# SSE Flakiness — Root-Cause Analysis

**Date:** 2026-04-21
**Tests:** `AgentSseControllerIT.sseConnect_unknownAgent_returns404`, `.lastEventIdHeader_connectionSucceeds`, `.pingKeepalive_receivedViaSseStream`, `SseSigningIT.deepTraceEvent_containsValidSignature`

## Summary

Not order-dependent flakiness (triage report was wrong). Three distinct root causes, one production bug and one test-infrastructure issue, all reproducible when running the classes in isolation.

## Reproduction

```bash
mvn -pl cameleer-server-app -am -Dit.test='AgentSseControllerIT' -Dtest='!*' \
    -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false verify
```

Result: 3 failures out of 7 tests with a cold CH container. Not order-dependent.

## Root causes

### 1. `AgentSseController.events` auto-heal is over-permissive (security bug)

**File:** `cameleer-server-app/src/main/java/com/cameleer/server/app/controller/AgentSseController.java:63-76`

```java
AgentInfo agent = registryService.findById(id);
if (agent == null) {
    var jwtResult = ...;
    if (jwtResult != null) {     // ← only checks JWT presence
        registryService.register(id, id, application, env, ...);
    } else {
        throw 404;
    }
}
```

**Bug:** auto-heal registers *any* path id when any valid JWT is present, regardless of whether the JWT subject matches the path id. A holder of agent X's JWT can open SSE for any path-id Y, silently spoofing Y.

**Surface symptom:** `sseConnect_unknownAgent_returns404` sends a JWT for `test-agent-sse-it` and requests SSE for `unknown-sse-agent`. Auto-heal kicks in, returns 200 with an infinite empty stream. Test's `statusFuture.get(5s)` — which uses `BodyHandlers.ofString()` and waits for the full body — times out instead of getting a synchronous 404.

**Fix:** only auto-heal when `jwtResult.subject().equals(id)`.

### 2. `SseConnectionManager.pingAll` reads an unprefixed property key (production bug)

**File:** `cameleer-server-app/src/main/java/com/cameleer/server/app/agent/SseConnectionManager.java:172`

```java
@Scheduled(fixedDelayString = "${agent-registry.ping-interval-ms:15000}")
```

**Bug:** `AgentRegistryConfig` is `@ConfigurationProperties(prefix = "cameleer.server.agentregistry")`. The scheduler reads an unprefixed `agent-registry.*` key that the YAML never defines — so the default 15s always applies, regardless of config. Same family of bug as the `MetricsFlushScheduler` fix in commit `a6944911`.

**Fix:** `${cameleer.server.agentregistry.ping-interval-ms:15000}`.

### 3. SSE response body doesn't flush until first event (test timing dependency)

**File:** `cameleer-server-app/src/main/java/com/cameleer/server/app/agent/SseConnectionManager.java:connect()`

Spring's `SseEmitter` holds the response open but doesn't flush headers to the client until the first `emitter.send()`. Until then, clients using `HttpResponse.BodyHandlers.ofInputStream()` block on the first byte.

**Surface symptom:**
- `lastEventIdHeader_connectionSucceeds` — asserts `awaitConnection(5000)` is `true`. The latch counts down in `.thenAccept(response -> ...)`, which in practice only fires once body bytes start flowing (JDK 21 behaviour with SSE streams). Default ping cadence is 15s → 5s assertion times out.
- `pingKeepalive_receivedViaSseStream` — waits 5s for a `:ping` line. The scheduler runs every 15s (both by default, and because of bug #2, unconditionally).
- `SseSigningIT.deepTraceEvent_containsValidSignature` — same family: `awaitConnection(5000).isTrue()`.

**Fix:** send an initial `: connected` comment as part of `connect()`. Spring flushes on the first `.send()`, so an immediate comment forces the response headers + first byte to hit the wire, which triggers the client's `thenAccept` callback. Also solves the ping-test: the initial comment is observed as a keepalive line within the test's polling window.

## Hypothesis ladder (ruled out)

- **Order-dependent singleton leak** — ruled out: every failure reproduces when the class is run solo.
- **Tomcat async thread pool exhaustion** — ruled out: `SseEmitter(Long.MAX_VALUE)` does hold threads, but the 7-test class doesn't reach Tomcat's defaults.
- **SseConnectionManager emitter-map contamination** — ruled out: each test uses a unique agent id (UUID-suffixed), and the `@Component` is the same instance across tests but the emitter map is keyed by agent id, no collisions.

## Verification

```
mvn -pl cameleer-server-app -am -Dit.test='AgentSseControllerIT,SseSigningIT' ... verify
# Tests run: 9, Failures: 0, Errors: 0, Skipped: 0
```

All 9 tests green with the three fixes applied.