docs: add multiple connections section, formatting

README.md

@@ -1,6 +1,7 @@
 # Prometheus SQL Exporter [![Go](https://github.com/burningalchemist/sql_exporter/workflows/Go/badge.svg)](https://github.com/burningalchemist/sql_exporter/actions?query=workflow%3AGo) [![Go Report Card](https://goreportcard.com/badge/github.com/burningalchemist/sql_exporter)](https://goreportcard.com/report/github.com/burningalchemist/sql_exporter) [![Docker Pulls](https://img.shields.io/docker/pulls/burningalchemist/sql_exporter)](https://hub.docker.com/r/burningalchemist/sql_exporter) ![Downloads](https://img.shields.io/github/downloads/burningalchemist/sql_exporter/total)
 
-This is a permanent fork of Database agnostic SQL exporter for [Prometheus](https://prometheus.io) created by [@free](https://github.com/free/sql_exporter).
+This is a permanent fork of Database agnostic SQL exporter for [Prometheus](https://prometheus.io) created by
+[@free](https://github.com/free/sql_exporter).
 
 ## Overview
 
@@ -59,7 +60,9 @@ By default we produce a binary with all the supported drivers with the following
 make build
 ```
 
-It's also possible to reduce the size of the binary by only including specific set of drivers like Postgres, MySQL and MSSQL. In this case we need to update `drivers.go`. To avoid manual manipulation there is a helper code generator available, so we can run the following commands:
+It's also possible to reduce the size of the binary by only including specific set of drivers like Postgres, MySQL and
+MSSQL. In this case we need to update `drivers.go`. To avoid manual manipulation there is a helper code generator
+available, so we can run the following commands:
 
 ```shell
 make drivers-minimal
@@ -70,7 +73,8 @@ The first command will regenerate `drivers.go` file with a minimal set of import
 
 Running `make drivers-all` will regenerate driver set back to the current defaults.
 
-Feel free to revisit and add more drivers as required. There's also the `custom` list that allows managing a separate list of drivers for special needs.
+Feel free to revisit and add more drivers as required. There's also the `custom` list that allows managing a separate
+list of drivers for special needs.
 
 ## Run as a Windows service
 
@@ -180,7 +184,7 @@ metrics:
       GROUP BY Market
 ```
 
-### Data Source Names
+### Data Source Names (DSN)
 
 To keep things simple and yet allow fully configurable database connections, SQL Exporter uses DSNs (like
 `sqlserver://prom_user:[email protected]:1433`) to refer to database instances.
@@ -194,33 +198,42 @@ mysql://user:pass@localhost/dbname - for TCP connection
 mysql:/var/run/mysqld/mysqld.sock - for Unix socket connection
 ```
 
-If your DSN contains special characters in any part of your connection string (including passwords), you might need to apply
-[URL encoding](https://en.wikipedia.org/wiki/URL_encoding#Reserved_characters) (percent-encoding) to them. 
+If your DSN contains special characters in any part of your connection string (including passwords), you might need to
+apply [URL encoding](https://en.wikipedia.org/wiki/URL_encoding#Reserved_characters) (percent-encoding) to them.
 For example, `p@$$w0rd#abc` then becomes `p%40%24%24w0rd%23abc`.
 
 For additional details please refer to [xo/dburl](https://github.com/xo/dburl) documentation.
+
 #### Using AWS Secrets Manager
 
-If the database runs on AWS EC2 instance, this is a secure option to store the `Data source name` without having it in the configuration file.
-To use this option:
-- Create a [secret](https://docs.aws.amazon.com/secretsmanager/latest/userguide/manage_create-basic-secret.html) in key/value pairs format, specify Key `data_source_name` and then for Value enter the DSN value.
-  For the secret name, enter a name for your secret, and pass that name in the configuration file as a value for `aws_secret_name` item under `target`. Secret json example:
+If the database runs on AWS EC2 instance, this is a secure option to store the DSN without having it in
+the configuration file. To use this option:
 
-```
+- Create a [secret](https://docs.aws.amazon.com/secretsmanager/latest/userguide/manage_create-basic-secret.html) in
+  key/value pairs format, specify Key `data_source_name` and then for Value enter the DSN value.
+  For the secret name, enter a name for your secret, and pass that name in the configuration file as a value for
+  `aws_secret_name` item under `target`. Secret json example:
+
+```json
 {
   "data_source_name": "sqlserver://prom_user:[email protected]:1433"
 }
 ```
 
-- Configuration file Example
-```
+- Configuration file example:
+
+```yaml
 ...
 target:
   aws_secret_name: '<AWS_SECRET_NAME>'
 ...
 ```
-- Allow read-only access from EC2 IAM role to the secret by attaching a [resource-based policy](https://docs.aws.amazon.com/secretsmanager/latest/userguide/auth-and-access_resource-based-policies.html) to the secret. Policy Example:
-```
+
+- Allow read-only access from EC2 IAM role to the secret by attaching a [resource-based
+policy](https://docs.aws.amazon.com/secretsmanager/latest/userguide/auth-and-access_resource-based-policies.html) to
+the secret. Policy example:
+
+```json
 {
   "Version" : "2012-10-17",
   "Statement" : [
@@ -234,6 +247,27 @@ target:
 }
 ```
 
+Currently, AWS Secret Manager integration is only available for a single target configuration.
+
+### Multiple database connections
+
+It is possible to run a single exporter instance against multiple database connections. In this case we need to
+configure `jobs` list instead of the `target` section as in the following example:
+
+```yaml
+jobs:
+  - job_name: db_targets
+    collectors: [pricing_data_freshness, pricing_*]
+    static_configs:
+        - targets:
+            pg1: 'pg://[email protected]:25432/postgres?sslmode=disable'
+            pg2: 'pg://[email protected]:25432/testdb?sslmode=disable'
+```
+
+, where DSN strings are assigned to the arbitrary instance names (i.e. pg1 and pg2).
+
+We can also define multiple jobs to run different collectors against different target sets.
+
 ### TLS and Basic Authentication
 
 SQL Exporter supports TLS and Basic Authentication. This enables better control of the various HTTP endpoints.