First please take the time to read and understand Redis security as described at https://redis.io/topics/security
It is important that you understand factors relating to the default Redis security model.
With the introduction of rebrow and Luminosity it
is very important that Redis and your environment are configured correctly in
terms of securing Redis and access to Redis. Please ensure that you implement
the recommendations described on redis.io security page and the Redis related
Skyline recommendations described on the installations page in this
Types of Skyline and Redis implementations¶
There are two different types of Skyline implementations:
- A single Skyline instance, Redis only needs to bind to 127.0.0.1
- Multiple Skyline instances running in a distributed fashion Redis still only needs to bind to 127.0.0.1 but stunnel need to be implmented to allow each Skyline server to connect to other Redis instances on Skyline servers via a stunnel SSL encrypted connection. See Running multiple Skyline instances
How are time series stored in Redis?¶
Part of the Horizon service’s job is to input data into Redis. Skyline uses
MessagePack to store data in Redis. When a data point comes in, a
Horizon worker will pack the data point with the schema
into a MessagePack-encoded binary string and make a
redis.append() call to
append this string to the appropriate metric key. This way, Horizon can very
easily make many updates to Redis at once, and this is how Skyline is able to
support a very large firehose of metrics.
One downside to this scheme is that once time series in Redis start to get very long, Redis’ performance suffers. Redis was not designed to contain very large strings. We may one day switch to an alternative storage design as proposed by Antirez - see https://github.com/antirez/redis-timeseries - but for now, this is how it is. And given that the last update to that repo was in 10 Oct 2012, it is highly probable that normal Redis will be used for the forseenable future.
Using the default mod:settings.FULL_DURATION of 86400 (24 hours) ensures that Redis does not hit performance issues in most cases. Now where Skyline needs greater than mod:settings.FULL_DURATION data to analyse in Mirage and Ionosphere, Skyline fetches that data from Graphite directly when required. This overcomes any Redis performance issues and the use of Graphite data removes the limitation of Skyline only being able to analyse data and be useful in the 24 hour time window.
What other data are stored in Redis?¶
In addition to all the metrics, there are a number of specialized Redis sets and keys:
mini.unique_metricsThese contain every key that exists in Redis, and they are used by the Analyzer to make it easier for the Analyzer to know what to mget from Redis (as opposed to doing a very expensive keys * query)
- analyzer.boring - a set of all metrics deemed Boring by Analyzer
- analyzer.stale - a set of all metrics deemed Stale by Analyzer
- analyzer.too_short - a set of all metrics deemed TooShort by Analyzer
- derivative_metrics - a set of all metrics that have been defined as metrics to analyse as derivatives by Analyzer.
- non_derivative_metrics - a set of all metrics that have been defined as to opposite of derivative_metrics by Analyzer.
- ionosphere.learn.work - a set of metric anomalies with details that require learning.
- ionosphere.training_data.* keys containing anomalies that need to be learnt e.g.
[['metric_timestamp', 1526755861], ['base_name', 'carbon.relays.graphite-a.metricsReceived'], ['timeseries_dir', 'carbon/relays/graphite-a/metricsReceived'], ['added_by', 'analyzer']]
- ionosphere.unique_metrics set
- <skyline_app>.last_alert.<alerter>.<metric> keys
- panorama.mysql_ids.* keys
- rebrow.client.key.* keys - expiring rebrow Redis password JWT encoded tokens
- etc, etc, feel free to browser Redis with rebrow and take a look and please free feel to PR update this doc if you find some that are missing here.
What’s with the ‘mini’ and ‘metrics’ namespaces?¶
The ‘mini’ namespace is used by the Webapp to display a settings.MINI_DURATION seconds long view.