Repository: influxdata/influxdb-client-go (go)

Issue:
WriteAPI Out Of Memory
Each time the method is called, a new instance is created and a slice of writeAPIs is placed.
So as you run the slice the capacity gets larger and larger and it doesn't get released.


```

 func (c *clientImpl) WriteAPI(org, bucket string) api.WriteAPI {
	w := api.NewWriteAPI(org, bucket, c.httpService, c.options.writeOptions)
	c.writeAPIs = append(c.writeAPIs, w)
	return w
}

```

Here is the actual running pprof：

```

Showing nodes accounting for 6.56GB, 99.41% of 6.60GB total
Dropped 20 nodes (cum <= 0.03GB)
Showing top 10 nodes out of 18
      flat  flat%   sum%        cum   cum%
    6.56GB 99.41% 99.41%     6.57GB 99.55%  github.com/influxdata/influxdb-client-go/api.NewWriteAPI

```

1. Each call creates a new one
2. And it's put into the slice 

__Expected behavior:__
 Instances can be reused or resources can be released exactly when they are used

__Actual behavior:__
Cannot reuse and cannot release resources

__Specifications:__
 - Client Version: Cannot reuse and cannot release resources
 - InfluxDB Version: 2.0
 - Platform: mac OSX & CentOS

Pooling is recommended for managing WriteAPI.


Pull request description:
fix:  WriteAPIs management
Closes #163 

## Proposed Changes

Keeping a single instance of WriteAPI and WriteAPIBlocking for each org and bucket pair.

## Checklist

- [X] CHANGELOG.md updated
- [X] Rebased/mergeable
- [X] A test has been added if appropriate
- [X] Tests pass
- [X] Commit messages are in [semantic format](https://seesparkbox.com/foundry/semantic_commit_messages)



Patch:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65873c4..4621616 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,10 +2,14 @@
 ### Breaking changes
 1. [#173](https://github.com/influxdata/influxdb-client-go/pull/173) Removed deprecated API.
 1. [#174](https://github.com/influxdata/influxdb-client-go/pull/174) Removed orgs labels API cause [it has been removed from the server API](https://github.com/influxdata/influxdb/pull/19104)
+1. [#175](https://github.com/influxdata/influxdb-client-go/pull/175) Removed WriteAPI.Close()
 
 ### Features
 1. [#165](https://github.com/influxdata/influxdb-client-go/pull/165) Allow overriding the http.Client for the http service.
 
+### Bug fixes 
+1. [#175](https://github.com/influxdata/influxdb-client-go/pull/175) Fixed WriteAPIs management. Keeping single instance for each org and bucket pair.
+
 ## 1.4.0 [2020-07-17]
 ### Breaking changes
 1. [#156](https://github.com/influxdata/influxdb-client-go/pull/156) Fixing Go naming and code style violations: 
diff --git a/api/write.go b/api/write.go
index da2f747..ff91115 100644
--- a/api/write.go
+++ b/api/write.go
@@ -27,16 +27,14 @@ type WriteAPI interface {
 	WritePoint(point *write.Point)
 	// Flush forces all pending writes from the buffer to be sent
 	Flush()
-	// Flushes all pending writes and stop async processes. After this the Write client cannot be used
-	Close()
 	// Errors returns a channel for reading errors which occurs during async writes.
 	// Must be called before performing any writes for errors to be collected.
 	// The chan is unbuffered and must be drained or the writer will block.
 	Errors() <-chan error
 }
 
-// writeAPI provides main implementation for WriteAPI
-type writeAPI struct {
+// WriteAPIImpl provides main implementation for WriteAPI
+type WriteAPIImpl struct {
 	service     *iwrite.Service
 	writeBuffer []string
 
@@ -56,8 +54,8 @@ type writeBuffInfoReq struct {
 	writeBuffLen int
 }
 
-func NewWriteAPI(org string, bucket string, service http.Service, writeOptions *write.Options) *writeAPI {
-	w := &writeAPI{
+func NewWriteAPI(org string, bucket string, service http.Service, writeOptions *write.Options) *WriteAPIImpl {
+	w := &WriteAPIImpl{
 		service:      iwrite.NewService(org, bucket, service, writeOptions),
 		writeBuffer:  make([]string, 0, writeOptions.BatchSize()+1),
 		writeCh:      make(chan *iwrite.Batch),
@@ -77,19 +75,19 @@ func NewWriteAPI(org string, bucket string, service http.Service, writeOptions *
 	return w
 }
 
