Support ALB advanced request routing

[ewbankkit]

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Add support for AWS Application Load Balancer advanced request routing.

[ewbankkit]

It looks like we need to add blocks to the aws_lb_listener_rule.condition attribute:

resource "aws_lb_listener_rule" "foo" {
  condition {
    host_header_config {
    }
  }

  condition {
    http_header_config {
    }
  }

  condition {
    http_request_method_config {
    }
  }

  condition {
    path_pattern_config {
    }
  }

  condition {
    query_string_config {
    }
  }

  condition {
    source_ip_config {
    }
  }
}

[excalq]

Right, in the case of http_header_config, you'll need a header key (e.g. user-agent), and a list of values (OR'd together). This would represent such a configuration:

[srhaber]

Below is my take.

Description

Application Load Balancers now have additional routing options as of 3/27/2019.

Conditions fields:

• Host header
• Path
• HTTP header (new)
• HTTP request method (new)
• Query string (new)
• Source IP (new)

Additionally, each condition can now accept multiple values.

New or Affected Resource(s)

• aws_alb_listener_rule

Potential Terraform Configuration

resource "aws_lb_listener_rule" "advanced_routing" {
  listener_arn = "${aws_lb_listener.front_end.arn}"
  priority     = 99

  action {
    type             = "forward"
    target_group_arn = "${aws_lb_target_group.static.arn}"
  }

  # Condition field: host-header
  condition {
    field  = "host-header"
    values = ["*.example.com"]
  }

  # Condition field: path-pattern
  condition {
    field  = "path-pattern"
    values = ["/img/*"]
  }

  # New condition field: http-header
  condition {
    field            = "http-header"
    http_header_name = "User-Agent"

    # Multiple values now acceptable
    values = [
      "*Chrome*",
      "*Safari*",
    ] 
  }

  # New condition field: http-request-method
  condition {
    field  = "http-request-method"

    values = [
      "GET",
      "POST"
    ]
  }

  # New condition field: query-string
  condition {
    field = "query-string"

    values = [
      {
        key   = "version"
        value = "v1"
      },
      {
        value = "example"
      }
    ]
  }

  # New condition field: source-ip
  condition {
    field = "source-ip"

    values = [
      "192.0.2.0/24", 
      "198.51.100.10/32",
    ]
  }
}

References

• https://aws.amazon.com/blogs/aws/new-advanced-request-routing-for-aws-application-load-balancers/
• https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-listeners.html#listener-rules

The query-string condition throws a curve by having values be a list of maps instead of a list of strings. Thus, it might be necessary to introduce the extra *_config blocks per condition in accordance with Amazon's API spec. See snippet below for example.

# Common structure specifies a list of strings
[
  {
      "Field": "host-header",
      "HostHeaderConfig": {
          "Values": ["*.example.com"]
      }
  }
]

# Query string specifies a list of maps
[
  {
      "Field": "query-string",
      "QueryStringConfig": {
          "Values": [
            {
                "Key": "version", 
                "Value": "v1"
            },
            {
                "Value": "example"
            }
          ]
      }
  }
]

# HTTP header introduces an additional field for header name
[
  {
      "Field": "http-header",
      "HttpHeaderConfig": {
          "HttpHeaderName": "User-Agent",
          "Values": ["*Chrome*", "*Safari*"]
      }
  }
]

[bharat109puri]

@ewbankkit Is this feature added.

[ewbankkit]

@bharat109puri We are still waiting on #8268 to be reviewed and merged.