Lambda
The benthos-lambda
distribution is a version of Benthos specifically tailored
for deployment as an AWS Lambda function on the go1.x
runtime,
which runs Amazon Linux on the x86_64
architecture.
The benthos-lambda-al2
distribution supports the provided.al2
runtime,
which runs Amazon Linux 2 on either the x86_64
or arm64
architecture.
Rather than bundle the distribution and configs yourself, check out makenew/serverless-benthos, which makes quick work of deploying a Benthos serverless project on AWS Lambda. For building and deploying distributions with custom plugins, look at makenew/benthos-plugin.
It uses the same configuration format as a regular Benthos instance, which can be provided in 1 of 2 ways:
- Inline via the
BENTHOS_CONFIG
environment variable (YAML format). - Via the filesystem using a layer, extension, or container image. By default,
the
benthos-lambda
distribution will look for a valid configuration file in the locations listed below. Alternatively, the configuration file path can be set explicity by passing aBENTHOS_CONFIG_PATH
environment variable.
./benthos.yaml
./config.yaml
/benthos.yaml
/etc/benthos/config.yaml
/etc/benthos.yaml
Also, the http
, input
and buffer
sections are ignored as the service wide
HTTP server is not used, and messages are inserted via function invocations.
If the output
section is omitted in your config then the result of the
processing pipeline is returned back to the caller, otherwise the resulting data
is sent to the output destination.
Running with an output
The flow of a Benthos lambda function with an output configured looks like this:
benthos-lambda
+------------------------------+
| |
-------> Processors ----> Output -----> Somewhere
invoke | | |
<-------------------------------------------/
| <Ack/Noack> |
| |
+------------------------------+
Where the call will block until the output target has confirmed receipt of the
resulting payload. When the message is successfully propagated a JSON payload is
returned of the form {"message":"request successful"}
, otherwise an error is
returned containing the reason for the failure.
Running without an output
The flow when an output is not configured looks like this:
benthos-lambda
+--------------------+
| |
-------> Processors --\ |
invoke | | |
<---------------------/ |
| <Result> |
| |
+--------------------+
Where the function returns the result of processing directly back to the caller. The format of the result differs depending on the number of batches and messages of a batch that resulted from the invocation:
- Single message of a single batch:
{}
(JSON object) - Multiple messages of a single batch:
[{},{}]
(Array of JSON objects) - Multiple batches:
[[{},{}],[{}]]
(Array of arrays of JSON objects, batches of size one are a single object array in this case)
Processing Errors
The default behaviour of a Benthos lambda is that the handler will not return an error unless the output fails. This means that errors that occur within your processors will not result in the handler failing, which will instead return the final state of the message.
In the next major version release (V4) this will change and the handler will
fail if messages have encountered an uncaught error during execution. However,
in the meantime it is possible to configure your output to use the new
reject
output in order to trigger a handler error on
processor errors:
output:
switch:
retry_until_success: false
cases:
- check: '!errored()'
output:
sync_response: {}
- output:
reject: "processing failed due to: ${! error() }"
Running a combination
It's possible to configure pipelines that send messages to third party
destinations and also return a result back to the caller. This is done by
configuring an output block and including an output of the type
sync_response
.
For example, if we wished for our lambda function to send a payload to Kafka and also return the same payload back to the caller we could use a broker:
output:
broker:
pattern: fan_out
outputs:
- kafka:
addresses:
- todo:9092
client_id: benthos_serverless
topic: example_topic
- sync_response: {}
Upload to AWS
go1.x on x86_64
Grab an archive labelled benthos-lambda
from the releases page
page and then create your function:
LAMBDA_ENV=`cat yourconfig.yaml | jq -csR {Variables:{BENTHOS_CONFIG:.}}`
aws lambda create-function \
--runtime go1.x \
--handler benthos-lambda \
--role benthos-example-role \
--zip-file fileb://benthos-lambda.zip \
--environment "$LAMBDA_ENV" \
--function-name benthos-example
There is also an example SAM template and Terraform resource in the repo to copy from.
provided.al2 on amd64
Grab an archive labelled benthos-lambda-al2
for arm64
from the releases page
page and then create your function (AWS CLI v2 only):
LAMBDA_ENV=`cat yourconfig.yaml | jq -csR {Variables:{BENTHOS_CONFIG:.}}`
aws lambda create-function \
--runtime provided.al2 \
--architectures arm64 \
--handler not.used.for.provided.al2.runtime \
--role benthos-example-role \
--zip-file fileb://benthos-lambda.zip \
--environment "$LAMBDA_ENV" \
--function-name benthos-example
There is also an example SAM template and Terraform resource in the repo to copy from.
Note that you can also run benthos-lambda-al2
on x86_64, just use the amd64
zip instead.
Invoke
aws lambda invoke \
--function-name benthos-example \
--payload '{"your":"document"}' \
out.txt && cat out.txt && rm out.txt
Build
You can build and archive the function yourself with:
go build github.com/benthosdev/benthos/v4/cmd/serverless/benthos-lambda
zip benthos-lambda.zip benthos-lambda