Support for scraping multiple mysqld hosts

Makefile

@@ -22,8 +22,9 @@ STATICCHECK_IGNORE =
 
 DOCKER_IMAGE_NAME ?= mysqld-exporter
 
-test-docker:
-	@echo ">> testing docker image"
+.PHONY: test-docker-single-exporter
+test-docker-single-exporter:
+	@echo ">> testing docker image for single exporter"
 	./test_image.sh "$(DOCKER_IMAGE_NAME):$(DOCKER_IMAGE_TAG)" 9104
 
 .PHONY: test-docker

README.md

@@ -30,15 +30,50 @@ NOTE: It is recommended to set a max connection limit for the user to avoid over
 
 ### Running
 
-Running using an environment variable:
-
-    export DATA_SOURCE_NAME='user:password@(hostname:3306)/'
-    ./mysqld_exporter <flags>
+#####  Single exporter mode
 
 Running using ~/.my.cnf:
 
     ./mysqld_exporter <flags>
 
+#####  Multi-target support
+
+This exporter supports the multi-target pattern. This allows running a single instance of this exporter for multiple MySQL targets.
+
+To use the multi-target functionality, send an http request to the endpoint /probe?target=foo:5432 where target is set to the DSN of the MySQL instance to scrape metrics from.
+
+To avoid putting sensitive information like username and password in the URL, you can have multiple configurations in `config.my-cnf` file and match it by adding `&auth_module=<section>` to the request.
+
+Sample config file for multiple configurations
+
+        [client]
+        user = foo
+        password = foo123
+        [client.servers]
+        user = bar
+        password = bar123
+
+On the prometheus side you can set a scrape config as follows
+
+        - job_name: mysql # To get metrics about the mysql exporter’s targets
+          params:
+            # Not required. Will match value to child in config file. Default value is `client`.
+            auth_module: client.servers
+          static_configs:
+            - targets:
+              # All mysql hostnames to monitor.
+              - server1:3306
+              - server2:3306
+          relabel_configs:
+            - source_labels: [__address__]
+              target_label: __param_target
+            - source_labels: [__param_target]
+              target_label: instance
+            - target_label: __address__
+              # The mysqld_exporter host:port
+              replacement: localhost:9104
+
+#####  Flag format
 Example format for flags for version > 0.10.0:
 
     --collect.auto_increment.columns
@@ -102,6 +137,8 @@ collect.heartbeat.utc                                        | 5.1           | U
 ### General Flags
 Name                                       | Description
 -------------------------------------------|--------------------------------------------------------------------------------------------------
+mysqld.address                             | Hostname and port used for connecting to MySQL server, format: `host:port`. (default: `locahost:3306`)
+mysqld.username                            | Username to be used for connecting to MySQL Server
 config.my-cnf                              | Path to .my.cnf file to read MySQL credentials from. (default: `~/.my.cnf`)
 log.level                                  | Logging verbosity (default: info)
 exporter.lock_wait_timeout                 | Set a lock_wait_timeout (in seconds) on the connection to avoid long metadata locking. (default: 2)
@@ -112,6 +149,15 @@ web.listen-address                         | Address to listen on for web interf
 web.telemetry-path                         | Path under which to expose metrics.
 version                                    | Print the version information.
 
+### Environment Variables
+Name                                       | Description
+-------------------------------------------|--------------------------------------------------------------------------------------------------
+MYSQLD_EXPORTER_PASSWORD                   | Password to be used for connecting to MySQL Server
+
+### Configuration precedence
+
+If you have configured cli with both `mysqld` flags and a valid configuration file, the options in the configuration file will override the flags for `client` section.
+
 ## TLS and basic authentication
 
 The MySQLd Exporter supports TLS and basic authentication.
@@ -120,12 +166,6 @@ To use TLS and/or basic authentication, you need to pass a configuration file
 using the `--web.config.file` parameter. The format of the file is described
 [in the exporter-toolkit repository](https://github.com/prometheus/exporter-toolkit/blob/master/docs/web-configuration.md).
 
