Provide more useful error message if MySQL version is not expected

diff --git a/main.go b/main.go
index 708a77a..4825729 100644 (file)
--- a/main.go
+++ b/main.go
@@ -4,11 +4,13 @@ package main
 
 import (
        "database/sql"
+       "errors"
        "flag"
        "fmt"
        "log"
        "os"
        "os/signal"
+       "regexp"
        "runtime/pprof"
        "syscall"
        "time"
@@ -27,14 +29,19 @@ const (
        db         = "performance_schema"
 )
 
-var flag_version = flag.Bool("version", false, "Show the version of "+lib.MyName())
-var flag_debug = flag.Bool("debug", false, "Enabling debug logging")
-var flag_help = flag.Bool("help", false, "Provide some help for "+lib.MyName())
-var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
+var (
+       flag_version = flag.Bool("version", false, "Show the version of "+lib.MyName())
+       flag_debug   = flag.Bool("debug", false, "Enabling debug logging")
+       flag_help    = flag.Bool("help", false, "Provide some help for "+lib.MyName())
+       cpuprofile   = flag.String("cpuprofile", "", "write cpu profile to file")
+
+       re_valid_version = regexp.MustCompile(`^(5\.[67]\.|10\.[01])`)
+)
 
 func get_db_handle() *sql.DB {
        var err error
        var dbh *sql.DB
+       lib.Logger.Println("get_db_handle() connecting to database")
 
        dbh, err = mysql_defaults_file.OpenUsingDefaultsFile(sql_driver, "", "performance_schema")
        if err != nil {
@@ -72,6 +79,24 @@ func usage() {
        fmt.Println("-version   show the version")
 }
 
+// pstop requires MySQL 5.6+ or MariaDB 10.0+. Check the version
+// rather than giving an error message if the requires P_S tables can't
+// be found.
+func validate_mysql_version(dbh *sql.DB) error {
+       lib.Logger.Println("validate_mysql_version()")
+
+       _, mysql_version := lib.SelectGlobalVariableByVariableName(dbh, "VERSION")
+
+       lib.Logger.Println("- mysql_version: '" + mysql_version + "'")
+       if !re_valid_version.MatchString(mysql_version) {
+               err := errors.New(lib.MyName() + " does not work with MySQL version " + mysql_version)
+               return err
+       }
+       lib.Logger.Println("- MySQL version is valid, continuing")
+
+       return nil
+}
+
 func main() {
        flag.Parse()
 
@@ -98,8 +123,13 @@ func main() {
        }
 
        lib.Logger.Println("Starting " + lib.MyName())
-       var state state.State
 
+       dbh := get_db_handle()
+       if err := validate_mysql_version(dbh); err != nil {
+               log.Fatal(err)
+       }
+
+       var state state.State
        interval := time.Second
        sigChan := make(chan os.Signal, 1)
        done := make(chan struct{})
@@ -110,7 +140,7 @@ func main() {
 
        ticker := time.NewTicker(interval) // generate a periodic signal
 
-       state.Setup(get_db_handle())
+       state.Setup(dbh)
 
        finished := false
        for !finished {