Mappings Declaration

Mappings match a key to a corresponding set of named values. For example, if you want to set values based on a region, you can create a mapping that uses the region name as a key and contains the values you want to specify for each specific region.

Mappings are declared in the Mappings section, with each mapping separated by a comma. The keys and values in mappings must be literal strings. Each mapping is formatted as a double-quoted key, a single colon, and braces enclosing the sets of values to map. The following example shows a Mappings section containing a single mapping named Mapping01.

"Mappings" : {
    "Mapping01" : {
        "Key01" : {
            "Value" : "Value01"
        },
        "Key02" : {
            "Value" : "Value02"
        },
        "Key03" : {
            "Value" : "Value03"
        }
    }
}

Within a mapping, each map is a key followed by a single colon and a set of name-value pairs surrounded by braces. The key identifies each map, and it must be unique within the mapping. Within the braces, you can declare multiple name-value pairs. Each pair is formatted as a double-quoted name, a single colon, and a value or an array of values.

The following example shows a Mappings section with a map RegionMap, which contains five keys that map to name-value pairs containing single string values. The keys are region names. Each name-value pair is the AMI ID for the 32-bit AMI in the region represented by the key.

"Mappings" : {
      "RegionMap" : {
        "us-east-1" : { "32" : "ami-6411e20d"},
        "us-west-1" : { "32" : "ami-c9c7978c"},
        "eu-west-1" : { "32" : "ami-37c2f643"},
        "ap-southeast-1" : { "32" : "ami-66f28c34"},
        "ap-northeast-1" : { "32" : "ami-9c03a89d"}
      }
}

The name-value pairs have a name (32 in the example) and a value. By naming the values, you can map more than one set of values to a key. The following example has region keys that are mapped to two sets of values: one named 32 and the other 64.

"RegionMap" : {
      "us-east-1" : { "32" : "ami-6411e20d", "64" : "ami-7a11e213" },
      "us-west-1" : { "32" : "ami-c9c7978c", "64" : "ami-cfc7978a" },
      "eu-west-1" : { "32" : "ami-37c2f643", "64" : "ami-31c2f645" },
      "ap-southeast-1" : { "32" : "ami-66f28c34", "64" : "ami-60f28c32" },
      "ap-northeast-1" : { "32" : "ami-9c03a89d", "64" : "ami-a003a8a1" }
}

You can use the Fn::FindInMap function to return a named value based on a specified key. The following example template contains an AWS::EC2::Instance resource whose ImageId property is assigned by the FindInMap function. The FindInMap function specifies key as the region where the stack is created (using the AWS::Region pseudo parameter) and 32 as the name of the value to map to.

{
  "AWSTemplateFormatVersion" : "2010-09-09",

  "Mappings" : {
    "RegionMap" : {
      "us-east-1" : { "32" : "ami-6411e20d", "64" : "ami-7a11e213" },
      "us-west-1" : { "32" : "ami-c9c7978c", "64" : "ami-cfc7978a" },
      "eu-west-1" : { "32" : "ami-37c2f643", "64" : "ami-31c2f645" },
      "ap-southeast-1" : { "32" : "ami-66f28c34", "64" : "ami-60f28c32" },
      "ap-northeast-1" : { "32" : "ami-9c03a89d", "64" : "ami-a003a8a1" }
    }
  },

  "Resources" : {
     "myEC2Instance" : {
        "Type" : "AWS::EC2::Instance",
        "Properties" : {
           "ImageId" : { "Fn::FindInMap" : [ "RegionMap", { "Ref" : "AWS::Region" }, "32"]},
           "InstanceType" : "m1.small"
        }
     }
 }
}

The following example shows a Mappings section with a mapping that contains three keys that map to arrays that contain multiple string values. The keys represent three regions, and the mapped values are the list of availability zones used in each region. The AWS::ElasticLoadBalancing::LoadBalancer resource uses the FindInMap function and the Region2AZ map to specify the AvailabilityZones property.

{
    "AWSTemplateFormatVersion" : "2010-09-09",

    "Mappings" : {
      "Region2AZ" : {
        "us-west-1" : { "AZ" : ["us-west-1a", "us-west-1b"] },
        "us-east-1" : { "AZ" : ["us-east-1a", "us-east-1b", "us-east-1c"] },
        "eu-west-1" : { "AZ" : ["eu-west-1a", "eu-west-1b"] }
      }
    },

    "Resources" : {
      "MyELB" : {
        "Type" : "AWS::ElasticLoadBalancing::LoadBalancer",
        "Properties" : {
          "AvailabilityZones" : { "Fn::FindInMap" : [ "Region2AZ", { "Ref" : "AWS::Region" }, "AZ" ] },
          "Listeners" : [ {
            "LoadBalancerPort" : "8888" ,
            "InstancePort" : "8888" ,
            "Protocol" : "HTTP"
          } ],
          "HealthCheck" : {
           "Target" : { "Fn::Join" : [ "", ["HTTP:", "8888", "/"]]},
            "HealthyThreshold" : "5",
            "UnhealthyThreshold" : "2",
            "Interval" : "10",
            "Timeout" : "8"
          }
        }
      }
    }
}