fix: use tini with unshare to preserve signals (e.g oom) (#7471)

* use tini with unshare to preserve signals (e.g oom)

* fix ci

* ci as nsjail

* simplify

* fix flaky go integration test

---------

Co-authored-by: Ruben Fiszel <ruben@windmill.dev>

.github/workflows/docker-image.yml

@@ -593,9 +593,10 @@ jobs:
             ${{ steps.meta-ee-public.outputs.labels }}
 
   build_ee_slim:
-    if: ${{ startsWith(github.ref, 'refs/tags/v') }} || ((github.event_name != 'workflow_dispatch') || (github.event.inputs.slim))
     needs: [build_ee]
     runs-on: ubicloud
+    if: (github.event_name != 'pull_request') && ((github.event_name != 'workflow_dispatch') || (github.event.inputs.ee || github.event.inputs.slim))
+
     steps:
       - uses: actions/checkout@v4
         with:

Dockerfile

@@ -129,7 +129,7 @@ ENV PATH /usr/local/bin:/root/.local/bin:/tmp/.local/bin:$PATH
 
 
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends netbase tzdata ca-certificates wget curl jq unzip build-essential unixodbc xmlsec1  software-properties-common \
+    && apt-get install -y --no-install-recommends netbase tzdata ca-certificates wget curl jq unzip build-essential unixodbc xmlsec1 software-properties-common tini \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 

backend/windmill-worker/src/common.rs

@@ -642,7 +642,19 @@ pub fn build_command_with_isolation(program: &str, args: &[&str]) -> Command {
                 cmd.arg(flag);
             }
 
-            cmd.arg("--");
+            // If tini is available, use it for proper PID 1 signal handling
+            // (especially OOM exit codes which return 137 instead of sigprocmask errors).
+            // Note: --fork should already be in the flags for proper namespace setup.
+            if let Some(tini_path) = crate::TINI_AVAILABLE.as_ref() {
+                cmd.arg("--");
+                cmd.arg(tini_path);
+                cmd.arg("-s");
+                cmd.arg("--");
+            } else {
+                // Without tini, just run the command directly (--fork is in flags)
+                cmd.arg("--");
+            }
+
             cmd.arg(program);
             cmd.args(args);
             cmd

backend/windmill-worker/src/worker.rs

@@ -315,16 +315,73 @@ lazy_static::lazy_static! {
         .and_then(|x| x.parse::<bool>().ok())
         .unwrap_or(false);
 
+    pub static ref UNSHARE_TINI_PATH: String = {
+        std::env::var("UNSHARE_TINI_PATH").unwrap_or_else(|_| "tini".to_string())
+    };
+
+    // --fork is required for unshare to work with --pid --mount-proc.
+    // When tini is available, it runs as PID 1 inside the forked namespace for proper signal handling.
     pub static ref UNSHARE_ISOLATION_FLAGS: String = {
         std::env::var("UNSHARE_ISOLATION_FLAGS")
             .unwrap_or_else(|_| "--user --map-root-user --pid --fork --mount-proc".to_string())
     };
 
+    // Check if tini is available for proper PID 1 handling in unshare namespaces.
+    // tini handles OOM signals correctly, returning exit code 137 instead of sigprocmask errors.
+    pub static ref TINI_AVAILABLE: Option<String> = {
+        let tini_path = UNSHARE_TINI_PATH.as_str();
+        let test_result = std::process::Command::new(tini_path)
+            .args(["-s", "--", "true"])
+            .output();
+
+        match test_result {
+            Ok(output) if output.status.success() => {
+                tracing::info!("tini available at: {}", tini_path);
+                Some(tini_path.to_string())
+            }
+            Ok(output) => {
+                let stderr = String::from_utf8_lossy(&output.stderr);
+                tracing::warn!(
+                    "tini test failed: {}. Proceeding without tini (OOM exit codes may be incorrect).",
+                    stderr.trim()
+                );
+                None
+            }
+            Err(e) => {
+                if e.kind() == std::io::ErrorKind::NotFound {
+                    tracing::warn!(
+                        "tini not found at '{}'. Install tini for correct OOM exit codes, or set UNSHARE_TINI_PATH.",
+                        tini_path
+                    );
+                } else {
+                    tracing::warn!(
+                        "Failed to test tini: {}. Proceeding without tini.",
+                        e
+                    );
+                }
+                None
+            }
+        }
+    };
+
     pub static ref UNSHARE_PATH: Option<String> = {
         let flags = UNSHARE_ISOLATION_FLAGS.as_str();
         let mut test_cmd_args: Vec<&str> = flags.split_whitespace().collect();
-        test_cmd_args.push("--");
-        test_cmd_args.push("true");
+
+        // Build the test command based on whether tini is available
+        // Note: --fork should already be in the flags for proper namespace setup
+        if let Some(tini_path) = TINI_AVAILABLE.as_ref() {
+            // Test with tini: unshare <flags> -- tini -s -- true
+            test_cmd_args.push("--");
+            test_cmd_args.push(tini_path.as_str());
+            test_cmd_args.push("-s");
+            test_cmd_args.push("--");
+            test_cmd_args.push("true");
+        } else {
+            // Fallback without tini: unshare <flags> -- true
+            test_cmd_args.push("--");
+            test_cmd_args.push("true");
+        }
 
         let test_result = std::process::Command::new("unshare")
             .args(&test_cmd_args)
@@ -332,7 +389,11 @@ lazy_static::lazy_static! {
 
         match test_result {
             Ok(output) if output.status.success() => {
-                tracing::info!("PID namespace isolation enabled. Flags: {}", flags);
+                if TINI_AVAILABLE.is_some() {
+                    tracing::info!("PID namespace isolation enabled with tini. Flags: {}", flags);
+                } else {
+                    tracing::info!("PID namespace isolation enabled. Flags: {}", flags);
+                }
                 Some("unshare".to_string())
             },
             Ok(output) => {
@@ -1140,12 +1201,6 @@ pub async fn run_worker(
     if *ENABLE_UNSHARE_PID {
         // Access UNSHARE_PATH to trigger lazy_static initialization and test
         let _ = &*UNSHARE_PATH;
-
-        tracing::info!(
-            worker = %worker_name, hostname = %hostname,
-            "PID namespace isolation enabled via unshare with flags: {}",
-            UNSHARE_ISOLATION_FLAGS.as_str()
-        );
     }
 
     let start_time = Instant::now();