为什么

如果你有这些问题：
1. golang 官方的 mongo driver 怎么执行了没有日志输出啊
2. golang mongo driver 如何记录sql，如何打印执行的命令
3. 想通过日志来检查 golang mongo 调用API是否符合预期

那么这篇文章可以继续看下去。

背景

在这之前我使用 MySQL 是比较多的，后来遇到有记录用户操作日志需求，随着数据量越来越大，MySQL 有些扛不住（慢），就换成了 Mongo，在使用Mongo过程中，发现没法记录日志，就是无法将打印代码发起的sql，之前使用gorm打印execute sql是很方便的。

在网上查了好久也没查到相关资料，就开始翻官方文档，和源码。

终于在不懈~ 打住，其实很简单，就在 ClientOptions 字段里：

// ClientOptions contains options to configure a Client instance. Each option can be set through setter functions. See
// documentation for each setter function for an explanation of the option.
type ClientOptions struct {
    AppName                  *string
    Auth                     *Credential
    AutoEncryptionOptions    *AutoEncryptionOptions
    ...
    MaxConnecting            *uint64
    PoolMonitor              *event.PoolMonitor
    Monitor                  *event.CommandMonitor // 执行的命令监视器(日志)
    ServerMonitor            *event.ServerMonitor
    ...

    err error
    uri string
    cs  *connstring.ConnString

github 代码地址

是的—— ClientOptions.Monitor 字段。

使用方法如下：

package mongolearn

import (
    "context"
    "fmt"
    "log"
    "time"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/event"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

var (
    mongoDsn = "mongodb://admin:123456@127.0.0.1:27017"
)

// TestConnUseDb sql monitor
func TestConnWithMonitor() {
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()

    // client option
    var clientOpt = options.Client().ApplyURI(mongoDsn)

    // log monitor
    var logMonitor = event.CommandMonitor{
        Started: func(ctx context.Context, startedEvent *event.CommandStartedEvent) {
            log.Printf("mongo reqId:%d start on db:%s cmd:%s sql:%+v", startedEvent.RequestID, startedEvent.DatabaseName,
                startedEvent.CommandName, startedEvent.Command)
        },
        Succeeded: func(ctx context.Context, succeededEvent *event.CommandSucceededEvent) {
            log.Printf("mongo reqId:%d exec cmd:%s success duration %d ns", succeededEvent.RequestID,
                succeededEvent.CommandName, succeededEvent.DurationNanos)
        },
        Failed: func(ctx context.Context, failedEvent *event.CommandFailedEvent) {
            log.Printf("mongo reqId:%d exec cmd:%s failed duration %d ns", failedEvent.RequestID,
                failedEvent.CommandName, failedEvent.DurationNanos)
        },
    }
    // cmd monitor set
    clientOpt.SetMonitor(&logMonitor)
    client, err := mongo.Connect(ctx, clientOpt)
    if nil != err {
        fmt.Printf("mongo connect err %v\n", err)
    } else {
        fmt.Printf("mongo connect success~\n")
        defer func() {
            if err = client.Disconnect(ctx); err != nil {
                panic(err)
            }
        }()
    }

    // update test
    if re, err := client.Database("test").Collection("test").UpdateOne(ctx, bson.M{"name": "cc"}, bson.M{"$set": bson.M{"age": 12}}); err != nil {
        log.Printf("%v", err)
    } else {
        log.Printf("mongo update one re %+v", re)
    }
}

输出结果

mongo connect success~
2023/08/20 13:22:43 mongo reqId:6 start on db:test cmd:update sql:{"update": "test","ordered": true,"lsid": {"id": {"$binary":{"base64":"qfrrzSt7SkCN5ChY04/T5A==","subType":"04"}}},"$db": "test","updates": [{"q": {"name": "cc"},"u": {"$set": {"age": {"$numberInt":"12"}}}}]}
2023/08/20 13:22:43 mongo reqId:6 exec cmd:update success duration 44489114 ns
2023/08/20 13:22:43 mongo update one re &{MatchedCount:0 ModifiedCount:0 UpsertedCount:0 UpsertedID:<nil>}

# 下面是断开 mongo 时触发的命令
2023/08/20 13:22:43 mongo reqId:7 start on db:admin cmd:endSessions sql:{"endSessions": [{"id": {"$binary":{"base64":"qfrrzSt7SkCN5ChY04/T5A==","subType":"04"}}}],"$db": "admin"}
2023/08/20 13:22:43 mongo reqId:7 exec cmd:endSessions success duration 58037162 ns

通过以上日志可以看到，mongo 的 monitor 按照 Started, Succeeded 顺序记录，最后才会执行函数外的 日志 。

结束

我看网上资料少，很多小伙伴都不知道，特此写一篇小文记录下。