Rule Engine

Uses SLY to process csv file containing rules. The output of the module is a dictionary with the truth value of each of the rules in the csv file.

Example output:

{
    'rule_snow': True,
    'rule_hybrid': True,
    'rule_rain': True,
    'rule_future-snow': False,
    'rule_future-hybrid': True,
    'rule_future-rain': True,
    ...
}

Setup

Project setup is automated by make.

make
source /tmp/p2a-re-venv/bin/activate

Manual Setup

If you do not wish to use make, follow the steps below to setup the project.

Step 1: Create venv

To run the program create and enter a python3 (3.6+) virtual environment.

python3 -m venv venv
source venv/bin/activate

Step 2: Install requirements

Once you have activated the venv you can install the required packages.

sudo apt-get install -y libpq-dev python3-dev libhdf5-dev libnetcdf-dev libgdal-dev
export CPLUS_INCLUDE_PATH=/usr/include/gdal
export C_INCLUDE_PATH=/usr/include/gdal
pip install -i https://pypi.pacificclimate.org/simple -r requirements.txt
pip install -e .

Step 3: .pgpass

To connect to the database the script expects there to be a .pgpass file for it to read. It should look like so:

database:port:*:username:password

You can find these items in TPM.

Step 4: Pre-commit hook

While not required, the pre-commit hook will help you avoid formatting errors in actions during development. While in venv run:

pre-commit install

This will check each of your commits against the .pre-commit-config.yml to ensure it meets the standard.

Run

To run the rule engine and view the results use process.py script.

(venv)$ process.py --csv data/rules.csv --date-range [date-option] --region [region-option]

If you wish to use the --thredds option please set the appropriate env variable:

export THREDDS_URL_ROOT=https://docker-dev03.pcic.uvic.ca/twitcher/ows/proxy/thredds/dodsC/datasets

Program Flow

Read csv and extract id and condition columns (resolver.py)
| | Input: csv file
| | Output: dictionary {rule: condition}
|/
Process conditions using SLY into parse trees (parser.py)
| | Input: string
| | Output: parse tree tuple
|/
Evaluate parse trees to determine truth value of each rule (evaluator.py)
| | Input: parse tree tuple
| | Output: truth value of parse tree (there are some cases where the output of the rule is actually a value)
|/
Return result dictionary {rule: True/False/Value} (resolver.py)

Testing

Uses pytest.

pytest tests/ --cov --flake8 --cov-report term-missing

Troubleshooting

Unhashable type: 'MaskedArray' error

Solution for this issue is ongoing. A temporary solution is to replace some code in the virtual environment.

Open up the file that's causing the issue.

$ vi venv/lib/python3.6/site-packages/ce/api/geo.py  

Find the definition for the make_mask_grid_key(...) method and replace this chunk:

latsteps = nc.variables['lat'].shape[0]
latmin = nc.variables['lat'][0]
latmax = nc.variables['lat'][latsteps - 1]
lonsteps = nc.variables['lon'].shape[0]
lonmin = nc.variables['lon'][0]
lonmax = nc.variables['lon'][lonsteps - 1]

With this:

latsteps = nc.variables['lat'].shape[0]
latmin = np.min(nc.variables['lat'][:])
latmax = np.max(nc.variables['lat'][:])
lonsteps = nc.variables['lon'].shape[0]
lonmin = np.min(nc.variables['lon'][:])
lonmax = np.max(nc.variables['lon'][:])

This should take care of the issue.

No such file or directory error

In the case that an error in this form occurs:

NETCDF:"file.nc":some_variable: No such file or directory

Try the following:

(venv)$ pip uninstall rasterio
(venv)$ pip install rasterio==1.0.22 --no-binary rasterio

This should fix the issue as it is likely that rasterio and GDAL were not working together properly.

Releasing

1. Increment __version__ in setup.py
2. Summarize release changes in NEWS.md
3. Commit these changes, then tag the release

   git add setup.py NEWS.md
   git commit -m"Bump to version x.x.x"
   git tag -a -m"x.x.x" x.x.x
   git push --follow-tags

4. Our Github Actions workflow will build and release the package