Invoke Services from Lambda Functions
This topic describes how to invoke services in the mesh from Lambda functions registered with Consul.
Lambda-to-mesh functionality is currently in beta: Functionality associated with beta features are subject to change. You should never use the beta release in secure environments or production scenarios. Features in beta may have performance issues, scaling issues, and limited support.
Introduction
The following steps describe the process:
- Deploy the destination service and mesh gateway.
- Deploy the Lambda extension layer.
- Deploy the Lambda registrator.
- Write the Lambda function code.
- Deploy the Lambda function.
- Invoke the Lambda function.
You must add the consul-lambda-extension
extension as a Lambda layer to enable Lambda functions to send requests to mesh services. Refer to the AWS Lambda documentation for instructions on how to add layers to your Lambda functions.
The layer runs an external Lambda extension that starts a sidecar proxy. The proxy listens on one port for each upstream service and upgrades the outgoing connections to mTLS. It then proxies the requests through to mesh gateways.
Prerequisites
You must deploy the destination services and mesh gateway prior to deploying your Lambda service with the consul-lambda-extension
layer.
Deploy the destination service
There are several methods for deploying services to Consul service mesh. The following example configuration deploys a service named static-server
with Consul on Kubernetes.
Deploy the mesh gateway
The mesh gateway must be running and registered to the Lambda function’s Consul datacenter. Refer to the following documentation and tutorials for instructions:
- Mesh Gateways between WAN-Federated Datacenters
- Mesh Gateways between Admin Partitions
- Establish cluster peering connections
- Connect Services Across Datacenters with Mesh Gateways
Deploy the Lambda extension layer
The consul-lambda-extension
extension runs during the Init
phase of the Lambda function execution. The extension retrieves the data that the Lambda registrator has been configured to store from AWS Parameter Store and creates a lightweight TCP proxy. The proxy creates a local listener for each upstream defined in the CONSUL_SERVICE_UPSTREAMS
environment variable.
The extension periodically retrieves the data from the AWS Parameter Store so that the function can process requests. When the Lambda function receives a shutdown event, the extension also stops.
Download the
consul-lambda-extension
extension from releases.hashicorp.com:Create the AWS Lambda layer in the same AWS region as the Lambda function. You can create the layer manually using the AWS CLI or AWS Console, but we recommend using Terraform:
consul-lambda-extension.tf
Deploy the Lambda registrator
Configure and deploy the Lambda registrator. Refer to the registrator configuration documentation and the registrator deployment documentation for instructions.
Write the Lambda function code
Refer to the AWS Lambda documentation for instructions on how to write a Lambda function. In the following example, the function calls an upstream service on port 2345
:
Deploy the Lambda function
Create and apply an IAM policy that allows the Lambda function’s role to fetch the Lambda extension’s data from the AWS Parameter Store. The following example, creates an IAM role for the Lambda function, creates an IAM policy with the necessary permissions and attaches the policy to the role:
lambda-iam-policy.tfConfigure and deploy the Lambda function. Refer to the Lambda extension configuration reference for information about all available options. There are several methods for deploying Lambda functions. The following example uses Terraform to deploy a function that can invoke the
static-server
upstream service using mTLS data stored under the/lambda_extension_data
prefix:lambda-function.tfRun the
terraform apply
command and Consul automatically configures a service for the Lambda function.
Lambda extension configuration
Define the following environment variables in your Lambda functions to configure the Lambda extension. The variables apply to each Lambda function in your environment:
Variable | Description | Default |
---|---|---|
CONSUL_MESH_GATEWAY_URI | Specifies the URI where the mesh gateways that the plugin makes requests are running. The mesh gateway should be registered in the same Consul datacenter and partition that the service is running in. For optimal performance, this mesh gateway should run in the same AWS region. | none |
CONSUL_EXTENSION_DATA_PREFIX | Specifies the prefix that the plugin pulls configuration data from. The data must be located in the following directory: "${CONSUL_EXTENSION_DATA_PREFIX}/${CONSUL_SERVICE_PARTITION}/${CONSUL_SERVICE_NAMESPACE}/<lambda-function-name>" | none |
CONSUL_SERVICE_NAMESPACE | Specifies the Consul namespace the service is registered into. | default |
CONSUL_SERVICE_PARTITION | Specifies the Consul partition the service is registered into. | default |
CONSUL_REFRESH_FREQUENCY | Specifies the amount of time the extension waits before re-pulling data from the Parameter Store. Use Go time.Duration string values, for example, "30s" . The time is added to the duration configured in the Lambda registrator sync_frequency_in_minutes configuration. Refer to Lambda registrator configuration options. The combined configurations determine how stale the data may become. Lambda functions can run for up to 14 hours, so we recommend configuring a value that results in acceptable staleness for certificates. | "5m" |
CONSUL_SERVICE_UPSTREAMS | Specifies a comma-separated list of upstream services that the Lambda function can call. Specify the value as an unlabelled annotation according to the consul.hashicorp.com/connect-service-upstreams annotation format in Consul on Kubernetes. For example, "[service-name]:[port]:[optional-datacenter]" | none |
Invoke the Lambda function
If intentions are enabled in the Consul service mesh, you must create an intention that allows the Lambda function's Consul service to invoke all upstream services prior to invoking the Lambda function. Refer to Service mesh intentions for additional information.
There are several ways to invoke Lambda functions. In the following example, the aws lambda invoke
CLI command invokes the function: