Example: Integrating data across multiple S3 accounts

This example illustrates how to create an API that merges data from two separate S3 buckets each under separate AWS accounts.

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We have been given two sets of credentials for two different S3 buckets, each of which contains JSON files of a specific format.

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If you want to try this example, you can deploy the following endpoint:

Read dta from S3 buckets across separate AWS accounts

Learn how to serve data live from two S3 buckets across two separate AWS accounts.

Overview

Usage:

/aws/s3/buckets

Code

main() =
    let
        // The type of each JSON file
        json_type = type record(creation_date: string, entries: list(record(hostname: string))),
        // Function returning the concatenated list of hostnames for a specific path & aws_config
        read_logs(bucket: string, path: string, aws_config: record(region: string, accessKey: string, secret: string)) =
            let
                // list all files of the bucket path
                bucket = S3.Build(
                    bucket,
                    path,
                    region = aws_config.region,
                    accessKey = aws_config.accessKey,
                    secretKey = aws_config.secret
                ),
                files = Location.Ls(bucket),
                // open each file as JSON
                contents = List.Transform(files, (f) -> Json.Read(f, json_type)),
                // `Explode` the entries field
                entries = List.Explode(contents, (c) -> c.entries)
            in
                // project only the 'hostname' column to obtain the expected list of strings
                entries.hostname
    in
        let
            awsAccountA = {
                region: "eu-west-1",
                accessKey: "AKIAZ6SK5NCTDAAESLXU",
                secret: "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"
            },
            awsAccountB = {
                region: "eu-west-1",
                accessKey: "AKIAZ6SK5NCTLPK7QE4N",
                secret: "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"
            }
        in
            // Union the lists returned by `read_logs` for both buckets/accounts.
            List.Union(
                read_logs("log-server-a", "/*.json", awsAccountA),
                read_logs("log-server-b", "/*.json", awsAccountB)
            )

Here's for example a file found in bucket s3://log-server-a.

{
    "creation_date": "2022-04-01",
    "entries": [{"hostname": "host01"}, {"hostname": "host02"}]
}

Here's a file found in the second bucket s3://log-server-b.

{
    "creation_date": "2022-04-03",
    "entries": [{"hostname": "host95"}, {"hostname": "host96"}, {"hostname": "host97"}]
}

We're interested in the content of the entries field of these JSON files. Our goal is to read every JSON file across both buckets and merge their entries lists into a single one.

["host01","host02", ...., "host95","host96","host97"]

The code executed by the REST API works as follows.

The read_logs function computes the list of all hostnames found in a given bucket.

read_logs(bucket: string, path: string, aws_config: record(region: string, accessKey: string, secret: string)) =
    let
        // list all files of the bucket path
        bucketLocation = S3.Build(
            bucket,
            path,
            region = aws_config.region,
            accessKey = aws_config.accessKey,
            secretKey = aws_config.secret
        ),
        files = Location.Ls(bucketLocation),
        // open each file as JSON
        contents = List.Transform(files, f -> Json.Read(f, json_type)),
        // `Explode` the entries field
        entries = List.Explode(contents, c -> c.entries)
    in
        // project only the 'hostname' column to obtain the expected list of strings
        entries.hostname

read_logs is called on both s3://log-server-a and s3://log-server-b with the corresponding set of credentials.

let
    awsAccountA = {region: "eu-west-1", accessKey: "<access-key-for-a>", secret: "<secret-for-a>"},
    awsAccountB = {region: "eu-west-1", accessKey: "<access-key-for-b>", secret: "<secret-for-b>"}
    // Union the lists returned by `read_logs` for both buckets/accounts.
    in List.Union(
        read_logs("log-bucket-a", "/*.json", awsAccountA),
        read_logs("log-bucket-b", "/*.json", awsAccountB)
    )

warning

Never store sensitive information as clear text in the code. Instead use secrets, which are key/value pairs that are stored securely outside of the source code. Secrets can be accessed using the built-in function Environment.Secret.

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