# Functions
MergeLabels merges two maps of labels.
NewNginxCollector creates an NginxCollector.
NewNginxPlusCollector creates an NginxPlusCollector.
NewVariableLabels creates a new struct for VariableNames for the collector.
# Structs
NginxCollector collects NGINX metrics.
NginxPlusCollector collects NGINX Plus metrics.
VariableLabelNames holds all the variable label names for the different metrics.
# Interfaces
LabelUpdater updates the labels of upstream server and server zone metrics.