casbin-postgresql-watcher 1.5.0
Casbin role watcher to be used for monitoring updates to policies for PyCasbin

# postgresql-watcher

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Casbin watcher based on PostgreSQL for monitoring updates to casbin policies.

## Installation
```bash
pip install casbin-postgresql-watcher
```

## Basic Usage Example

```python
from flask_authz import CasbinEnforcer
from postgresql_watcher import PostgresqlWatcher
from flask import Flask
from casbin.persist.adapters import FileAdapter

casbin_enforcer = CasbinEnforcer(app, adapter)
watcher = PostgresqlWatcher(host=HOST, port=PORT, user=USER, password=PASSWORD, dbname=DBNAME)
watcher.set_update_callback(casbin_enforcer.load_policy)
casbin_enforcer.set_watcher(watcher)

# Call should_reload before every call of enforce to make sure
# the policy is update to date
watcher.should_reload()
if casbin_enforcer.enforce("alice", "data1", "read"):
    # permit alice to read data1
    pass
else:
    # deny the request, show an error
    pass
```

alternatively, if you need more control

```python
from flask_authz import CasbinEnforcer
from postgresql_watcher import PostgresqlWatcher
from flask import Flask
from casbin.persist.adapters import FileAdapter

casbin_enforcer = CasbinEnforcer(app, adapter)
watcher = PostgresqlWatcher(host=HOST, port=PORT, user=USER, password=PASSWORD, dbname=DBNAME)
casbin_enforcer.set_watcher(watcher)

# Call should_reload before every call of enforce to make sure
# the policy is update to date
if watcher.should_reload():
    casbin_enforcer.load_policy()

if casbin_enforcer.enforce("alice", "data1", "read"):
    # permit alice to read data1
    pass
else:
    # deny the request, show an error
    pass
```

## Basic Usage Example With SSL Enabled

See [PostgresQL documentation](https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-PARAMKEYWORDS) for full details of SSL parameters.

```python
...
watcher = PostgresqlWatcher(host=HOST, port=PORT, user=USER, password=PASSWORD, dbname=DBNAME, sslmode="verify_full", sslcert=SSLCERT, sslrootcert=SSLROOTCERT, sslkey=SSLKEY)
...
```


## Django setup with casbin django orm adapter

Enforcer and Watcher setup
```
# settings.py
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

INSTALLED_APPS += [
    'casbin_adapter.apps.CasbinAdapterConfig',
]

CASBIN_MODEL = os.path.join(BASE_DIR, 'casbin.conf')

from postgresql_watcher.watcher import PostgresqlWatcher
from casbin_adapter.enforcer import enforcer

watcher = PostgresqlWatcher(host=BANK_CONNECT_APIS_PG_HOST_URL, port=BANK_CONNECT_APIS_PG_PORT,
            user=BANK_CONNECT_APIS_PG_USER, password=BANK_CONNECT_APIS_PG_PASSWORD, dbname=BANK_CONNECT_APIS_PG_DBNAME)

def update_enforcer():
    print("before loading policy", enforcer)
    enforcer.load_policy()

watcher.set_update_callback(update_enforcer)
CASBIN_WATCHER = watcher
```

Usage of enforcer

```
#views.py or any other file
from casbin_adapter.enforcer import enforcer

roles = enforcer.get_filtered_named_grouping_policy("g", 1, str(member_id))
```

### Reload Casbin enforcer
In current setup enforcer does not automatically refresh in memory data, we can call watcher.should_reload() before every data access from enforcer.
```
from setting import watcher 
watcher.should_reload()
```
If there are any changes in db this call will refresh in memory data from database

For automatic reloading of data, parent process need to poll child process for messages and call should_reload function if there is any message in pipe between child and parent process