floci-io/floci · error · AwsException

NameAlreadyExistsException

NameAlreadyExistsException

Error message

StackSet already exists: ${name}

What it means

NameAlreadyExistsException (HTTP 409) from createStackSet when a StackSet with the same name is already registered in the emulator's stackset storage. StackSet names are unique per account.

Source

Thrown at src/main/java/io/github/hectorvent/floci/services/cloudformation/StackSetService.java:64

    public StackSetService(CloudFormationService cfnService, StorageFactory storageFactory) {
        this.cfnService = cfnService;
        this.stackSets = storageFactory.create("cloudformation", "cloudformation-stacksets.json",
                new TypeReference<Map<String, StackSet>>() {});
        this.instances = storageFactory.create("cloudformation", "cloudformation-stackset-instances.json",
                new TypeReference<Map<String, StackInstance>>() {});
        this.operations = storageFactory.create("cloudformation", "cloudformation-stackset-operations.json",
                new TypeReference<Map<String, StackSetOperation>>() {});
    }

    // ── StackSet lifecycle ─────────────────────────────────────────────────────

    public StackSet createStackSet(String name, String templateBody, Map<String, String> parameters,
                                   List<String> capabilities, Map<String, String> tags, String description) {
        if (name == null || name.isBlank()) {
            throw new AwsException("ValidationError", "StackSetName must not be empty", 400);
        }
        if (stackSets.get(name).isPresent()) {
            throw new AwsException("NameAlreadyExistsException",
                    "StackSet already exists: " + name, 409);
        }
        // AWS rejects CreateStackSet with no template; the handler resolves TemplateBody/TemplateURL
        // to null when neither is supplied. Without this guard a later CreateStackInstances would
        // deploy empty ("{}") stacks into every target account.
        if (templateBody == null || templateBody.isBlank()) {
            throw new AwsException("ValidationError",
                    "Either TemplateBody or TemplateURL must be specified", 400);
        }
        StackSet ss = new StackSet();
        ss.setStackSetName(name);
        ss.setStackSetId(name + ":" + UUID.randomUUID());
        ss.setTemplateBody(templateBody);
        ss.setDescription(description);
        if (parameters != null) {
            ss.setParameters(new LinkedHashMap<>(parameters));
        }
        if (capabilities != null) {

View on GitHub (pinned to 62ff490619)

Solutions

1. Check first: aws --endpoint-url http://localhost:4566 cloudformation describe-stack-set --stack-set-name <name>; only create when absent.
2. Delete the existing set before recreating — delete stack instances first (DeleteStackInstances), then DeleteStackSet.
3. For ephemeral test runs, use unique names per session (suffix with a run id) or reset the emulator's persistent storage.

Example fix

# before
aws ... cloudformation create-stack-set --stack-set-name shared --template-body file://t.yml

# after
aws ... cloudformation delete-stack-instances --stack-set-name shared \
  --accounts 111122223333 --regions us-east-1 --no-retain-stacks || true
aws ... cloudformation delete-stack-set --stack-set-name shared || true
aws ... cloudformation create-stack-set --stack-set-name shared --template-body file://t.yml

boolean exists = false;
try {
    cfn.describeStackSet(req -> req.stackSetName(name));
    exists = true;
} catch (CloudFormationException e) { /* absent */ }

catch CloudFormationException with statusCode 409 / code NameAlreadyExistsException: either delete-and-recreate (instances first, then the set) or adopt the existing set; do not blindly retry create.

When it happens

Trigger: Calling CreateStackSet twice with the same name without deleting the first, or re-running a setup script against an emulator whose persistent storage still holds the previous StackSet.

Common situations: Idempotent provisioning scripts that create-on-every-run, emulator state persisting between test sessions, or a previous deletion skipped because stack instances remained (DeleteStackSet refuses non-empty sets).

Related errors

• StackSetNotEmptyException
• ValidationError
• ResourceInUseException
• ConflictException
• ConflictException

AI-assisted analysis of floci-io/floci@62ff490619 (2026-08-14). Data as JSON: /api/errors/fd2635a7d9fff9a0. Report an issue: GitHub.