aws_cloudwatch_logs sink

Batches `log` events to AWS CloudWatch Logs via the `PutLogEvents` API endpoint.

The aws_cloudwatch_logs sink is in beta. Please see the current enhancements and bugs for known issues. We kindly ask that you add any missing issues as it will help shape the roadmap of this component.

The aws_cloudwatch_logs sink batches log events to AWS CloudWatch Logs via the PutLogEvents API endpoint.

Config File

vector.toml (example)
vector.toml (schema)
vector.toml (specification)
# REQUIRED - General
type = "aws_cloudwatch_logs" # must be: "aws_cloudwatch_logs"
inputs = ["my-source-id"]
group_name = "/var/log/{{ file }}.log"
region = "us-east-1"
stream_name = "{{ instance_id }}"
# OPTIONAL - General
create_missing_group = true # default
create_missing_stream = true # default
healthcheck = true # default
hostname = ""
# OPTIONAL - Batching
batch_size = 1049000 # default, bytes
batch_timeout = 1 # default, seconds
# OPTIONAL - Requests
encoding = "json" # no default, enum: "json" or "text"
rate_limit_duration = 1 # default, seconds
rate_limit_num = 5 # default
request_in_flight_limit = 5 # default
request_timeout_secs = 30 # default, seconds
retry_attempts = 5 # default
retry_backoff_secs = 5 # default, seconds
# OPTIONAL - Buffer
type = "memory" # default, enum: "memory" or "disk"
when_full = "block" # default, enum: "block" or "drop_newest"
max_size = 104900000 # no default, bytes, relevant when type = "disk"
num_items = 500 # default, events, relevant when type = "memory"





REQUIRED - General



The component type required must be: "aws_cloudwatch_logs"



A list of upstream source or transform IDs. See Config Composition for more info. required example: ["my-source-id"]



The group name of the target CloudWatch Logs stream.This option supports dynamic values via Vector's template syntax. See Partitioning and Template Syntax for more info. required example: "/var/log/{{ file }}.log"



The AWS region of the target CloudWatch Logs stream resides. required example: "us-east-1"



The stream name of the target CloudWatch Logs stream.This option supports dynamic values via Vector's template syntax. See Partitioning and Template Syntax for more info. required example: "{{ instance_id }}"

OPTIONAL - General



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



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



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



Custom hostname to send requests to. Useful for testing. default: "<aws-service-hostname>"

OPTIONAL - Batching



The maximum size of a batch before it is flushed. See Buffers & Batches for more info. default: 1049000 unit: bytes



The maximum age of a batch before it is flushed. See Buffers & Batches for more info. default: 1 unit: seconds

OPTIONAL - Requests



The encoding format used to serialize the events before flushing. The default is dynamic based on if the event is structured or not. See Encodings for more info. no default enum: "json" or "text"



The window used for the request_rate_limit_num option See Rate Limits for more info. default: 1 unit: seconds



The maximum number of requests allowed within the rate_limit_duration window. See Rate Limits for more info. default: 5



The maximum number of in-flight requests allowed at any given time. See Rate Limits for more info. default: 5



The maximum time a request can take before being aborted. See Timeouts for more info. default: 30 unit: seconds



The maximum number of retries to make for failed requests. See Retry Policy for more info. default: 5



The amount of time to wait before attempting a failed request again. See Retry Policy for more info. default: 5 unit: seconds




The buffer's type / location. disk buffers are persistent and will be retained between restarts. default: "memory" enum: "memory" or "disk"



The behavior when the buffer becomes full. default: "block" enum: "block" or "drop_newest"



The maximum size of the buffer on the disk. Only relevant when type = "disk" no default example: 104900000 unit: bytes



The maximum number of events allowed in the buffer. Only relevant when type = "memory" default: 500 unit: events


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": <timestamp>,
"message": "<encoded_event>"
"timestamp": <timestamp>,
"message": "<encoded_event>"
"timestamp": <timestamp>,
"message": "<encoded_event>"

How It Works


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)

  2. 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.

Buffers types

The buffer.type option allows you to control buffer resource usage:




Pros: Fast. Cons: Not persisted across restarts. Possible data loss in the event of a crash. Uses more memory.


Pros: Persisted across restarts, durable. Uses much less memory. Cons: Slower, see below.

Buffer overflow

The buffer.when_full option allows you to control the behavior when the buffer overflows:




Applies back pressure until the buffer makes room. This will help to prevent data loss but will cause data to pile up on the edge.


Drops new data as it's received. This data is lost. This should be used when performance is the highest priority.

Batch flushing

Batches are flushed when 1 of 2 conditions are met:

  1. The batch age meets or exceeds the configured batch_timeout (default: 1 seconds).

  2. The batch size meets or exceeds the configured batch_size (default: 1049000 bytes).

Delivery Guarantee

This component offers an at least once delivery guarantee if your pipeline is configured to achieve this.


The aws_cloudwatch_logs sink encodes events before writing them downstream. This is controlled via the encoding option which accepts the following options:




The payload will be encoded as a single JSON payload.


The payload will be encoded as new line delimited text, each line representing the value of the "message" key.

Dynamic encoding

By default, the encoding chosen is dynamic based on the explicit/implcit nature of the event's structure. For example, if this event is parsed (explicit structuring), Vector will use json to encode the structured data. If the event was not explicitly structured, the text encoding will be used.

To further explain why Vector adopts this default, take the simple example of accepting data over the tcp source and then connecting it directly to the aws_cloudwatch_logs sink. It is less surprising that the outgoing data reflects the incoming data exactly since it was not explicitly structured.

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

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

And finally, if you'd like to disable health checks entirely for this sink you can set the healthcheck option to false.


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 strftime specifiers are allowed in the values, enabling this partitioning. The interpolated result is effectively the internal partition key. Let's look at a few examples:






Partitions data by the event's day.



Partitions data by the event's year.



Partitions data by the unix timestamp.

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 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 request_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 strftime specifiers as well as the {{ field_name }} syntax for accessing event fields. For example:

# ...
group_name = "/var/log/{{ file }}.log"
group_name = "ec2/{{ instance_id }}"
# ...

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


To ensure the pipeline does not halt when a service fails to respond Vector will abort requests after 30 seconds. This can be adjsuted with the request_timeout_secs option.

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.


The best place to start with troubleshooting is to check the Vector logs. This is typically located at /var/log/vector.log, then proceed to follow the Troubleshooting Guide.

If the Troubleshooting Guide does not resolve your issue, please:

  1. If encountered a bug, please file a bug report.

  2. If encountered a missing feature, please file a feature request.

  3. If you need help, join our chat/forum community. You can post a question and search previous questions.