========= Returners ========= By default the return values of the commands sent to the Salt minions are returned to the Salt master, however anything at all can be done with the results data. By using a Salt returner, results data can be redirected to external data-stores for analysis and archival. Returners pull their configuration values from the Salt minions. Returners are only configured once, which is generally at load time. The returner interface allows the return data to be sent to any system that can receive data. This means that return data can be sent to a Redis server, a MongoDB server, a MySQL server, or any system. .. seealso:: :ref:`Full list of builtin returners ` Using Returners =============== All Salt commands will return the command data back to the master. Specifying returners will ensure that the data is _also_ sent to the specified returner interfaces. Specifying what returners to use is done when the command is invoked: .. code-block:: bash salt '*' test.ping --return redis_return This command will ensure that the redis_return returner is used. It is also possible to specify multiple returners: .. code-block:: bash salt '*' test.ping --return mongo_return,redis_return,cassandra_return In this scenario all three returners will be called and the data from the test.ping command will be sent out to the three named returners. Writing a Returner ================== A returner is a Python module containing at minimum a ``returner`` function. Other optional functions can be included to add support for :ref:`master_job_cache`, :ref:`external_job_cache`, and `Event Returners`_. ``returner`` The ``returner`` function must accept a single argument. The argument contains return data from the called minion function. If the minion function ``test.ping`` is called, the value of the argument will be a dictionary. Run the following command from a Salt master to get a sample of the dictionary: .. code-block:: bash salt-call --local --metadata test.ping --out=pprint .. code-block:: python import redis import json def returner(ret): ''' Return information to a redis server ''' # Get a redis connection serv = redis.Redis( host='redis-serv.example.com', port=6379, db='0') serv.sadd("%(id)s:jobs" % ret, ret['jid']) serv.set("%(jid)s:%(id)s" % ret, json.dumps(ret['return'])) serv.sadd('jobs', ret['jid']) serv.sadd(ret['jid'], ret['id']) The above example of a returner set to send the data to a Redis server serializes the data as JSON and sets it in redis. Master Job Cache Support ------------------------ :ref:`master_job_cache`, :ref:`external_job_cache`, and `Event Returners`_. Salt's :ref:`master_job_cache` allows returners to be used as a pluggable replacement for the :ref:`default_job_cache`. In order to do so, a returner must implement the following functions: .. note:: The code samples contained in this section were taken from the cassandra_cql returner. ``prep_jid`` Ensures that job ids (jid) don't collide, unless passed_jid is provided. ``nochache`` is an optional boolean that indicates if return data should be cached. ``passed_jid`` is a caller provided jid which should be returned unconditionally. .. code-block:: python def prep_jid(nocache, passed_jid=None): # pylint: disable=unused-argument ''' Do any work necessary to prepare a JID, including sending a custom id ''' return passed_jid if passed_jid is not None else salt.utils.jid.gen_jid() ``save_load`` Save job information. The ``jid`` is generated by ``prep_jid`` and should be considered a unique identifier for the job. The jid, for example, could be used as the primary/unique key in a database. The ``load`` is what is returned to a Salt master by a minion. The following code example stores the load as a JSON string in the salt.jids table. .. code-block:: python def save_load(jid, load): ''' Save the load to the specified jid id ''' query = '''INSERT INTO salt.jids ( jid, load ) VALUES ( '{0}', '{1}' );'''.format(jid, json.dumps(load)) # cassandra_cql.cql_query may raise a CommandExecutionError try: __salt__['cassandra_cql.cql_query'](query) except CommandExecutionError: log.critical('Could not save load in jids table.') raise except Exception as e: log.critical('''Unexpected error while inserting into jids: {0}'''.format(str(e))) raise ``get_load`` must accept a job id (jid) and return the job load stored by ``save_load``, or an empty dictionary when not found. .. code-block:: python def get_load(jid): ''' Return the load data that marks a specified jid ''' query = '''SELECT load FROM salt.jids WHERE jid = '{0}';'''.format(jid) ret = {} # cassandra_cql.cql_query may raise a CommandExecutionError try: data = __salt__['cassandra_cql.cql_query'](query) if data: load = data[0].get('load') if load: ret = json.loads(load) except CommandExecutionError: log.critical('Could not get load from jids table.') raise