我正在研究一个Go项目，该项目使用gRPC作为服务器，使用Voltdb作为DB。向gRPC服务器发送许多数据库读/写请求时出现问题。请求已处理，但在操作员完成后不会释放数据库连接。因此，当池中的连接用完时，会出现此错误：

  

因为已达到9940的连接限制，所以拒绝了/127.0.0.1:63015的连接

原始文件

syntax = "proto3";
package grpc;

import "google/protobuf/struct.proto";

option java_multiple_files = true;
option java_package = "com.io.test";

service TestService {
    rpc updateUser (UserRequest) returns (Status) {};
}
message UserRequest {
    string userId = 1;
    string name = 2;
}
message Status {
    string code = 1;
}

Go中的GRPC工具

package service

import (
    "context"
    "log"
    api "testgrpc/pkg/api/grpc"
    "testgrpc/pkg/db"
    "testgrpc/pkg/model"
)

var voltDbClient *db.VoltDBClient

func init() {
    voltDbClient = db.NewVoltDBClient()
}

type GrpcService struct {
}

func NewGrpcService() *GrpcService {
    return &GrpcService{}
}
func (sv *GrpcService) UpdateUser(ctx context.Context,req *api.UserRequest) (*api.Status,error) {
    user,err := voltDbClient.FindByID(req.GetUserId())
    if user == nil || err != nil {
        log.Print("error while reading")
    } else {
        log.Println(user.(*model.User).UserId)
        log.Println(user.(*model.User).Name)
    }
    err = voltDbClient.Put(req.GetUserId(),req.GetName())
    if err != nil {
        log.Print("error while writing")
    }
    return &api.Status{Code: "0"},nil
}

数据库客户端

package db

import (
    "database/sql"
    "log"

    "testgrpc/pkg/model"

    _ "github.com/VoltDB/voltdb-client-go/voltdbclient"
)

var Db *sql.DB

func init() {
    if Db == nil {
        var err error
        Db,err = sql.Open("voltdb","localhost:21212")
        if err != nil {
            log.Fatal(err)
        }
        //limit max connection to reproduce issue
        Db.SetMaxOpenConns(20)
    }
}

type VoltDBClient struct {
}

func NewVoltDBClient() *VoltDBClient {
    return &VoltDBClient{}
}

//Put add or update record
func (dbClient *VoltDBClient) Put(key interface{},value interface{}) error {
    res,err := Db.Exec("GROUPINFO.upsert",key,value)
    if err != nil {
        log.Println(err)
        return err
    }
    rowCnt,err := res.RowsAffected()
    if err != nil {
        log.Println(err)
        return err
    }
    log.Printf("affected = %d\n",rowCnt)
    return nil
}

//FindByID find a record by ID
func (dbClient *VoltDBClient) FindByID(key interface{}) (interface{},error) {
    rows,err := Db.Query("GROUPSELECT",key)
    if err != nil {
        log.Println(err)
        return nil,err
    }
    for rows.Next() {
        user := model.User{UserId: "",Name: ""}
        err := rows.Scan(&user.UserId,&user.Name)
        if err != nil {
            log.Println(err)
            return nil,err
        }
        return &user,nil
    }
    return nil,nil
}

注意：我曾尝试在不使用grpc的情况下运行项目，读/写运算符效果很好。