Issue with python code in lambda function using boto3 using send_command

Question

Issue with parsing string in python boto3 code

In my lambda function has following code

    instance_id = "'" + str(instance[0]) + "'"

    ssmresponse = ssm_client.send_command(InstanceIds=[ instance_id ],DocumentName='AWS- 
      RunShellScript',Parameters={'commands': ['ls -l']}, )
    command_id = ssmresponse['Command']['CommandId']

if I specify the instance_id as

 instance_id = str(instance[0])

send_command is erroring out with

"WARN: Exception occured An error occurred (ValidationException) when calling the SendCommand operation: 1 validation error detected: Value '[ec2.Instance(id='i-0xxxxxxxxxxxxxxx')]' at 'instanceIds' failed to satisfy constraint: Member must satisfy constraint: [Member must have length less than or equal to 20, Member must have length greater than or equal to 10, Member must satisfy regular expression pattern: (^i-(\w{8}|\w{17})$)|(^mi-\w{17}$)]."

if I specify instance_id as

instance_id = "'" + str(instance[0]) + "'"

send_command is erroring out with

"WARN: Exception occured An error occurred (ValidationException) when calling the SendCommand operation: 1 validation error detected: Value '['ec2.Instance(id='xxxxxxxxxxxxxxxxxx')']' at 'instanceIds' failed to satisfy constraint: Member must satisfy constraint: [Member must have length less than or equal to 20, Member must have length greater than or equal to 10, Member must satisfy regular expression pattern: (^i-(\w{8}|\w{17})$)|(^mi-\w{17}$)]."

When I hardcode the instance id within the send_command, there are no errors

ssmresponse = ssm_client.send_command(InstanceIds=[ 'i-xxxxxxxxxxxxxxxx' ],DocumentName='AWS-RunShellScript',Parameters={'commands': ['ls -l']}, )

there are no errors

I need to dynamically set the instance_id. What could possibly be wrong in this?

Any help is appreciated.

Thanks D

Answer 1

I am guessing you are first querying instances using Ec2 Service Resource and getting back a resource object, which would have instance[0].id as "i-123..." but when you specify it just as 'instance[0], it is simply returning the first instance "object"

For context, boto3 has clients and resources. When dealing with client, you get back text (mostly json) but resource returns pythonic 'objects'.

Service Resource: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/ec2.html#service-resource

vs Client: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/ec2.html#client

In case it is still not clear, use: (InstanceIds=[ instance[0].id ]