Files
T
Sharon KatzandClaude Opus 4.6 b36be84e85 Add native Splunk HEC log destination (#48455 )
**Related issue:** Resolves #25574

# Checklist for submitter

- [x] Changes file added for user-visible changes in `changes/`
- [x] Input data is properly validated, `SELECT *` is avoided, SQL
injection is prevented (using placeholders for values in statements), JS
inline code is prevented especially for url redirects, and untrusted
data interpolated into shell scripts/commands is validated against shell
metacharacters.
- [x] Timeouts are implemented and retries are limited to avoid infinite
loops

## Testing

- [x] Added/updated automated tests
- [x] QA'd all new/changed functionality manually

---

## Summary

- Adds a new `splunk` log plugin that sends osquery logs directly to
Splunk's HTTP Event Collector (HEC) endpoint
- Eliminates the need for middleware like AWS Firehose when using Splunk
as a log destination
- Follows the same pattern as existing log destinations (Firehose, Kafka
REST, NATS, etc.)
- Includes `insecure_skip_verify` option for environments with
self-signed TLS certs

## UI changes

Follows the same pattern as the NATS log destination PR (#36527) --
adding "Splunk" to the display name, tooltip, and TypeScript type union.
No new components, pages, or styles.

### Manage automations modal -- "Log destination: Splunk"
<img width="822" height="527" alt="image"
src="https://github.com/user-attachments/assets/2533207f-fa95-4364-8ee0-3c39cd3e8e4d"
/>


### Query details page -- "Log destination: Splunk"
<img width="1905" height="662" alt="image"
src="https://github.com/user-attachments/assets/069a5005-f95c-4562-a819-fd8bdcc349f7"
/>



### Tooltip on hover
<img width="639" height="348" alt="image"
src="https://github.com/user-attachments/assets/809a47a6-b82a-4f45-b731-77b2d2c87947"
/>



### Edit query form -- "sent to your log destination: Splunk"
<img width="451" height="814" alt="image"
src="https://github.com/user-attachments/assets/b78b9a57-1f0c-4413-8b7c-654de1fd40a2"
/>



### Save new query modal -- "sent to your log destination: Splunk"
<img width="536" height="698" alt="image"
src="https://github.com/user-attachments/assets/d0a0ab01-66fe-4d63-9190-9c5e840e456d"
/>

---

### How it works

The Splunk writer (`server/logging/splunk.go`) implements the
`fleet.JSONLogger` interface. On startup it performs a health check
against the HEC `/services/collector/health` endpoint. On each `Write()`
call, it wraps each log entry in Splunk's HEC event format (adding
`time`, `index`, `source`, `sourcetype`), batches them up to 1 MB, and
POSTs to `/services/collector/event` with the `Authorization: Splunk
<token>` header. If a batch exceeds 1 MB it flushes and starts a new
one. Events over 1 MB are dropped with a log warning. Transient errors
(HTTP 503) are retried with exponential backoff (up to 8 retries).

### Configuration

```yaml
osquery:
  status_log_plugin: splunk
  result_log_plugin: splunk

splunk:
  url: https://splunk.example.com:8088
  token: <HEC token>
  index: main
  source: fleet
  source_type: fleet:json
  insecure_skip_verify: false  # set true for self-signed certs
```

Or via environment variables:
```
FLEET_OSQUERY_STATUS_LOG_PLUGIN=splunk
FLEET_OSQUERY_RESULT_LOG_PLUGIN=splunk
FLEET_SPLUNK_URL=https://splunk.example.com:8088
FLEET_SPLUNK_TOKEN=<HEC token>
FLEET_SPLUNK_INDEX=main
FLEET_SPLUNK_SOURCE=fleet
FLEET_SPLUNK_SOURCE_TYPE=fleet:json
```

### Files changed
- `server/logging/splunk.go` -- Splunk HEC log writer with batching,
retry, and health check
- `server/logging/splunk_test.go` -- 9 unit tests
- `server/logging/splunk_integration_test.go` -- 3 integration tests
against real Splunk (gated by env var)
- `server/logging/logging.go` -- Added `SplunkConfig` and `case
"splunk"` to factory
- `server/config/config.go` -- Added `SplunkConfig` struct and config
flags
- `cmd/fleet/logging.go` -- Wired Splunk config into logging builder
- `server/fleet/app.go` -- Added `SplunkConfig` type for API responses
(excludes token)
- `server/service/service_appconfig.go` -- Added `case "splunk"` to
logging plugin validation
- `frontend/interfaces/config.ts` -- Added `"splunk"` to LogDestination
type
-
`frontend/components/LogDestinationIndicator/LogDestinationIndicator.tsx`
-- Added Splunk display name and tooltip
- `docs/Configuration/fleet-server-configuration.md` -- Splunk config
documentation
- `docs/Get started/FAQ.md` -- Updated plugin list
- `articles/log-destinations.md` -- Updated Splunk section with native
HEC docs
- `changes/25574-splunk-log-destination` -- Change file

## Test plan

### Unit tests (9 tests)
- [x] `TestSplunkWrite` -- sends 3 events, verifies HEC format, auth
header, index/source/sourcetype
- [x] `TestSplunkWriteEmpty` -- empty logs don't trigger HTTP request
- [x] `TestSplunkServerError` -- HEC 403 propagates as error
- [x] `TestSplunkHealthCheckFailure` -- constructor fails on bad health
- [x] `TestSplunkRecordTooBig` -- oversized events (>1MB) are dropped,
normal events still sent
- [x] `TestSplunkSplitBatchBySize` -- logs exceeding 1MB batch limit are
split into multiple requests
- [x] `TestSplunkRetryOnServiceUnavailable` -- 503 retried with backoff,
succeeds on 3rd attempt
- [x] `TestSplunkRetryExhausted` -- after 9 attempts (1 + 8 retries)
returns error
- [x] `TestSplunkMissingConfig` -- empty URL/token returns descriptive
error

### Integration tests (3 tests, gated by `SPLUNK_INTEGRATION_TEST=1`)
- [x] `TestSplunkIntegration` -- 3 events sent via writer, queried back
from Splunk REST API
- [x] `TestSplunkIntegrationBatch` -- 100 events in one Write(), all
confirmed indexed
- [x] `TestSplunkIntegrationBadToken` -- bad token Write() returns 403

### End-to-end test (macOS ARM64, real osquery agent)

1. Started Splunk Enterprise, MySQL, Redis via Docker
2. Built Fleet server from this branch with
`--osquery_status_log_plugin=splunk`
3. Set up Fleet, enrolled a real osquery 5.23.0 agent on this MacBook
4. **83 real osquery status log events indexed in Splunk** with correct
source/sourcetype/index
5. Each event contained full osquery data (`hostIdentifier`,
`host_uuid`, `calendarTime`, `severity`, `message`, `decorations`)

### Splunk showing real osquery events from Fleet
<img width="1910" height="861" alt="image"
src="https://github.com/user-attachments/assets/192490bf-d594-4424-a3e3-a18306892873"
/>


Generated with [Claude Code](https://claude.ai/code)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added native Splunk HEC logging destination for status, result, and
audit logs.
* Updated the log destination UI to display **Splunk** with a dedicated
tooltip.
* Added Splunk HEC configuration (URL/token/index/source/source type)
including TLS verification control.
* **Bug Fixes**
* Improved log delivery with batching, retries for temporary HTTP
failures, and safeguards for oversized events.
* **Tests**
* Added unit tests and optional integration tests covering routing,
batching, retries, and error scenarios.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>