Amazon CloudWatch

Send logs and metrics to Amazon CloudWatch

Amazon CloudWatch

The Amazon CloudWatch output plugin lets you ingest your records into the CloudWatch Logs service. Support for CloudWatch Metrics is also provided using Embedded Metric Format (EMF).

This is the documentation for the core Fluent Bit CloudWatch plugin written in C. It can replace the aws/amazon-cloudwatch-logs-for-fluent-bit Golang Fluent Bit plugin (cloudwatch). This CloudWatch plugin is called cloudwatch_logs to prevent conflicts or confusion. Check the Amazon repository for the Golang plugin for details about the deprecation and migration plan for the original plugin.

See AWS credentials for details about how AWS credentials are fetched.

Configuration parameters

Key	Description	Default
add_enity	Add entity to PutLogEvent calls.	false
alias	Sets an alias, useful for multiple instances of the same output plugin.	none
auto_create_group	Automatically create the log group. Allowed values: true, false (case insensitive).	false
auto_retry_requests	Immediately retry failed requests to AWS services once. This option doesn't affect the normal Fluent Bit retry mechanism with backoff. Instead, it enables an immediate retry with no delay for networking errors, which can help improve throughput when there are transient/random networking issues.	true
endpoint	Specify a custom endpoint for the CloudWatch Logs API.	none
external_id	Specify an external ID for the STS API, can be used with the role_arn parameter if your role requires an external ID.	none
extra_user_agent	This option appends a string to the default user agent. AWS asks that you not manually set this field yourself, it is reserved for use in our vended configurations, for example, EKS Container Insights.	none
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.	none
log_group_class	Specifies the log storage class for new log groups when auto_create_group is set to true. You can't modify the storage class of existing log groups. Allowed values: STANDARD, INFREQUENT_ACCESS.	STANDARD
log_group_name	The name of the CloudWatch log group that you want log records sent to.	none
log_group_template	OTemplate for CW Log Group name using record accessor syntax. Plugin falls back to the log_group_name configured if needed.	none
log_key	By default, the whole log record will be sent to CloudWatch. If you specify a key name with this option, then only the value of that key will be sent to CloudWatch. For example, if you are using the Fluentd Docker log driver, you can specify log_key log and only the log message will be sent to CloudWatch.	none
log_level	Specifies the log level for output plugin. If not set here, plugin uses global log level in service section.	info
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. Allowed values: [1, 3, 5, 7, 14, 30, 60, 90, 120, 150, 180, 365, 400, 545, 731, 1827, 3653]	0
log_stream_name	The name of the CloudWatch log stream that you want log records sent to.	none
log_stream_prefix	Prefix for the log stream name. The tag is appended to the prefix to construct the full log stream name. Not compatible with the log_stream_name option.	none
log_stream_template	Template for CloudWatch Log Stream name using record accessor syntax. Plugin falls back to the log_stream_name or log_stream_prefix configured if needed.	none
log_supress_interval	Suppresses log messages from output plugin that appear similar within a specified time interval. 0 no suppression.	0
match	Set a tag pattern to match records that output should process. Exact matches or wildcards (for example *).	none
match_regex	Set a regular expression to match tags for output routing. This allows more flexible matching compared to simple wildcards.	none
metric_dimensions	Metric dimensions is a list of lists. If you have only one list of dimensions, put the values as a comma seperated string. If you want to put list of lists, use the list as semicolon seperated strings. If your value is d1,d2;d3, it will consider it as [[d1, d2],[d3]].	none
metric_namespace	An optional string representing the CloudWatch namespace for the metrics. See the Metrics tutorial section for a full configuration.	none
profile	Option to specify an AWS Profile for credentials.	none
region	The AWS region to send logs to.	none
retry_limit	Set retry limit for output plugin when delivery fails. Integer, no_limits, false, or off to disable, or no_retries to disable retries entirely.	1
role_arn	ARN of an IAM role to assume for cross account access.	none
sts_endpoint	Specify a custom STS endpoint for the AWS STS API.	none
tls.windows.certstore_name	Sets the certificate store name on an output (Windows).	none
tls.windows.use_enterprise_store	Sets whether using enterprise certificate store or not on an output (Windows).	none

Get started

To send records into Amazon CloudWatch, you can run the plugin from the command line or through the configuration file.

Command line

The CloudWatch plugin can read the parameters from the command line using the -p argument (property):

fluent-bit -i cpu -o cloudwatch_logs -p log_group_name=group -p log_stream_name=stream -p region=us-west-2 -m '*' -f 1

Configuration file

In your main configuration file append the following:

fluent-bit.yaml

pipeline:

  outputs:
    - name: cloudwatch_logs
      match: '*'
      region: us-east-1
      log_group_name: fluent-bit-cloudwatch
      log_stream_prefix: from-fluent-bit-
      auto_create_group: on

fluent-bit.conf

Integration with LocalStack (CloudWatch logs)

For an instance of Localstack running at http://localhost:4566, use the following configuration:

fluent-bit.yaml

pipeline:

  outputs:
    - name: cloudwatch_logs
      match: '*'
      region: us-east-1
      log_group_name: fluent-bit-cloudwatch
      log_stream_prefix: from-fluent-bit-
      auto_create_group: on
      endpoint: localhost
      port: 4566

fluent-bit.conf

Any testing credentials can be exported as local variables, such as AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY.

