Error writing JSON!! (Main JSON file save was skipped)

[jiangzhenjerry]

Describe the bug
Whenever the program tries to save url-watches.json, it will fail and throw out an error message. url-watches.json will not be saved; instead, url-watches.json.tmp is created.

Sample LOG:

2025-06-11 19:53:07.958 | INFO     | changedetectionio.store:sync_to_json:398 - Saving JSON..
2025-06-11 19:53:08.022 | ERROR    | changedetectionio.store:sync_to_json:418 - Error writing JSON!! (Main JSON file save was skipped) : [WinError 32] The process cannot access the file because it is being used by another process: 'datastore/url-watches.json.tmp' -> 'datastore/url-watches.json'

Version
0.50.3

How did you install?
pip install changedetection.io

To Reproduce

Steps to reproduce the behavior:

1. Run changedection
2. Wait until it tries to auto-save JSON.

Expected behavior
url-watches.json should be updated.

Desktop (please complete the following information):

• OS: Windows 11
• Browser: Any browser

[dgtlmoon]

we need logs.. please provide the first 200 lines of startup, and a few lines around where it throws exception

this is defintely something in your setup, what about -d ? did you set anything?

[jiangzhenjerry]

There is nothing in my setup. It's the factory setting. I do use -d to point to a test folder for the testing purpose, so that I don't accidentally ruin my main settings.

Below is exactly what I did:

1. changedetection.py -d datastore. Note: This datastore folder does not contain any prior configuration, so it's brand-new factory setting.
2. Just wait a bit and do nothing. The console starts to throw errors once in a while.
3. ctrl+c to close the session. The console throws one last error.

Below is the log. Search Saving JSON.. for the errors. And BTW 0.50.2 does not have this issue. So it's definitely a 0.50.3 thing.

2025-06-12 00:02:52.034 | DEBUG    | changedetectionio.store:add_tag:592 - >>> Adding new tag - 'tech news'
2025-06-12 00:02:52.073 | DEBUG    | changedetectionio.store:add_watch:368 - Adding URL 'https://news.ycombinator.com/' - 1d86f11f-c674-437e-bdb8-5c4b2674687e
2025-06-12 00:02:52.073 | DEBUG    | changedetectionio.model.Watch:ensure_data_dir_exists:72 - > Creating data dir datastore\1d86f11f-c674-437e-bdb8-5c4b2674687e
2025-06-12 00:02:52.074 | INFO     | changedetectionio.store:sync_to_json:398 - Saving JSON..
2025-06-12 00:02:52.075 | ERROR    | changedetectionio.store:sync_to_json:418 - Error writing JSON!! (Main JSON file save was skipped) : [WinError 32] The process cannot access the file because it is being used by another process: 'datastore/url-watches.json.tmp' -> 'datastore/url-watches.json'
2025-06-12 00:02:52.075 | DEBUG    | changedetectionio.store:add_watch:384 - Added 'https://news.ycombinator.com/'
2025-06-12 00:02:52.075 | DEBUG    | changedetectionio.store:add_tag:592 - >>> Adding new tag - 'changedetection.io'
2025-06-12 00:02:52.075 | DEBUG    | changedetectionio.store:add_watch:368 - Adding URL 'https://changedetection.io/CHANGELOG.txt' - 8960764c-69fe-45b0-a99b-278804a8fc49
2025-06-12 00:02:52.075 | DEBUG    | changedetectionio.model.Watch:ensure_data_dir_exists:72 - > Creating data dir datastore\8960764c-69fe-45b0-a99b-278804a8fc49
2025-06-12 00:02:52.076 | INFO     | changedetectionio.store:sync_to_json:398 - Saving JSON..
2025-06-12 00:02:52.077 | ERROR    | changedetectionio.store:sync_to_json:418 - Error writing JSON!! (Main JSON file save was skipped) : [WinError 32] The process cannot access the file because it is being used by another process: 'datastore/url-watches.json.tmp' -> 'datastore/url-watches.json'
2025-06-12 00:02:52.077 | DEBUG    | changedetectionio.store:add_watch:384 - Added 'https://changedetection.io/CHANGELOG.txt'
2025-06-12 00:02:52.078 | INFO     | changedetectionio.store:sync_to_json:398 - Saving JSON..
2025-06-12 00:02:52.085 | ERROR    | changedetectionio.store:sync_to_json:418 - Error writing JSON!! (Main JSON file save was skipped) : [WinError 32] The process cannot access the file because it is being used by another process: 'datastore/url-watches.json.tmp' -> 'datastore/url-watches.json'
2025-06-12 00:02:52.241 | INFO     | changedetectionio.realtime.socket_server:init_socketio:275 - SOCKETIO_MODE=threading: Using threading mode for Socket.IO
2025-06-12 00:02:52.241 | INFO     | changedetectionio.realtime.socket_server:init_socketio:282 - Platform: windows, Python: 3.13, Socket.IO mode: threading
2025-06-12 00:02:52.263 | INFO     | changedetectionio.realtime.socket_server:init_socketio:294 - Socket.IO: Registering connect event handler
2025-06-12 00:02:52.263 | INFO     | changedetectionio.realtime.socket_server:__init__:35 - SignalHandler: Connected to notification_event signal
2025-06-12 00:02:52.263 | INFO     | changedetectionio.realtime.socket_server:polling_emit_running_or_queued_watches_threaded:119 - Queue update thread started (threading mode)
2025-06-12 00:02:52.263 | INFO     | changedetectionio.realtime.socket_server:__init__:44 - Started polling thread using threading (eventlet-free)
2025-06-12 00:02:52.264 | INFO     | changedetectionio.realtime.socket_server:init_socketio:394 - Socket.IO initialized and attached to main Flask app
2025-06-12 00:02:52.264 | INFO     | changedetectionio.realtime.socket_server:init_socketio:395 - Socket.IO: Registered event handlers: []
2025-06-12 00:02:52.264 | INFO     | changedetectionio.flask_app:changedetection_app:507 - Socket.IO server initialized
2025-06-12 00:02:52.265 | INFO     | changedetectionio.flask_app:changedetection_app:597 - Starting 10 workers during app initialization
2025-06-12 00:02:52.266 | INFO     | changedetectionio.worker_handler:start_async_event_loop:29 - Starting async event loop for workers
2025-06-12 00:02:52.266 | DEBUG    | changedetectionio.worker_handler:start_async_event_loop:37 - Event loop created and set: <ProactorEventLoop running=False closed=False debug=False>
2025-06-12 00:02:52.566 | INFO     | changedetectionio.worker_handler:start_async_workers:76 - Starting 10 async workers
2025-06-12 00:02:52.569 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 0
2025-06-12 00:02:52.569 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 0
2025-06-12 00:02:52.569 | DEBUG    | changedetectionio.flask_app:ticker_thread_check_time_launch_checks:702 - System env MINIMUM_SECONDS_RECHECK_TIME 3
2025-06-12 00:02:52.571 | INFO     | changedetectionio:main:194 - SIGUSR1 handler only registered on Linux, skipped.
2025-06-12 00:02:52.571 | DEBUG    | changedetectionio.flask_app:ticker_thread_check_time_launch_checks:821 - > Queued watch UUID 1d86f11f-c674-437e-bdb8-5c4b2674687e last checked at 0 queued at 1749711772.57 priority 1749711772 jitter 0.00s, 1749711772.57s since last checked
2025-06-12 00:02:52.570 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 1
2025-06-12 00:02:52.573 | DEBUG    | changedetectionio.flask_app:ticker_thread_check_time_launch_checks:821 - > Queued watch UUID 8960764c-69fe-45b0-a99b-278804a8fc49 last checked at 0 queued at 1749711772.57 priority 1749711772 jitter 0.00s, 1749711772.57s since last checked
2025-06-12 00:02:52.574 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 1
2025-06-12 00:02:52.576 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 2
2025-06-12 00:02:52.576 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 2
2025-06-12 00:02:52.577 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 3
2025-06-12 00:02:52.577 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 3
2025-06-12 00:02:52.577 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 4
2025-06-12 00:02:52.578 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 4
2025-06-12 00:02:52.578 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 5
 * Serving Flask app 'changedetectionio.flask_app'
2025-06-12 00:02:52.578 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 5
 * Debug mode: off
2025-06-12 00:02:52.578 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 6
2025-06-12 00:02:52.579 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 6
2025-06-12 00:02:52.579 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 7
2025-06-12 00:02:52.579 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 7
2025-06-12 00:02:52.579 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 8
2025-06-12 00:02:52.579 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 8
2025-06-12 00:02:52.580 | INFO     | changedetectionio.worker_handler:start_single_async_worker:106 - Starting async worker 9
2025-06-12 00:02:52.580 | INFO     | changedetectionio.async_update_worker:async_update_worker:33 - Starting async worker 9
2025-06-12 00:02:52.581 | DEBUG    | changedetectionio.realtime.socket_server:handle_queue_length:86 - SignalHandler: Queue length update received: 1
2025-06-12 00:02:52.581 | DEBUG    | changedetectionio.realtime.socket_server:handle_queue_length:86 - SignalHandler: Queue length update received: 2
2025-06-12 00:02:52.582 | DEBUG    | changedetectionio.realtime.socket_server:handle_queue_length:86 - SignalHandler: Queue length update received: 1
2025-06-12 00:02:52.582 | DEBUG    | changedetectionio.worker_handler:set_uuid_processing:179 - Started processing UUID: 1d86f11f-c674-437e-bdb8-5c4b2674687e
2025-06-12 00:02:52.582 | INFO     | changedetectionio.async_update_worker:async_update_worker:70 - Worker 0 processing watch UUID 1d86f11f-c674-437e-bdb8-5c4b2674687e Priority 1749711772 URL https://news.ycombinator.com/
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on all addresses (0.0.0.0)
 * Running on http://127.0.0.1:5000
 * Running on http://10.0.0.119:5000
Press CTRL+C to quit
2025-06-12 00:02:52.597 | DEBUG    | changedetectionio.realtime.socket_server:handle_queue_length:86 - SignalHandler: Queue length update received: 0
2025-06-12 00:02:52.598 | DEBUG    | changedetectionio.worker_handler:set_uuid_processing:179 - Started processing UUID: 8960764c-69fe-45b0-a99b-278804a8fc49
2025-06-12 00:02:52.598 | INFO     | changedetectionio.async_update_worker:async_update_worker:70 - Worker 1 processing watch UUID 8960764c-69fe-45b0-a99b-278804a8fc49 Priority 1749711772 URL https://changedetection.io/CHANGELOG.txt
2025-06-12 00:02:52.805 | DEBUG    | changedetectionio.processors.text_json_diff.processor:run_changedetection:367 - Watch UUID 1d86f11f-c674-437e-bdb8-5c4b2674687e content check - Previous MD5: de21991d7bbcb6f1e5993698a152adee, Fetched MD5 de21991d7bbcb6f1e5993698a152adee
2025-06-12 00:02:52.870 | DEBUG    | changedetectionio.model.Watch:history:199 - Reading watch history index for 1d86f11f-c674-437e-bdb8-5c4b2674687e
2025-06-12 00:02:52.871 | DEBUG    | changedetectionio.worker_handler:set_uuid_processing:182 - Finished processing UUID: 1d86f11f-c674-437e-bdb8-5c4b2674687e
2025-06-12 00:02:52.872 | DEBUG    | changedetectionio.async_update_worker:async_update_worker:380 - Worker 0 completed watch 1d86f11f-c674-437e-bdb8-5c4b2674687e in -0.13s
2025-06-12 00:02:53.116 | DEBUG    | changedetectionio.processors.text_json_diff.processor:run_changedetection:367 - Watch UUID 8960764c-69fe-45b0-a99b-278804a8fc49 content check - Previous MD5: 812646f33aae84426bd4c033ba1b86ab, Fetched MD5 812646f33aae84426bd4c033ba1b86ab
2025-06-12 00:02:53.340 | DEBUG    | changedetectionio.model.Watch:history:199 - Reading watch history index for 8960764c-69fe-45b0-a99b-278804a8fc49
2025-06-12 00:02:53.341 | DEBUG    | changedetectionio.worker_handler:set_uuid_processing:182 - Finished processing UUID: 8960764c-69fe-45b0-a99b-278804a8fc49
2025-06-12 00:02:53.342 | DEBUG    | changedetectionio.async_update_worker:async_update_worker:380 - Worker 1 completed watch 8960764c-69fe-45b0-a99b-278804a8fc49 in 0.34s