except Exception as e: log.critical('''Unexpected error while getting load from jids: {0}'''.format(str(e))) raise return ret External Job Cache Support -------------------------- Salt's :ref:`external_job_cache` extends the :ref:`master_job_cache`. External Job Cache support requires the following functions in addition to what is required for Master Job Cache support: ``get_jid`` Return a dictionary containing the information (load) returned by each minion when the specified job id was executed. Sample: .. code-block:: JSON { "local": { "master_minion": { "fun_args": [], "jid": "20150330121011408195", "return": true, "retcode": 0, "success": true, "cmd": "_return", "_stamp": "2015-03-30T12:10:12.708663", "fun": "test.ping", "id": "master_minion" } } } ``get_fun`` Return a dictionary of minions that called a given Salt function as their last function call. Sample: .. code-block:: JSON { "local": { "minion1": "test.ping", "minion3": "test.ping", "minion2": "test.ping" } } ``get_jids`` Return a list of all job ids. Sample: .. code-block:: JSON { "local": [ "20150330121011408195", "20150330195922139916" ] } ``get_minions`` Returns a list of minions Sample: .. code-block:: JSON { "local": [ "minion3", "minion2", "minion1", "master_minion" ] } Please refer to one or more of the existing returners (i.e. mysql, cassandra_cql) if you need further clarification. Event Support ------------- An ``event_return`` function must be added to the returner module to allow events to be logged from a master via the returner. A list of events are passed to the function by the master. The following example was taken from the MySQL returner. In this example, each event is inserted into the salt_events table keyed on the event tag. The tag contains the jid and therefore is guaranteed to be unique. .. code-block:: python def event_return(events): ''' Return event to mysql server Requires that configuration be enabled via 'event_return' option in master config. ''' with _get_serv(events, commit=True) as cur: for event in events: tag = event.get('tag', '') data = event.get('data', '') sql = '''INSERT INTO `salt_events` (`tag`, `data`, `master_id` ) VALUES (%s, %s, %s)''' cur.execute(sql, (tag, json.dumps(data), __opts__['id'])) Custom Returners ---------------- Place custom returners in a ``_returners`` directory within the :conf_master:`file_roots` specified by the master config file. Custom returners are distributed when any of the following are called: :mod:`state.highstate ` :mod:`saltutil.sync_returners ` :mod:`saltutil.sync_all ` Any custom returners which have been synced to a minion that are named the same as one of Salt's default set of returners will take the place of the default returner with the same name. Naming the Returner ------------------- Note that a returner's default name is its filename (i.e. ``foo.py`` becomes returner ``foo``), but that its name can be overridden by using a :ref:`__virtual__ function `. A good example of this can be found in the `redis`_ returner, which is named ``redis_return.py`` but is loaded as simply ``redis``: .. code-block:: python try: import redis HAS_REDIS = True except ImportError: HAS_REDIS = False __virtualname__ = 'redis' def __virtual__(): if not HAS_REDIS: return False return __virtualname__ Testing the Returner -------------------- The ``returner``, ``prep_jid``, ``save_load``, ``get_load``, and ``event_return`` functions can be tested by configuring the :ref:`master_job_cache` and `Event Returners`_ in the master config file and submitting a job to ``test.ping`` each minion from the master. Once you have successfully exercised the Master Job Cache functions, test the External Job Cache functions using the ``ret`` execution module. .. code-block:: bash salt-call ret.get_jids cassandra_cql --output=json salt-call ret.get_fun cassandra_cql test.ping --output=json salt-call ret.get_minions cassandra_cql --output=json salt-call ret.get_jid cassandra_cql 20150330121011408195 --output=json Event Returners =============== For maximimum visibility into the history of events across a Salt infrastructure, all events seen by a salt master may be logged to a returner. To enable event logging, set the ``event_return`` configuration option in the master config to returner which should be designated as the handler for event returns. .. note:: Not all returners support event returns. Verify a returner has an ``event_return()`` function before using. .. note:: On larger installations, many hundreds of events may be generated on a busy master every second. Be certain to closely monitor the storage of a given returner as Salt can easily overwhealm an underpowered server with thousands of returns. Full List of Returners ====================== .. toctree:: all/index .. _`redis`: https://github.com/saltstack/salt/tree/develop/salt/returners/redis_return.py