Configuration¶
-
asab.
Config
¶
The configuration is provided by Config
object which is a singleton. It means that you can access Config
from any place of your code, without need of explicit initialisation.
import asab
# Initialize application object and hence the configuration
app = asab.Application()
# Access configuration values anywhere
my_conf_value = asab.Config['section_name']['key1']
Based on ConfigParser¶
The Config
is inherited from Python Standard Library configparser.ConfigParser
class. which implements a basic configuration language which provides a structure similar to what’s found in Microsoft Windows INI files.
Example of the configuration file:
[bitbucket.org]
User = hg
[topsecret.server.com]
Port = 50022
ForwardX11 = no
And this is how you access configuration values:
>>> asab.Config['topsecret.server.com']['ForwardX11']
'no'
Multiline configuration entry¶
A multiline configuration entries are supported. An example:
[section]
key=
line1
line2
line3
another_key=foo
Automatic load of configuration¶
If a configuration file name is specified, the configuration is automatically loaded from a configuration file during initialiation time of Application
.
The configuration file name can be specified by one of -c
command-line argument (1), ASAB_CONFIG
environment variable (2) or config [general] config_file
default value (3).
./sample_app.py -c ./etc/sample.conf
Including other configuration files¶
You can specify one or more additional configuration files that are loaded and merged from an main configuration file.
It is done by [general] include
configuration value. Multiple paths are separated by os.pathsep
(:
on Unix).
The path can be specified as a glob (e.g. use of *
and ?
wildcard characters), it will be expanded by glob
module from Python Standard Library.
Included configuration files may not exists, this situation is silently ignored.
[general]
include=./etc/site.conf:./etc/site.d/*.conf
You can also use a multiline configuration entry:
[general]
include=
./etc/site.conf
./etc/site.d/*.conf
Including ZooKeeper node in the configuration¶
The separator between includes is newline or space - it means that space MUST NOT be in the names of nodes in the ZooKeeper.
The ZooKeeper node can contain a configuration file in .conf, .json or .yaml format.
You can specify servers and path of the ZooKeeper node directly in the include option:
[general]
include=zookeeper://localhost:2181/asab/config/config-test.yaml
It is also possible to name only the node path in this section and use zookeeper` configuration section to read the location of ZooKeeper servers. Using the environment variable ASAB_ZOOKEEPERS_SERVERS is also a possible option.
[general]
include=zookeeper:///asab/config/config-test.yaml
Configuration default values¶
-
Config.
add_defaults
(dictionary)¶
This is how you can extend configuration default values:
asab.Config.add_defaults(
{
'section_name': {
'key1': 'value',
'key2': 'another value'
},
'other_section': {
'key3': 'value',
},
}
)
Only simple types (string
, int
and float
) are allowed in the configuration values.
Don’t use complex types such as lists, dictionaries or objects because these are impossible to provide via configuration files etc.
Environment variables in configration¶
Environment variables found in values are automatically expanded.
[section_name]
persistent_dir=${HOME}/.myapp/
>>> asab.Config['section_name']['persistent_dir']
'/home/user/.myapp/'
There is a special environment variable ${THIS_DIR} that is expanded to a directory that contains a current configuration file. It is useful in complex configurations that utilizes included configuration files etc.
[section_name]
my_file=${THIS_DIR}/my_file.txt
Another environment variable ${HOSTNAME} contains the application hostname to be used f. e. in logging file path.
[section_name]
my_file=${THIS_DIR}/${HOSTNAME}/my_file.txt
Passwords in configration¶
[passwords] section in the configuration serves to securely store passwords, which are then not shown publicly in the default API config endpoint’s output.
It is convenient for the user to store passwords at one place, so that they are not repeated in many sections of the config file(s).
Usage is as follows:
[connection:KafkaConnection]
password=${passwords:kafka_password}
[passwords]
kafka_password=<MY_SECRET_PASSWORD>
Obtaining seconds¶
-
Config.
getseconds
()¶
The seconds can be obtained using getseconds() method for values with different time units specified in the configuration:
[sleep]
sleep_time=5.2s
another_sleep_time=10d
The available units are:
y
… yearsM
… monthsw
… weeksd
… daysh
… hoursm
… minutess
… secondsms
.. miliseconds
If no unit is specified, float of seconds is expected.
The obtainment of the second value in the code can be achieved in two ways:
self.SleepTime = asab.Config["sleep"].getseconds("sleep_time")
self.AnotherSleepTime = asab.Config.getseconds("sleep", "another_sleep_time")
Obtaining URLs¶
-
Config.
geturl
(section, option, scheme=None:str, tuple)¶
A URL can be obtained using a geturl() method that takes the URL from the config and removes leading and trailing whitespaces and trailing backslashes.
There is an optional parameter called scheme that can have any URL scheme like http, https, mongodb etc. Setting it to None, scheme validation gets bypassed.
Setting the scheme parameter to the same scheme as in the config, it will return the URL. If it’s not the same it will raise an error.
There are two ways of obtaining the URL:
asab.Config["urls"].geturl("teskalabs", scheme="https")
asab.Config.geturl("urls", "github", scheme=None)
Example:
>>> asab.Config["urls"].geturl("teskalabs", scheme="https")
'https://www.teskalabs.com'
For reference this would be the configuration file:
[urls]
teskalabs=https://www.teskalabs.com/
github=github.com