Update README file and options descriptions

README.md

@@ -4,16 +4,50 @@ Program to make a proxy (ie HAProxy) capable of monitoring Percona XtraDB Cluste
 
 ## Usage
 
-Basic Haproxy config
+Basic Haproxy config:
 ```
 listen pxc
   bind 127.0.0.1:3306
   balance leastconn
-  option httpchk
+  option httpchk HEAD /
   mode tcp
   default-server check port 9200 inter 500 rise 5 fall 5
     server node1 1.2.3.4:3306 check port 9200
     server node2 1.2.3.5:3306 check port 9200
     server node3 1.2.3.6:3306 check port 9200 backup
 ```
 
+## Setup
+
+1. Create MySQL user:
+    ```sql
+    create user 'pxc_checker'@'localhost' IDENTIFIED BY 'YourStrongPassword'; GRANT PROCESS ON *.* TO 'pxc_checker'@'localhost';
+    ```
+2. Get program binary. You can choose one of the following methods:
+    -  Build it from source code with:
+          ```
+          go get
+          go build -o pxc-checker ./...
+          ```
+    - Download latest compiled binary from [Releases page](https://github.com/larrabee/pxc-checker/releases).
+3. Copy binary to `/usr/bin/pxc-checker`
+4. Copy systemd unit from `systemd/pxc-check@.service` to `/etc/systemd/system/pxc-checker@.service`
+5. Copy example config from `config/example.conf` to `/etc/pxc/checker/cluster.conf` and modify it.
+6. Enable and start unit with command: `systemctl enable --now pxc-checker@cluster`
+7. Check node status with command: `curl http://127.0.0.1:9200`
+
+## Configuration file options
+You can override any of the following values in configuration file:
+
+- `WEB_LISTEN`: Web server listening interface and port in format `{IPADDR}:{PORT}` or `:PORT` for all interfaces. Default: `:9200`
+- `WEB_READ_TIMEOUT`: Web server request read timeout in milliseconds. Default: `30000`
+- `WEB_WRITE_TIMEOUT`: Web server request write timeout in milliseconds. Default: `30000`
+- `CHECK_RO_ENABLED`: Mark 'read_only' node as available. Default: `false`
+- `CHECK_FORCE_ENABLE`: Ignoring the status of the checks and always marking the node as available. Default: `false`
+- `CHECK_INTERVAL`: Mysql checks interval in milliseconds. Default: `500`
+- `CHECK_FAIL_TIMEOUT`: Mark the node inaccessible if for the specified time (in milliseconds) there were no successful checks. Default: `3000`
+- `MYSQL_HOST`: MySQL host address. Default: `127.0.0.1`
+- `MYSQL_PORT`: MySQL port. Default: `3306`
+- `MYSQL_USER`: MySQL username. Default: `pxc_checker`
+- `MYSQL_PASS`: Mysql password. Default: no password
+

main.go

@@ -68,21 +68,22 @@ func main() {
 func getRouter() *fasthttprouter.Router {
 	router := fasthttprouter.New()
 	router.GET("/", checkerHandler)
+	router.HEAD("/", checkerHandler)
 	return router
 }
 
 func parseFlags() (*Config, error) {
 	config := Config{}
-	flag.StringVar(&config.WebListen, "WEB_LISTEN", ":9200", "Listen interface and port")
-	flag.IntVar(&config.WebReadTimeout, "WEB_READ_TIMEOUT", 30000, "Request read timeout, ms")
-	flag.IntVar(&config.WebWriteTimeout, "WEB_WRITE_TIMEOUT", 30000, "Request write timeout, ms")
-	flag.BoolVar(&config.CheckROEnabled, "CHECK_RO_ENABLED", false, "Make 'read_only' nodes availible")
-	flag.BoolVar(&config.CheckForceEnable, "CHECK_FORCE_ENABLE", false, "Ignoring checks status and force enable node")
+	flag.StringVar(&config.WebListen, "WEB_LISTEN", ":9200", "Web server listening interface and port")
+	flag.IntVar(&config.WebReadTimeout, "WEB_READ_TIMEOUT", 30000, "Web server request read timeout, ms")
+	flag.IntVar(&config.WebWriteTimeout, "WEB_WRITE_TIMEOUT", 30000, "Web server request write timeout, ms")
+	flag.BoolVar(&config.CheckROEnabled, "CHECK_RO_ENABLED", false, "Mark 'read_only' node as available")
+	flag.BoolVar(&config.CheckForceEnable, "CHECK_FORCE_ENABLE", false, "Ignoring the status of the checks and always marking the node as available")
 	flag.IntVar(&config.CheckInterval, "CHECK_INTERVAL", 500, "Mysql checks interval, ms")
-	flag.IntVar(&config.CheckFailTimeout, "CHECK_FAIL_TIMEOUT", 3000, "To count a node inaccessible if for the specified time there were no successful checks, ms")
+	flag.IntVar(&config.CheckFailTimeout, "CHECK_FAIL_TIMEOUT", 3000, "Mark the node inaccessible if for the specified time there were no successful checks, ms")
 	flag.StringVar(&config.MysqlHost, "MYSQL_HOST", "127.0.0.1", "MySQL host addr")
-	flag.IntVar(&config.MysqlPort, "MYSQL_PORT", 3306, "MySQL port addr")
-	flag.StringVar(&config.MysqlUser, "MYSQL_USER", "monitor", "MySQL username")
+	flag.IntVar(&config.MysqlPort, "MYSQL_PORT", 3306, "MySQL port")
+	flag.StringVar(&config.MysqlUser, "MYSQL_USER", "pxc_checker", "MySQL username")
 	flag.StringVar(&config.MysqlPass, "MYSQL_PASS", "", "MySQL password")
 
 	flag.Parse()

systemd/pxc-check@.service

@@ -6,6 +6,7 @@ After=network.target
 EnvironmentFile=/etc/pxc/checker/%i.conf
 ExecStart=/usr/bin/pxc-checker
 KillMode=process
+Restart=always
 User=mysql
 Group=mysql