Document multiple custom metrics files (#117)

Signed-off-by: Anders Swanson <anders.swanson@oracle.com>

Author: anders-swanson

README.md

@@ -648,11 +648,11 @@ variables:
 
 ## Custom metrics
 
-The exporter allows definition of arbitrary custom metrics in a TOML file. To specify this file to the
+The exporter allows definition of arbitrary custom metrics in one or more TOML files. To specify this file to the
 exporter, you can:
 
-- Use `--custom.metrics` flag followed by the name of the TOML file, or
-- Export `CUSTOM_METRICS` variable environment (`export CUSTOM_METRICS=my-custom-metrics.toml`)
+- Use `--custom.metrics` flag followed by a comma separated list of TOML files, or
+- Export `CUSTOM_METRICS` variable environment (`export CUSTOM_METRICS=my-custom-metrics.toml,my-other-custom-metrics.toml`)
 
 This file must contain the following elements:
 

main.go

@@ -37,7 +37,7 @@ var (
 	Version            = "0.0.0.dev"
 	metricPath         = kingpin.Flag("web.telemetry-path", "Path under which to expose metrics. (env: TELEMETRY_PATH)").Default(getEnv("TELEMETRY_PATH", "/metrics")).String()
 	defaultFileMetrics = kingpin.Flag("default.metrics", "File with default metrics in a TOML file. (env: DEFAULT_METRICS)").Default(getEnv("DEFAULT_METRICS", "default-metrics.toml")).String()
-	customMetrics      = kingpin.Flag("custom.metrics", "File that may contain various custom metrics in a TOML file. (env: CUSTOM_METRICS)").Default(getEnv("CUSTOM_METRICS", "")).String()
+	customMetrics      = kingpin.Flag("custom.metrics", "Comma separated list of file(s) that contain various custom metrics in a TOML format. (env: CUSTOM_METRICS)").Default(getEnv("CUSTOM_METRICS", "")).String()
 	queryTimeout       = kingpin.Flag("query.timeout", "Query timeout (in seconds). (env: QUERY_TIMEOUT)").Default(getEnv("QUERY_TIMEOUT", "5")).Int()
 	maxIdleConns       = kingpin.Flag("database.maxIdleConns", "Number of maximum idle connections in the connection pool. (env: DATABASE_MAXIDLECONNS)").Default(getEnv("DATABASE_MAXIDLECONNS", "0")).Int()
 	maxOpenConns       = kingpin.Flag("database.maxOpenConns", "Number of maximum open connections in the connection pool. (env: DATABASE_MAXOPENCONNS)").Default(getEnv("DATABASE_MAXOPENCONNS", "10")).Int()