-### Setting the MySQL server's data source name
-
-The MySQL server's [data source name](http://en.wikipedia.org/wiki/Data_source_name)
-must be set via the `DATA_SOURCE_NAME` environment variable.
-The format of this variable is described at https://github.com/go-sql-driver/mysql#dsn-data-source-name.
-
 ## Customizing Configuration for a SSL Connection
 
 If The MySQL server supports SSL, you may need to specify a CA truststore to verify the server's chain-of-trust. You may also need to specify a SSL keypair for the client side of the SSL connection. To configure the mysqld exporter to use a custom CA certificate, add the following to the mysql cnf file:
@@ -141,8 +181,6 @@ ssl-key=/path/to/ssl/client/key
 ssl-cert=/path/to/ssl/client/cert
 ```
 
-Customizing the SSL configuration is only supported in the mysql cnf file and is not supported if you set the mysql server's data source name in the environment variable DATA_SOURCE_NAME.
-
 
 ## Using Docker
 
@@ -157,9 +195,8 @@ docker pull prom/mysqld-exporter
 docker run -d \
   -p 9104:9104 \
   --network my-mysql-network  \
-  -e DATA_SOURCE_NAME="user:password@(hostname:3306)/" \
   prom/mysqld-exporter
-```
+  --config.my-cnf=<path_to_cnf>
 
 ## heartbeat
 

config/config.go

@@ -0,0 +1,229 @@
+// Copyright 2022 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"net"
+	"os"
+	"sync"
+
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+
+	"github.com/go-sql-driver/mysql"
+	"github.com/prometheus/client_golang/prometheus"
+
+	"gopkg.in/ini.v1"
+)
+
+var (
+	configReloadSuccess = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "mysqld_exporter",
+		Name:      "config_last_reload_successful",
+		Help:      "Mysqld exporter config loaded successfully.",
+	})
+
+	configReloadSeconds = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "mysqld_exporter",
+		Name:      "config_last_reload_success_timestamp_seconds",
+		Help:      "Timestamp of the last successful configuration reload.",
+	})
+
+	cfg *ini.File
+
+	opts = ini.LoadOptions{
+		// Do not error on nonexistent file to allow empty string as filename input
+		Loose: true,
+		// MySQL ini file can have boolean keys.
+		AllowBooleanKeys: true,
+	}
+
+	err error
+)
+
+type Config struct {
+	Sections map[string]MySqlConfig
+}
+
+type MySqlConfig struct {
+	User                  string `ini:"user"`
+	Password              string `ini:"password"`
+	Host                  string `ini:"host"`
+	Port                  int    `ini:"port"`
+	Socket                string `ini:"socket"`
+	SslCa                 string `ini:"ssl-ca"`
+	SslCert               string `ini:"ssl-cert"`
+	SslKey                string `ini:"ssl-key"`
+	TlsInsecureSkipVerify bool   `ini:"ssl-skip-verfication"`
+}
+
+type MySqlConfigHandler struct {
+	sync.RWMutex
+	TlsInsecureSkipVerify bool
+	Config                *Config
+}
+
+func (ch *MySqlConfigHandler) GetConfig() *Config {
+	ch.RLock()
+	defer ch.RUnlock()
+	return ch.Config
+}
+
+func (ch *MySqlConfigHandler) ReloadConfig(filename string, mysqldAddress string, mysqldUser string, tlsInsecureSkipVerify bool, logger log.Logger) error {
+	var host, port string
+	defer func() {
+		if err != nil {
+			configReloadSuccess.Set(0)
+		} else {
+			configReloadSuccess.Set(1)
+			configReloadSeconds.SetToCurrentTime()
+		}
+	}()
+
+	if cfg, err = ini.LoadSources(
+		opts,
+		[]byte("[client]\npassword = ${MYSQLD_EXPORTER_PASSWORD}\n"),
+		filename,
+	); err != nil {
