log : refactored acquire and release semantic to meet the context manager protocol

lib/spack/llnl/util/tty/log.py

@@ -101,19 +101,23 @@ def __exit__(self, exc_type, exception, traceback):
 
 
 class log_output(object):
-    """Redirects output and error of enclosed block to a file.
+    """Spawns a daemon that reads from a pipe and writes to a file
 
     Usage:
-        with log_output('logfile.txt', 'w'):
-           # do things ... output will be logged.
+        # Spawns the daemon
+        with log_output('logfile.txt', 'w') as log_redirection:
+           # do things ... output is not redirected
+           with log_redirection:
+                # do things ... output will be logged
 
     or:
-        with log_output('logfile.txt', echo=True):
+        with log_output('logfile.txt', echo=True) as log_redirection:
+           # do things ... output is not redirected
+           with log_redirection:
                # do things ... output will be logged
                # and also printed to stdout.
 
-    Opens a stream in 'w' mode at instance creation and closes
-    it at instance deletion
+    Opens a stream in 'w' mode at daemon spawning and closes it at daemon joining.
     If echo is True, also prints the output to stdout.
     """
     def __init__(self, filename, echo=False, force_color=False, debug=False):
@@ -128,32 +132,21 @@ def __init__(self, filename, echo=False, force_color=False, debug=False):
         self.directAssignment = False
         self.read, self.write = os.pipe()
 
-        # Spawn a daemon that writes what it reads from a pipe
-        self.p = multiprocessing.Process(target=self._forward_redirected_pipe, args=(self.read,), name='logger_daemon')
+        # Sets a daemon that writes to file what it reads from a pipe
+        self.p = multiprocessing.Process(target=self._spawn_writing_daemon, args=(self.read,), name='logger_daemon')
         self.p.daemon = True
-        # I just need this to communicate to un-summon the daemon
+        # Needed to un-summon the daemon
         self.parent_pipe, self.child_pipe = multiprocessing.Pipe()
 
-    def acquire(self):
+    def __enter__(self):
         self.p.start()
+        return log_output.OutputRedirection(self)
 
-    def release(self):
+    def __exit__(self, exc_type, exc_val, exc_tb):
         self.parent_pipe.send(True)
         self.p.join(60.0)  # 1 minute to join the child
 
-    def __enter__(self):
-        """Redirect output from the with block to a file.
-
-        Hijacks stdout / stderr and writes to the pipe
-        connected to the logger daemon
-        """
-        # remember these values for later.
-        self._force_color = color._force_color
-        self._debug = tty._debug
-        # Redirect this output to a pipe
-        self._redirect_to_pipe(self.write)
-
-    def _forward_redirected_pipe(self, read):
+    def _spawn_writing_daemon(self, read):
         # Parent: read from child, skip the with block.
         read_file = os.fdopen(read, 'r', 0)
         with open(self.filename, 'w') as log_file:
@@ -187,7 +180,26 @@ def _forward_redirected_pipe(self, read):
                     if self.child_pipe.poll():
                         break
 
-    def _redirect_to_pipe(self, write):
+    def __del__(self):
+        """Closes the pipes"""
+        os.close(self.write)
+        os.close(self.read)
+
+    class OutputRedirection(object):
+        def __init__(self, other):
+            self.__dict__.update(other.__dict__)
+
+        def __enter__(self):
+            """Redirect output from the with block to a file.
+
+            Hijacks stdout / stderr and writes to the pipe
+            connected to the logger daemon
+            """
+            # remember these values for later.
+            self._force_color = color._force_color
+            self._debug = tty._debug
+            # Redirect this output to a pipe
+            write = self.write
             try:
                 # Save old stdout and stderr
                 self._stdout = os.dup(sys.stdout.fileno())
@@ -226,8 +238,3 @@ def __exit__(self, exc_type, exception, traceback):
             # restore output options.
             color._force_color = self._force_color
             tty._debug = self._debug
-
-    def __del__(self):
-        """Closes the pipes"""
-        os.close(self.write)
-        os.close(self.read)

lib/spack/spack/package.py

@@ -1136,13 +1136,13 @@ def build_process():
                         self.log_path = log_path
                         self.env_path = env_path
                         dump_environment(env_path)
-                        log_redirection = log_output(log_path, verbose, sys.stdout.isatty(), True)
-                        log_redirection.acquire()
+                        # Spawn a daemon that reads from a pipe and redirects everything to log_path
+                        with log_output(log_path, verbose, sys.stdout.isatty(), True) as log_redirection:
                             for phase_name, phase in zip(self.phases, self._InstallPhase_phases):
                                 tty.msg('Executing phase : \'{0}\''.format(phase_name))
+                                # Redirect stdout and stderr to daemon pipe
                                 with log_redirection:
                                     getattr(self, phase)(self.spec, self.prefix)
-                        log_redirection.release()
                         self.log()
                     # Run post install hooks before build stage is removed.
                     spack.hooks.post_install(self)