fix:install prometheus and npe (#881)

Author: chuntaojun

deploy/standalone/vm/install-linux.sh

@@ -227,10 +227,7 @@ function installPolarisLimiter() {
     echo -e "polaris-limiter-release.tar.gz has been decompressed, skip."
   fi
 
-  cd ${polaris_limiter_dirname} || (
-    echo "no such directory ${polaris_limiter_dirname}"
-    exit -1
-  )
+  pushd ${polaris_limiter_dirname}
 
   # 备份 polaris-limiter.yaml
   cp polaris-limiter.yaml polaris-limiter.yaml.bak
@@ -242,10 +239,7 @@ function installPolarisLimiter() {
 
   /bin/bash ./tool/start.sh
   echo -e "install polaris limiter finish."
-  cd ${install_path} || (
-    echo "no such directory ${install_path}"
-    exit -1
-  )
+  popd
 }
 
 function checkPort() {
@@ -255,7 +249,6 @@ function checkPort() {
     echo "" >&2
     exit 1
   fi
-  keyLength=$(echo ${key} | awk '{print length($0)}')
   lineNumStr=$(cat ${proFilePath} | wc -l)
   lineNum=$((${lineNumStr}))
   for ((i = 1; i <= ${lineNum}; i++)); do
@@ -265,6 +258,8 @@ function checkPort() {
     if [ "${pid}" != "" ]; then
       echo "port ${port} already used, you can modify port.properties to adjust port"
       exit -1
+	else
+      echo "port ${port} is checked ,and is not used"	
     fi
   done
 }

store/sqldb/config_file_group.go

@@ -19,6 +19,7 @@ package sqldb
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"strconv"
 	"strings"
@@ -28,6 +29,10 @@ import (
 	"github.com/polarismesh/polaris/store"
 )
 
+var (
+	ErrMultipleConfigFileGroupFound error = errors.New("multiple config_file_group found")
+)
+
 type configFileGroupStore struct {
 	db *BaseDB
 }
@@ -180,6 +185,14 @@ func (fg *configFileGroupStore) GetConfigFileGroupById(id uint64) (*model.Config
 		return nil, err
 	}
 
+	if len(cfgs) == 0 {
+		return nil, nil
+	}
+
+	if len(cfgs) > 1 {
+		return nil, ErrMultipleConfigFileGroupFound
+	}
+
 	return cfgs[0], nil
 }