connecting AWS SAM Local with dynamodb in docker - amazon-web-services

Question

I've set up an api gateway/aws lambda pair using AWS sam local and confirmed I can call it successfully after running
sam local start-api
I've then added a local dynamodb instance in a docker container and created a table on it using the aws cli
But, having added the code to the lambda to write to the dynamodb instance I receive:
2018-02-22T11:13:16.172Z ed9ab38e-fb54-18a4-0852-db7e5b56c8cd error:
could not write to table: {"message":"connect ECONNREFUSED
0.0.0.0:8000","code":"NetworkingError","errno":"ECONNREFUSED","syscall":"connect","address":"0.0.0.0","port":8000,"region":"eu-west-2","hostname":"0.0.0.0","retryable":true,"time":"2018-02-22T11:13:16.165Z"}
writing event from command:
{"name":"test","geolocation":"xyz","type":"createDestination"} END
RequestId: ed9ab38e-fb54-18a4-0852-db7e5b56c8cd
I saw online that you might need to connect to the same docker network so I created a network docker network create lambda-local and have changed my start commands to:
sam local start-api --docker-network lambda-local
and
docker run -v "$PWD":/dynamodb_local_db -p 8000:8000 --network=lambda-local cnadiminti/dynamodb-local:latest
but still receive the same error
sam local is printing out 2018/02/22 11:12:51 Connecting container 98b19370ab92f3378ce380e9c840177905a49fc986597fef9ef589e624b4eac3 to network lambda-local
I'm creating the dynamodbclient using:
const AWS = require('aws-sdk')
const dynamodbURL = process.env.dynamodbURL || 'http://0.0.0.0:8000'
const awsAccessKeyId = process.env.AWS_ACCESS_KEY_ID || '1234567'
const awsAccessKey = process.env.AWS_SECRET_ACCESS_KEY || '7654321'
const awsRegion = process.env.AWS_REGION || 'eu-west-2'
console.log(awsRegion, 'initialising dynamodb in region: ')
let dynamoDbClient
const makeClient = () => {
dynamoDbClient = new AWS.DynamoDB.DocumentClient({
endpoint: dynamodbURL,
accessKeyId: awsAccessKeyId,
secretAccessKey: awsAccessKey,
region: awsRegion
})
return dynamoDbClient
}
module.exports = {
connect: () => dynamoDbClient || makeClient()
}
and inspecting the dynamodbclient my code is creating shows
DocumentClient {
options:
{ endpoint: 'http://0.0.0.0:8000',
accessKeyId: 'my-key',
secretAccessKey: 'my-secret',
region: 'eu-west-2',
attrValue: 'S8' },
service:
Service {
config:
Config {
credentials: [Object],
credentialProvider: [Object],
region: 'eu-west-2',
logger: null,
apiVersions: {},
apiVersion: null,
endpoint: 'http://0.0.0.0:8000',
httpOptions: [Object],
maxRetries: undefined,
maxRedirects: 10,
paramValidation: true,
sslEnabled: true,
s3ForcePathStyle: false,
s3BucketEndpoint: false,
s3DisableBodySigning: true,
computeChecksums: true,
convertResponseTypes: true,
correctClockSkew: false,
customUserAgent: null,
dynamoDbCrc32: true,
systemClockOffset: 0,
signatureVersion: null,
signatureCache: true,
retryDelayOptions: {},
useAccelerateEndpoint: false,
accessKeyId: 'my-key',
secretAccessKey: 'my-secret' },
endpoint:
Endpoint {
protocol: 'http:',
host: '0.0.0.0:8000',
port: 8000,
hostname: '0.0.0.0',
pathname: '/',
path: '/',
href: 'http://0.0.0.0:8000/' },
_clientId: 1 },
attrValue: 'S8' }
Should this setup work? How do I get them talking to each other?
---- edit ----
Based on a twitter conversation it's worth mentioning (maybe) that I can interact with dynamodb at the CLI and in the web shell

