vpc.subnets.all() is not a superset of vpc.subnets.filter(...)

[kislyuk]

ec2 = boto3.resource("ec2")
for vpc in ec2.vpcs.all():
    for subnet in vpc.subnets.all():
        print(vpc, "all:", subnet)
    for az in ec2.meta.client.describe_availability_zones()["AvailabilityZones"]:
        for subnet in vpc.subnets.filter(Filters=[{"Name": "availabilityZone", "Values": [az["ZoneName"]]}]):
            print(vpc, "filter:", subnet)

It appears vpc.subnets.filter(...) admits subnets from other VPCs, while all() does not. This is confusing.

[kyleknap]

That seems strange. I tried it and I can account for all of my subnets with the filter() and all() method. If some of the subnets are missing, it must have been omitted by the availability zone filter you used for the filter() method.

Could you identify the availability zone of the missing subnets?

[kislyuk]

ec2 = boto3.resource("ec2")
for vpc in ec2.vpcs.all():
    for subnet in vpc.subnets.all():
        print(vpc, "all:", subnet)
    for az in ec2.meta.client.describe_availability_zones()["AvailabilityZones"]:
        for subnet in vpc.subnets.filter(Filters=[{"Name": "availabilityZone", "Values": [az["ZoneName"]]}]):
            print(vpc, az["ZoneName"], "filter:", subnet)

ec2.Vpc(id='vpc-71979a15') us-east-1c filter: ec2.Subnet(id='subnet-65b8557e')
ec2.Vpc(id='vpc-f0979a96') us-east-1c filter: ec2.Subnet(id='subnet-65b8557e')
ec2.Vpc(id='vpc-b86defde') all: ec2.Subnet(id='subnet-65b8557e')
ec2.Vpc(id='vpc-b86defde') us-east-1c filter: ec2.Subnet(id='subnet-65b8557e')
ec2.Vpc(id='vpc-fb979a9d') us-east-1c filter: ec2.Subnet(id='subnet-65b8557e')
ec2.Vpc(id='vpc-d9979abd') us-east-1c filter: ec2.Subnet(id='subnet-65b8557e')

(IDs changed)

What I see is a particular subnet showing up in the all() listing for all VPCs in a region, not just for the one that it really belongs to. I believe the other VPCs are empty.

[kyleknap]

I can confirm the issue. What is happening is that the use of Filter in the filter() method clobbers another filter that was injected into the parameter for the VPC Id, thus you were just getting all of the subnets for the particular availability zone instead of the all of the subnets for a particular availability zone and VPC Id.

The PR that is referenced in the issue fixes the issue.

[kyleknap]

This should be fixed now that both PR's are merged. Closing issue. Please reopen if the issue persists.