replacing multiprocessing pool with pipe (#491)

* replacing multiprocessing pool with pipe

* code styling fix

* dropping obsolete chunk_size config parameter

docs/source/usage.md

@@ -126,8 +126,6 @@ The full set of configuration options are:
   - `log_file` - str: Write log messages to a file at this path
   - `n_procs` - int: Number of process to run in parallel when
       parsing in CLI mode (Default: `1`)
-  - `chunk_size` - int: Number of files to give to each process
-      when running in parallel.
 
     :::{note}
     Setting this to a number larger than one can improve

parsedmarc/cli.py

@@ -8,13 +8,12 @@ import os
 from configparser import ConfigParser
 from glob import glob
 import logging
+import math
 from collections import OrderedDict
 import json
 from ssl import CERT_NONE, create_default_context
-from multiprocessing import Pool, Value
-from itertools import repeat
+from multiprocessing import Pipe, Process
 import sys
-import time
 from tqdm import tqdm
 
 from parsedmarc import get_dmarc_reports_from_mailbox, watch_inbox, \
@@ -42,7 +41,7 @@ def _str_to_list(s):
 
 
 def cli_parse(file_path, sa, nameservers, dns_timeout,
-              ip_db_path, offline, parallel=False):
+              ip_db_path, offline, conn, parallel=False):
     """Separated this function for multiprocessing"""
     try:
         file_results = parse_report_file(file_path,
@@ -52,18 +51,11 @@ def cli_parse(file_path, sa, nameservers, dns_timeout,
                                          dns_timeout=dns_timeout,
                                          strip_attachment_payloads=sa,
                                          parallel=parallel)
+        conn.send([file_results, file_path])
     except ParserError as error:
-        return error, file_path
+        conn.send([error, file_path])
     finally:
-        global counter
-        with counter.get_lock():
-            counter.value += 1
-    return file_results, file_path
-
-
-def init(ctr):
-    global counter
-    counter = ctr
+        conn.close()
 
 
 def _main():
@@ -481,7 +473,6 @@ def _main():
                      gmail_api_oauth2_port=8080,
                      log_file=args.log_file,
                      n_procs=1,
-                     chunk_size=1,
                      ip_db_path=None,
                      la_client_id=None,
                      la_client_secret=None,
@@ -551,8 +542,6 @@ def _main():
                 opts.log_file = general_config["log_file"]
             if "n_procs" in general_config:
                 opts.n_procs = general_config.getint("n_procs")
-            if "chunk_size" in general_config:
-                opts.chunk_size = general_config.getint("chunk_size")
             if "ip_db_path" in general_config:
                 opts.ip_db_path = general_config["ip_db_path"]
             else:
@@ -1144,29 +1133,49 @@ def _main():
     for mbox_path in mbox_paths:
         file_paths.remove(mbox_path)
 
-    counter = Value('i', 0)
-    pool = Pool(opts.n_procs, initializer=init, initargs=(counter,))
-    results = pool.starmap_async(cli_parse,
-                                 zip(file_paths,
-                                     repeat(opts.strip_attachment_payloads),
-                                     repeat(opts.nameservers),
-                                     repeat(opts.dns_timeout),
-                                     repeat(opts.ip_db_path),
-                                     repeat(opts.offline),
-                                     repeat(opts.n_procs >= 1)),
-                                 opts.chunk_size)
+    counter = 0
+
+    results = []
+
     if sys.stdout.isatty():
         pbar = tqdm(total=len(file_paths))
-        while not results.ready():
-            pbar.update(counter.value - pbar.n)
-            time.sleep(0.1)
-        pbar.close()
-    else:
-        while not results.ready():
-            time.sleep(0.1)
-    results = results.get()
-    pool.close()
-    pool.join()
+
+    for batch_index in range(math.ceil(len(file_paths) / opts.n_procs)):
+        processes = []
+        connections = []
+
+        for proc_index in range(
+                opts.n_procs * batch_index,
+                opts.n_procs * (batch_index + 1)):
+            if proc_index >= len(file_paths):
+                break
+
+            parent_conn, child_conn = Pipe()
+            connections.append(parent_conn)
+
+            process = Process(target=cli_parse, args=(
+                file_paths[proc_index],
+                opts.strip_attachment_payloads,
+                opts.nameservers,
+                opts.dns_timeout,
+                opts.ip_db_path,
+                opts.offline,
+                child_conn,
+                opts.n_procs >= 1,
+            ))
+            processes.append(process)
+
+        for proc in processes:
+            proc.start()
+
+        for proc in processes:
+            proc.join()
+            if sys.stdout.isatty():
+                counter += 1
+                pbar.update(counter - pbar.n)
+
+        for conn in connections:
+            results.append(conn.recv())
 
     for result in results:
         if type(result[0]) is ParserError: