Make smart futures avoid polling.

[python_utils.git] / exec_utils.py

diff --git a/exec_utils.py b/exec_utils.py
index c669f5460b2d97490d308c38b285233f431a9ffa..89cfbd7bf15f23a7a0effaed24954f7b4480aded 100644 (file)
--- a/exec_utils.py
+++ b/exec_utils.py
@@ -1,29 +1,64 @@
 #!/usr/bin/env python3
 
+import atexit
+import logging
 import shlex
 import subprocess
-from typing import List
+from typing import List, Optional
 
 
-def cmd_with_timeout(command: str, timeout_seconds: float) -> int:
+logger = logging.getLogger(__file__)
+
+
+def cmd_with_timeout(command: str, timeout_seconds: Optional[float]) -> int:
+    """
+    Run a command but do not let it run for more than timeout seconds.
+
+    >>> cmd_with_timeout('/bin/echo foo', 10.0)
+    0
+
+    >>> cmd_with_timeout('/bin/sleep 2', 0.1)
+    Traceback (most recent call last):
+    ...
+    subprocess.TimeoutExpired: Command '['/bin/bash', '-c', '/bin/sleep 2']' timed out after 0.1 seconds
+
+    """
     return subprocess.check_call(
         ["/bin/bash", "-c", command], timeout=timeout_seconds
     )
 
 
-def cmd(command: str) -> str:
+def cmd(command: str, timeout_seconds: Optional[float] = None) -> str:
     """Run a command with everything encased in a string and return
     the output text as a string.  Raises subprocess.CalledProcessError.
+
+    >>> cmd('/bin/echo foo')[:-1]
+    'foo'
+
+    >>> cmd('/bin/sleep 2', 0.1)
+    Traceback (most recent call last):
+    ...
+    subprocess.TimeoutExpired: Command '/bin/sleep 2' timed out after 0.1 seconds
+
     """
     ret = subprocess.run(
-        command, shell=True, capture_output=True, check=True
+        command, shell=True, capture_output=True, check=True, timeout=timeout_seconds,
     ).stdout
     return ret.decode("utf-8")
 
 
 def run_silently(command: str) -> None:
     """Run a command silently but raise subprocess.CalledProcessError if
-    it fails."""
+    it fails.
+
+    >>> run_silently("/usr/bin/true")
+
+    >>> run_silently("/usr/bin/false")
+    Traceback (most recent call last):
+    ...
+    subprocess.CalledProcessError: Command '/usr/bin/false' returned non-zero exit status 1.
+
+    """
     subprocess.run(
         command, shell=True, stderr=subprocess.DEVNULL,
         stdout=subprocess.DEVNULL, capture_output=False, check=True
@@ -35,13 +70,23 @@ def cmd_in_background(
 ) -> subprocess.Popen:
     args = shlex.split(command)
     if silent:
-        return subprocess.Popen(args,
-                                stdin=subprocess.DEVNULL,
-                                stdout=subprocess.DEVNULL,
-                                stderr=subprocess.DEVNULL)
+        subproc = subprocess.Popen(args,
+                                   stdin=subprocess.DEVNULL,
+                                   stdout=subprocess.DEVNULL,
+                                   stderr=subprocess.DEVNULL)
     else:
-        return subprocess.Popen(args,
-                                stdin=subprocess.DEVNULL)
+        subproc = subprocess.Popen(args, stdin=subprocess.DEVNULL)
+
+    def kill_subproc() -> None:
+        try:
+            if subproc.poll() is None:
+                logger.info("At exit handler: killing {}: {}".format(subproc, command))
+                subproc.terminate()
+                subproc.wait(timeout=10.0)
+        except BaseException as be:
+            logger.exception(be)
+    atexit.register(kill_subproc)
+    return subproc
 
 
 def cmd_list(command: List[str]) -> str:
@@ -50,3 +95,8 @@ def cmd_list(command: List[str]) -> str:
     """
     ret = subprocess.run(command, capture_output=True, check=True).stdout
     return ret.decode("utf-8")
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()