实现pipe-filter framework

Pipe-Filter 模式:

  • ⾮常适合与数据处理及数据分析系统
  • Filter封装数据处理的功能
  • Pipe⽤于连接Filter传递数据或者在异步处理过程中缓冲数据流
  • 进程内同步调⽤时,pipe演变为数据在⽅法调⽤间传递
  • 松耦合:Filter只跟数据(格式)耦合

Filter和组合模式:

示例:

简单示例代码:

filter.go

// Package pipefilter is to define the interfaces and the structures for pipe-filter style implementation
package pipefilter

// Request is the input of the filter
type Request interface{}

// Response is the output of the filter
type Response interface{}

// Filter interface is the definition of the data processing components
// Pipe-Filter structure
type Filter interface {
    Process(data Request) (Response, error)
}

split_filter.go

package pipefilter

import (
    "errors"
    "strings"
)

var SplitFilterWrongFormatError = errors.New("input data should be string")

type SplitFilter struct {
    delimiter string
}

func NewSplitFilter(delimiter string) *SplitFilter {
    return &SplitFilter{delimiter}
}

func (sf *SplitFilter) Process(data Request) (Response, error) {
    str, ok := data.(string) //检查数据格式/类型,是否可以处理
    if !ok {
        return nil, SplitFilterWrongFormatError
    }
    parts := strings.Split(str, sf.delimiter)
    return parts, nil
}

split_filter_test.go

package pipefilter

import (
    "reflect"
    "testing"
)

func TestStringSplit(t *testing.T) {
    sf := NewSplitFilter(",")
    resp, err := sf.Process("1,2,3")
    if err != nil {
        t.Fatal(err)
    }
    parts, ok := resp.([]string)
    if !ok {
        t.Fatalf("Repsonse type is %T, but the expected type is string", parts)
    }
    if !reflect.DeepEqual(parts, []string{"1", "2", "3"}) {
        t.Errorf("Expected value is {\"1\",\"2\",\"3\"}, but actual is %v", parts)
    }
}

func TestWrongInput(t *testing.T) {
    sf := NewSplitFilter(",")
    _, err := sf.Process(123)
    if err == nil {
        t.Fatal("An error is expected.")
    }
}

实现micro-kernel framework

  • 特点

    • 易于扩展
    • 错误隔离
    • 保持架构⼀致性
  • 要点
  • 内核包含公共流程或通⽤逻辑

    • 将可变或可扩展部分规划为扩展点
  • 抽象扩展点⾏为,定义接⼝

    • 利⽤插件进⾏扩展

示例:

简单示例代码:

agent.go

package microkernel

import (
    "context"
    "errors"
    "fmt"
    "strings"
    "sync"
)

const (
    Waiting = iota
    Running
)

var WrongStateError = errors.New("can not take the operation in the current state")

type CollectorsError struct {
    CollectorErrors []error
}

func (ce CollectorsError) Error() string {
    var strs []string
    for _, err := range ce.CollectorErrors {
        strs = append(strs, err.Error())
    }
    return strings.Join(strs, ";")
}

type Event struct {
    Source  string
    Content string
}

type EventReceiver interface {
    OnEvent(evt Event)
}

type Collector interface {
    Init(evtReceiver EventReceiver) error
    Start(agtCtx context.Context) error
    Stop() error
    Destory() error
}

type Agent struct {
    collectors map[string]Collector
    evtBuf     chan Event
    cancel     context.CancelFunc
    ctx        context.Context
    state      int
}

func (agt *Agent) EventProcessGroutine() {
    var evtSeg [10]Event
    for {
        for i := 0; i < 10; i++ {
            select {
            case evtSeg[i] = <-agt.evtBuf:
            case <-agt.ctx.Done():
                return
            }
        }
        fmt.Println(evtSeg)
    }