Answer 1

Many thanks to Heitor Lessa who answered me on Twitter with an example repo
Which pointed me at the answer...
dynamodb's docker container is on 127.0.0.1 from the context of my
machine (which is why I could interact with it)
SAM local's docker container is on 127.0.0.1 from the context of my
machine
But they aren't on 127.0.0.1 from each other's context
So: https://github.com/heitorlessa/sam-local-python-hot-reloading/blob/master/users/users.py#L14
Pointed me at changing my connection code to:
const AWS = require('aws-sdk')
const awsRegion = process.env.AWS_REGION || 'eu-west-2'
let dynamoDbClient
const makeClient = () => {
const options = {
region: awsRegion
}
if(process.env.AWS_SAM_LOCAL) {
options.endpoint = 'http://dynamodb:8000'
}
dynamoDbClient = new AWS.DynamoDB.DocumentClient(options)
return dynamoDbClient
}
module.exports = {
connect: () => dynamoDbClient || makeClient()
}
with the important lines being:
if(process.env.AWS_SAM_LOCAL) {
options.endpoint = 'http://dynamodb:8000'
}
from the context of the SAM local docker container the dynamodb container is exposed via its name
My two startup commands ended up as:
docker run -d -v "$PWD":/dynamodb_local_db -p 8000:8000 --network lambda-local --name dynamodb cnadiminti/dynamodb-local
and
AWS_REGION=eu-west-2 sam local start-api --docker-network lambda-local
with the only change here being to give the dynamodb container a name

Answer 2

If your using sam-local on a mac like alot of devs you should be able to just use
options.endpoint = "http://docker.for.mac.localhost:8000"
Or on newer installs of docker https://docs.docker.com/docker-for-mac/release-notes/#docker-community-edition-18030-ce-mac59-2018-03-26
options.endpoint = "http://host.docker.internal:8000"
Instead of having to do multiple commands like Paul showed above (but that might be more platform agnostic?).

Answer 3

The other answers were too overly complicated / unclear for me. Here is what I came up with.
Step 1: use docker-compose to get DynamoDB local running on a custom network
docker-compose.yml
Note the network name abp-sam-backend, service name dynamo and that dynamo service is using the backend network.
version: '3.5'
services:
dynamo:
container_name: abp-sam-nestjs-dynamodb
image: amazon/dynamodb-local
networks:
- backend
ports:
- '8000:8000'
volumes:
- dynamodata:/home/dynamodblocal
working_dir: /home/dynamodblocal
command: '-jar DynamoDBLocal.jar -sharedDb -dbPath .'
networks:
backend:
name: abp-sam-backend
volumes:
dynamodata: {}
Start DyanmoDB local container via:
docker-compose up -d dynamo
Step 2: Write your code to handle local DynamoDB endpoint
import { DynamoDB, Endpoint } from 'aws-sdk';
const ddb = new DynamoDB({ apiVersion: '2012-08-10' });
if (process.env['AWS_SAM_LOCAL']) {
ddb.endpoint = new Endpoint('http://dynamo:8000');
} else if ('local' == process.env['APP_STAGE']) {
// Use this when running code directly via node. Much faster iterations than using sam local
ddb.endpoint = new Endpoint('http://localhost:8000');
}
Note that I'm using the hostname alias dynamo. This alias is auto-created for me by docker inside the abp-sam-backend network. The alias name is just the service name.
Step 3: Launch the code via sam local
sam local start-api -t sam-template.yml --docker-network abp-sam-backend --skip-pull-image --profile default --parameter-overrides 'ParameterKey=StageName,ParameterValue=local ParameterKey=DDBTableName,ParameterValue=local-SingleTable'
Note that I'm telling sam local to use the existing network abp-sam-backend that was defined in my docker-compose.yml
End-to-end example
I made a working example (plus a bunch of other features) that can be found at https://github.com/rynop/abp-sam-nestjs