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/styles/styles.css?v=0.50.3 HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/realtime.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/watch-overview.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/styles/pure-min.css HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/toggle-theme.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/jquery-3.6.0.min.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/feather-icons.min.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/csrf.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/js/socket.io.min.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/pause.svg HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/play.svg HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/generic_feed-icon.svg HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/spread-white.svg HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/spread.svg HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/bell-off.svg HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:13] "GET /static/images/google-chrome-icon.png HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:14] "GET /static/js/jquery-3.6.0.min.js HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:14] "GET /static/favicons/apple-touch-icon.png HTTP/1.1" 200 -
127.0.0.1 - - [12/Jun/2025 00:03:14] "GET /static/favicons/favicon-32x32.png HTTP/1.1" 200 -
2025-06-12 00:03:14.102 | DEBUG    | changedetectionio.realtime.socket_server:handle_connect:345 - Socket.IO: Sent initial queue size 0 to new client
2025-06-12 00:03:14.102 | INFO     | changedetectionio.realtime.socket_server:handle_connect:349 - Socket.IO: Client connected
2025-06-12 00:03:29.831 | CRITICAL | changedetectionio:sigshutdown_handler:32 - Shutdown: Got Signal - SIGINT (2), Fast shutdown initiated
2025-06-12 00:03:29.831 | INFO     | changedetectionio.worker_handler:shutdown_workers:211 - Fast shutdown of async workers initiated...
2025-06-12 00:03:29.836 | INFO     | changedetectionio.worker_handler:start_single_async_worker:115 - Async worker 0 cancelled
2025-06-12 00:03:29.836 | INFO     | changedetectionio.worker_handler:start_single_async_worker:124 - Async worker 0 shutdown complete
2025-06-12 00:03:29.837 | INFO     | changedetectionio.worker_handler:start_single_async_worker:115 - Async worker 1 cancelled
2025-06-12 00:03:29.837 | INFO     | changedetectionio.worker_handler:start_single_async_worker:124 - Async worker 1 shutdown complete
2025-06-12 00:03:29.837 | INFO     | changedetectionio.worker_handler:start_single_async_worker:115 - Async worker 2 cancelled
2025-06-12 00:03:29.837 | INFO     | changedetectionio.worker_handler:start_single_async_worker:124 - Async worker 2 shutdown complete
2025-06-12 00:03:29.837 | INFO     | changedetectionio.worker_handler:start_single_async_worker:115 - Async worker 3 cancelled
2025-06-12 00:03:29.838 | INFO     | changedetectionio.worker_handler:start_single_async_worker:124 - Async worker 3 shutdown complete
2025-06-12 00:03:29.838 | INFO     | changedetectionio.worker_handler:start_single_async_worker:115 - Async worker 4 cancelled
2025-06-12 00:03:29.838 | INFO     | changedetectionio.worker_handler:start_single_async_worker:124 - Async worker 4 shutdown complete
2025-06-12 00:03:29.839 | INFO     | changedetectionio.worker_handler:start_single_async_worker:115 - Async worker 5 cancelled
2025-06-12 00:03:29.839 | INFO     | changedetectionio.worker_handler:start_single_async_worker:124 - Async worker 5 shutdown complete
2025-06-12 00:03:29.839 | INFO     | changedetectionio.worker_handler:start_async_event_loop:48 - Async event loop stopped
2025-06-12 00:03:29.840 | INFO     | changedetectionio.worker_handler:shutdown_workers:237 - Async workers fast shutdown complete
2025-06-12 00:03:29.840 | INFO     | changedetectionio.realtime.socket_server:shutdown:373 - Socket.IO: Fast shutdown initiated...
2025-06-12 00:03:29.840 | INFO     | changedetectionio.realtime.socket_server:shutdown:378 - Socket.IO: Waiting 1 second for polling thread to stop...
2025-06-12 00:03:30.127 | CRITICAL | changedetectionio.store:save_datastore:438 - Shutting down datastore thread
2025-06-12 00:03:30.288 | INFO     | changedetectionio.realtime.socket_server:polling_emit_running_or_queued_watches_threaded:182 - Queue update thread stopped (threading mode)
2025-06-12 00:03:30.289 | INFO     | changedetectionio.realtime.socket_server:shutdown:383 - Socket.IO: Polling thread stopped quickly
2025-06-12 00:03:30.290 | INFO     | changedetectionio.realtime.socket_server:shutdown:387 - Socket.IO: Fast shutdown complete
2025-06-12 00:03:30.290 | INFO     | changedetectionio.store:sync_to_json:398 - Saving JSON..
2025-06-12 00:03:30.293 | ERROR    | changedetectionio.store:sync_to_json:418 - Error writing JSON!! (Main JSON file save was skipped) : [WinError 32] The process cannot access the file because it is being used by another process: 'datastore/url-watches.json.tmp' -> 'datastore/url-watches.json'
2025-06-12 00:03:30.293 | SUCCESS  | changedetectionio:sigshutdown_handler:56 - Fast sync to disk complete.

