Export SendNotificationToAllClients

[scottfeldman]

[First PR to project]

Export sendNotificationToAllClients so it can be called from the MCP server to send unsolicited notifications to all clients (sessions).

I have a use-case for my MCP server where I need to send notifications of state change to all sessions. My MCP server is fronting a device hub, and the device's on the hub would like to send notifications up to the LLM.

There is probably a reason why this was not exported, so please forgive this PR if that's the case. I just could not figure out what the spec says about this.

In any case, I added a test and tested with the Inspector. The Inspectory sees the unsolicited notifications. Cool! I also tried with Cursor and Claude, but neither seem to recognize notifications, no matter how hard I tried to convince them.

Summary by CodeRabbit

• Tests
  • Added tests to verify that notifications are correctly sent to all active client sessions.

[coderabbitai]

Walkthrough

This change makes the sendNotificationToAllClients method of the MCPServer struct exported by renaming it to SendNotificationToAllClients, updating all internal references accordingly. Additionally, a new test function is introduced to verify that notifications are correctly sent to all active client sessions. The test ensures that each session receives the expected notifications and that no extra notifications remain in the session channels after processing.

Changes

Files	Change Summary
server/server.go	Renamed and exported sendNotificationToAllClients to SendNotificationToAllClients; updated references in AddTools and DeleteTools methods.
server/server_test.go	Added TestMCPServer_SendNotificationToAllClients to test notification delivery to all active sessions.

Possibly related PRs

• Add per-session notifications handling #46: Originally introduced the sendNotificationToAllClients method, per-session notification handling, and session management, which are directly affected by this PR's changes.

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📥 Commits

Reviewing files that changed from the base of the PR and between 71b910b and d453b0b.

📒 Files selected for processing (2)

• server/server.go (3 hunks)
• server/server_test.go (1 hunks)

🧰 Additional context used

🧬 Code Graph Analysis (1)

server/server_test.go (2)

server/server.go (3)

• MCPServer (143-166)
• ClientSession (54-63)
• NewMCPServer (375-401)

mcp/types.go (2)

• JSONRPCNotification (192-195)
• Params (104-104)

🔇 Additional comments (7)

server/server.go (4)

214-215: Good change to export the function for external usage.

The capitalization of the function name from sendNotificationToAllClients to SendNotificationToAllClients properly exports this method, allowing external packages to call it directly. This aligns with the PR objective of enabling the MCP server to send unsolicited notifications to all connected clients.

---

214-239: The implementation is robust for concurrent session handling.

The implementation correctly:

1. Handles concurrent access to the sessions map using sync.Map
2. Only sends notifications to initialized sessions
3. Uses a non-blocking send to avoid getting stuck on full channels
4. Continues iteration even if some notification channels are blocked

This makes the function reliable for use with many concurrent clients.

---

475-475: References properly updated to use the exported function name.

The internal call has been correctly updated to use the exported function name.

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495-495: References properly updated to use the exported function name.

The internal call has been correctly updated to use the exported function name.

server/server_test.go (3)

576-643: Well-structured test for the newly exported function.

This test comprehensively validates the functionality of SendNotificationToAllClients by:

1. Creating multiple active sessions with buffered notification channels
2. Sending multiple notifications with different parameters
3. Verifying that all sessions receive each notification with correct parameters in sequence
4. Checking that no extra notifications remain in the channels

The test covers the primary use case and edge cases effectively.

---

592-598: Good test data with incrementing values.

Using incrementing values in the notification parameters allows the test to verify both the reception of notifications and their correct ordering, which is important for ensuring deterministic behavior.

---

600-631: Thorough validation of notifications in each session.

The test correctly:

1. Iterates through all registered sessions
2. Verifies method names
3. Checks that parameters match the expected values
4. Ensures the notifications are received in the correct order
5. Confirms no extra notifications remain

This level of detail in the test helps ensure the function works as expected in all scenarios.

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