Storing Data in Other Databases¶

SDB Configuration¶

In order to use the SDB interface, a configuration profile must be set up in either the master or minion configuration file. The configuration stanza includes the name/ID that the profile will be referred to as, a driver setting, and any other arguments that are necessary for the SDB module that will be used. For instance, a profile called mykeyring, which uses the system service in the keyring module would look like:

mykeyring:
  driver: keyring
  service: system

It is recommended to keep the name of the profile simple, as it is used in the SDB URI as well.

SDB URIs¶

SDB is designed to make small database queries (hence the name, SDB) using a compact URL. This allows users to reference a database value quickly inside a number of Salt configuration areas, without a lot of overhead. The basic format of an SDB URI is:

sdb://<profile>/<args>

The profile refers to the configuration profile defined in either the master or the minion configuration file. The args are specific to the module referred to in the profile, but will typically only need to refer to the key of a key/value pair inside the database. This is because the profile itself should define as many other parameters as possible.

For example, a profile might be set up to reference credentials for a specific OpenStack account. The profile might look like:

kevinopenstack:
  driver: keyring
  service: salt.cloud.openstack.kevin

And the URI used to reference the password might look like:

sdb://kevinopenstack/password

Getting and Setting SDB Values¶

Once an SDB driver is configured, you can use the sdb execution module to set and get values from it. There are two functions that will appear in any SDB module: set and get.

Getting a value requires only the SDB URI to be specified. To retreive a value from the kevinopenstack profile above, you would use:

salt-call sdb.get sdb://kevinopenstack/password

Some drivers use slightly more complex URIs. For instance, the vault driver requires the full path to where the key is stored, followed by a question mark, followed by the key to be retrieved. If you were using a profile called myvault, you would use a URI that looks like:

salt-call sdb.get 'sdb://myvault/secret/salt?saltstack'

Setting a value uses the same URI as would be used to retrieve it, followed by the value as another argument. For the above myvault URI, you would set a new value using a command like:

salt-call sdb.set 'sdb://myvault/secret/salt?saltstack' 'super awesome'

The sdb.get and sdb.set functions are also available in the runner system:

salt-run sdb.get 'sdb://myvault/secret/salt?saltstack'
salt-run sdb.set 'sdb://myvault/secret/salt?saltstack' 'super awesome'

Using SDB URIs in Files¶

SDB URIs can be used in both configuration files, and files that are processed by the renderer system (jinja, mako, etc.). In a configuration file (such as /etc/salt/master, /etc/salt/minion, /etc/salt/cloud, etc.), make an entry as usual, and set the value to the SDB URI. For instance:

mykey: sdb://myetcd/mykey

To retrieve this value using a module, the module in question must use the config.get function to retrive configuration values. This would look something like:

mykey = __salt__['config.get']('mykey')

Templating renderers use a similar construct. To get the mykey value from above in Jinja, you would use:

{{ salt['config.get']('mykey') }}

When retrieving data from configuration files using config.get, the SDB URI need only appear in the configuration file itself.

If you would like to retrieve a key directly from SDB, you would call the sdb.get function directly, using the SDB URI. For instance, in Jinja:

{{ salt['sdb.get']('sdb://myetcd/mykey') }}

When writing Salt modules, it is not recommended to call sdb.get directly, as it requires the user to provide vaules in SDB, using a specific URI. Use config.get instead.

Writing SDB Modules¶

There is currently one function that MUST exist in any SDB module (get()) and one that SHOULD exist (set_()). If using a (set_()) function, a __func_alias__ dictionary MUST be declared in the module as well:

__func_alias__ = {
    'set_': 'set',
}

This is because set is a Python built-in, and therefore functions should not be created which are called set(). The __func_alias__ functionality is provided via Salt's loader interfaces, and allows legally-named functions to be referred to using names that would otherwise be unwise to use.

The get() function is required, as it will be called via functions in other areas of the code which make use of the sdb:// URI. For example, the config.get function in the config execution module uses this function.

The set_() function may be provided, but is not required, as some sources may be read-only, or may be otherwise unwise to access via a URI (for instance, because of SQL injection attacks).

A simple example of an SDB module is salt/sdb/keyring_db.py, as it provides basic examples of most, if not all, of the types of functionality that are available not only for SDB modules, but for Salt modules in general.