}

func NewAgent(sizeEvtBuf int) *Agent {
    agt := Agent{
        collectors: map[string]Collector{},
        evtBuf:     make(chan Event, sizeEvtBuf),
        state:      Waiting,
    }

    return &agt
}

func (agt *Agent) RegisterCollector(name string, collector Collector) error {
    if agt.state != Waiting {
        return WrongStateError
    }
    agt.collectors[name] = collector
    return collector.Init(agt)
}

func (agt *Agent) startCollectors() error {
    var err error
    var errs CollectorsError
    var mutex sync.Mutex

    for name, collector := range agt.collectors {
        go func(name string, collector Collector, ctx context.Context) {
            defer func() {
                mutex.Unlock()
            }()
            err = collector.Start(ctx)
            mutex.Lock()
            if err != nil {
                errs.CollectorErrors = append(errs.CollectorErrors,
                    errors.New(name+":"+err.Error()))
            }
        }(name, collector, agt.ctx)
    }
    if len(errs.CollectorErrors) == 0 {
        return nil
    }
    return errs
}

func (agt *Agent) stopCollectors() error {
    var err error
    var errs CollectorsError
    for name, collector := range agt.collectors {
        if err = collector.Stop(); err != nil {
            errs.CollectorErrors = append(errs.CollectorErrors,
                errors.New(name+":"+err.Error()))
        }
    }
    if len(errs.CollectorErrors) == 0 {
        return nil
    }

    return errs
}

func (agt *Agent) destoryCollectors() error {
    var err error
    var errs CollectorsError
    for name, collector := range agt.collectors {
        if err = collector.Destory(); err != nil {
            errs.CollectorErrors = append(errs.CollectorErrors,
                errors.New(name+":"+err.Error()))
        }
    }
    if len(errs.CollectorErrors) == 0 {
        return nil
    }
    return errs
}

func (agt *Agent) Start() error {
    if agt.state != Waiting {
        return WrongStateError
    }
    agt.state = Running
    agt.ctx, agt.cancel = context.WithCancel(context.Background())
    go agt.EventProcessGroutine()
    return agt.startCollectors()
}

func (agt *Agent) Stop() error {
    if agt.state != Running {
        return WrongStateError
    }
    agt.state = Waiting
    agt.cancel()
    return agt.stopCollectors()
}

func (agt *Agent) Destory() error {
    if agt.state != Waiting {
        return WrongStateError
    }
    return agt.destoryCollectors()
}

func (agt *Agent) OnEvent(evt Event) {
    agt.evtBuf <- evt
}

agent_test.go

package microkernel

import (
    "context"
    "errors"
    "fmt"
    "testing"
    "time"
)

type DemoCollector struct {
    evtReceiver EventReceiver
    agtCtx      context.Context
    stopChan    chan struct{}
    name        string
    content     string
}

func NewCollect(name string, content string) *DemoCollector {
    return &DemoCollector{
        stopChan: make(chan struct{}),
        name:     name,
        content:  content,
    }
}

func (c *DemoCollector) Init(evtReceiver EventReceiver) error {
    fmt.Println("initialize collector", c.name)
    c.evtReceiver = evtReceiver
    return nil
}

func (c *DemoCollector) Start(agtCtx context.Context) error {
    fmt.Println("start collector", c.name)
    for {
        select {
        case <-agtCtx.Done():
            c.stopChan <- struct{}{}
            break
        default:
            time.Sleep(time.Millisecond * 50)
            c.evtReceiver.OnEvent(Event{c.name, c.content})
        }
    }
}

func (c *DemoCollector) Stop() error {
    fmt.Println("stop collector", c.name)
    select {
    case <-c.stopChan:
        return nil
    case <-time.After(time.Second * 1):
        return errors.New("failed to stop for timeout")
    }
}

func (c *DemoCollector) Destory() error {
    fmt.Println(c.name, "released resources.")
    return nil
}

func TestAgent(t *testing.T) {
    agt := NewAgent(100)
    c1 := NewCollect("c1", "1")
    c2 := NewCollect("c2", "2")
    agt.RegisterCollector("c1", c1)
    agt.RegisterCollector("c2", c2)
    if err := agt.Start(); err != nil {
        fmt.Printf("start error %v\n", err)
    }
    fmt.Println(agt.Start())
    time.Sleep(time.Second * 1)
    agt.Stop()
    agt.Destory()
}
最后修改:2020 年 05 月 31 日 04 : 54 PM