AWS Cloudwatch Logs Sink

The Vector aws_cloudwatch_logs sink batches log events to Amazon Web Service's CloudWatch Logs service via the PutLogEvents API endpoint.

Configuration

  • Common
  • Advanced
vector.toml
[sinks.my_sink_id]
# REQUIRED
type = "aws_cloudwatch_logs" # must be: "aws_cloudwatch_logs"
inputs = ["my-source-id"] # example
group_name = "{{ file }}" # example
region = "us-east-1" # example
stream_name = "{{ instance_id }}" # example
# OPTIONAL
create_missing_group = true # default
create_missing_stream = true # default

Options

12 items
stringoptional

assume_role

The ARN of an IAM role to assume at startup.

No default
View examples
tableoptional

batch

Configures the sink batching behavior.

intbytesoptional

max_events

The maximum size of a batch before it is flushed. See Buffers & Batches for more info.

Default: 1049000
View examples
intsecondsoptional

timeout_secs

The maximum age of a batch before it is flushed. See Buffers & Batches for more info.

Default: 1
View examples
tableoptional

buffer

Configures the sink buffer behavior.

inteventsoptional

max_events

The maximum number of events allowed in the buffer. See Buffers & Batches for more info.

Default: 500
Only relevant when: type = "memory"
View examples
intbytesoptional

max_size

The maximum size of the buffer on the disk.

No default
Only relevant when: type = "disk"
View examples
stringenumoptional

type

The buffer's type / location. disk buffers are persistent and will be retained between restarts.

Default: "memory"
Enum, must be one of: "memory" "disk"
View examples
stringenumoptional

when_full

The behavior when the buffer becomes full.

Default: "block"
Enum, must be one of: "block" "drop_newest"
View examples
commonbooloptional

create_missing_group

Dynamically create a log group if it does not already exist. This will ignore create_missing_stream directly after creating the group and will create the first stream.

Default: true
View examples
commonbooloptional

create_missing_stream

Dynamically create a log stream if it does not already exist.

Default: true
View examples
stringenumoptional

encoding

The encoding format used to serialize the events before outputting.

No default
Enum, must be one of: "json" "text"
View examples
stringoptional

endpoint

Custom endpoint for use with AWS-compatible services. Providing a value for this option will make region moot.

No default
View examples
commontemplateablestringrequired

group_name

The group name of the target CloudWatch Logs stream. See Partitioning and Template Syntax for more info.

No default
View examples
booloptional

healthcheck

Enables/disables the sink healthcheck upon start. See Health Checks for more info.

Default: true
View examples
commonstringrequired

region

The AWS region of the target service. If endpoint is provided it will override this value since the endpoint includes the region.

No default
View examples
tableoptional

request

Configures the sink request behavior.

intoptional

in_flight_limit

The maximum number of in-flight requests allowed at any given time. See Rate Limits for more info.

Default: 5
View examples
intsecondsoptional

rate_limit_duration_secs

The window used for the rate_limit_num option See Rate Limits for more info.

Default: 1
View examples
intoptional

rate_limit_num

The maximum number of requests allowed within the rate_limit_duration_secs window. See Rate Limits for more info.

Default: 5
View examples
intoptional

retry_attempts

The maximum number of retries to make for failed requests. See Retry Policy for more info.

Default: 5
View examples
intsecondsoptional

retry_initial_backoff_secs

The amount of time to wait before attempting the first retry for a failed request. Once, the first retry has failed the fibonacci sequence will be used to select future backoffs.

Default: 1
View examples
intsecondsoptional

retry_max_duration_secs

The maximum amount of time to wait between retries.

Default: 10
View examples
intsecondsoptional

timeout_secs

The maximum time a request can take before being aborted. It is highly recommended that you do not lower value below the service's internal timeout, as this could create orphaned requests, pile on retries, and result in deuplicate data downstream. See Buffers & Batches for more info.

Default: 30
View examples
commontemplateablestringrequired

stream_name

The stream name of the target CloudWatch Logs stream. See Partitioning and Template Syntax for more info.

No default
View examples

Env Vars

2 items
stringoptional

AWS_ACCESS_KEY_ID

Used for AWS authentication when communicating with AWS services. See relevant AWS components for more info. See AWS Authentication for more info.

