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.
See also
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:
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:
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.
A returner is a Python module containing at minimum a returner function. Other optional functions can be included to add support for Master Job Cache, External Job Cache, and Event Returners.
salt-call --local --metadata test.ping --out=pprint
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, External Job Cache, and Event Returners. Salt's Master Job Cache allows returners to be used as a pluggable replacement for the 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.
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.
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()
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
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
Salt's External Job Cache extends the Master Job Cache. External Job Cache support requires the following functions in addition to what is required for Master Job Cache support:
Sample:
{
"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"
}
}
}
Sample:
{
"local": {
"minion1": "test.ping",
"minion3": "test.ping",
"minion2": "test.ping"
}
}
Sample:
{
"local": [
"20150330121011408195",
"20150330195922139916"
]
}
Sample:
{
"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.
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.
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']))
Place custom returners in a _returners directory within the file_roots specified by the master config file.
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.
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 __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:
try:
import redis
HAS_REDIS = True
except ImportError:
HAS_REDIS = False
__virtualname__ = 'redis'
def __virtual__():
if not HAS_REDIS:
return False
return __virtualname__
The returner, prep_jid, save_load, get_load, and event_return functions can be tested by configuring the 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.
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
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.
Docs for previous releases are available on readthedocs.org.
Latest Salt release: 2014.7.2
22.22.5.1.14. salt.renderers.yamlex