Detailed graphic and text explanation of log collection system implemented in go language

I have sorted out the frame of this log collection system, as shown below

The overall logic of the code to be implemented this time is:

The complete code address is: https://github.com/pythonsite/logagent

etcd introduction

Highly available distributed Key-value storage can be used for configuration sharing and service discovery

Similar projects: zookeeper and consul

Development language: go

Interface: Provide restful interface, use Simple

Implementation algorithm: strong consistency based on raft algorithm, highly available service storage directory

application scenarios of etcd:

1. Service discovery and service registration

2. Configuration center (need to be used by the log collection client we implemented)

3. Distributed lock

4. Master election

Official website for etcd There is a very concise introduction:

##etcd build:

Download address: https://github.com/coreos/etcd/releases/
Based on Just download the corresponding version in your own environment and start it.

After starting, you can verify it with the following command:

[root@localhost etcd-v3.2.18-linux-amd64]# ./etcdctl set name zhaofan 

zhaofan
[root@localhost etcd-v3.2.18-linux-amd64]# ./etcdctl get name
zhaofan
[root@localhost etcd-v3.2.18-linux-amd64]#

context Introduction and use

In fact, this thing is translated as context management. So what is the role of context? It mainly has the following two functions:

1. Control the timeout of goroutine

2 , Save context data

Understand through the following simple example:

package main

import (
    "fmt"
    "time"
    "net/http"
    "context"
    "io/ioutil"
)


type Result struct{
    r *http.Response
    err error
}

func process(){
    ctx,cancel := context.WithTimeout(context.Background(),2*time.Second)
    defer cancel()
    tr := &http.Transport{}
    client := &http.Client{Transport:tr}
    c := make(chan Result,1)
    req,err := http.NewRequest("GET","http://www.google.com",nil)
    if err != nil{
        fmt.Println("http request failed,err:",err)
        return
    }
    // 如果请求成功了会将数据存入到管道中
    go func(){
        resp,err := client.Do(req)
        pack := Result{resp,err}
        c <- pack
    }()

    select{
    case <- ctx.Done():
        tr.CancelRequest(req)
        fmt.Println("timeout!")
    case res := <-c:
        defer res.r.Body.Close()
        out,_:= ioutil.ReadAll(res.r.Body)
        fmt.Printf("server response:%s",out)
    }
    return

}

func main() {
    process()
}

Write a context to save context through context, code example is:

package main

import (
    "github.com/Go-zh/net/context"
    "fmt"
)

func add(ctx context.Context,a,b int) int {
    traceId := ctx.Value("trace_id").(string)
    fmt.Printf("trace_id:%v\n",traceId)
    return a+b
}

func calc(ctx context.Context,a, b int) int{
    traceId := ctx.Value("trace_id").(string)
    fmt.Printf("trace_id:%v\n",traceId)
    //再将ctx传入到add中
    return add(ctx,a,b)
}

func main() {
    //将ctx传递到calc中
    ctx := context.WithValue(context.Background(),"trace_id","123456")
    calc(ctx,20,30)

}

Combining etcd and context

A simple example of connecting etcd through go: (There is a small problem that needs attention here is the startup method of etcd. The default startup may not connect, especially if you It is installed virtually, so you need to start it with the following command:

./etcd --listen-client-urls http://0.0.0.0:2371 --advertise-client-urls http://0.0.0.0: 2371 --listen-peer-urls http://0.0.0.0:2381
)

package main

import (
    etcd_client "github.com/coreos/etcd/clientv3"
    "time"
    "fmt"
)

func main() {
    cli, err := etcd_client.New(etcd_client.Config{
        Endpoints:[]string{"192.168.0.118:2371"},
        DialTimeout:5*time.Second,
    })
    if err != nil{
        fmt.Println("connect failed,err:",err)
        return
    }

    fmt.Println("connect success")
    defer cli.Close()
}

The following example is to connect etcd, save and get the value

package main

import (
    "github.com/coreos/etcd/clientv3"
    "time"
    "fmt"
    "context"
)

func main() {
    cli,err := clientv3.New(clientv3.Config{
        Endpoints:[]string{"192.168.0.118:2371"},
        DialTimeout:5*time.Second,
    })
    if err != nil{
        fmt.Println("connect failed,err:",err)
        return
    }
    fmt.Println("connect succ")
    defer cli.Close()
    ctx,cancel := context.WithTimeout(context.Background(),time.Second)
    _,err = cli.Put(ctx,"logagent/conf/","sample_value")
    cancel()
    if err != nil{
        fmt.Println("put failed,err",err)
        return
    }
    ctx, cancel = context.WithTimeout(context.Background(),time.Second)
    resp,err := cli.Get(ctx,"logagent/conf/")
    cancel()
    if err != nil{
        fmt.Println("get failed,err:",err)
        return
    }
    for _,ev := range resp.Kvs{
        fmt.Printf("%s:%s\n",ev.Key,ev.Value)
    }
}

