Merge pull request #4 from mborders/cron-jobs

Added DispatchCron to allow for creating cron-based jobs

README.md

@@ -9,6 +9,8 @@ Simple in-memory job queue for Golang using worker-based dispatching
 
 Documentation here: https://godoc.org/github.com/mborders/artifex
 
+Cron jobs use the robfig/cron library: https://godoc.org/github.com/robfig/cron
+
 ## Example Usage
 
 ```go
@@ -32,6 +34,14 @@ dt, err := d.DispatchEvery(func() {
 // Stop a given DispatchTicker
 dt.Stop()
 
+// Returns a DispatchCron
+dc, err := d.DispatchCron(func() {
+  // do something every 1s
+}, "*/1 * * * * *")
+
+// Stop a given DispatchCron
+dc.Stop()
+
 // Stop a dispatcher and all its workers/tickers
 d.Stop()
 ```

dispatcher.go

@@ -2,6 +2,7 @@ package artifex
 
 import (
 	"errors"
+	"github.com/robfig/cron/v3"
 	"time"
 )
 
@@ -12,6 +13,7 @@ type Dispatcher struct {
 	maxQueue   int
 	workers    []*Worker
 	tickers    []*DispatchTicker
+	crons      []*DispatchCron
 	workerPool chan chan Job
 	jobQueue   chan Job
 	quit       chan bool
@@ -34,6 +36,7 @@ func NewDispatcher(maxWorkers int, maxQueue int) *Dispatcher {
 func (d *Dispatcher) Start() {
 	d.workers = []*Worker{}
 	d.tickers = []*DispatchTicker{}
+	d.crons = []*DispatchCron{}
 	d.workerPool = make(chan chan Job, d.maxWorkers)
 	d.jobQueue = make(chan Job, d.maxQueue)
 	d.quit = make(chan bool)
@@ -78,8 +81,13 @@ func (d *Dispatcher) Stop() {
 		d.tickers[i].Stop()
 	}
 
+	for i := range d.crons {
+		d.crons[i].Stop()
+	}
+
 	d.workers = []*Worker{}
 	d.tickers = []*DispatchTicker{}
+	d.crons = []*DispatchCron{}
 	d.quit <- true
 }
 
@@ -134,6 +142,28 @@ func (d *Dispatcher) DispatchEvery(run func(), interval time.Duration) (*Dispatc
 	return dt, nil
 }
 
+// DispatchEvery pushes the given job into the job queue
+// each time the cron definition is met
+func (d *Dispatcher) DispatchCron(run func(), cronStr string) (*DispatchCron, error) {
+	if !d.active {
+		return nil, errors.New("dispatcher is not active")
+	}
+
+	dc := &DispatchCron{cron: cron.New(cron.WithSeconds())}
+	d.crons = append(d.crons, dc)
+
+	_, err := dc.cron.AddFunc(cronStr, func() {
+		d.jobQueue <- Job{Run: run}
+	})
+
+	if err != nil {
+		return nil, errors.New("invalid cron definition")
+	}
+
+	dc.cron.Start()
+	return dc, nil
+}
+
 // DispatchTicker represents a dispatched job ticker
 // that executes on a given interval. This provides
 // a means for stopping the execution cycle from continuing.
@@ -147,3 +177,14 @@ func (dt *DispatchTicker) Stop() {
 	dt.ticker.Stop()
 	dt.quit <- true
 }
+
+// DispatchCron represents a dispatched cron job
+// that executes using cron expression formats.
+type DispatchCron struct {
+	cron *cron.Cron
+}
+
+// Stops ends the execution cycle for the given cron.
+func (c *DispatchCron) Stop() {
+	c.cron.Stop()
+}

dispatcher_test.go

@@ -160,6 +160,10 @@ func TestDispatcher_Stop(t *testing.T) {
 	}, time.Millisecond*100)
 	assert.NotNil(t, err)
 
+	_, err = d.DispatchCron(func() {
+	}, "*/1 * * * * *")
+	assert.NotNil(t, err)
+
 	time.Sleep(time.Millisecond * 100)
 	assert.Equal(t, 1, c)
 }
@@ -209,3 +213,45 @@ func TestDispatcher_StopTwice(t *testing.T) {
 	d.Stop()
 	d.Stop()
 }
+
+func TestDispatcher_DispatchCron(t *testing.T) {
+	c := 0
+	d := NewDispatcher(1, 3)
+	d.Start()
+
+	_, err := d.DispatchCron(func() {
+		c++
+	}, "*/1 * * * * *")
+	assert.Nil(t, err)
+
+	time.Sleep(time.Millisecond * 3000)
+	assert.Equal(t, 3, c)
+}
+
+func TestDispatcher_DispatchCron_Stop(t *testing.T) {
+	c := 0
+	d := NewDispatcher(1, 3)
+	d.Start()
+
+	_, err := d.DispatchCron(func() {
+		c++
+	}, "*/1 * * * * *")
+	assert.Nil(t, err)
+
+	time.Sleep(time.Millisecond * 3000)
+	d.Stop()
+	assert.Equal(t, 3, c)
+
+	time.Sleep(time.Second * 1)
+	assert.Equal(t, 3, c)
+}
+
+func TestDispatcher_DispatchCron_InvalidDefinition(t *testing.T) {
+	d := NewDispatcher(1, 3)
+	d.Start()
+
+	_, err := d.DispatchCron(func() {
+	}, "foobar")
+	assert.NotNil(t, err)
+	assert.Equal(t, "invalid cron definition", err.Error())
+}

go.mod

@@ -2,5 +2,6 @@ module github.com/mborders/artifex
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/robfig/cron/v3 v3.0.1
 	github.com/stretchr/testify v1.3.0
 )

go.sum

@@ -3,6 +3,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/robfig/cron/v3 v3.0.1 h1:WdRxkvbJztn8LMz/QEvLN5sBU+xKpSqwwUO1Pjr4qDs=
+github.com/robfig/cron/v3 v3.0.1/go.mod h1:eQICP3HwyT7UooqI/z+Ov+PtYAWygg1TEWWzGIFLtro=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=