# SNS

**Protocol:** Query (XML) and JSON 1.0 (both supported)
**Endpoint:** `POST http://localhost:4566/`

## Supported Actions

| Action | Description |
|---|---|
| `CreateTopic` | Create a topic |
| `DeleteTopic` | Delete a topic |
| `ListTopics` | List all topics |
| `GetTopicAttributes` | Get topic configuration |
| `SetTopicAttributes` | Update topic configuration |
| `Subscribe` | Subscribe an endpoint (SQS, HTTP, Lambda, email) |
| `Unsubscribe` | Remove a subscription |
| `ListSubscriptions` | List all subscriptions |
| `ListSubscriptionsByTopic` | List subscriptions for a specific topic |
| `GetSubscriptionAttributes` | Get subscription settings |
| `SetSubscriptionAttributes` | Update subscription settings |
| `ConfirmSubscription` | Confirm a pending subscription |
| `Publish` | Publish a message to a topic |
| `PublishBatch` | Publish up to 10 messages in one call |
| `TagResource` | Tag a topic |
| `UntagResource` | Remove tags from a topic |
| `ListTagsForResource` | List tags on a topic |
| `CreatePlatformApplication` | Create a mobile push platform app (iOS or Android) |
| `DeletePlatformApplication` | Delete a platform app and its endpoints |
| `GetPlatformApplicationAttributes` | Read platform app attributes |
| `SetPlatformApplicationAttributes` | Update platform app attributes (e.g. `Enabled`) |
| `ListPlatformApplications` | List platform applications in the region |
| `CreatePlatformEndpoint` | Register a device token under a platform app |
| `DeleteEndpoint` | Delete a platform endpoint |
| `GetEndpointAttributes` | Read endpoint attributes |
| `SetEndpointAttributes` | Update endpoint attributes (e.g. `Enabled=false` to simulate token expiry) |
| `ListEndpointsByPlatformApplication` | List endpoints under a platform app |

## Configuration

| Variable | Default | Description |
|---|---|---|
| `FLOCI_SERVICES_SNS_ENABLED` | `true` | Enable or disable the service |
| `FLOCI_STORAGE_SERVICES_SNS_MODE` | *(global default)* | Storage mode override for SNS (`memory`, `persistent`, `hybrid`, `wal`) |
| `FLOCI_STORAGE_SERVICES_SNS_FLUSH_INTERVAL_MS` | `5000` | Flush interval for `hybrid`/`wal` storage modes (milliseconds) |

## Examples

```bash
export AWS_ENDPOINT_URL=http://localhost:4566

# Create a topic
TOPIC_ARN=$(aws sns create-topic --name notifications \
  --query TopicArn --output text \
  --endpoint-url $AWS_ENDPOINT_URL)

# Subscribe an SQS queue
QUEUE_ARN=$(aws sqs get-queue-attributes \
  --queue-url $AWS_ENDPOINT_URL/000000000000/orders \
  --attribute-names QueueArn \
  --query Attributes.QueueArn --output text \
  --endpoint-url $AWS_ENDPOINT_URL)

aws sns subscribe \
  --topic-arn $TOPIC_ARN \
  --protocol sqs \
  --notification-endpoint $QUEUE_ARN \
  --endpoint-url $AWS_ENDPOINT_URL

# Publish a message
aws sns publish \
  --topic-arn $TOPIC_ARN \
  --message '{"event":"user.registered"}' \
  --endpoint-url $AWS_ENDPOINT_URL

# Fan-out: publish and verify the SQS queue received the message
aws sqs receive-message \
  --queue-url $AWS_ENDPOINT_URL/000000000000/orders \
  --endpoint-url $AWS_ENDPOINT_URL
```

## SNS → SQS Fan-Out

Floci supports real SNS → SQS fan-out. When you publish to a topic, all SQS-subscribed queues receive the message immediately.

Supported subscription protocols:
- `sqs`: delivers to a Floci SQS queue
- `lambda`: invokes a Floci Lambda function
- `firehose`: puts records to a Floci Firehose delivery stream
- `http` / `https`: posts to an HTTP endpoint
- `application`: fans out to a mobile push platform endpoint (see [Mobile push](#mobile-push-mock))

## Message size

`MaximumMessageSize` is the per-topic limit, in bytes, on a published payload. It accepts `1024`
to `1048576` (1 MiB) and defaults to `262144` (256 KiB). AWS raised the maximum in September 2026
but left the default alone, so a topic that never sets the attribute behaves exactly as it did
before. `GetTopicAttributes` omits the attribute until it is set rather than reporting the
default.

```bash
aws sns set-topic-attributes --topic-arn $TOPIC_ARN \
  --attribute-name MaximumMessageSize --attribute-value 1048576 \
  --endpoint-url $AWS_ENDPOINT_URL
```

The limit counts the message body plus, per message attribute, its name, data type and value.
`Subject` is not counted. `PublishBatch` counts the sum of all its entries against the same
limit and fails the whole call rather than individual entries.

