Redis

Read-only access to Redis servers is provided by the redis() function.

redis([port=6379][, db=0])

Returns a connection to the Redis server at <host>:<port>, where <host> is the value of the current entity’s host attribute, and <port> is the given port (default 6379). See below for a list of methods provided by the returned connection object.

Please also have a look at the Redis documentation.

Methods of the Redis Connection

The object returned by the redis() function provides the following methods:

llen(key)

Returns the length of the list stored at key. If key does not exist, it’s value is treated as if it were an empty list, and 0 is returned. If key exists but is not a list, an error is raised.

redis().llen("prod_eventlog_queue")
lrange(key, start, stop)

Returns the elements of the list stored at key in the range [start, stop]. If key does not exist, it’s value is treated as if it were an empty list. If key exists but is not a list, an error is raised.

The parameters start and stop are zero-based indexes. Negative numbers are converted to indexes by adding the length of the list, so that -1 is the last element of the list, -2 the second-to-last element of the list, and so on.

Indexes outside the range of the list are not an error: If both start and stop are less than 0 or greater than or equal to the length of the list, an empty list is returned. Otherwise, if start is less than 0, it is treated as if it were 0, and if stop is greater than or equal to the the length of the list, it is treated as if it were equal to the length of the list minus 1. If start is greater than stop, an empty list is returned.

Note that this method is subtly different from Python’s list slicing syntax, where list[start:stop] returns elements in the range [start, stop).

redis().lrange("prod_eventlog_queue", 0, 9)   # Returns *ten* elements!
redis().lrange("prod_eventlog_queue", 0, -1)  # Returns the entire list.
get(key)

Returns the string stored at key. If key does not exist, returns None. If key exists but is not a string, an error is raised.

redis().get("example_redis_key")
keys(pattern)

Returns list of keys from Redis matching pattern.

redis().keys("*downtime*")
hget(key, field)

Returns the value of the field field of the hash key. If key does not exist or does not have a field named field, returns None. If key exists but is not a hash, an error is raised.

redis().hget("example_hash_key", "example_field_name")
hgetall(key)

Returns a dict of all fields of the hash key. If key does not exist, returns an empty dict. If key exists but is not a hash, an error is raised.

redis().hgetall("example_hash_key")
scan(cursor[, match=None][, count=None])

Returns a set with the next cursor and the results from this scan. Please see the Redis documentation on how to use this function exactly: http://redis.io/commands/scan

redis().scan(0, 'prefix*', 10)
smembers(key)

Returns members of set key in Redis.

redis().smembers("zmon:alert:1")
ttl(key)

Return the time to live of an expiring key.

redis().ttl('lock')
scard(key)

Return the number of elements in set key

redis().scard("example_hash_key")
zcard(key)

Return the number of elements in the sorted set key

redis().zcard("example_sorted_set_key")
statistics()

Returns a dict with general Redis statistics such as memory usage and operations/s. All values are extracted using the Redis INFO command.

Example result:

{
    "blocked_clients": 2,
    "commands_processed_per_sec": 15946.48,
    "connected_clients": 162,
    "connected_slaves": 0,
    "connections_received_per_sec": 0.5,
    "dbsize": 27351,
    "evicted_keys_per_sec": 0.0,
    "expired_keys_per_sec": 0.0,
    "instantaneous_ops_per_sec": 29626,
    "keyspace_hits_per_sec": 1195.43,
    "keyspace_misses_per_sec": 1237.99,
    "used_memory": 50781216,
    "used_memory_rss": 63475712
}

Please note that the values for both used_memory and used_memory_rss are in Bytes.