join("cache"), dirname, MAX_OUTPUT_SIZE)?
+        } else {
+            eprintln!("no cache");
+            Self::create_tar(tmp.path().join("cache"), empty.path())?
+        };
 
         eprintln!("deps drive");
         let deps_drive = if let Some(dirname) = &self.dependencies {
@@ -154,6 +166,18 @@ impl Qemu {
         let output = child.wait_with_output().map_err(QemuError::Run)?;
         if output.status.success() {
             eprintln!("kvm OK");
+            if let Some(dirname) = &self.cache {
+                eprintln!("persisting cache");
+                if dirname.exists() {
+                    eprintln!("removing old cache");
+                    std::fs::remove_dir_all(dirname)
+                        .map_err(|e| QemuError::RemoveCache(dirname.into(), e))?
+                }
+                eprintln!("extracting cache");
+                cache_drive
+                    .extract_to(dirname)
+                    .map_err(|e| QemuError::ExtractCache(dirname.into(), e))?;
+            }
             Ok(())
         } else {
             let out = String::from_utf8_lossy(&output.stdout);
@@ -285,6 +309,12 @@ pub enum QemuError {
 
     #[error("failed to create a tar archive from {0}")]
     Tar(PathBuf, #[source] VirtualDriveError),
+
+    #[error("failed to remove cache (so it can be replaced): {0}")]
+    RemoveCache(PathBuf, #[source] std::io::Error),
+
+    #[error("failed to extract cache drive to {0}")]
+    ExtractCache(PathBuf, #[source] VirtualDriveError),
 }
 
 #[cfg(test)]