Terraform使用for_each时出现Missing resource instance key报错如何解决

错误根因 #

• 所有使用for_each参数批量创建的Terraform资源会以集合形式存在，不能直接调用资源整体的属性，必须指定具体实例索引
• each对象仅能在同样配置了for_each参数的resource/module块内部使用，无for_each的块调用each会直接报错

修复步骤 #

1. 给两个aws_sqs_queue_policy资源块添加和对应SQS资源一致的for_each参数，保证实例key一一对应
2. 所有引用批量创建的SQS资源属性的位置，补充[each.key]实例索引

修复后完整配置示例 #

# 原有业务SQS队列配置保持不变
resource "aws_sqs_queue" "CloudTrail_SQS"{
  for_each                   = var.sqs_queue_names
  name                       = each.value
  visibility_timeout_seconds = var.visibility_timeout_seconds
  max_message_size           = var.max_message_size
  message_retention_seconds  = var.message_retention_seconds
  delay_seconds              = var.delay_seconds
  receive_wait_time_seconds  = var.receive_wait_time_seconds
  redrive_policy = jsonencode({
    deadLetterTargetArn    = aws_sqs_queue.CloudTrail_SQS_DLQ[each.key].arn
    maxReceiveCount        = var.max_receive_count
  })
  tags = var.default_tags
}

# 原有死信队列配置保持不变
resource "aws_sqs_queue" "CloudTrail_SQS_DLQ"{
  for_each                   = var.dead_queue_names
  name                       = each.value
  visibility_timeout_seconds = var.visibility_timeout_seconds
  max_message_size           = var.max_message_size
  message_retention_seconds  = var.message_retention_seconds
  delay_seconds              = var.delay_seconds
  receive_wait_time_seconds  = var.receive_wait_time_seconds
  tags = var.default_tags
}

# 修复后的业务SQS队列策略
resource "aws_sqs_queue_policy" "Cloudtrail_SQS_Policy" {
  # 新增for_each，和业务SQS队列用同一个变量保证key对齐
  for_each  = var.sqs_queue_names
  queue_url = aws_sqs_queue.CloudTrail_SQS[each.key].id

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect   = "Allow"
        Action   = "sqs:SendMessage"
        Resource = aws_sqs_queue.CloudTrail_SQS[each.key].arn
        Principal = {
          Service = "cloudtrail.amazonaws.com"
        }
      }
    ]
  })
}

# 修复后的死信队列策略
resource "aws_sqs_queue_policy" "CloudTrail_SQS_DLQ" {
  # 新增for_each，和死信队列用同一个变量保证key对齐
  for_each  = var.dead_queue_names
  queue_url = aws_sqs_queue.CloudTrail_SQS_DLQ[each.key].id

  # 可根据实际需求调整DLQ的策略规则
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect   = "Allow"
        Action   = "sqs:*"
        Resource = aws_sqs_queue.CloudTrail_SQS_DLQ[each.key].arn
        Principal = {
          AWS = "*"
        }
      }
    ]
  })
}

报错对应修复说明 #

• 原Missing resource instance key报错：补充[each.key]指定具体实例即可解决
• 原Reference to "each" in context without for_each报错：给对应资源块加上匹配的for_each参数即可解决

内容的提问来源于stack exchange，提问作者bibi