Merge pull request #395 from bigchaindb/feat/394/change-config-system

Change config precedence so that env variables can override config.

bigchaindb/config_utils.py

@@ -183,6 +183,20 @@ def set_config(config):
     bigchaindb.config['CONFIGURED'] = True
 
 
+def update_config(config):
+    """Update bigchaindb.config with whatever is in the provided config dict,
+    and then set bigchaindb.config['CONFIGURED'] = True
+
+    Args:
+        config (dict): the config dict to read for changes
+                       to the default config
+    """
+
+    # Update the default config with whatever is in the passed config
+    update(bigchaindb.config, update_types(config, bigchaindb.config))
+    bigchaindb.config['CONFIGURED'] = True
+
+
 def write_config(config, filename=None):
     """Write the provided configuration to a specific location.
 
@@ -206,13 +220,18 @@ def autoconfigure(filename=None, config=None, force=False):
         logger.debug('System already configured, skipping autoconfiguration')
         return
 
-    newconfig = env_config(bigchaindb.config)
+    # start with the current configuration
+    newconfig = bigchaindb.config
 
+    # update configuration from file
     try:
         newconfig = update(newconfig, file_config(filename=filename))
     except FileNotFoundError as e:
         logger.warning('Cannot find config file `%s`.' % e.filename)
 
+    # override configuration with env variables
+    newconfig = env_config(newconfig)
+
     if config:
         newconfig = update(newconfig, config)
 

bigchaindb/core.py

@@ -38,11 +38,11 @@ class Bigchain(object):
         A Bigchain instance has several configuration parameters (e.g. host).
         If a parameter value is passed as an argument to the Bigchain
         __init__ method, then that is the value it will have.
-        Otherwise, the parameter value will be the value from the local
+        Otherwise, the parameter value will come from an environment variable.
-        configuration file. If it's not set in that file, then the value
+        If that environment variable isn't set, then the value
-        will come from an environment variable. If that environment variable
+        will come from the local configuration file. And if that variable
-        isn't set, then the parameter will have its default value (defined in
+        isn't in the local configuration file, then the parameter will have
-        bigchaindb.__init__).
+        its default value (defined in bigchaindb.__init__).
 
         Args:
             host (str): hostname where RethinkDB is running.

docs/source/nodes/configuration.md

@@ -81,11 +81,13 @@ the `server` section accepts all the options specified in the
 
 ## Order of Precedence in Determining Configuration Values
 
-All configuration values start with their default values (defined in `bigchaindb.__init__`), but a default value can be overriden by an environment variable, and a value set by an environment variable can be overriden by a value in a local configuration file (`$HOME/.bigchaindb` or the location specified by the `-c` command-line option).
+All configuration values start with their default values (defined in `bigchaindb.__init__`), but a default value
+can be overriden by a value in a local configuration file (`$HOME/.bigchaindb` or the location specified by the
+`-c` command-line option), and a value set by a local configuration file can be overriden by a value in an environment variable
 
 In summary, there is an order of precedence in reading configuration values:
-1. local configuration file
+1. environment variables
-2. environment variables
+2. local configuration file
 3. default configuration file (defined in ``bigchaindb.__init__``)
 
 This means that if the default configuration contains:
@@ -93,6 +95,7 @@ This means that if the default configuration contains:
 ```json
 {
     "database": {
+        "name": "bigchain",
         "host": "localhost",
         "port": 28015
     }
@@ -103,7 +106,8 @@ while the local file `local.json` contains:
 ```json
 {
     "database": {
-        "host": "ec2-xx-xx-xxx-xxx.eu-central-1.compute.amazonaws.com"
+        "host": "ec2-xx-xx-xxx-xxx.eu-central-1.compute.amazonaws.com",
+        "port": 5000
     }
 }
 
@@ -111,8 +115,7 @@ while the local file `local.json` contains:
 
 and you run this command:
 ```
-$ BIGCHAINDB_DATABASE_HOST=anotherhost.com \
+$ BIGCHAINDB_DATABASE_PORT=4242 \
-  BIGCHAINDB_DATABASE_PORT=4242 \
   BIGCHAINDB_KEYRING=pubkey0:pubkey1 \
   bigchaindb -c local.json show-config
 ```

tests/utils/test_config_utils.py

@@ -168,3 +168,41 @@ def test_autoconfigure_read_both_from_file_and_env(monkeypatch):
         'consensus_plugin': 'default',
     }
 
+
+def test_autoconfigure_env_precedence(monkeypatch):
+    file_config = {
+        'database': {'host': 'test-host', 'name': 'bigchaindb', 'port': 28015}
+    }
+    monkeypatch.setattr('bigchaindb.config_utils.file_config', lambda *args, **kwargs: file_config)
+    monkeypatch.setattr('os.environ', {'BIGCHAINDB_DATABASE_NAME': 'test-dbname',
+                                       'BIGCHAINDB_DATABASE_PORT': '4242',
+                                       'BIGCHAINDB_SERVER_BIND': 'localhost:9985'})
+
+    import bigchaindb
+    from bigchaindb import config_utils
+    config_utils.autoconfigure()
+
+    assert bigchaindb.config['CONFIGURED']
+    assert bigchaindb.config['database']['host'] == 'test-host'
+    assert bigchaindb.config['database']['name'] == 'test-dbname'
+    assert bigchaindb.config['database']['port'] == 4242
+    assert bigchaindb.config['server']['bind'] == 'localhost:9985'
+
+
+def test_update_config(monkeypatch):
+    import bigchaindb
+    from bigchaindb import config_utils
+
+    file_config = {
+        'database': {'host': 'test-host', 'name': 'bigchaindb', 'port': 28015}
+    }
+    monkeypatch.setattr('bigchaindb.config_utils.file_config', lambda *args, **kwargs: file_config)
+    config_utils.autoconfigure()
+
+    # update configuration, retaining previous changes
+    config_utils.update_config({'database': {'port': 28016, 'name': 'bigchaindb_other'}})
+
+    assert bigchaindb.config['database']['host'] == 'test-host'
+    assert bigchaindb.config['database']['name'] == 'bigchaindb_other'
+    assert bigchaindb.config['database']['port'] == 28016
+