-func (w *writeAPI) Errors() <-chan error {
+func (w *WriteAPIImpl) Errors() <-chan error {
 	if w.errCh == nil {
 		w.errCh = make(chan error)
 	}
 	return w.errCh
 }
 
-func (w *writeAPI) Flush() {
+func (w *WriteAPIImpl) Flush() {
 	w.bufferFlush <- struct{}{}
 	w.waitForFlushing()
 }
 
-func (w *writeAPI) waitForFlushing() {
+func (w *WriteAPIImpl) waitForFlushing() {
 	for {
 		w.bufferInfoCh <- writeBuffInfoReq{}
 		writeBuffInfo := <-w.bufferInfoCh
@@ -108,10 +106,9 @@ func (w *writeAPI) waitForFlushing() {
 		log.Log.Info("Waiting buffer is flushed")
 		time.Sleep(time.Millisecond)
 	}
-	//time.Sleep(time.Millisecond)
 }
 
-func (w *writeAPI) bufferProc() {
+func (w *WriteAPIImpl) bufferProc() {
 	log.Log.Info("Buffer proc started")
 	ticker := time.NewTicker(time.Duration(w.writeOptions.FlushInterval()) * time.Millisecond)
 x:
@@ -139,20 +136,16 @@ x:
 	w.doneCh <- struct{}{}
 }
 
-func (w *writeAPI) flushBuffer() {
+func (w *WriteAPIImpl) flushBuffer() {
 	if len(w.writeBuffer) > 0 {
-		//go func(lines []string) {
 		log.Log.Info("sending batch")
 		batch := iwrite.NewBatch(buffer(w.writeBuffer), w.writeOptions.RetryInterval())
 		w.writeCh <- batch
-		//	lines = lines[:0]
-		//}(w.writeBuffer)
-		//w.writeBuffer = make([]string,0, w.service.clientImpl.Options.BatchSize+1)
 		w.writeBuffer = w.writeBuffer[:0]
 	}
 }
 
-func (w *writeAPI) writeProc() {
+func (w *WriteAPIImpl) writeProc() {
 	log.Log.Info("Write proc started")
 x:
 	for {
@@ -174,7 +167,7 @@ x:
 	w.doneCh <- struct{}{}
 }
 
-func (w *writeAPI) Close() {
+func (w *WriteAPIImpl) Close() {
 	if w.writeCh != nil {
 		// Flush outstanding metrics
 		w.Flush()
@@ -203,14 +196,13 @@ func (w *writeAPI) Close() {
 	}
 }
 
-func (w *writeAPI) WriteRecord(line string) {
+func (w *WriteAPIImpl) WriteRecord(line string) {
 	b := []byte(line)
 	b = append(b, 0xa)
 	w.bufferCh <- string(b)
 }
 
-func (w *writeAPI) WritePoint(point *write.Point) {
-	//w.bufferCh <- point.ToLineProtocol(w.service.clientImpl.Options().Precision)
+func (w *WriteAPIImpl) WritePoint(point *write.Point) {
 	line, err := w.service.EncodePoints(point)
 	if err != nil {
 		log.Log.Errorf("point encoding error: %s\n", err.Error())
diff --git a/client.go b/client.go
index b7dd851..83253db 100644
--- a/client.go
+++ b/client.go
@@ -60,18 +60,19 @@ type Client interface {
 
 // clientImpl implements Client interface
 type clientImpl struct {
-	serverURL   string
-	options     *Options
-	writeAPIs   []api.WriteAPI
-	lock        sync.Mutex
-	httpService ihttp.Service
-	apiClient   *domain.ClientWithResponses
-	authAPI     api.AuthorizationsAPI
-	orgAPI      api.OrganizationsAPI
-	usersAPI    api.UsersAPI
-	deleteAPI   api.DeleteAPI
-	bucketsAPI  api.BucketsAPI
-	labelsAPI   api.LabelsAPI
+	serverURL     string
+	options       *Options
+	writeAPIs     map[string]api.WriteAPI
+	syncWriteAPIs map[string]api.WriteAPIBlocking
+	lock          sync.Mutex
+	httpService   ihttp.Service
+	apiClient     *domain.ClientWithResponses
+	authAPI       api.AuthorizationsAPI
+	orgAPI        api.OrganizationsAPI
+	usersAPI      api.UsersAPI
+	deleteAPI     api.DeleteAPI
+	bucketsAPI    api.BucketsAPI
+	labelsAPI     api.LabelsAPI
 }
 