Permissions

The following AWS IAM permissions are required to use this plugin:

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": [
      "logs:CreateLogStream",
      "logs:CreateLogGroup",
      "logs:PutLogEvents",
      "logs:PutRetentionPolicy"
    ],
    "Resource": "*"
  }]
}

Log stream and group name templating using record_accessor syntax

You might want the log group or stream name to be based on the contents of the log record itself. This plugin supports templating log group and stream names using Fluent Bit record_accessor syntax.

The following example outlines a common use case-templating log group and stream names based on Kubernetes metadata.

The Kubernetes filter can add metadata which will look like the following:

kubernetes: {
  annotations: {
    "kubernetes.io/psp": "eks.privileged"
  },
  container_hash: "<some hash>",
  container_name: "myapp",
  docker_id: "<some id>",
  host: "ip-10-1-128-166.us-east-2.compute.internal",
  labels: {
    app: "myapp",
    "pod-template-hash": "<some hash>"
  },
  namespace_name: "my-namespace",
  pod_id: "198f7dd2-2270-11ea-be47-0a5d932f5920",
  pod_name: "myapp-5468c5d4d7-n2swr"
}

Using record_accessor, you can build a template based on this object.

Here is the configuration:

fluent-bit.yaml

pipeline:

  outputs:
    - name: cloudwatch_logs
      match: '*'
      region: us-east-1
      log_group_name: fallback-group
      log_stream_prefix: fallback-stream
      auto_create_group: on
      log_group_template: application-logs-$kubernetes['host'].$kubernetes['namespace_name']
      log_stream_template: $kubernetes['pod_name'].$kubernetes['container_name']

fluent-bit.conf

With the Kubernetes metadata, the log group name will be application-logs-ip-10-1-128-166.us-east-2.compute.internal.my-namespace, and the log stream name will be myapp-5468c5d4d7-n2swr.myapp.

If the Kubernetes structure isn't found in the log record, then the log_group_name and log_stream_prefix are used, and Fluent Bit will log an error like:

[2022/06/30 06:09:29] [ warn] [record accessor] translation failed, root key=kubernetes

Limitations of record_accessor syntax

In the previous example, the template values are separated by dot (.) characters. The Fluent Bit record_accessor library has a limitation in the characters that can separate template variables. Only dots and commas (. and ,) can come after a template variable. This is because the templating library must parse the template and determine the end of a variable.

Assume that your log records contain the metadata keys container_name and task. The following would be invalid templates because the two template variables aren't separated by commas or dots:

• $task-$container_name

• $task/$container_name

• $task_$container_name

• $taskfooo$container_name

However, the following are valid:

• $task.$container_name

• $task.resource.$container_name

• $task.fooo.$container_name

And the following are valid since they only contain one template variable with nothing after it:

• fooo$task

• fooo____$task

• fooo/bar$container_name

Metrics tutorial

Fluent Bit has input plugins (cpu, mem, disk, netif) to collect host resource usage metrics. The cloudwatch_logs output plugin can be used to send these host metrics to CloudWatch in Embedded Metric Format (EMF). If data comes from any of the mentioned input plugins, the cloudwatch_logs output plugin will convert them to EMF format and send to CloudWatch as JSON log. Additionally, if json/emf is set as the value of the log_format configuration option, CloudWatch will extract custom metrics from embedded JSON payload.

Only cpu and mem metrics can be sent to CloudWatch.

For using the mem input plugin and sending memory usage metrics to CloudWatch, consider the following example configuration file. This example uses the aws filter which adds ec2_instance_id and az (availability zone) to the log records. Later, the output configuration section sets ec2_instance_id as the metric dimension.

fluent-bit.yaml

service:
  log_level: info

pipeline:
  inputs:
    - name: mem
      tag: mem

  filters:
    - name: aws
      match: '*'

  outputs:
    - name: cloudwatch_logs
      match: '*'
      region: us-west-2
      log_stream_name: fluent-bit-cloudwatch
      log_group_name: fluent-bit-cloudwatch
      log_format: json/emf
      metric_namespace: fluent-bit-metrics
      metric_dimensions: ec2_instance_id
      auto_create_group: true

fluent-bit.conf

The following configuration will set two dimensions to all of the metrics: ec2_instance_id and az.

fluent-bit.yaml

service:
  log_level: info

pipeline:
  inputs:
    - name: mem
      tag: mem

  filters:
    - name: aws
      match: '*'

  outputs:
    - name: cloudwatch_logs
      match: '*'
      region: us-west-2
      log_stream_name: fluent-bit-cloudwatch
      log_group_name: fluent-bit-cloudwatch
      log_format: json/emf
      metric_namespace: fluent-bit-metrics
      metric_dimensions: ec2_instance_id,az
      auto_create_group: true

fluent-bit.conf

AWS for Fluent Bit

Amazon distributes a container image with Fluent Bit and these plugins.

GitHub

github.com/aws/aws-for-fluent-bit

Amazon ECR Public Gallery

aws-for-fluent-bit

Images are available in Amazon ECR Public Gallery. You can download images with different tags by following command:

docker pull public.ecr.aws/aws-observability/aws-for-fluent-bit:<tag>

For example, you can pull the image with latest version by:

docker pull public.ecr.aws/aws-observability/aws-for-fluent-bit:latest

If you see errors for image pull limits, try log into public ECR with your AWS credentials:

aws ecr-public get-login-password --region us-east-1 | docker login --username AWS --password-stdin public.ecr.aws

You can check the Amazon ECR Public official doc for more details

Docker Hub

amazon/aws-for-fluent-bit

Amazon ECR

You can use SSM public parameters to find the Amazon ECR image URI in your region:

aws ssm get-parameters-by-path --path /aws/service/aws-for-fluent-bit/

For more see the AWS for Fluent Bit GitHub repository.