Add result buffering/batch processing example.

examples/buffer_results.py

@@ -0,0 +1,44 @@
+"""
+Process 20 lines of output at a time.
+
+Example runs:
+python buffer_results.py
+"""
+import sys
+import time
+import drainers
+
+# fake this
+def setup_cruncher():
+    time.sleep(1)
+
+def do_something_expensive(file):
+    time.sleep(0.005)
+
+def destroy_cruncher():
+    time.sleep(0.8)
+
+files = []
+
+def crunch(files):
+    print 'Setting up cruncher...'
+    setup_cruncher()
+    while len(files) > 0:
+        f = files.pop(0)
+        print '- Crunching file %s...' % f.strip()
+        do_something_expensive(f)
+    print 'Releasing cruncher...'
+    destroy_cruncher()
+
+def add_to_buffer(line, is_err):
+    if is_err:
+        # ignore all errors
+        return
+    files.append(line)
+
+    # start crunch synchronously after 20 items have been read
+    if len(files) >= 20:
+        crunch(files)
+
+d = drainers.Drainer(['find', '.', '-type', 'f'], read_event_cb=add_to_buffer)
+d.start()