[dgtlmoon]

2025-06-12 00:02:52.077 | ERROR | changedetectionio.store:sync_to_json:418 - Error writing JSON!! (Main JSON file save was skipped) : [WinError 32] The process cannot access the file because it is being used by another process: 'datastore/url-watches.json.tmp' -> 'datastore/url-watches.json'

so hmmmm

[dgtlmoon]

you have 2 copies running somehow

[jiangzhenjerry]

No there is just a single copy. After reverting back to 0.50.2 this issue is gone.

[jiangzhenjerry]

Also, for testing purpose, this datastore folder I pointed to was an empty folder. Nothing else is reading/writing to it, other than changedetection.py.

[1KuX]

I'm having the exact same issue. For some reason, the JSON is not saving after the update to version 50.3. Nothing initiates the second instance. This problem is fixed and everything functions properly when you go back to the earlier version.

[dgtlmoon]

I cant do much if people dont give me any information, like operating system, how you installed, a little big of the logs etc etc

[1KuX]

As I wrote, I have exactly the same error as above.
Windows 11 installation from the wiki https://github.com/dgtlmoon/changedetection.io/wiki/Microsoft-Windows

The error is identical. 1:1 below is a copy of the entry if it changes anything
Version
0.50.3

How did you install?
pip install changedetection.io

To Reproduce

Steps to reproduce the behavior:

Run changedection 50.3
Wait until it tries to auto-save JSON.
Expected behavior
url-watches.json should be updated.

Desktop (please complete the following information):

OS: Windows 11
Browser: Any browser

[1KuX]

[dgtlmoon]

Maybe this will help #3265

[jiangzhenjerry]

Tested on 0.50.4. The issue persists.