No default
View examples
stringoptional

AWS_SECRET_ACCESS_KEY

Used for AWS authentication when communicating with AWS services. See relevant AWS components for more info. See AWS Authentication for more info.

No default
View examples

Output

The aws_cloudwatch_logs sink batches log events to Amazon Web Service's CloudWatch Logs service via the PutLogEvents API endpoint. Batches are flushed via the batch_size or batch_timeout options. You can learn more in the buffers & batches section. For example:

POST / HTTP/1.1
Host: logs.<region>.<domain>
X-Amz-Date: <date>
Accept: application/json
Content-Type: application/x-amz-json-1.1
Content-Length: <byte_size>
Connection: Keep-Alive
X-Amz-Target: Logs_20140328.PutLogEvents
{
"logGroupName": "<group_name>",
"logStreamName": "<stream_name>",
"logEvents": [
{
"timestamp": <log_timestamp>,
"message": "<json_encoded_log>"
},
{
"timestamp": <log_timestamp>,
"message": "<json_encoded_log>"
},
{
"timestamp": <log_timestamp>,
"message": "<json_encoded_log>"
}
]
}

How It Works

AWS Authentication

Vector checks for AWS credentials in the following order:

  1. Environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY.
  2. The credential_process command in the AWS config file. (usually located at ~/.aws/config)
  3. The AWS credentials file. (usually located at ~/.aws/credentials)
  4. The IAM instance profile. (will only work if running on an EC2 instance with an instance profile/role)

If credentials are not found the healtcheck will fail and an error will be logged.

Obtaining an access key

In general, we recommend using instance profiles/roles whenever possible. In cases where this is not possible you can generate an AWS access key for any user within your AWS account. AWS provides a detailed guide on how to do this.

Buffers & Batches

The aws_cloudwatch_logs sink buffers & batches data as shown in the diagram above. You'll notice that Vector treats these concepts differently, instead of treating them as global concepts, Vector treats them as sink specific concepts. This isolates sinks, ensuring services disruptions are contained and delivery guarantees are honored.

Batches are flushed when 1 of 2 conditions are met:

  1. The batch age meets or exceeds the configured timeout_secs.
  2. The batch size meets or exceeds the configured max_events.

Buffers are controlled via the buffer.* options.

Environment Variables

Environment variables are supported through all of Vector's configuration. Simply add ${MY_ENV_VAR} in your Vector configuration file and the variable will be replaced before being evaluated.

You can learn more in the Environment Variables section.

Health Checks

Health checks ensure that the downstream service is accessible and ready to accept data. This check is performed upon sink initialization. If the health check fails an error will be logged and Vector will proceed to start.

Require Health Checks

If you'd like to exit immediately upon a health check failure, you can pass the --require-healthy flag:

vector --config /etc/vector/vector.toml --require-healthy

Disable Health Checks

If you'd like to disable health checks for this sink you can set the healthcheck option to false.

Partitioning

Partitioning is controlled via the group_name and stream_name options and allows you to dynamically partition data on the fly. You'll notice that Vector's template sytax is supported for these options, enabling you to use field values as the partition's key.

Rate Limits

Vector offers a few levers to control the rate and volume of requests to the downstream service. Start with the rate_limit_duration_secs and rate_limit_num options to ensure Vector does not exceed the specified number of requests in the specified window. You can further control the pace at which this window is saturated with the in_flight_limit option, which will guarantee no more than the specified number of requests are in-flight at any given time.

Please note, Vector's defaults are carefully chosen and it should be rare that you need to adjust these. If you found a good reason to do so please share it with the Vector team by opening an issie.

Retry Policy

Vector will retry failed requests (status == 429, >= 500, and != 501). Other responses will not be retried. You can control the number of retry attempts and backoff rate with the retry_attempts and retry_backoff_secs options.

Template Syntax

The group_name and stream_name options support Vector's template syntax, enabling dynamic values derived from the event's data. This syntax accepts strptime specifiers as well as the {{ field_name }} syntax for accessing event fields. For example:

vector.toml
[sinks.my_aws_cloudwatch_logs_sink_id]
# ...
group_name = "{{ file }}"
group_name = "ec2/{{ instance_id }}"
group_name = "group-name"
# ...

You can read more about the complete syntax in the template syntax section.