fix(process-files): quit Python interpreter after every batch to prev…

…ent "too many open files" error (DEV-2268) (#402)

docs/cli-commands.md

@@ -312,3 +312,26 @@ dsp-tools rosetta
 ```
 
 A DSP stack must be running before executing this command.
+
+
+
+## `process-files`
+
+DaSCH-internal command to process multimedia files locally,
+before uploading them to a DSP server.
+See [here](./internal/fast-xmlupload.md) for more information.
+
+
+
+## `upload-files`
+
+DaSCH-internal command to upload processed multimedia files to a DSP server.
+See [here](./internal/fast-xmlupload.md) for more information.
+
+
+
+## `fast-xmlupload`
+
+DaSCH-internal command to create the resources of an XML file
+after the processed multimedia files have been uploaded already.
+See [here](./internal/fast-xmlupload.md) for more information.

docs/internal/fast-xmlupload.md

@@ -62,19 +62,45 @@ The following options are available:
 - `--output-dir` (mandatory): path to the output directory where the processed/transformed files should be written to
 - `--nthreads` (optional, default computed by the concurrent library, dependent on the machine): 
   number of threads to use for processing
+- `--batchsize` (optional, default 5000): number of files to process in one batch
 
 All files referenced in the `<bitstream>` tags of the XML 
 are expected to be in the input directory 
 which is provided with the `--input-dir` option.
+
 The processed files 
 (derivative, .orig file, sidecar file, as well as the preview file for movies) 
 will be stored in the given `--output-dir` directory.
 If the output directory doesn't exist, it will be created automatically.
+
 Additionally to the output directory,
 a pickle file is written with the name `processing_result_[timestamp].pkl`.
 It contains a mapping from the original files to the processed files,
-e.g. "multimedia/dog.jpg" -> "tmp/0b/22/0b22570d-515f-4c3d-a6af-e42b458e7b2b.jp2".
+e.g. `multimedia/dog.jpg` -> `tmp/0b/22/0b22570d-515f-4c3d-a6af-e42b458e7b2b.jp2`.
+
+
+### Important note
 
+**Due to a resource leak, Python must be quitted after a certain time.**
+**For big datasets, only a batch of files is processed, then Python exits with exit code 2.**
+**In this case, you need to restart the command several times, until the exit code is 0.**
+**Only then, all files are processed.**
+**Unexpected errors result in exit code 1.**
+
+You can orchestrate this with a shell script, e.g.:
+
+```bash
+exit_code=2
+while [ $exit_code -eq 2 ]; do
+    dsp-tools process-files --input-dir=multimedia --output-dir=tmp data.xml
+    exit_code=$?
+done
+
+if [ $exit_code -ne 0 ]; then
+    echo "Error: exit code $exit_code"
+    exit $exit_code
+fi
+```
 
 ## 3. `dsp-tools upload-files`
 

src/dsp_tools/dsp_tools.py

@@ -140,6 +140,9 @@ def make_parser() -> argparse.ArgumentParser:
         "--output-dir", help="path to the output directory where the processed/transformed files should be written to"
     )
     parser_process_files.add_argument("--nthreads", type=int, default=None, help="number of threads to use")
+    parser_process_files.add_argument(
+        "--batchsize", type=int, default=5000, help="number of files to process before Python exits"
+    )
     parser_process_files.add_argument("xml_file", help="path to XML file containing the data")
 
     # upload-files
@@ -376,13 +379,13 @@ def call_requested_action(
                 save_metrics=args.metrics,
                 preprocessing_done=False,
             )
-
     elif args.action == "process-files":
         success = process_files(
             input_dir=args.input_dir,
             output_dir=args.output_dir,
             xml_file=args.xml_file,
             nthreads=args.nthreads,
+            batch_size=args.batchsize,
         )
     elif args.action == "upload-files":
         success = upload_files(