Answer 4

SAM starts a docker container lambci/lambda under the hood, if you have another container hosting dynamodb for example or any other services to which you want to connect your lambda, so you should have both in the same network
Suppose dynamodb (notice --name, this is the endpoint now)
docker run -d -p 8000:8000 --name DynamoDBEndpoint amazon/dynamodb-local
This will result in something like this
0e35b1c90cf0....
To know which network this was created inside:
docker inspect 0e35b1c90cf0
It should give you something like
...
Networks: {
"services_default": {//this is the <<myNetworkName>>
....
If you know your networks and want to put docker container inside specific network, you can save the above steps and do this in one command while starting container using --network option
docker run -d -p 8000:8000 --network myNetworkName --name DynamoDBEndpoint amazon/dynamodb-local
Important: Your lambda code now should have endpoint to dynamo to DynamoDBEndpoint
To say for example:
if(process.env.AWS_SAM_LOCAL) {
options.endpoint = 'http://DynamoDBEndpoint:8000'
}
Testing everything out:
Using lambci:lambda
This should only list all tables inside your other dynamodb container
docker run -ti --rm --network myNetworkName lambci/lambda:build-go1.x \
aws configure set aws_access_key_id "xxx" && \
aws configure set aws_secret_access_key "yyy" && \
aws --endpoint-url=http://DynamoDBEndpoint:4569 --region=us-east-1 dynamodb list-tables
Or to invoke a function: (Go Example, same as NodeJS)
#Golang
docker run --rm -v "$PWD":/var/task lambci/lambda:go1.x handlerName '{"some": "event"}'
#Same for NodeJS
docker run --rm -v "$PWD":/var/task lambci/lambda:nodejs10.x index.handler
More Info about lambci/lambda can be found here
Using SAM (which uses the same container lmabci/lambda):
sam local invoke --event myEventData.json --docker-network myNetworkName MyFuncName
You can always use --debug option in case you want to see more details.
Alternatively, You can also use http://host.docker.internal:8000 without the hassle of playing with docker, this URL is reserved internally and gives you an access to your host machine but make sure you expose port 8000 when you start dynamodb container. Although it is quite easy but it doesn't work in all operating systems. For more details about this feature, please check docker documentation

Answer 5

As #Paul mentioned, it is about configuring your network between the docker containers - lambda and database.
Another approach that worked for me (using docker-compose).
docker-compose:
version: '2.1'
services:
db:
image: ...
ports:
- "3306:3306"
networks:
- my_network
environment:
...
volumes:
...
networks:
my_network:
Then, after docker-compose up, running docker network ls will show:
NETWORK ID NAME DRIVER SCOPE
7eb440d5c0e6 dev_my_network bridge local
My docker container name is dev_db_1.
My js code is:
const connection = mysql.createConnection({
host: "dev_db_1",
port: 3306,
...
});
Then, running the sam command:
sam local invoke --docker-network dev_my_network -e my.json
Stack:
Docker: 18.03.1-ce
Docker-compose: 1.21.1
MacOS HighSierra 10.13.6

Answer 6

If you are using LocalStack to run DynamoDB, I believe the correct command to use the LocalStack network for SAM is:
sam local start-api --env-vars env.json --docker-network localstack_default
And in your code, the LocalStack hostname should be localstack_localstack_1
const dynamoDbDocumentClient = new AWS.DynamoDB.DocumentClient({
endpoint: process.env.AWS_SAM_LOCAL ?
'http://localstack_localstack_1:4569' :
undefined,
});
However, I launched LocalStack using docker-compose up. Using the pip CLI tool to launch LocalStack may result in different identifiers.

Answer 7

This may be helpful for someone who are still facing the same issue:
I also faced the same problem recently. I followed all the steps mentioned by rynop (Thanks #rynop)
I fixed the issue (on my windows) by replacing the endpoint (http://localhost:8000) with my (private) IP address (i.e http://192.168.8.101:8000) in the following code:
import { DynamoDB, Endpoint } from 'aws-sdk';
const ddb = new DynamoDB({ apiVersion: '2012-08-10' });
if (process.env['AWS_SAM_LOCAL']) {
ddb.endpoint = new Endpoint('http://dynamo:8000');
} else if ('local' == process.env['APP_STAGE']) {
// Use this when running code directly via node. Much faster iterations than using sam local
ddb.endpoint = new Endpoint('http://localhost:8000');
}