## Changes
- fix(server): keep SSE connection open until explicitly cancelled
- conformance: add logging to test_tool_with_logging and update
troubleshooting documentation
- chore(conformance): remove 5 passing server tests from conformance
baselines:
- tools-call-with-logging
- tools-call-with-progress
- tools-call-sampling
- tools-call-elicitation
- elicitation-sep1034-defaults
## Motivation and Context
Two bugs in StreamableHttpServerTransport caused server-to-client
notifications (e.g. notifications/message during tool calls) to be
silently dropped.
**Bug 1 — GET SSE stream closed immediately**
`handleGetRequest` rejected GET requests with 405 when
`enableJsonResponse = true` (which `mcpStreamableHttp` always sets).
Since the Ktor `sse {}` handler commits response headers before the body
runs, the reject failed silently and the function returned, causing Ktor
to close the SSE stream. There was also no `awaitCancellation()` to keep
the connection alive.
**Bug 2 — Notifications discarded in JSON mode**
In `send()`, notifications with a relatedRequestId entered the
POST-stream path but hit `if (!isTerminated) return` without being
forwarded anywhere.
**Fix**
- Remove the enableJsonResponse guard from handleGetRequest. The GET SSE
stream is an always-required notification channel, orthogonal to how
POST responses are delivered.
- Add `awaitCancellation()` to keep the GET SSE connection open until
the client disconnects or the transport closes.
- In `send()`, route notifications with a relatedRequestId to the
standalone GET SSE stream when `enableJsonResponse = true`.
## How Has This Been Tested?
Verified against the MCP conformance test suite — the
ToolsCallWithLogging scenario now passes. ngrep confirms the `GET /mcp`
stream stays open and `notifications/message` events arrive before the
`tools/call` response.
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
## Additional context
Fixes #587
Requires #585 to be merged first.
---------
Co-authored-by: devcrocod <devcrocod@gmail.com>
This commit is contained in:
Konstantin Pavlov
GitHub
parent
e88b34170c
commit
736efe9dc0
5 changed files with 37 additions and 24 deletions
|
|
@ -114,16 +114,11 @@ Tests the conformance server against all server scenarios:
|
|||
8 scenarios are expected to fail due to current SDK limitations (tracked in [
|
||||
`conformance-baseline.yml`](conformance-baseline.yml).
|
||||
|
||||
| Scenario | Suite | Root Cause |
|
||||
|---------------------------------------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------|
|
||||
| `tools-call-with-logging` | server | Notifications from tool handlers have no `relatedRequestId`; transport routes them to the standalone SSE stream instead of the request-specific stream |
|
||||
| `tools-call-with-progress` | server | *(same as above)* |
|
||||
| `tools-call-sampling` | server | *(same as above)* |
|
||||
| `tools-call-elicitation` | server | *(same as above)* |
|
||||
| `elicitation-sep1034-defaults` | server | *(same as above)* |
|
||||
| `elicitation-sep1330-enums` | server | *(same as above)* |
|
||||
| `resources-templates-read` | server | SDK does not implement `addResourceTemplate()` with URI pattern matching; resources are looked up by exact URI |
|
||||
| `elicitation-sep1034-client-defaults` | client | SDK does not fill in `default` values from the elicitation request schema before sending the response |
|
||||
| Scenario | Suite | Root Cause |
|
||||
|---------------------------------------|--------|----------------------------------------------------------------------------------------------------------------|
|
||||
| `elicitation-sep1330-enums` | server | *(same as above)* |
|
||||
| `resources-templates-read` | server | SDK does not implement `addResourceTemplate()` with URI pattern matching; resources are looked up by exact URI |
|
||||
| `elicitation-sep1034-client-defaults` | client | SDK does not fill in `default` values from the elicitation request schema before sending the response |
|
||||
|
||||
These failures reveal SDK gaps and are intentionally not fixed in this module.
|
||||
|
||||
|
|
|
|||
|
|
@ -1,11 +1,6 @@
|
|||
# Conformance test baseline - expected failures
|
||||
# Add entries here as tests are identified as known SDK limitations
|
||||
server:
|
||||
- tools-call-with-logging
|
||||
- tools-call-with-progress
|
||||
- tools-call-sampling
|
||||
- tools-call-elicitation
|
||||
- elicitation-sep1034-defaults
|
||||
- elicitation-sep1330-enums
|
||||
- resources-templates-read
|
||||
|
||||
|
|
|
|||
|
|
@ -1,5 +1,6 @@
|
|||
package io.modelcontextprotocol.kotlin.sdk.conformance
|
||||
|
||||
import io.github.oshai.kotlinlogging.KotlinLogging
|
||||
import io.modelcontextprotocol.kotlin.sdk.server.Server
|
||||
import io.modelcontextprotocol.kotlin.sdk.types.AudioContent
|
||||
import io.modelcontextprotocol.kotlin.sdk.types.CallToolResult
