Support server to client notifications from the stateless transport #472
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Randgalt
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Aug 8, 2025
| * @param method notification method name | ||
| * @param params any parameters or {@code null} | ||
| */ | ||
| default void sendNotification(String method, Object params) { |
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An alternative to this might be a separate McpNotifier instance that would be accessed by calling McpTransportContext.get() with a lib-defined key. wdyt?
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The MCP spec allows stateless servers to send notifications to the client during a request. The response needs to be upgraded to SSE and the notifications are send in a stream until the final result is sent. This commit adds a `sendNotification` method to the transport context allowing each transport implementation to implement it or not. In this commit, HttpServletStatelessServerTransport implements the method and when the caller first sends a notification, the response is changed to `TEXT_EVENT_STREAM` and events are then streamed until the final result. This change will allow future features such as logging, list changes, etc. should we ever decide to support sessions in some manner. Even if we don't support sessions, sending progress notifications is a useful feature by itself.
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@tzolov do you have plans to support sessions for the stateless transport/server? We have some ideas that we will likely implement in our own code but could contribute here if there's interest. |
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Noe: I've only done |
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@tzolov any interest in this? If so, I can rebase, etc. |
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I will update the PR if the project is positive on the idea |
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The MCP spec allows stateless servers to send notifications to the client during a request. The response needs to be upgraded to SSE and the notifications are send in a stream until the final result is sent.
This commit adds a
sendNotificationmethod to the transport context allowing each transport implementation to implement it or not. In this commit, HttpServletStatelessServerTransport implements the method and when the caller first sends a notification, the response is changed toTEXT_EVENT_STREAMand events are then streamed until the final result.This change will allow future features such as logging, list changes, etc. should we ever decide to support sessions in some manner. Even if we don't support sessions, sending progress notifications is a useful feature by itself.
Motivation and Context
We would like to have support for progress notifications in the stateless implementation.
How Has This Been Tested?
testNotifications()added toHttpServletStatelessIntegrationTestsBreaking Changes
none
Types of changes
Checklist