Terraform AWS Athena to use Glue catalog as db

Question

I'm confused as to how I should use terraform to connect Athena to my Glue Catalog database.

I use

resource "aws_glue_catalog_database" "catalog_database" {
    name = "${var.glue_db_name}"
}

resource "aws_glue_crawler" "datalake_crawler" {
    database_name = "${var.glue_db_name}"
    name          = "${var.crawler_name}"
    role          = "${aws_iam_role.crawler_iam_role.name}"
    description   = "${var.crawler_description}"
    table_prefix  = "${var.table_prefix}"
    schedule      = "${var.schedule}" 

    s3_target {
      path = "s3://${var.data_bucket_name[0]}"
  }
    s3_target {
      path = "s3://${var.data_bucket_name[1]}"
  }
 }

to create a Glue DB and the crawler to crawl an s3 bucket (here only two), but I don't know how I link the Athena query service to the Glue DB. In the terraform documentation for Athena, there doesn't appear to be a way to connect Athena to a Glue catalog but only to an S3 Bucket. Clearly, however, Athena can be integrated with Glue.

How can I terraform an Athena database to use my Glue catalog as its data source rather than an S3 bucket?

Answer 1

Our current basic setup for having Glue crawl one S3 bucket and create/update a table in a Glue DB, which can then be queried in Athena, looks like this:

Crawler role and role policy:

• The assume_role_policy of the IAM role needs only Glue as principal
• The IAM role policy allows actions for Glue, S3, and logs
• The Glue actions and resources can probably be narrowed down to the ones really needed
• The S3 actions are limited to those needed by the crawler

resource "aws_iam_role" "glue_crawler_role" {
  name = "analytics_glue_crawler_role"

  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "Service": "glue.amazonaws.com"
      },
      "Effect": "Allow",
      "Sid": ""
    }
  ]
}
EOF
}

resource "aws_iam_role_policy" "glue_crawler_role_policy" {
  name = "analytics_glue_crawler_role_policy"
  role = "${aws_iam_role.glue_crawler_role.id}"
  policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "glue:*",
      ],
      "Resource": [
        "*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "s3:GetBucketLocation",
        "s3:ListBucket",
        "s3:GetBucketAcl",
        "s3:GetObject",
        "s3:PutObject",
        "s3:DeleteObject"
      ],
      "Resource": [
        "arn:aws:s3:::analytics-product-data",
        "arn:aws:s3:::analytics-product-data/*",
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup",
        "logs:CreateLogStream",
        "logs:PutLogEvents"
      ],
      "Resource": [
        "arn:aws:logs:*:*:/aws-glue/*"
      ]
    }
  ]
}
EOF
}

S3 Bucket, Glue Database and Crawler:

resource "aws_s3_bucket" "product_bucket" {
  bucket = "analytics-product-data"
  acl = "private"
}

resource "aws_glue_catalog_database" "analytics_db" {
  name = "inventory-analytics-db"
}

resource "aws_glue_crawler" "product_crawler" {
  database_name = "${aws_glue_catalog_database.analytics_db.name}"
  name = "analytics-product-crawler"
  role = "${aws_iam_role.glue_crawler_role.arn}"

  schedule = "cron(0 0 * * ? *)"

  configuration = "{\"Version\": 1.0, \"CrawlerOutput\": { \"Partitions\": { \"AddOrUpdateBehavior\": \"InheritFromTable\" }, \"Tables\": {\"AddOrUpdateBehavior\": \"MergeNewColumns\" } } }"

  schema_change_policy {
    delete_behavior = "DELETE_FROM_DATABASE"
  }

  s3_target {
    path = "s3://${aws_s3_bucket.product_bucket.bucket}/products"
  }
}

Answer 2

I had many things wrong in my Terraform code. To start with:

1. The S3 bucket argument in the aws_athena_database code refers to the bucket for query output not the data the table should be built from.
2. I had set up my aws_glue_crawler to write to a Glue database rather than an Athena db. Indeed, as Martin suggested above, once correctly set up, Athena was able to see the tables in the Glue db.

3. I did not have the correct policies attached to my crawler. Initially, the only policy attached to the crawler role was

   resource "aws_iam_role_policy_attachment" "crawler_attach" {
       policy_arn = "arn:aws:iam::aws:policy/service-role/AWSGlueServiceRole"
       role = "${aws_iam_role.crawler_iam_role.name}"
   } 
   

   after setting a second policy that explicitly allowed all S3 access to all of the buckets I wanted to crawl and attaching that policy to the same crawler role, the crawler ran and updated tables successfully.

The second policy:

resource "aws_iam_policy" "crawler_bucket_policy" {
    name = "crawler_bucket_policy"
    path = "/"
    description = "Gives crawler access to buckets"
    policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1553807998309",
      "Action": "*",
      "Effect": "Allow",
      "Resource": "*"
    },
    {
      "Sid": "Stmt1553808056033",
      "Action": "s3:*",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::bucket0"
    },
    {
      "Sid": "Stmt1553808078743",
      "Action": "s3:*",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::bucket1"
    },
    {
      "Sid": "Stmt1553808099644",
      "Action": "s3:*",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::bucket2"
    },
    {
      "Sid": "Stmt1553808114975",
      "Action": "s3:*",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::bucket3"
    },
    {
      "Sid": "Stmt1553808128211",
      "Action": "s3:*",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::bucket4"
    }
  ]
}
EOF
}

I'm confident that I can get away from hardcoding the bucket names in this policy but I don't yet know how to do that.