|
||||
|
|
@ -33,6 +34,8 @@ internal const val PNG_BASE64 =
|
|||
// Minimal WAV (base64)
|
||||
internal const val WAV_BASE64 = "UklGRiYAAABXQVZFZm10IBAAAAABAAEAQB8AAAB9AAACABAAZGF0YQIAAAA="
|
||||
|
||||
private val logger = KotlinLogging.logger {}
|
||||
|
||||
@Suppress("LongMethod")
|
||||
fun Server.registerConformanceTools() {
|
||||
// 1. Simple text
|
||||
|
|
@ -429,6 +432,7 @@ fun Server.registerConformanceTools() {
|
|||
name = "test_tool_with_logging",
|
||||
description = "test_tool_with_logging",
|
||||
) {
|
||||
logger.debug { "[test_tool_with_logging] Sending message 1" }
|
||||
sendLoggingMessage(
|
||||
LoggingMessageNotification(
|
||||
LoggingMessageNotificationParams(
|
||||
|
|
@ -439,6 +443,7 @@ fun Server.registerConformanceTools() {
|
|||
),
|
||||
)
|
||||
delay(50.milliseconds)
|
||||
logger.debug { "[test_tool_with_logging] Sending message #2" }
|
||||
sendLoggingMessage(
|
||||
LoggingMessageNotification(
|
||||
LoggingMessageNotificationParams(
|
||||
|
|
@ -449,6 +454,7 @@ fun Server.registerConformanceTools() {
|
|||
),
|
||||
)
|
||||
delay(50.milliseconds)
|
||||
logger.debug { "[test_tool_with_logging] Sending message 3" }
|
||||
sendLoggingMessage(
|
||||
LoggingMessageNotification(
|
||||
LoggingMessageNotificationParams(
|
||||
|
|
@ -458,6 +464,7 @@ fun Server.registerConformanceTools() {
|
|||
),
|
||||
),
|
||||
)
|
||||
|
||||
CallToolResult(listOf(TextContent("Simple text content")))
|
||||
}
|
||||
|
||||
|
|
|
|||
|
|
@ -0,0 +1,9 @@
|
|||
# Level of logging for the ROOT logger: ERROR, WARN, INFO, DEBUG, TRACE (default is INFO)
|
||||
org.slf4j.simpleLogger.defaultLogLevel=INFO
|
||||
org.slf4j.simpleLogger.showThreadName=true
|
||||
org.slf4j.simpleLogger.showDateTime=false
|
||||
|
||||
# Log level for specific packages or classes
|
||||
org.slf4j.simpleLogger.log.io.ktor.server=DEBUG
|
||||
org.slf4j.simpleLogger.log.io.modelcontextprotocol=DEBUG
|
||||
org.slf4j.simpleLogger.log.io.modelcontextprotocol.kotlin.sdk.conformance=INFO
|
||||
|
|
@ -28,6 +28,7 @@ import io.modelcontextprotocol.kotlin.sdk.types.RPCError
|
|||
import io.modelcontextprotocol.kotlin.sdk.types.RPCError.ErrorCode.REQUEST_TIMEOUT
|
||||
import io.modelcontextprotocol.kotlin.sdk.types.RequestId
|
||||
import io.modelcontextprotocol.kotlin.sdk.types.SUPPORTED_PROTOCOL_VERSIONS
|
||||
import kotlinx.coroutines.awaitCancellation
|
||||
import kotlinx.coroutines.job
|
||||
import kotlinx.coroutines.sync.Mutex
|
||||
import kotlinx.coroutines.sync.withLock
|
||||
|
|
@ -242,7 +243,15 @@ public class StreamableHttpServerTransport(private val configuration: Configurat
|
|||
}
|
||||
|
||||
val isTerminated = message is JSONRPCResponse || message is JSONRPCError
|
||||
if (!isTerminated) return
|
||||
if (!isTerminated) {
|
||||
if (configuration.enableJsonResponse) {
|
||||
// In JSON response mode there is no per-request SSE stream, so route notifications
|
||||
// that are logically associated with a request to the standalone GET SSE stream.
|
||||
val standaloneStream = streamsMapping[STANDALONE_SSE_STREAM_ID]
|
||||
standaloneStream?.let { emitOnStream(STANDALONE_SSE_STREAM_ID, it.session, message) }
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
requestToResponseMapping[responseRequestId!!] = message
|
||||
val relatedIds = requestToStreamMapping.filterValues { it == streamId }.keys
|
||||
|
|
@ -411,14 +420,9 @@ public class StreamableHttpServerTransport(private val configuration: Configurat
|
|||
|
||||
@Suppress("ReturnCount")
|
||||
public suspend fun handleGetRequest(session: ServerSSESession?, call: ApplicationCall) {
|
||||
if (configuration.enableJsonResponse) {
|
||||
call.reject(
|
||||
HttpStatusCode.MethodNotAllowed,
|
||||
RPCError.ErrorCode.CONNECTION_CLOSED,
|
||||
"Method not allowed.",
|
||||
)
|
||||
return
|
||||
}
|
||||
// NOTE: enableJsonResponse only controls how POST responses are delivered (JSON vs. SSE).
|
||||
// The standalone GET SSE stream is always supported — it is the only channel available
|
||||
// for server-to-client notifications when enableJsonResponse = true.
|
||||
val sseSession = session ?: error("Server session can't be null for streaming GET requests")
|
||||
|
||||
val acceptHeader = call.request.header(HttpHeaders.Accept)
|
||||
|
|
@ -456,6 +460,9 @@ public class StreamableHttpServerTransport(private val configuration: Configurat
|
|||
sseSession.coroutineContext.job.invokeOnCompletion {
|
||||
streamsMapping.remove(STANDALONE_SSE_STREAM_ID)
|
||||
}
|
||||
// Keep the SSE connection open until the client disconnects or the transport is closed.
|
||||
// Without this, the Ktor sse{} handler returns immediately, closing the stream.
|
||||
awaitCancellation()
|
||||
}
|
||||
|
||||
public suspend fun handleDeleteRequest(call: ApplicationCall) {
|
||||
|
|
|
|||
Loading…
Reference in a new issue