PromQL:
PromQL expressions has classified as follows:
Instant Vector
Range Vector
Scalar
String
Instant and Range vector has a basic syntax consist of metric name along with label matchers. A metric name in Prometheus is a label named __name__ under the value.
example:
{__name__="prometheus_build_info"}
PromQL will query directly by name [prometheus_build_info]
Label matchers are defined using a label key, a label matching operator, and the label value. Some possible label-matching operators:
=: The label value matches the specified string
!=: The label value does not match the specified string
=~: The label value matches the regex in the specified string
!~: The label value does not match the regex in the specified string
Instant Vector are selectors that select the data at this instant using a recent available data for the time series which you are selected.
Range Vector is retriving data over a given time range. This time range is specified as duration followed by unit.
The following are valid units for a duration:
ms: Milliseconds
s: Seconds
m: Minutes
h: Hours
d: Days (assumes a day is always 24 hours)
w: Weeks (assumes a week is always 7 days)
y: Years (assumes a year is always 365 days)
These range vector selectors are often more useful when aggregating data to perform an analysis to drive results such as the number of requests per second a service experienced over a particular time range.
Prometheus has two primary API endpoints that are used to retrive time series data /api/v1/query and /api/v1/query_range.
Note : Both instant vectors and range vectors are valid for the /query endpoint, but only instant vectors are valid for the /query_range endpoint.
Offsets:
It will allow us to pull the time series data from the past based on offset values.
Example:
my_cool_custom_metric offset 5m
Group Modifier and Vector Matching:
Prometheus has provided ways to join the labels of different matrics together when using the group_left and group_right query modifiers. This option allows for many-to-one and one-to-many matching of vectors.
Logical and set binary operators
PromQL used the boolean operators of and,or and unless query operators
Example:
vector1 and vector2
It requires that for every series in vector1, there must be an exactly matching label set in vector2 (besides the __name__ label). If there is no match for the label set of a series in vector1 inside of vector2, then that series is not included in the results.
