Fix the issue that SSE connection can not be disconnected in some cases [INS-5464]

[yaoweiprc]

When connecting the Insomnia client to a locally running backend service, switching between multiple organizations causes HTTP requests to remain in a pending state.

I captured and analyzed the client’s network traffic and found that when switching organizations, the old SSE connections are not being closed. Once the number of SSE connections exceeds 6, all new requests remain in a pending state.

In the renderer process, the EventSource.close method is explicitly called to close old connections when switching organizations, but it clearly doesn’t take effect.

In the Insomnia app, we are not sending requests directly from the renderer process — instead, they are forwarded from the main process using electron.net.fetch.

net.fetch is indeed built on top of Chromium's native networking library, so it makes sense that it's subject to Chromium's per-domain connection limits.

The root cause of the issue was that under certain network conditions, Electron's net.fetch method fails to properly close SSE (Server-Sent Events) connections.

To work around this problem, I explored alternative solutions. I eventually found that using net.request inside protocol.handle, and manually constructing a Response object, provided a viable workaround. By using a ReadableStream as the Response.body and listening for its cancel event, I was able to accurately detect when the SSE connection was closed from the renderer process.

However, this workaround introduced a new problem. Since we're also forwarding regular HTTP requests through protocol.handle, the SSE requests made with net.request are inadvertently intercepted again by the handler designed for HTTP forwarding. That handler uses net.fetch, which brings us back to the original issue—SSE connections still can't be properly closed.

Electron does not provide a way to make net.request bypass other protocol handlers.

As a result, the only viable solution is to avoid using Electron’s built-in networking APIs for SSE entirely. Instead, I switched to using node-libcurl, which successfully establishes and closes SSE connections as expected.

[gatzjames]

🙏👏 Awesome write-up and explanation!

Electron does not provide a way to make net.request bypass other protocol handlers.

Curious if you tried the bypassCustomProtocolHandlers option in net.fetch.

We should double check the system Certificates and Proxy options work as before
but overall looks good to me! 👍