floci-dev-assistant

name

floci-dev-assistant

description

Expert guide for developing with Floci — the Java/Quarkus-based open-source local AWS emulator. Use this skill whenever someone asks about adding a new AWS service to Floci, implementing AWS protocol-compatible handlers, writing integration or unit tests for Floci services, debugging AWS SDK compatibility issues, configuring storage modes, understanding Floci's architecture, working on the Floci codebase, or using Floci as a local AWS development environment. Always trigger this skill when the user mentions Floci, AWS emulator development, service implementation, AwsQueryController, AwsJson11Controller, StorageFactory, or any task involving the floci codebase — even if they don't explicitly say "Floci skill."

Floci Developer Assistant

Floci is a Java 25 + Quarkus 3.x local AWS emulator. It listens on port 4566 and speaks real AWS wire protocols — meaning any unmodified AWS SDK or CLI can point at it and just work.

Before diving into tasks, understand what kind of help is needed:

• "Add a new service" → Read agents/service-implementer.md
• "Write tests" → Read agents/test-writer.md
• "Debug an AWS compatibility issue" → Read agents/debug-assistant.md
• "Explain the architecture" → Use the Architecture section below
• "Configure storage / config entries" → Use the Configuration section below
• "Run or build" → See Quick Commands below

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Quick Commands

./mvnw quarkus:dev                              # Dev mode with hot reload on port 4566
./mvnw test                                     # All tests
./mvnw test -Dtest=SsmIntegrationTest           # One test class
./mvnw test -Dtest=SsmIntegrationTest#putParameter  # One test method
./mvnw clean package -DskipTests               # Build JAR (skip tests)
docker compose up                               # Run via Docker

---

Architecture (3 Layers)

Request → Controller/Handler → Service → Storage
              (thin)           (logic)    (via StorageFactory)

Layer 1: Controller / Handler

• Parses AWS protocol input (form-encoded, JSON, XML, REST path)
• Produces AWS-compatible responses
• Must stay thin — no business logic here

Layer 2: Service (@ApplicationScoped)

• All domain logic lives here
• Always throws AwsException for errors (never raw HTTP exceptions)
• Injected via @Inject

Layer 3: Model

• Plain Java POJOs / records
• No framework annotations

Key Infrastructure Classes

Class	Purpose
AwsQueryController	Base for Query-protocol services (SQS, SNS, IAM, STS…)
AwsJson11Controller	Base for JSON 1.1 services (SSM, EventBridge, KMS…)
AwsException	Throw this for all AWS-level errors
AwsExceptionMapper	Converts AwsException to correct wire-format error response
StorageFactory	Always use this — never instantiate storage directly
EmulatorConfig	All configuration lives here
ServiceRegistry	Service metadata and enablement checks
ResolvedServiceCatalog	Register ServiceDescriptor for each service here
XmlBuilder	Build XML responses (do not concatenate strings)
XmlParser	Parse XML (do not use regex)
AwsNamespaces	Constants for AWS XML namespaces
EmulatorLifecycle	Load/flush hooks for startup and shutdown

Package Layout

io.github.hectorvent.floci.config         ← EmulatorConfig and config interfaces
io.github.hectorvent.floci.core.common    ← Shared infrastructure (see table above)
io.github.hectorvent.floci.core.storage   ← StorageBackend, StorageFactory
io.github.hectorvent.floci.lifecycle      ← EmulatorLifecycle
io.github.hectorvent.floci.services.<svc> ← One package per AWS service
  └── <Svc>Controller.java or <Svc>Handler.java
  └── <Svc>Service.java
  └── model/

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AWS Protocol Quick Reference

Floci must implement the same wire protocol that the real AWS uses. Never invent custom endpoints — the AWS SDK must work without modification.