About context The official website also has a very useful example, which is used to control the exit of an opened goroutine. The code is as follows:

package main

import (
    "context"
    "fmt"
)

func main() {
    // gen generates integers in a separate goroutine and
    // sends them to the returned channel.
    // The callers of gen need to cancel the context once
    // they are done consuming generated integers not to leak
    // the internal goroutine started by gen.
    gen := func(ctx context.Context) <-chan int {
        dst := make(chan int)
        n := 1
        go func() {
            for {
                select {
                case <-ctx.Done():
                    return // returning not to leak the goroutine
                case dst <- n:
                    n++
                }
            }
        }()
        return dst
    }

    ctx, cancel := context.WithCancel(context.Background())
    defer cancel() // cancel when we are finished consuming integers

    for n := range gen(ctx) {
        fmt.Println(n)
        if n == 5 {
            break
        }
    }
}

Regarding the code example of the WithDeadline demonstration in the official website document:

package main


import (
    "context"
    "fmt"
    "time"
)

func main() {
    d := time.Now().Add(50 * time.Millisecond)
    ctx, cancel := context.WithDeadline(context.Background(), d)

    // Even though ctx will be expired, it is good practice to call its
    // cancelation function in any case. Failure to do so may keep the
    // context and its parent alive longer than necessary.
    defer cancel()

    select {
    case <-time.After(1 * time.Second):
        fmt.Println("overslept")
    case <-ctx.Done():
        fmt.Println(ctx.Err())
    }

}

Through the above code, we have A basic use, then if we use etcd for configuration management, if the configuration changes, how do we notify the corresponding server of the configuration change? The following example demonstrates:

package main

import (
    "github.com/coreos/etcd/clientv3"
    "time"
    "fmt"
    "context"
)

func main() {
    cli,err := clientv3.New(clientv3.Config{
        Endpoints:[]string{"192.168.0.118:2371"},
        DialTimeout:5*time.Second,
    })
    if err != nil {
        fmt.Println("connect failed,err:",err)
        return
    }
    defer cli.Close()
    // 这里会阻塞
    rch := cli.Watch(context.Background(),"logagent/conf/")
    for wresp := range rch{
        for _,ev := range wresp.Events{
            fmt.Printf("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
        }
    }
}

Simple implementation of a kafka consumer code Example:

package main

import (
    "github.com/Shopify/sarama"
    "strings"
    "fmt"
    "time"
)

func main() {
    consumer,err := sarama.NewConsumer(strings.Split("192.168.0.118:9092",","),nil)
    if err != nil{
        fmt.Println("failed to start consumer:",err)
        return
    }
    partitionList,err := consumer.Partitions("nginx_log")
    if err != nil {
        fmt.Println("Failed to get the list of partitions:",err)
        return
    }
    fmt.Println(partitionList)
    for partition := range partitionList{
        pc,err := consumer.ConsumePartition("nginx_log",int32(partition),sarama.OffsetNewest)
        if err != nil {
            fmt.Printf("failed to start consumer for partition %d:%s\n",partition,err)
            return
        }
        defer pc.AsyncClose()
        go func(partitionConsumer sarama.PartitionConsumer){
            for msg := range pc.Messages(){
                fmt.Printf("partition:%d Offset:%d Key:%s Value:%s",msg.Partition,msg.Offset,string(msg.Key),string(msg.Value))
            }
        }(pc)
    }
    time.Sleep(time.Hour)
    consumer.Close()