A topic above `262144` is restricted: at most 100 subscriptions, every one of them `sqs`,
`firehose` or `lambda`. Floci enforces the protocol rule on `Subscribe` and `SetTopicAttributes`
alike, and the subscription count on `SetTopicAttributes` only — matching AWS, which lets an
already-raised topic drift past 100 and catches it the next time the attribute is set. Pending
confirmations count towards both.

| Action | Condition | Error code | HTTP |
|---|---|---|---|
| `CreateTopic`, `SetTopicAttributes` | `MaximumMessageSize` not an integer between 1024 and 1048576 | `InvalidParameter` | 400 |
| `SetTopicAttributes` | Raised above 262144 with a subscription that is not `sqs`, `firehose` or `lambda` | `InvalidParameter` | 400 |
| `SetTopicAttributes` | Raised above 262144 with more than 100 subscriptions | `InvalidParameter` | 400 |
| `Subscribe` | Unsupported protocol on a topic above 262144 | `InvalidParameter` | 400 |
| `Publish` | Payload exceeds the topic's `MaximumMessageSize` | `InvalidParameter` | 400 |
| `PublishBatch` | Entries sum to more than the topic's `MaximumMessageSize` | `BatchRequestTooLong` | 400 |

CloudFormation carries the setting through: `AWS::SNS::Topic` forwards `MaximumMessageSize`, and
an update that drops the property returns the topic to the default.

A raised topic fanning out to SQS needs headroom. The notification envelope wraps the body in a
few hundred bytes of JSON, so a publish at 1 MiB no longer fits a queue at the SQS maximum and is
dropped on delivery — silently, as any delivery failure is. Keep the topic below the queue's own
`MaximumMessageSize`, or subscribe with `RawMessageDelivery=true` so the body is forwarded
unwrapped.

## FIFO topics

A topic whose name ends in `.fifo` is a FIFO topic. `Publish` and `PublishBatch` require a
`MessageGroupId`, and a message is deduplicated against its `MessageDeduplicationId` for five
minutes. Set `ContentBasedDeduplication` on the topic to derive that id from the message body.

The `FifoThroughputScope` attribute decides how wide that deduplication reaches:

| Value | Deduplication scope |
|---|---|
| `Topic` (default) | Across the whole topic: the same `MessageDeduplicationId` is a duplicate no matter which message group it arrives under |
| `MessageGroup` | Within a single message group: the same `MessageDeduplicationId` under two different `MessageGroupId`s is two distinct messages |

`MessageGroup` is what a fan-out that reuses one deduplication id per group needs, for example
publishing the same event to a topic once per tenant with the tenant as the message group.

```bash
aws sns create-topic --name events.fifo \
  --attributes FifoTopic=true,FifoThroughputScope=MessageGroup \
  --endpoint-url $AWS_ENDPOINT_URL
```

When the topic forwards to an SQS FIFO queue, set the matching queue attributes
(`DeduplicationScope=messageGroup` and `FifoThroughputLimit=perMessageGroupId`), otherwise the
queue deduplicates topic-wide on the way in.

CloudFormation carries both settings through: `AWS::SNS::Topic` forwards `FifoThroughputScope` and
`ContentBasedDeduplication`, and a FIFO topic left unnamed gets a generated name ending in `.fifo`.

## Control Tower managed topic

AWS Control Tower creates the regional
`aws-controltower-AggregateSecurityNotifications` topic before Landing Zone
Accelerator deploys its audit notification forwarder. Floci lazily materializes that
exact same-account managed topic when `Subscribe` first references it, matching the
Control Tower prerequisite without weakening normal SNS validation. Subscribing to
any other missing topic still returns `NotFound`.

## Mobile push (mock)

Floci mocks SNS mobile push for iOS and Android. No real APNS or FCM connection is
made — every push is captured in memory so tests can assert what would have been sent.

**Supported platforms:** `APNS`, `APNS_SANDBOX`, `GCM`, `FCM`. Any other platform
value returns `InvalidParameter`.

### End-to-end flow

```bash
APP_ARN=$(aws sns create-platform-application \
  --name ios-app --platform APNS \
  --attributes PlatformCredential=fake-cert \
  --endpoint-url http://localhost:4566 --query PlatformApplicationArn --output text)

ENDPOINT_ARN=$(aws sns create-platform-endpoint \
  --platform-application-arn $APP_ARN \
  --token ios-device-token-abc \
  --endpoint-url http://localhost:4566 --query EndpointArn --output text)

# Plain string payload
aws sns publish --target-arn $ENDPOINT_ARN --message '{"aps":{"alert":"hi"}}' \
  --endpoint-url http://localhost:4566

# Platform-specific payloads with MessageStructure=json
aws sns publish --target-arn $ENDPOINT_ARN --message-structure json \
  --message '{"default":"fallback","APNS":"{\"aps\":{\"alert\":\"ios\"}}","GCM":"{\"notification\":{\"body\":\"android\"}}"}' \
  --endpoint-url http://localhost:4566
```

When `MessageStructure="json"`, Floci picks the key matching the endpoint's platform
(`APNS`, `APNS_SANDBOX`, `GCM`, or `FCM`), falling back to `default`. The envelope
must be a JSON object and must include `default` — otherwise `InvalidParameter`.