Protocol	Example Services	Request Shape	Response	Base Class
Query	SQS, SNS, IAM, STS, RDS, CloudFormation	form-encoded POST with Action=	XML	AwsQueryController
JSON 1.1	SSM, EventBridge, Kinesis, KMS, Cognito, Secrets Manager	POST with X-Amz-Target header	JSON	AwsJson11Controller
REST JSON	Lambda, API Gateway, SES v2	REST path (GET/POST/DELETE…)	JSON	JAX-RS @Path
REST XML	S3	REST path	XML	JAX-RS @Path
TCP proxy	ElastiCache, RDS	Raw socket	native	Custom proxy

Special cases to remember:

• CloudWatch supports both Query AND JSON 1.1 — keep both aligned
• Cognito well-known endpoints (/.well-known/openid-configuration) are OIDC REST, not AWS management
• SQS and SNS have multiple compatibility paths — do not let them drift

---

Error Handling

Always use AwsException:

throw new AwsException("ParameterNotFound",
    "Parameter /app/db/host does not exist.", 400);

AwsExceptionMapper automatically converts this to the correct wire-format:

• JSON 1.1: {"__type": "ParameterNotFound", "message": "..."}
• Query (XML): <ErrorResponse><Error><Code>ParameterNotFound</Code>...

---

Storage Rules

Storage modes supported: memory, persistent, hybrid, wal.

// In a Service constructor — inject via StorageFactory
@Inject
public MyService(StorageFactory storageFactory) {
    this.store = storageFactory.create("my-service-key", MyModel.class);
}

When adding storage-backed behavior, update all four locations:

1. EmulatorConfig — add a StorageConfig entry
2. src/main/resources/application.yml — add default values
3. src/test/resources/application.yml — add test values (usually memory mode)
4. Register in StorageFactory if a new storage type is introduced

---

Configuration

Config lives under floci.*. Environment variables follow FLOCI_* convention (e.g., floci.base-url → FLOCI_BASE_URL).

When adding config:

1. Add a field to EmulatorConfig (or a nested config interface)
2. Add a default to src/main/resources/application.yml
3. Add a test default to src/test/resources/application.yml if needed
4. Update docs/configuration/ if the setting is user-facing

---

Adding a New AWS Service (checklist)

For a detailed walkthrough read agents/service-implementer.md.

1. Create package services/<svc>/ with Handler, Service, model/
2. Choose the correct protocol (see table above)
3. Extend AwsQueryController or AwsJson11Controller, or add JAX-RS @Path
4. Implement a switch on Action / X-Amz-Target
5. Add a ServiceDescriptor to ResolvedServiceCatalog
6. Add config to EmulatorConfig and application.yml
7. Write *IntegrationTest.java (RestAssured + @QuarkusTest) and *ServiceTest.java (JUnit 5 unit tests)

---

Writing Tests (quick reference)

For a detailed guide read agents/test-writer.md.

Integration test skeleton (JSON 1.1 protocol):

@QuarkusTest
class MyServiceIntegrationTest {
    @Test
    void createResource() {
        given()
            .header("X-Amz-Target", "MyService.CreateResource")
            .contentType("application/x-amz-json-1.1")
            .body("""{"Name": "test"}""")
        .when()
            .post("/")
        .then()
            .statusCode(200)
            .body("ResourceId", notNullValue());
    }
}

Unit test skeleton:

class MyServiceTest {
    private MyService service;

    @BeforeEach
    void setUp() {
        service = new MyService(new InMemoryStorage<>());
    }

    @Test
    void createThrowsWhenNameExists() {
        service.create("foo");
        assertThrows(AwsException.class, () -> service.create("foo"));
    }
}

---

Debugging AWS Compatibility Issues

For a systematic approach read agents/debug-assistant.md.

Quick checklist:

• Is the response shape exactly matching AWS? (field names, nesting, casing)
• Is the error code matching what the real AWS returns?
• Is the Content-Type correct for the protocol?
• Does the XML namespace match AwsNamespaces constants?
• Is the AWS SDK using X-Amz-Target (JSON 1.1) or Action= (Query)?

---

Commit Message Format (Conventional Commits)

Prefix	When	Bump
feat:	New AWS API action or service	minor
fix:	Bug fix or AWS compat correction	patch
perf:	Performance improvement	patch
docs:	Documentation only	none
chore:	Build, CI, dependencies	none
BREAKING CHANGE:	In footer or ! suffix	major

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