fix: improve uv dependency install reliability with an atomic success file

* Revert solution with Mutex

* Implement valid.windmill logic

* Remove unused import

* valid.windmill -> .valid.windmill

Just like .lock

* Dont delete wheels if cancelled/failed

Now we dont clean up requirement folder if it was failed.

This way we can fully utilize uv's flock system.

Also if we left wheel dir, but it was partially filled (resulting to invalid wheel)
we use --reinstall flag in order to overwrite any content of wheels

* Add comment

* Add --reinstall to nsjail

Author: pyranota

backend/windmill-worker/nsjail/download_deps.py.sh

@@ -30,6 +30,7 @@ CMD="/usr/local/bin/uv pip install
 $INDEX_URL_ARG $EXTRA_INDEX_URL_ARG $TRUSTED_HOST_ARG
 --index-strategy unsafe-best-match
 --system
+--reinstall
 "
 
 echo $CMD

backend/windmill-worker/src/python_executor.rs

@@ -7,7 +7,6 @@ use std::{
 };
 
 use anyhow::anyhow;
-use futures::lock::Mutex;
 use itertools::Itertools;
 use regex::Regex;
 use serde_json::value::RawValue;
@@ -36,8 +35,6 @@ use windmill_common::variables::get_secret_value_as_admin;
 use windmill_queue::{append_logs, CanceledBy};
 
 lazy_static::lazy_static! {
-    static ref BUSY_WITH_UV_INSTALL: Mutex<()> = Mutex::new(());
-
     static ref PYTHON_PATH: String =
     std::env::var("PYTHON_PATH").unwrap_or_else(|_| "/usr/local/bin/python3".to_string());
 
@@ -1248,6 +1245,8 @@ async fn spawn_uv_install(
                 "--target",
                 venv_p,
                 "--no-cache",
+                // If we invoke uv pip install, then we want to overwrite existing data
+                "--reinstall",
             ]
         };
 
@@ -1356,7 +1355,6 @@ pub async fn handle_python_reqs(
     mut no_uv_install: bool,
     is_ansible: bool,
 ) -> error::Result<Vec<String>> {
-    let lock = BUSY_WITH_UV_INSTALL.lock().await;
     let counter_arc = Arc::new(tokio::sync::Mutex::new(0));
     // Append logs with line like this:
     // [9/21]   +  requests==2.32.3            << (S3) |  in 57ms
@@ -1486,10 +1484,11 @@ pub async fn handle_python_reqs(
             "{py_prefix}/{}",
             req.replace(' ', "").replace('/', "").replace(':', "")
         );
-        if metadata(&venv_p).await.is_ok() {
+        if metadata(venv_p.clone() + "/.valid.windmill").await.is_ok() {
             req_paths.push(venv_p);
             in_cache.push(req.to_string());
         } else {
+            // There is no valid or no wheel at all. Regardless of if there is content or not, we will overwrite it with --reinstall flag
             req_with_penv.push((req.to_string(), venv_p));
         }
     }
@@ -1520,12 +1519,6 @@ pub async fn handle_python_reqs(
     let pids = Arc::new(tokio::sync::Mutex::new(vec![None; total_to_install]));
     let mem_peak_thread_safe = Arc::new(tokio::sync::Mutex::new(0));
     {
-        // when we cancel the job, it has up to 1 second window before actually getting cancelled 
-        // Thus the directory with wheel in windmill's cache cleaned only after that. 
-        // If we manage to start new job during that period windmill might see that wanted wheel is already there (because we have not cleaned it yet)
-        // and write it to installed wheels, meanwhile previous job will clean that wheel. 
-        // To fix that we create lock, which will pipeline all uv installs on worker
-        let _lock = lock;
         let pids = pids.clone();
         let mem_peak_thread_safe = mem_peak_thread_safe.clone();
         tokio::spawn(async move {
@@ -1866,6 +1859,17 @@ pub async fn handle_python_reqs(
             );
 
             pids.lock().await.get_mut(i).and_then(|e| e.take());
+            // Create a file to indicate that installation was successfull
+            let valid_path = venv_p.clone() + "/.valid.windmill";
+            // This is atomic operation, meaning, that it either completes and wheel is valid, 
+            // or it does not and wheel is invalid and will be reinstalled next run
+            if let Err(e) = File::create(&valid_path).await{
+                tracing::error!(
+                workspace_id = %w_id,
+                job_id = %job_id,
+                    "Failed to create {}!\n{e}\n
+                    This file needed for python jobs to function", valid_path)
+            };
             Ok(())
         }));
     }
@@ -1882,13 +1886,6 @@ pub async fn handle_python_reqs(
                 "Env installation failed: {:?}",
                 e
             );
-            if let Err(e) = fs::remove_dir_all(&venv_p) {
-                tracing::warn!(
-                    workspace_id = %w_id,
-                    "Failed to remove cache dir: {:?}",
-                    e
-                );
-            }
         } else {
             req_paths.push(venv_p);
         }