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|
# frozen_string_literal: true
module Prometheus
class ProxyVariableSubstitutionService < BaseService
include Stepable
VARIABLE_INTERPOLATION_REGEX = /
{{ # Variable needs to be wrapped in these chars.
\s* # Allow whitespace before and after the variable name.
(?<variable> # Named capture.
\w+ # Match one or more word characters.
)
\s*
}}
/x.freeze
steps :validate_variables,
:add_params_to_result,
:substitute_params,
:substitute_variables
# @param environment [Environment]
# @param params [Hash<Symbol,Any>]
# @param params - query [String] The Prometheus query string.
# @param params - start [String] (optional) A time string in the rfc3339 format.
# @param params - start_time [String] (optional) A time string in the rfc3339 format.
# @param params - end [String] (optional) A time string in the rfc3339 format.
# @param params - end_time [String] (optional) A time string in the rfc3339 format.
# @param params - variables [ActionController::Parameters] (optional) Variables with their values.
# The keys in the Hash should be the name of the variable. The value should be the value of the
# variable. Ex: `ActionController::Parameters.new(variable1: 'value 1', variable2: 'value 2').permit!`
# @return [Prometheus::ProxyVariableSubstitutionService]
#
# Example:
# Prometheus::ProxyVariableSubstitutionService.new(environment, {
# params: {
# start_time: '2020-07-03T06:08:36Z',
# end_time: '2020-07-03T14:08:52Z',
# query: 'up{instance="{{instance}}"}',
# variables: { instance: 'srv1' }
# }
# })
def initialize(environment, params = {})
@environment = environment
@params = params.deep_dup
end
# @return - params [Hash<Symbol,Any>] Returns a Hash containing a params key which is
# similar to the `params` that is passed to the initialize method with 2 differences:
# 1. Variables in the query string are substituted with their values.
# If a variable present in the query string has no known value (values
# are obtained from the `variables` Hash in `params` or from
# `Gitlab::Prometheus::QueryVariables.call`), it will not be substituted.
# 2. `start` and `end` keys are added, with their values copied from `start_time`
# and `end_time`.
#
# Example output:
#
# {
# params: {
# start_time: '2020-07-03T06:08:36Z',
# start: '2020-07-03T06:08:36Z',
# end_time: '2020-07-03T14:08:52Z',
# end: '2020-07-03T14:08:52Z',
# query: 'up{instance="srv1"}',
# variables: { instance: 'srv1' }
# }
# }
def execute
execute_steps
end
private
def validate_variables(_result)
return success unless variables
unless variables.is_a?(ActionController::Parameters)
return error(_('Optional parameter "variables" must be a Hash. Ex: variables[key1]=value1'))
end
success
end
def add_params_to_result(result)
result[:params] = params
success(result)
end
def substitute_params(result)
start_time = result[:params][:start_time]
end_time = result[:params][:end_time]
result[:params][:start] = start_time if start_time
result[:params][:end] = end_time if end_time
success(result)
end
def substitute_variables(result)
return success(result) unless query(result)
result[:params][:query] = gsub(query(result), full_context(result))
success(result)
end
def gsub(string, context)
# Search for variables of the form `{{variable}}` in the string and replace
# them with their value.
string.gsub(VARIABLE_INTERPOLATION_REGEX) do |match|
# Replace with the value of the variable, or if there is no such variable,
# replace the invalid variable with itself. So,
# `up{instance="{{invalid_variable}}"}` will remain
# `up{instance="{{invalid_variable}}"}` after substitution.
context.fetch($~[:variable], match)
end
end
def predefined_context(result)
Gitlab::Prometheus::QueryVariables.call(
@environment,
start_time: start_timestamp(result),
end_time: end_timestamp(result)
).stringify_keys
end
def full_context(result)
@full_context ||= predefined_context(result).reverse_merge(variables_hash)
end
def variables
params[:variables]
end
def variables_hash
variables.to_h
end
def start_timestamp(result)
Time.rfc3339(result[:params][:start])
rescue ArgumentError
end
def end_timestamp(result)
Time.rfc3339(result[:params][:end])
rescue ArgumentError
end
def query(result)
result[:params][:query]
end
end
end
|