### Broadcast to devices via a topic

Subscribe platform endpoints to a topic with `Protocol="application"`, then publish to
the topic to fan out to every subscribed device — each endpoint is captured exactly as
if you had published to it directly (same platform-payload resolution, same `Enabled`
gating). A disabled endpoint in the fan-out is skipped; the rest still receive the push.

```bash
aws sns subscribe --topic-arn $TOPIC_ARN \
  --protocol application --notification-endpoint $ENDPOINT_ARN \
  --endpoint-url http://localhost:4566

aws sns publish --topic-arn $TOPIC_ARN --message-structure json \
  --message '{"default":"market open","GCM":"{\"notification\":{\"body\":\"market alert\"}}"}' \
  --endpoint-url http://localhost:4566
```

Broadcast pushes surface in the same retrospection API, keyed by `EndpointArn`.

### Per-protocol payloads on topic publish

`MessageStructure="json"` resolves per subscriber, not just for mobile endpoints. Each
subscription receives the value under its own protocol key — `sqs`, `lambda`, `http`,
`https`, `email`, `email-json`, `sms`, or the push platform (`APNS`, `GCM`, …) for
`application` — falling back to `default` when that key is absent.

```bash
aws sns publish --topic-arn $TOPIC_ARN --message-structure json \
  --message '{"default":"hello","sqs":"hi sqs","GCM":"{\"notification\":{\"body\":\"hi device\"}}"}' \
  --endpoint-url http://localhost:4566
```

The SQS subscriber receives `hi sqs`, the platform endpoint receives the `GCM` payload,
and every other subscriber receives `hello`. As with any topic publish, the envelope must
be a JSON object carrying `default`, validated before fan-out begins.

### Inspecting captured pushes

```bash
# All captured pushes (newest first), or filtered by endpoint
curl http://localhost:4566/_aws/sns/push-notifications
curl "http://localhost:4566/_aws/sns/push-notifications?EndpointArn=$ENDPOINT_ARN"

# Reset between tests
curl -X DELETE http://localhost:4566/_aws/sns/push-notifications
```

### Simulating expired tokens

Two ways to make `Publish` fail with `EndpointDisabledException`:

1. **Explicit** — call `SetEndpointAttributes` with `Enabled=false`. Matches the
   real AWS flow after an async APNS/FCM failure.
2. **Sentinel** — create an endpoint whose token contains `EXPIRED`
   (case-insensitive). Floci marks it `Enabled=false` on creation, so the first
   publish fails. Lets you exercise the unhappy path with a single API call.

### Error codes

| Action | Condition | Error code | HTTP |
|---|---|---|---|
| `CreatePlatformApplication` | Missing `Name` | `InvalidParameter` | 400 |
| `CreatePlatformApplication` | Unsupported `Platform` (e.g. `WNS`, `ADM`) | `InvalidParameter` | 400 |
| `CreatePlatformEndpoint` | Missing `Token` | `InvalidParameter` | 400 |
| `CreatePlatformEndpoint` | Unknown `PlatformApplicationArn` | `NotFound` | 404 |
| `CreatePlatformEndpoint` | Same `Token`, different `CustomUserData` or attrs | `InvalidParameter` | 400 |
| `CreatePlatformEndpoint` | Platform app disabled | `PlatformApplicationDisabledException` | 400 |
| `Publish` | Unknown endpoint ARN | `NotFound` | 404 |
| `Publish` | `TargetArn` is a platform application ARN | `InvalidParameter` | 400 |
| `Publish` | Endpoint `Enabled=false` | `EndpointDisabledException` | 400 |
| `Publish` | Platform application `Enabled=false` | `PlatformApplicationDisabledException` | 400 |
| `Publish` | `MessageStructure=json` missing `default` key | `InvalidParameter` | 400 |
| `Publish` | `MessageStructure=json` message is not valid JSON | `InvalidParameter` | 400 |
| `GetPlatformApplicationAttributes` | Unknown ARN | `NotFound` | 404 |
| `GetEndpointAttributes` | Unknown ARN | `NotFound` | 404 |
| `SetEndpointAttributes` | Unknown ARN | `NotFound` | 404 |

`DeletePlatformApplication` and `DeleteEndpoint` are idempotent — they succeed
silently if the resource does not exist, matching real SNS behavior.