Use Environment Variables in Lambda Functions

Back in the Configure DynamoDB in Serverless chapter, we are creating our table through CloudFormation. The table that is created is based on the stage we are currently in. This means that in our Lambda functions when we talk to our database, we cannot simply hard code the table names. Since, in the dev stage it would be called dev-notes and in prod it’ll be called prod-notes.

This requires us to use environment variables in our Lambda functions to figure out which table we should be talking to. Currently, if you pull up create.js you’ll notice the following section.

const params = {
  TableName: "notes",
  Item: {
    userId: event.requestContext.identity.cognitoIdentityId,
    noteId: uuid.v1(),
    content: data.content,
    attachment: data.attachment,
    createdAt: new Date().getTime()
  }
};

We need to change the TableName: "notes" line to use the relevant table name. In the Configure DynamoDB in Serverless chapter, we also added tableName: to our serverless.yml under the environment: block.

# These environment variables are made available to our functions
# under process.env.
environment:
  tableName:
    Ref: NotesTable

As we noted there, we can reference this in our Lambda functions as process.env.tableName.

So let’s go ahead and make the change.

Replace this line in create.js.

TableName: "notes",

with this:

TableName: process.env.tableName,

Similarly, in the get.js, replace this:

TableName: "notes",

with this:

TableName: process.env.tableName,

In list.js, replace this:

TableName: "notes",

with this:

TableName: process.env.tableName,

Also in update.js, replace this:

TableName: "notes",

with this:

TableName: process.env.tableName,

Finally in delete.js, replace this:

TableName: "notes",

with this:

TableName: process.env.tableName,

Commit Your Code

Make sure to commit your code using:

$ git add .
$ git commit -m "Use environment variables in our functions"

Next let’s deploy our newly configured serverless backend API.