GetParameter VS GetParameters - amazon-web-services

Question

What is the difference between AWS SSM GetParameter and GetParameters ?
I have a machine with an IAM policy GetParameters and try to read a variable with terraform with the following code:
data "aws_ssm_parameter" "variable" { name = "variable"}
I get an error indicating I'm not authorized to perform GetParameter.

Answer 1

Like the name suggests.
GetParameter provides details about only one parameter per API call.
GetParameters provides details about multiple parameters in one API call.
The parameter details returned are exactly same for both calls, as the two calls return Parameter object:
"Parameter": {
"ARN": "string",
"DataType": "string",
"LastModifiedDate": number,
"Name": "string",
"Selector": "string",
"SourceResult": "string",
"Type": "string",
"Value": "string",
"Version": number
}
The key benefit of the GetParameters is that you can fetch many parameters in a single API call which saves time.
Example use of GetParameter:
aws ssm get-parameter --name /db/password
{
"Parameter": {
"Name": "/db/password",
"Type": "String",
"Value": "secret password",
"Version": 1,
"LastModifiedDate": 1589285865.183,
"ARN": "arn:aws:ssm:us-east-1:xxxxxxxxx:parameter/db/password",
"DataType": "text"
}
}
Example use of GetParameters with two parameters:
aws ssm get-parameters --name /db/password /db/url
{
"Parameters": [
{
"Name": "/db/password",
"Type": "String",
"Value": "secret password",
"Version": 1,
"LastModifiedDate": 1589285865.183,
"ARN": "arn:aws:ssm:us-east-1:xxxxxxxxx:parameter/db/password",
"DataType": "text"
},
{
"Name": "/db/url",
"Type": "String",
"Value": "url to db",
"Version": 1,
"LastModifiedDate": 1589285879.912,
"ARN": "arn:aws:ssm:us-east-1:xxxxxxxxx:parameter/db/url",
"DataType": "text"
}
],
"InvalidParameters": []
}
Example use of GetParameters with non-existing second parameter (/db/wrong)
aws ssm get-parameters --name /db/password /db/wrong
{
"Parameters": [
{
"Name": "/db/password",
"Type": "String",
"Value": "secret password",
"Version": 1,
"LastModifiedDate": 1589285865.183,
"ARN": "arn:aws:ssm:us-east-1:xxxxxxxxx:parameter/db/password",
"DataType": "text"
}
],
"InvalidParameters": [
"/db/wrong"
]
}