+		return fmt.Errorf("failed to load %s: %w", filename, err)
+	}
+
+	if host, port, err = net.SplitHostPort(mysqldAddress); err != nil {
+		return fmt.Errorf("failed to parse address: %w", err)
+	}
+
+	if clientSection := cfg.Section("client"); clientSection != nil {
+		if cfgHost := clientSection.Key("host"); cfgHost.String() == "" {
+			cfgHost.SetValue(host)
+		}
+		if cfgPort := clientSection.Key("port"); cfgPort.String() == "" {
+			cfgPort.SetValue(port)
+		}
+		if cfgUser := clientSection.Key("user"); cfgUser.String() == "" {
+			cfgUser.SetValue(mysqldUser)
+		}
+	}
+
+	cfg.ValueMapper = os.ExpandEnv
+	config := &Config{}
+	m := make(map[string]MySqlConfig)
+	for _, sec := range cfg.Sections() {
+		sectionName := sec.Name()
+
+		if sectionName == "DEFAULT" {
+			continue
+		}
+
+		mysqlcfg := &MySqlConfig{
+			TlsInsecureSkipVerify: tlsInsecureSkipVerify,
+		}
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to load config", "section", sectionName, "err", err)
+			continue
+		}
+
+		err = sec.StrictMapTo(mysqlcfg)
+		if err != nil {
+			level.Error(logger).Log("msg", "failed to parse config", "section", sectionName, "err", err)
+			continue
+		}
+		if err := mysqlcfg.validateConfig(); err != nil {
+			level.Error(logger).Log("msg", "failed to validate config", "section", sectionName, "err", err)
+			continue
+		}
+
+		m[sectionName] = *mysqlcfg
+	}
+	config.Sections = m
+	if len(config.Sections) == 0 {
+		return fmt.Errorf("no configuration found")
+	}
+	ch.Lock()
+	ch.Config = config
+	ch.Unlock()
+	return nil
+}
+
+func (m MySqlConfig) validateConfig() error {
+	if m.User == "" {
+		return fmt.Errorf("no user specified in section or parent")
+	}
+	if m.Password == "" {
+		return fmt.Errorf("no password specified in section or parent")
+	}
+
+	return nil
+}
+
+func (m MySqlConfig) FormDSN(target string) (string, error) {
+	var dsn, host, port string
+
+	user := m.User
+	password := m.Password
+	if target == "" {
+		host := m.Host
+		port := m.Port
+		socket := m.Socket
+		if socket != "" {
+			dsn = fmt.Sprintf("%s:%s@unix(%s)/", user, password, socket)
+		} else {
+			dsn = fmt.Sprintf("%s:%s@tcp(%s:%d)/", user, password, host, port)
+		}
+	} else {
+		if host, port, err = net.SplitHostPort(target); err != nil {
+			return dsn, fmt.Errorf("failed to parse target: %s", err)
+		}
+		dsn = fmt.Sprintf("%s:%s@tcp(%s:%s)/", user, password, host, port)
+	}
+
+	if m.SslCa != "" {
+		if err := m.CustomizeTLS(); err != nil {
+			err = fmt.Errorf("failed to register a custom TLS configuration for mysql dsn: %w", err)
+			return dsn, err
+		}
+		dsn = fmt.Sprintf("%s?tls=custom", dsn)
+	}
+
+	return dsn, nil
+}
+
+func (m MySqlConfig) CustomizeTLS() error {
+	var tlsCfg tls.Config
+	caBundle := x509.NewCertPool()
+	pemCA, err := os.ReadFile(m.SslCa)
+	if err != nil {
+		return err
+	}
+	if ok := caBundle.AppendCertsFromPEM(pemCA); ok {
+		tlsCfg.RootCAs = caBundle
+	} else {
+		return fmt.Errorf("failed parse pem-encoded CA certificates from %s", m.SslCa)
+	}
+	if m.SslCert != "" && m.SslKey != "" {
+		certPairs := make([]tls.Certificate, 0, 1)
+		keypair, err := tls.LoadX509KeyPair(m.SslCert, m.SslKey)
+		if err != nil {
+			return fmt.Errorf("failed to parse pem-encoded SSL cert %s or SSL key %s: %w",
+				m.SslCert, m.SslKey, err)
+		}
+		certPairs = append(certPairs, keypair)
+		tlsCfg.Certificates = certPairs
+	}
+	tlsCfg.InsecureSkipVerify = m.TlsInsecureSkipVerify
+	mysql.RegisterTLSConfig("custom", &tlsCfg)
+	return nil
+}