# Mongo Debug Toolbar Panel

```{eval-rst}
.. versionchanged:: 2.0.0
```

Mongo Debug Toolbar Panel was completely rewritten in version **2.0.0**. Before this
version Mongo Debug Toolbar Panel used patching of main [pymongo] create/update/delete
methods. This was not the best approach, as raised some compatibility issues during
[pymongo] project updates. Since version **2.0.0** we use [pymongo] monitoring functions
to track requests and timings. This approach completely removes patching of external
packages and more compatibility friendly.

New approach require some user side actions to proper panel installation. This is done
to exclude 'silent' registration of event loggers, to prevent performance degradation in
external projects and in projects, that do not require Mongo Debug Toolbar Panel
functional.

Described approach change brings several side effects, that user should be aware of:

1. Now Mongo Debug Toolbar Panel shows real database time, as reported by database
   engine. Excluding time required for data delivery from database instance to Flask
   instance.
2. Mongo Debug Toolbar Panel do not display and track tracebacks anymore. It only
   monitors database requests. Nothing more.
3. Mongo Debug Toolbar Panel do not do anything, if monitoring engine not registered
   before Flask application connection setup. Monitoring listener should be
   registered before first database connection. This is external requirement.
4. Mongo Debug Toolbar Panel code is now covered by internal tests, raising overall
   project code quality.
5. Mongo Debug Toolbar Panel can work without any usage of other
   ``flask_mongoengine`` functions.
6. Mongo Debug Toolbar Panel do not split requests types anymore, this is because
   now it handle any requests, including aggregations, collection creating/deleting
   and any other, reported by [pymongo] monitoring. Making splitting of incomming
   events will bring high complexity to parsers, as there are a lot of mongoDb
   commmands exist.

## Installation

To install and use Mongo Debug Toolbar Panel:

1. Add ``'flask_mongoengine.panels.MongoDebugPanel'`` to ``DEBUG_TB_PANELS`` of
   [Flask Debug Toolbar].
2. Import ``mongo_command_logger`` in your Flask application initialization file.
3. Import ``monitoring`` from ``pymongo`` package in your Flask application
   initialization file.
4. Register ``mongo_command_logger`` as event listener in ``pymongo``.
5. Init Flask app instance.

Example:

```python
import flask
from flask_debugtoolbar import DebugToolbarExtension
from pymongo import monitoring

from flask_mongoengine.panels import mongo_command_logger
from flask_mongoengine import MongoEngine


app = flask.Flask(__name__)
app.config.from_object(__name__)
app.config["MONGODB_SETTINGS"] = {"DB": "testing", "host": "mongo"}
app.config["TESTING"] = True
app.config["SECRET_KEY"] = "some_key"
app.debug = True
app.config["DEBUG_TB_PANELS"] = ("flask_mongoengine.panels.MongoDebugPanel",)
DebugToolbarExtension(app)
monitoring.register(mongo_command_logger)
db = MongoEngine()
db.init_app(app)
```

```{note}
Working toolbar installation code can be found and tested in example_app, shipped with
project codebase.
```

## Configuration

You can add ``MONGO_DEBUG_PANEL_SLOW_QUERY_LIMIT`` variable to flask application
config, to set a limit for queries highlight in web interface. By default, 100 ms.

## Usage

```{eval-rst}
.. image:: _static/debug_toolbar.png
  :target: _static/debug_toolbar.png
```

- Mongo Debug Toolbar Panel logs every mongoDb query, in executed order.
- You can expand ``Server command`` to check what command was send to server.
- You can expand ``Response data`` to check raw response from server side.

## Known issues

There is some HTML rendering related issues, that I cannot fix, as do not work with
front end at all. If you have a little HTML/CSS knowledge, please help.

- [#469] Mongo Debug Toolbar Panel: Update HTML view to use wide screens
- Objects sizes may be incorrect, as calculated in python. This part is copied from
  previous version, and may be removed in the future, if there will be confirmation,
  that this size data completely incorrect.

[Flask Debug Toolbar]: https://github.com/flask-debugtoolbar/flask-debugtoolbar
[#469]: https://github.com/MongoEngine/flask-mongoengine/issues/469
[pymongo]: https://pymongo.readthedocs.io/en/stable/