feat: truncates log files on restart

- added flag for clearing log files at restart
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

- refactor: renaming + login
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

- refactor: creates instead of delete
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

- warn of error
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

- revert format
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

- some renaming + cleaner code
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

- clean up
Signed-off-by: Aminu 'Seun Joshua <seun.aminujoshua@gmail.com>

Author: seun-ja

crates/runtime-factors/src/build.rs

@@ -50,6 +50,7 @@ impl RuntimeFactorsBuilder for FactorsBuilder {
         executor.add_hooks(StdioLoggingExecutorHooks::new(
             config.follow_components.clone(),
             runtime_config.log_dir(),
+            config.truncate_logs,
         ));
         executor.add_hooks(SqlStatementExecutorHook::new(
             args.sqlite_statements.clone(),

crates/trigger/src/cli.rs

@@ -27,6 +27,7 @@ pub use stdio::StdioLoggingExecutorHooks;
 pub use summary::{KeyValueDefaultStoreSummaryHook, SqliteDefaultStoreSummaryHook};
 
 pub const APP_LOG_DIR: &str = "APP_LOG_DIR";
+pub const SPIN_TRUNCATE_LOGS: &str = "SPIN_TRUNCATE_LOGS";
 pub const DISABLE_WASMTIME_CACHE: &str = "DISABLE_WASMTIME_CACHE";
 pub const FOLLOW_LOG_OPT: &str = "FOLLOW_ID";
 pub const WASMTIME_CACHE_FILE: &str = "WASMTIME_CACHE_FILE";
@@ -54,6 +55,13 @@ pub struct FactorsTriggerCommand<T: Trigger<B::Factors>, B: RuntimeFactorsBuilde
     )]
     pub log: Option<PathBuf>,
 
+    /// If set, Spin truncates the log files before starting the application.
+    #[clap(
+        name = SPIN_TRUNCATE_LOGS,
+        long = "truncate-logs",
+    )]
+    pub truncate_logs: bool,
+
     /// Disable Wasmtime cache.
     #[clap(
         name = DISABLE_WASMTIME_CACHE,
@@ -139,6 +147,8 @@ pub struct FactorsConfig {
     pub follow_components: FollowComponents,
     /// Log directory for component stdout/stderr.
     pub log_dir: UserProvidedPath,
+    /// If set, Spin truncates the log files before starting the application.
+    pub truncate_logs: bool,
 }
 
 /// An empty implementation of clap::Args to be used as TriggerExecutor::RunConfig
@@ -220,6 +230,7 @@ impl<T: Trigger<B::Factors>, B: RuntimeFactorsBuilder> FactorsTriggerCommand<T,
             local_app_dir: local_app_dir.clone(),
             follow_components,
             log_dir,
+            truncate_logs: self.truncate_logs,
         };
 
         let run_fut = builder

crates/trigger/src/cli/stdio.rs

@@ -12,6 +12,9 @@ use spin_factors::RuntimeFactors;
 use spin_factors_executor::ExecutorHooks;
 use tokio::io::AsyncWrite;
 
+pub const STDOUT_LOG_FILE_SUFFIX: &str = "stdout";
+pub const STDERR_LOG_FILE_SUFFIX: &str = "stderr";
+
 /// Which components should have their logs followed on stdout/stderr.
 #[derive(Clone, Debug, Default)]
 pub enum FollowComponents {
@@ -39,13 +42,19 @@ impl FollowComponents {
 pub struct StdioLoggingExecutorHooks {
     follow_components: FollowComponents,
     log_dir: Option<PathBuf>,
+    truncate_log: bool,
 }
 
 impl StdioLoggingExecutorHooks {
-    pub fn new(follow_components: FollowComponents, log_dir: Option<PathBuf>) -> Self {
+    pub fn new(
+        follow_components: FollowComponents,
+        log_dir: Option<PathBuf>,
+        truncate_log: bool,
+    ) -> Self {
         Self {
             follow_components,
             log_dir,
+            truncate_log,
         }
     }
 
@@ -56,8 +65,7 @@ impl StdioLoggingExecutorHooks {
         log_dir: Option<&Path>,
     ) -> Result<ComponentStdioWriter> {
         let sanitized_component_id = sanitize_filename::sanitize(component_id);
-        let log_path = log_dir
-            .map(|log_dir| log_dir.join(format!("{sanitized_component_id}_{log_suffix}.txt",)));
+        let log_path = sanitized_log_path(log_dir, &sanitized_component_id, log_suffix);
         let log_path = log_path.as_deref();
 
         let follow = self.follow_components.should_follow(component_id);
@@ -86,6 +94,35 @@ impl StdioLoggingExecutorHooks {
             _ => Ok(()),
         }
     }
+
+    fn truncate_log_files<F: RuntimeFactors>(
+        &self,
+        configured_app: &spin_factors::ConfiguredApp<F>,
+    ) {
+        let sanitized_component_ids: Vec<String> = configured_app
+            .app()
+            .components()
+            .map(|c| sanitize_filename::sanitize(c.locked.id.clone()))
+            .collect();
+
+        for sanitized_component_id in sanitized_component_ids {
+            if let Some(stdout_log_path) = sanitized_log_path(
+                self.log_dir.as_deref(),
+                &sanitized_component_id,
+                STDOUT_LOG_FILE_SUFFIX,
+            ) {
+                _ = std::fs::File::create(stdout_log_path);
+            }
+
+            if let Some(stderr_log_path) = sanitized_log_path(
+                self.log_dir.as_deref(),
+                &sanitized_component_id,
+                STDERR_LOG_FILE_SUFFIX,
+            ) {
+                _ = std::fs::File::create(stderr_log_path);
+            }
+        }
+    }
 }
 
 #[async_trait]
@@ -95,11 +132,16 @@ impl<F: RuntimeFactors, U> ExecutorHooks<F, U> for StdioLoggingExecutorHooks {
         configured_app: &spin_factors::ConfiguredApp<F>,
     ) -> anyhow::Result<()> {
         self.validate_follows(configured_app.app())?;
+
         if let Some(dir) = &self.log_dir {
             // Ensure log dir exists if set
             std::fs::create_dir_all(dir)
                 .with_context(|| format!("Failed to create log dir {}", quoted_path(dir)))?;
 
+            if self.truncate_log {
+                self.truncate_log_files(configured_app);
+            }
+
             println!("Logging component stdio to {}", quoted_path(dir.join("")))
         }
         Ok(())
@@ -115,12 +157,12 @@ impl<F: RuntimeFactors, U> ExecutorHooks<F, U> for StdioLoggingExecutorHooks {
         };
         wasi_builder.stdout_pipe(self.component_stdio_writer(
             &component_id,
-            "stdout",
+            STDOUT_LOG_FILE_SUFFIX,
             self.log_dir.as_deref(),
         )?);
         wasi_builder.stderr_pipe(self.component_stdio_writer(
             &component_id,
-            "stderr",
+            STDERR_LOG_FILE_SUFFIX,
             self.log_dir.as_deref(),
         )?);
         Ok(())
@@ -328,3 +370,11 @@ fn bullet_list<S: std::fmt::Display>(items: impl IntoIterator<Item = S>) -> Stri
         .collect::<Vec<_>>()
         .join("\n")
 }
+
+fn sanitized_log_path(
+    log_dir: Option<&Path>,
+    sanitized_component_id: &str,
+    log_suffix: &str,
+) -> Option<PathBuf> {
+    log_dir.map(|log_dir| log_dir.join(format!("{sanitized_component_id}_{log_suffix}.txt",)))
+}