[core] [5/N] Check uv existence before installation (ray-project#48632)

Signed-off-by: hjiang <[email protected]>

python/ray/_private/runtime_env/uv.py

@@ -63,6 +63,8 @@ def __init__(
 
         logger.debug("Setting up uv for runtime_env: %s", runtime_env)
         self._target_dir = target_dir
+        # An empty directory is created to execute cmd.
+        self._exec_cwd = os.path.join(self._target_dir, "exec_cwd")
         self._runtime_env = runtime_env
         self._logger = logger
 
@@ -91,6 +93,26 @@ async def _install_uv(
         logger.info("Installing package uv to %s", virtualenv_path)
         await check_output_cmd(uv_install_cmd, logger=logger, cwd=cwd, env=pip_env)
 
+    async def _check_uv_existence(
+        self, path: str, cwd: str, env: dict, logger: logging.Logger
+    ) -> bool:
+        """Check and return the existence of `uv` in virtual env."""
+        python = virtualenv_utils.get_virtualenv_python(path)
+
+        check_existence_cmd = [
+            python,
+            "-m",
+            "uv",
+            "version",
+        ]
+
+        try:
+            # If `uv` doesn't exist, exception will be thrown.
+            await check_output_cmd(check_existence_cmd, logger=logger, cwd=cwd, env=env)
+            return True
+        except Exception:
+            return False
+
     async def _install_uv_packages(
         self,
         path: str,
@@ -99,13 +121,18 @@ async def _install_uv_packages(
         pip_env: Dict,
         logger: logging.Logger,
     ):
+        """Install required python packages via `uv`."""
         virtualenv_path = virtualenv_utils.get_virtualenv_path(path)
         python = virtualenv_utils.get_virtualenv_python(path)
         # TODO(fyrestone): Support -i, --no-deps, --no-cache-dir, ...
         requirements_file = dependency_utils.get_requirements_file(path, uv_packages)
 
+        # Check existence for `uv` and see if we could skip `uv` installation.
+        uv_exists = await self._check_uv_existence(python, cwd, pip_env, logger)
+
         # Install uv, which acts as the default package manager.
-        await self._install_uv(path, cwd, pip_env, logger)
+        if not uv_exists:
+            await self._install_uv(path, cwd, pip_env, logger)
 
         # Avoid blocking the event loop.
         loop = get_running_loop()
@@ -138,17 +165,18 @@ async def _run(self):
         # We create an empty directory for exec cmd so that the cmd will
         # run more stable. e.g. if cwd has ray, then checking ray will
         # look up ray in cwd instead of site packages.
-        exec_cwd = os.path.join(path, "exec_cwd")
-        os.makedirs(exec_cwd, exist_ok=True)
+        os.makedirs(self._exec_cwd, exist_ok=True)
         try:
-            await virtualenv_utils.create_or_get_virtualenv(path, exec_cwd, logger)
+            await virtualenv_utils.create_or_get_virtualenv(
+                path, self._exec_cwd, logger
+            )
             python = virtualenv_utils.get_virtualenv_python(path)
-            async with dependency_utils.check_ray(python, exec_cwd, logger):
+            async with dependency_utils.check_ray(python, self._exec_cwd, logger):
                 # Install packages with uv.
                 await self._install_uv_packages(
                     path,
                     uv_packages,
-                    exec_cwd,
+                    self._exec_cwd,
                     self._uv_env,
                     logger,
                 )