Merge pull request #201 from mdboom/improve-documentation-of-subproce…

…ss-hooks

Separate subprocess writing/parsing into their own functions

pyperf/_command.py

@@ -8,6 +8,26 @@
 from pyperf._worker import WorkerTask
 
 
+def parse_subprocess_data(output):
+    # Parse the data send from the subprocess.
+    # It is three lines containing:
+    #    - The runtime (in seconds)
+    #    - max_rss (or -1, if not able to compute)
+    #    - The metadata to add to the benchmark entry, as a JSON dictionary
+
+    rss = None
+    metadata = {}
+    try:
+        lines = output.splitlines()
+        timing = float(lines[0])
+        rss = int(lines[1])
+        metadata = json.loads(lines[2])
+    except ValueError:
+        raise ValueError("failed to parse worker output: %r" % output)
+
+    return timing, rss, metadata
+
+
 def bench_command(command, task, loops):
     path = os.path.dirname(__file__)
     script = os.path.join(path, '_process_time.py')
@@ -23,15 +43,7 @@ def bench_command(command, task, loops):
         raise Exception("Command failed with exit code %s"
                         % proc.returncode)
 
-    rss = None
-    metadata = {}
-    try:
-        lines = output.splitlines()
-        timing = float(lines[0])
-        rss = int(lines[1])
-        metadata = json.loads(lines[2])
-    except ValueError:
-        raise ValueError("failed to parse script output: %r" % output)
+    timing, rss, metadata = parse_subprocess_data(output)
 
     if rss and rss > 0:
         # store the maximum

pyperf/_process_time.py

@@ -114,6 +114,18 @@ def load_hooks(metadata):
     return hook_managers
 
 
+def write_data(dt, max_rss, metadata, out=sys.stdout):
+    # Write the data that is communicated back to the main orchestration process.
+    # It is three lines containing:
+    #    - The runtime (in seconds)
+    #    - max_rss (or -1, if not able to compute)
+    #    - The metadata to add to the benchmark entry, as a JSON dictionary
+    print(dt, file=out)
+    print(max_rss or -1, file=out)
+    json.dump(metadata, fp=out)
+    print(file=out)
+
+
 def main():
     # Make sure that the pyperf module wasn't imported
     if 'pyperf' in sys.modules:
@@ -162,10 +174,7 @@ def main():
     for hook in hook_managers.values():
         hook.teardown(metadata)
 
-    # Write timing in seconds into stdout
-    print(dt)
-    print(max_rss or -1)
-    print(json.dumps(metadata))
+    write_data(dt, max_rss, metadata)
 
 
 if __name__ == "__main__":