Add the ability to disable multiprocessing and threading entirely #185

Signed-off-by: tdruez <tdruez@nexb.com>

CHANGELOG.rst

@@ -3,6 +3,11 @@
 
 ### unreleased
 
+- Add the ability to disable multiprocessing and threading entirely through the
+  SCANCODEIO_PROCESSES setting. Use 0 to disable multiprocessing and use -1 to also
+  disable threading.
+  https://github.com/nexB/scancode.io/issues/185
+
 - Missing project workspace are restored on reports (xlsx, json) creation. This allow
   to download reports even if the project workspace (input, codebase) was deleted.
   https://github.com/nexB/scancode.io/issues/154

docs/scancodeio-settings.rst

@@ -45,14 +45,19 @@ SCANCODEIO_PROCESSES
 
 By default, multiprocessing is enabled and setup to use the number of available CPUs on
 the machine, minus 1.
+
 You can control the number of parallel processes available to ScanCode.io using the
 SCANCODE_PROCESSES setting::
 
     SCANCODE_PROCESSES=4
 
-To disable multiprocessing and run on a single process::
+Multiprocessing can be disable entirely using "0"::
+
+    SCANCODE_PROCESSES=0
+
+To disable multiprocessing and threading use "-1"::
 
-    SCANCODE_PROCESSES=1
+    SCANCODE_PROCESSES=-1
 
 SCANCODE_DEFAULT_OPTIONS
 ------------------------

scanpipe/pipes/scancode.py

@@ -53,7 +53,7 @@
 scanpipe_app = apps.get_app_config("scanpipe")
 
 # The maximum number of processes that can be used to execute multiprocessing calls.
-# If None or not give,n then as many worker processes, minus one, will be created as the
+# If None or not given, then as many worker processes, minus one, will be created as the
 # machine has CPUs.
 SCANCODEIO_PROCESSES = getattr(settings, "SCANCODEIO_PROCESSES", None)
 
@@ -123,7 +123,7 @@ def get_resource_info(location):
     return file_info
 
 
-def _scan_resource(location, scanners):
+def _scan_resource(location, scanners, with_threading=True):
     """
     Wrap the scancode-toolkit `scan_resource` method to support timeout on direct
     scanner functions calls.
@@ -132,11 +132,15 @@ def _scan_resource(location, scanners):
     """
     # `rid` is not needed in this context, yet required in the scan_resource args
     location_rid = location, 0
-    _, _, errors, _, results, _ = scancode_cli.scan_resource(location_rid, scanners)
+    _, _, errors, _, results, _ = scancode_cli.scan_resource(
+        location_rid,
+        scanners,
+        with_threading=with_threading,
+    )
     return results, errors
 
 
-def scan_file(location):
+def scan_file(location, with_threading=True):
     """
     Run a license, copyright, email, and url scan on provided `location`,
     using the scancode-toolkit direct API.
@@ -149,10 +153,10 @@ def scan_file(location):
         Scanner("emails", scancode_api.get_emails),
         Scanner("urls", scancode_api.get_urls),
     ]
-    return _scan_resource(location, scanners)
+    return _scan_resource(location, scanners, with_threading)
 
 
-def scan_for_package_info(location):
+def scan_for_package_info(location, with_threading=True):
     """
     Run a package scan on provided `location` using the scancode-toolkit direct API.
 
@@ -161,7 +165,7 @@ def scan_for_package_info(location):
     scanners = [
         Scanner("packages", scancode_api.get_package_info),
     ]
-    return _scan_resource(location, scanners)
+    return _scan_resource(location, scanners, with_threading)
 
 
 def save_scan_file_results(codebase_resource, scan_results, scan_errors):
@@ -196,13 +200,20 @@ def save_scan_package_results(codebase_resource, scan_results, scan_errors):
         codebase_resource.save()
 
 
+def _log_progress(scan_func, resource, resource_count, index):
+    progress = f"{index / resource_count * 100:.1f}% ({index}/{resource_count})"
+    logger.info(f"{scan_func.__name__} {progress} pk={resource.pk}")
+
+
 def _scan_and_save(project, scan_func, save_func):
     """
     Run the `scan_func` on files without status for `project`.
     The `save_func` is called to save the results.
 
     Multiprocessing is enabled by default on this pipe, the number of processes can be
-    controlled through the SCANCODEIO_PROCESSES setting.
+    controlled through the `SCANCODEIO_PROCESSES` setting.
+    Multiprocessing can be disable using `SCANCODEIO_PROCESSES=0`,
+    and threading can also be disabled `SCANCODEIO_PROCESSES=-1`
 
     The codebase resources QuerySet is chunked in 2000 results at the time,
     this can result in a significant reduction in memory usage.
@@ -214,7 +225,19 @@ def _scan_and_save(project, scan_func, save_func):
     resource_count = codebase_resources.count()
     logger.info(f"Scan {resource_count} codebase resources with {scan_func.__name__}")
     resource_iterator = codebase_resources.iterator(chunk_size=2000)
-    max_workers = SCANCODEIO_PROCESSES or os.cpu_count() - 1 or 1
+
+    if SCANCODEIO_PROCESSES is None:
+        max_workers = os.cpu_count() - 1 or 1
+    else:
+        max_workers = SCANCODEIO_PROCESSES
+
+    if max_workers <= 0:
+        with_threading = True if max_workers == 0 else False
+        for index, resource in enumerate(resource_iterator):
+            _log_progress(scan_func, resource, resource_count, index)
+            scan_results, scan_errors = scan_func(resource.location, with_threading)
+            save_func(resource, scan_results, scan_errors)
+        return
 
     with concurrent.futures.ProcessPoolExecutor(max_workers) as executor:
         future_to_resource = {
@@ -227,10 +250,7 @@ def _scan_and_save(project, scan_func, save_func):
 
         for index, future in enumerate(future_as_completed):
             resource = future_to_resource[future]
-
-            progress = f"{index / resource_count * 100:.1f}% ({index}/{resource_count})"
-            logger.info(f"{scan_func.__name__} {progress} pk={resource.pk}")
-
+            _log_progress(scan_func, resource, resource_count, index)
             scan_results, scan_errors = future.result()
             save_func(resource, scan_results, scan_errors)