Changing a weight can remove a backend from a director

[drastawi]

Terraform Version

0.11.13

Affected Resource(s)

fastly_service_v1

Terraform Configuration Files

I updated the weight from 99 to 9 in the file below:

resource "fastly_service_v1" "fastly_service" {
  name = "${var.fastly_project_name}"

  domain {
    name = "${var.domain_name}"
  }

  backend ="${var.backends}" 

  // To fix the issue https://github.com/terraform-providers/terraform-provider-fastly/issues/109,
  // we only put the backends with weight greater than 0 in the director.
  director {
    name = "director"
    backends = [ "${compact(data.null_data_source.non_zero_weight_backends.*.outputs.name)}"]
    quorum = 1
  }
}
data "null_data_source" "non_zero_weight_backends" {
  count = "${length(var.backends)}"
  inputs = {
    name = "${lookup(var.backends[count.index], "weight") == 0 ? "" : lookup(var.backends[count.index], "name")}"
  }
}

backends = [
    {
      name = "xxxxx Public API (xxxxx)"
      address = xxxxx
      port = 443
      ssl_cert_hostname = xxxxx
      ssl_check_cert = true
      use_ssl = true
      min_tls_version = "1.2"

      weight = 9
    },
    {
      name = "xxxx Public API"
      address = xxxxx
      port = 443
      ssl_cert_hostname = xxxxx
      ssl_check_cert = true
      use_ssl = true
      min_tls_version = "1.2"

      weight = 1
    }
  ]

Debug Output

  backend.205921849.address:                "xxxx"
  backend.205921849.auto_loadbalance:       "true" => "true"
  backend.205921849.between_bytes_timeout:  "10000" => "10000"
  backend.205921849.connect_timeout:        "1000" => "1000"
  backend.205921849.error_threshold:        "0" => "0"
  backend.205921849.first_byte_timeout:     "15000" => "15000"
  backend.205921849.healthcheck:            "" => ""
  backend.205921849.max_conn:               "200" => "200"
  backend.205921849.max_tls_version:        "" => ""
  backend.205921849.min_tls_version:        "1.2" => "1.2"
  backend.205921849.name:                   "xxx"
  backend.205921849.port:                   "443" => "443"
  backend.205921849.request_condition:      "" => ""
  backend.205921849.shield:                 "" => ""
  backend.205921849.ssl_ca_cert:            "" => ""
  backend.205921849.ssl_cert_hostname:      "xxx"
  backend.205921849.ssl_check_cert:         "true" => "true"
  backend.205921849.ssl_ciphers:            "" => ""
  backend.205921849.ssl_client_cert:        "<sensitive>" => "<sensitive>"
  backend.205921849.ssl_client_key:         "<sensitive>" => "<sensitive>"
  backend.205921849.ssl_hostname:           "" => ""
  backend.205921849.ssl_sni_hostname:       "" => ""
  backend.205921849.use_ssl:                "true" => "true"
  backend.205921849.weight:                 "1" => "1"
  backend.2547690010.address:               "" => "xxxx"
  backend.2547690010.auto_loadbalance:      "" => "true"
  backend.2547690010.between_bytes_timeout: "" => "10000"
  backend.2547690010.connect_timeout:       "" => "1000"
  backend.2547690010.error_threshold:       "" => "0"
  backend.2547690010.first_byte_timeout:    "" => "15000"
  backend.2547690010.healthcheck:           "" => ""
  backend.2547690010.max_conn:              "" => "200"
  backend.2547690010.max_tls_version:       "" => ""
  backend.2547690010.min_tls_version:       "" => "1.2"
  backend.2547690010.name:                  "" => "xxxx"
  backend.2547690010.port:                  "" => "443"
  backend.2547690010.request_condition:     "" => ""
  backend.2547690010.shield:                "" => ""
  backend.2547690010.ssl_ca_cert:           "" => ""
  backend.2547690010.ssl_cert_hostname:     "" => "xxxx"
  backend.2547690010.ssl_check_cert:        "" => "true"
  backend.2547690010.ssl_ciphers:           "" => ""
  backend.2547690010.ssl_client_cert:       "<sensitive>" => "<sensitive>"
  backend.2547690010.ssl_client_key:        "<sensitive>" => "<sensitive>"
  backend.2547690010.ssl_hostname:          "" => ""
  backend.2547690010.ssl_sni_hostname:      "" => ""
  backend.2547690010.use_ssl:               "" => "true"
  backend.2547690010.weight:                "" => "9"
  backend.2898937851.address:               "xxx" => ""
  backend.2898937851.auto_loadbalance:      "true" => "false"
  backend.2898937851.between_bytes_timeout: "10000" => "0"
  backend.2898937851.connect_timeout:       "1000" => "0"
  backend.2898937851.error_threshold:       "0" => "0"
  backend.2898937851.first_byte_timeout:    "15000" => "0"
  backend.2898937851.healthcheck:           "" => ""
  backend.2898937851.max_conn:              "200" => "0"
  backend.2898937851.max_tls_version:       "" => ""
  backend.2898937851.min_tls_version:       "1.2" => ""
  backend.2898937851.name:                  "xxx" => ""
  backend.2898937851.port:                  "443" => "0"
  backend.2898937851.request_condition:     "" => ""
  backend.2898937851.shield:                "" => ""
  backend.2898937851.ssl_ca_cert:           "" => ""
  backend.2898937851.ssl_cert_hostname:     "xxxx" => ""
  backend.2898937851.ssl_check_cert:        "true" => "false"
  backend.2898937851.ssl_ciphers:           "" => ""
  backend.2898937851.ssl_client_cert:       "" => ""
  backend.2898937851.ssl_client_key:        "" => ""
  backend.2898937851.ssl_hostname:          "" => ""
  backend.2898937851.ssl_sni_hostname:      "" => ""
  backend.2898937851.use_ssl:               "true" => "false"
  backend.2898937851.weight:                "99" => "0"

Expected Behavior

The director should update the weight in the VCL

Actual Behavior

The API removed the backend with the updated weight from the director.

Steps to Reproduce

1. Updated the weight on one backend
2. terraform apply

Important Factoids

Running apply again fixes the issue with the plan:

  director.1777961031.backends.#:          "0" => "2"
  director.1777961031.backends.3220782306: "" => "xxxx"
  director.1777961031.backends.3231695452: "" => "xxxx"
  director.1777961031.capacity:            "" => "100"
  director.1777961031.comment:             "" => ""
  director.1777961031.name:                "" => "director"
  director.1777961031.quorum:              "" => "1"
  director.1777961031.retries:             "" => "5"
  director.1777961031.shield:              "" => ""
  director.1777961031.type:                "" => "1"
  director.2719870166.backends.#:          "1" => "0"
  director.2719870166.backends.3220782306: "xxxxI" => ""
  director.2719870166.capacity:            "100" => "0"
  director.2719870166.comment:             "" => ""
  director.2719870166.name:                "director" => ""
  director.2719870166.quorum:              "1" => "0"
  director.2719870166.retries:             "5" => "0"
  director.2719870166.shield:              "" => ""
  director.2719870166.type:                "1" => "0"

[libc]

This seems to happen on any backend update, not just weights. The underlying problem is that there're no in-place updates of backends, all changes are done by deleting and adding them. After deletion the link between director and backend is lost.

[phamann]

Hi all, just a quick update to say this has now been fixed (#304) and released in version v0.20.1 of the provider. Feel free to reopen if you have further issues.