Fixes (prometheus-community#364) (prometheus-community#387)

Have a custom prefix for each of the default metrics created by postgres_exporter Co-authored-by: Will Rouesnel <wrouesnel@wrouesnel.com>

Author: ajaybhat

README.md

@@ -140,6 +140,9 @@ The following environment variables configure the exporter:
 * `PG_EXPORTER_EXCLUDE_DATABASES`
  A comma-separated list of databases to remove when autoDiscoverDatabases is enabled. Default is empty string.
 
+* `PG_EXPORTER_METRIC_PREFIX`
+ A prefix to use for each of the default metrics exported by postgres-exporter. Default is `pg`
+
 Settings set by environment variables starting with `PG_` will be overwritten by the corresponding CLI flag if given.
 
 ### Setting the Postgres server's data source name

cmd/postgres_exporter/postgres_exporter.go

@@ -53,6 +53,7 @@ var (
 onlyDumpMaps = kingpin.Flag("dumpmaps", "Do not run, simply dump the maps.").Bool()
 constantLabelsList = kingpin.Flag("constantLabels", "A list of label=value separated by comma(,).").Default("").Envar("PG_EXPORTER_CONSTANT_LABELS").String()
 excludeDatabases = kingpin.Flag("exclude-databases", "A list of databases to remove when autoDiscoverDatabases is enabled").Default("").Envar("PG_EXPORTER_EXCLUDE_DATABASES").String()
+metricPrefix = kingpin.Flag("metric-prefix", "A metric prefix can be used to have non-default (not \"pg\") prefixes for each of the metrics").Default("pg").Envar("PG_EXPORTER_METRIC_PREFIX").String()
 )
 
 // Metric name parts.
@@ -626,6 +627,8 @@ func makeDescMap(pgVersion semver.Version, serverLabels prometheus.Labels, metri
 }
 }
 
+namespace := strings.Replace(namespace, "pg", *metricPrefix, 1)
+
 // Determine how to convert the column based on its usage.
 // nolint: dupl
 switch columnMapping.usage {