Add auto_create_stream

README.md

@@ -34,6 +34,7 @@ Run `make` to build `./bin/cloudwatch.so`. Then use with Fluent Bit:
 * `log_format`: An optional parameter that can be used to tell CloudWatch the format of the data. A value of `json/emf` enables CloudWatch to extract custom metrics embedded in a JSON payload. See the [Embedded Metric Format](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format_Specification.html).
 * `role_arn`: ARN of an IAM role to assume (for cross account access).
 * `auto_create_group`: Automatically create log groups (and add tags). Valid values are "true" or "false" (case insensitive). Defaults to false. If you use dynamic variables in your log group name, you may need this to be `true`.
+* `auto_create_stream`: Automatically create log streams. Valid values are "true" or "false" (case insensitive). Defaults to true.
 * `new_log_group_tags`: Comma/equal delimited string of tags to include with _auto created_ log groups. Example: `"tag=val,cooltag2=my other value"`
 * `log_retention_days`: If set to a number greater than zero, and newly create log group's retention policy is set to this many days.
 * `endpoint`: Specify a custom endpoint for the CloudWatch Logs API.

cloudwatch/cloudwatch.go

@@ -97,6 +97,11 @@ type TaskMetadata struct {
 	TaskID  string `json:"TaskID,omitempty"`
 }
 
+type streamDoesntExistError struct {
+	streamName string
+	groupName  string
+}
+
 func (stream *logStream) isExpired() bool {
 	if len(stream.logEvents) == 0 && stream.expiration.Before(time.Now()) {
 		return true
@@ -130,6 +135,7 @@ type OutputPlugin struct {
 	logGroupTags                  map[string]*string
 	logGroupRetention             int64
 	autoCreateGroup               bool
+	autoCreateStream              bool
 	bufferPool                    bytebufferpool.Pool
 	ecsMetadata                   TaskMetadata
 	runningInECS                  bool
@@ -148,6 +154,7 @@ type OutputPluginConfig struct {
 	LogKey               string
 	RoleARN              string
 	AutoCreateGroup      bool
+	AutoCreateStream     bool
 	NewLogGroupTags      string
 	LogRetentionDays     int64
 	CWEndpoint           string
@@ -227,6 +234,7 @@ func NewOutputPlugin(config OutputPluginConfig) (*OutputPlugin, error) {
 		logGroupTags:                  tagKeysToMap(config.NewLogGroupTags),
 		logGroupRetention:             config.LogRetentionDays,
 		autoCreateGroup:               config.AutoCreateGroup,
+		autoCreateStream:              config.AutoCreateStream,
 		groups:                        make(map[string]struct{}),
 		ecsMetadata:                   TaskMetadata{},
 		runningInECS:                  runningInECS,
@@ -431,22 +439,23 @@ func (output *OutputPlugin) cleanUpExpiredLogStreams() {
 	}
 }
 
+func (err *streamDoesntExistError) Error() string {
+	return fmt.Sprintf("error: stream %s doesn't exist in log group %s", err.streamName, err.groupName)
+}
+
 func (output *OutputPlugin) getLogStream(e *Event) (*logStream, error) {
 	stream, ok := output.streams[e.group+e.stream]
 	if !ok {
-		// stream doesn't exist, create it
-		stream, err := output.createStream(e)
+		// assume the stream exists
+		stream, err := output.existingLogStream(e)
 		if err != nil {
-			if awsErr, ok := err.(awserr.Error); ok {
-				if awsErr.Code() == cloudwatchlogs.ErrCodeResourceAlreadyExistsException {
-					// existing stream
-					return output.existingLogStream(e)
-				}
+			// if it doesn't then create it
+			if _, ok := err.(*streamDoesntExistError); ok {
+				return output.createStream(e)
 			}
 		}
 		return stream, err
 	}
-
 	return stream, nil
 }
 
@@ -478,7 +487,10 @@ func (output *OutputPlugin) existingLogStream(e *Event) (*logStream, error) {
 		}
 
 		if stream == nil && resp.NextToken == nil {
-			return nil, fmt.Errorf("error: does not compute: Log Stream %s could not be created, but also could not be found in the log group", e.stream)
+			return nil, &streamDoesntExistError{
+				streamName: e.stream,
+				groupName:  e.group,
+			}
 		}
 
 		nextToken = resp.NextToken
@@ -545,6 +557,9 @@ func (output *OutputPlugin) setGroupStreamNames(e *Event) {
 }
 
 func (output *OutputPlugin) createStream(e *Event) (*logStream, error) {
+	if !output.autoCreateStream {
+		return nil, fmt.Errorf("error: Log Stream %s does not exist in the log group %s and can't be created as autoCreateStream is disabled", e.stream, e.group)
+	}
 	output.timer.Check()
 	_, err := output.client.CreateLogStream(&cloudwatchlogs.CreateLogStreamInput{
 		LogGroupName:  aws.String(e.group),