}

But the above code is not the best code because we end up waiting for the execution of goroutine through time.sleep. We can change it to implement it through sync.WaitGroup

package main

import (
    "github.com/Shopify/sarama"
    "strings"
    "fmt"
    "sync"
)

var (
    wg sync.WaitGroup
)

func main() {
    consumer,err := sarama.NewConsumer(strings.Split("192.168.0.118:9092",","),nil)
    if err != nil{
        fmt.Println("failed to start consumer:",err)
        return
    }
    partitionList,err := consumer.Partitions("nginx_log")
    if err != nil {
        fmt.Println("Failed to get the list of partitions:",err)
        return
    }
    fmt.Println(partitionList)
    for partition := range partitionList{
        pc,err := consumer.ConsumePartition("nginx_log",int32(partition),sarama.OffsetNewest)
        if err != nil {
            fmt.Printf("failed to start consumer for partition %d:%s\n",partition,err)
            return
        }
        defer pc.AsyncClose()
        go func(partitionConsumer sarama.PartitionConsumer){
            wg.Add(1)
            for msg := range partitionConsumer.Messages(){
                fmt.Printf("partition:%d Offset:%d Key:%s Value:%s",msg.Partition,msg.Offset,string(msg.Key),string(msg.Value))
            }
            wg.Done()
        }(pc)
    }

    //time.Sleep(time.Hour)
    wg.Wait()
    consumer.Close()

}

Put the log information that the client needs to collect into etcd

The code for etcd processing is:

package main

import (
    "github.com/coreos/etcd/clientv3"
    "time"
    "github.com/astaxie/beego/logs"
    "context"
    "fmt"
)

var Client *clientv3.Client
var logConfChan chan string


// 初始化etcd
func initEtcd(addr []string,keyfmt string,timeout time.Duration)(err error){

    var keys []string
    for _,ip := range ipArrays{
        //keyfmt = /logagent/%s/log_config
        keys = append(keys,fmt.Sprintf(keyfmt,ip))
    }

    logConfChan = make(chan string,10)
    logs.Debug("etcd watch key:%v timeout:%v", keys, timeout)

    Client,err = clientv3.New(clientv3.Config{
        Endpoints:addr,
        DialTimeout: timeout,
    })
    if err != nil{
        logs.Error("connect failed,err:%v",err)
        return
    }
    logs.Debug("init etcd success")
    waitGroup.Add(1)
    for _, key := range keys{
        ctx,cancel := context.WithTimeout(context.Background(),2*time.Second)
        // 从etcd中获取要收集日志的信息
        resp,err := Client.Get(ctx,key)
        cancel()
        if err != nil {
            logs.Warn("get key %s failed,err:%v",key,err)
            continue
        }

        for _, ev := range resp.Kvs{
            logs.Debug("%q : %q\n",  ev.Key, ev.Value)
            logConfChan <- string(ev.Value)
        }
    }
    go WatchEtcd(keys)
    return
}

func WatchEtcd(keys []string){
    // 这里用于检测当需要收集的日志信息更改时及时更新
    var watchChans []clientv3.WatchChan
    for _,key := range keys{
        rch := Client.Watch(context.Background(),key)
        watchChans = append(watchChans,rch)
    }

    for {
        for _,watchC := range watchChans{
            select{
            case wresp := <-watchC:
                for _,ev:= range wresp.Events{
                    logs.Debug("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
                    logConfChan <- string(ev.Kv.Value)
                }
            default:

            }
        }
        time.Sleep(time.Second)
    }
    waitGroup.Done()
}

func GetLogConf()chan string{
    return logConfChan
}

Similarly, add the right limit here After all, the log collection program cannot affect the performance of the current business, so limit.go is added to limit the speed:

package main

import (
    "time"
    "sync/atomic"
    "github.com/astaxie/beego/logs"
)

type SecondLimit struct {
    unixSecond int64
    curCount int32
    limit int32
}

func NewSecondLimit(limit int32) *SecondLimit {
    secLimit := &SecondLimit{
        unixSecond:time.Now().Unix(),
        curCount:0,
        limit:limit,
    }
    return secLimit
}

func (s *SecondLimit) Add(count int) {
    sec := time.Now().Unix()
    if sec == s.unixSecond {
        atomic.AddInt32(&s.curCount,int32(count))
        return
    }
    atomic.StoreInt64(&s.unixSecond,sec)
    atomic.StoreInt32(&s.curCount, int32(count))
}

func (s *SecondLimit) Wait()bool {
    for {
        sec := time.Now().Unix()
        if (sec == atomic.LoadInt64(&s.unixSecond)) && s.curCount == s.limit {
            time.Sleep(time.Microsecond)
            logs.Debug("limit is running,limit:%d s.curCount:%d",s.limit,s.curCount)
            continue
        }

        if sec != atomic.LoadInt64(&s.unixSecond) {
            atomic.StoreInt64(&s.unixSecond,sec)
            atomic.StoreInt32(&s.curCount,0)
        }
        logs.Debug("limit is exited")
        return false
    }
}

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