 // NewClient creates Client for connecting to given serverURL with provided authentication token, with the default options.
@@ -93,11 +94,12 @@ func NewClientWithOptions(serverURL string, authToken string, options *Options)
 	}
 	service := ihttp.NewService(normServerURL, "Token "+authToken, options.httpOptions)
 	client := &clientImpl{
-		serverURL:   serverURL,
-		options:     options,
-		writeAPIs:   make([]api.WriteAPI, 0, 5),
-		httpService: service,
-		apiClient:   domain.NewClientWithResponses(service),
+		serverURL:     serverURL,
+		options:       options,
+		writeAPIs:     make(map[string]api.WriteAPI, 5),
+		syncWriteAPIs: make(map[string]api.WriteAPIBlocking, 5),
+		httpService:   service,
+		apiClient:     domain.NewClientWithResponses(service),
 	}
 	log.Log.SetDebugLevel(client.Options().LogLevel())
 	log.Log.Infof("Using URL '%s', token '%s'", serverURL, authToken)
@@ -165,20 +167,40 @@ func (c *clientImpl) Health(ctx context.Context) (*domain.HealthCheck, error) {
 	return response.JSON200, nil
 }
 
+func createKey(org, bucket string) string {
+	return org + "\t" + bucket
+}
+
 func (c *clientImpl) WriteAPI(org, bucket string) api.WriteAPI {
-	w := api.NewWriteAPI(org, bucket, c.httpService, c.options.writeOptions)
-	c.writeAPIs = append(c.writeAPIs, w)
-	return w
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	key := createKey(org, bucket)
+	if _, ok := c.writeAPIs[key]; !ok {
+		w := api.NewWriteAPI(org, bucket, c.httpService, c.options.writeOptions)
+		c.writeAPIs[key] = w
+	}
+	return c.writeAPIs[key]
 }
 
 func (c *clientImpl) WriteAPIBlocking(org, bucket string) api.WriteAPIBlocking {
-	w := api.NewWriteAPIBlocking(org, bucket, c.httpService, c.options.writeOptions)
-	return w
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	key := createKey(org, bucket)
+	if _, ok := c.syncWriteAPIs[key]; !ok {
+		w := api.NewWriteAPIBlocking(org, bucket, c.httpService, c.options.writeOptions)
+		c.syncWriteAPIs[key] = w
+	}
+	return c.syncWriteAPIs[key]
 }
 
 func (c *clientImpl) Close() {
-	for _, w := range c.writeAPIs {
-		w.Close()
+	for key, w := range c.writeAPIs {
+		wa := w.(*api.WriteAPIImpl)
+		wa.Close()
+		delete(c.writeAPIs, key)
+	}
+	for key := range c.syncWriteAPIs {
+		delete(c.syncWriteAPIs, key)
 	}
 }
 


Test patch:
diff --git a/client_test.go b/client_test.go
index 1b63814..11c3a3d 100644
--- a/client_test.go
+++ b/client_test.go
@@ -45,6 +45,37 @@ func TestUrls(t *testing.T) {
 	}
 }
 
+func TestWriteAPIManagement(t *testing.T) {
+	data := []struct {
+		org          string
+		bucket       string
+		expectedCout int
+	}{
+		{"o1", "b1", 1},
+		{"o1", "b2", 2},
+		{"o1", "b1", 2},
+		{"o2", "b1", 3},
+		{"o2", "b2", 4},
+		{"o1", "b2", 4},
+		{"o1", "b3", 5},
+		{"o2", "b2", 5},
+	}
+	c := NewClient("http://localhost", "x").(*clientImpl)
+	for i, d := range data {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			w := c.WriteAPI(d.org, d.bucket)
+			assert.NotNil(t, w)
+			assert.Len(t, c.writeAPIs, d.expectedCout)
+			wb := c.WriteAPIBlocking(d.org, d.bucket)
+			assert.NotNil(t, wb)
+			assert.Len(t, c.syncWriteAPIs, d.expectedCout)
+		})
+	}
+	c.Close()
+	assert.Len(t, c.writeAPIs, 0)
+	assert.Len(t, c.syncWriteAPIs, 0)
+}
+
 func TestUserAgent(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		time.Sleep(100 * time.Millisecond)