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fix: connection resilience, sync-on-save — fixes #287, #299, #309, #323 #374

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fix: connection resilience, sync-on-save — fixes #287, #299, #309, #323 #374

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3610590
fix: enhance connection resilience and fix TCP RST causing spurious c…
May 8, 2026
f2e3f63
fix(scm): sync on save not fs changes (fixes #323, fixes #299)
May 8, 2026
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4 changes: 4 additions & 0 deletions l10n/bundle.l10n.json
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,9 @@
"Cannot init SocketIOAPI for {serverName}": "Cannot init SocketIOAPI for {serverName}",
"Connection lost: {serverName}": "Connection lost: {serverName}",
"Reload": "Reload",
"Retry": "Retry",
"Connection lost": "Connection lost",
"Reconnecting to {serverName}...": "Reconnecting to {serverName}...",
"Refreshing": "Refreshing",
"Done": "Done",
"From Another Project": "From Another Project",
Expand Down Expand Up @@ -98,6 +100,8 @@
"At {docPath}, Line {row}": "At {docPath}, Line {row}",
"Select a collaborator below to jump to.": "Select a collaborator below to jump to.",
"Not connected": "Not connected",
"Reconnecting...": "Reconnecting...",
"Connection interrupted, attempting to reconnect...": "Connection interrupted, attempting to reconnect...",
"Online": "Online",
"Active": "Active",
"Idle": "Idle",
Expand Down
183 changes: 125 additions & 58 deletions src/api/base.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -243,7 +243,14 @@ export class BaseAPI {
_initSocketV0(identity:Identity, query?:string) {
const url = new URL(this.url).origin + (query ?? '');
return (require('socket.io-client').connect as any)(url, {
reconnect: false,
// Enable auto-reconnect to avoid creating new TCP connections on transient failures.
// Creating new connections without proper teardown of old ones causes TCP RST packets
// when the server sends data on abandoned connections (see issue #309).
// Note: socket.io-client 0.9.x uses space-separated option names.
reconnect: true,
'reconnection delay': 1000,
'reconnection limit': 16000,
'max reconnection attempts': 10,
'force new connection': true,
extraHeaders: {
'Origin': new URL(this.url).origin,
Expand Down Expand Up @@ -340,68 +347,128 @@ export class BaseAPI {
return this;
}

/**
* Check if an HTTP error is transient (worth retrying).
* Retries on: 5xx server errors, network errors (fetch failures), and 429 rate limiting.
*/
private isTransientError(statusCode: number | undefined, errorMessage?: string): boolean {
if (statusCode === undefined) {
// Network-level error (DNS, connection refused, reset, timeout)
return true;
}
// Server errors and rate limiting
if (statusCode >= 500 || statusCode === 429) {
return true;
}
// Common transient network error messages
if (errorMessage && (
errorMessage.includes('ECONNRESET') ||
errorMessage.includes('ETIMEDOUT') ||
errorMessage.includes('ECONNREFUSED') ||
errorMessage.includes('ENOTFOUND') ||
errorMessage.includes('socket hang up')
)) {
return true;
}
return false;
}

protected async request(type:'GET'|'POST'|'PUT'|'DELETE', route:string, body?:FormData|object, callback?: (res?:string)=>object|undefined, extraHeaders?:object ): Promise<ResponseSchema> {
if (this.identity===undefined) { return Promise.reject(); }

let res = undefined;
switch(type) {
case 'GET':
res = await fetch(this.url+route, {
method: 'GET', redirect: 'manual', agent: this.agent,
headers: {
'Connection': 'keep-alive',
'Cookie': this.identity.cookies,
...extraHeaders
}
});
break;
case 'POST':
// if body is FormData, then it is a raw body
const content_type = body instanceof FormData ? undefined : {'Content-Type': 'application/json'};
const raw_body = body instanceof FormData ? body : JSON.stringify({
_csrf: this.identity.csrfToken,
...body
});
res = await fetch(this.url+route, {
method: 'POST', redirect: 'manual', agent: this.agent,
headers: {
'Connection': 'keep-alive',
'Cookie': this.identity.cookies,
...content_type,
...extraHeaders
},
body: raw_body
});
break;
case 'PUT':
break;
case 'DELETE':
res = await fetch(this.url+route, {
method: 'DELETE', redirect: 'manual', agent: this.agent,
headers: {
'Connection': 'keep-alive',
'Cookie': this.identity.cookies,
'X-Csrf-Token': this.identity.csrfToken,
...extraHeaders
}
});
break;
};
const MAX_HTTP_RETRIES = 2;
let lastError: {statusCode?: number, message?: string} = {};

for (let attempt = 0; attempt <= MAX_HTTP_RETRIES; attempt++) {
try {
let res = undefined;
switch(type) {
case 'GET':
res = await fetch(this.url+route, {
method: 'GET', redirect: 'manual', agent: this.agent,
headers: {
'Connection': 'keep-alive',
'Cookie': this.identity!.cookies,
...extraHeaders
}
});
break;
case 'POST':
// if body is FormData, then it is a raw body
const content_type = body instanceof FormData ? undefined : {'Content-Type': 'application/json'};
const raw_body = body instanceof FormData ? body : JSON.stringify({
_csrf: this.identity!.csrfToken,
...body
});
res = await fetch(this.url+route, {
method: 'POST', redirect: 'manual', agent: this.agent,
headers: {
'Connection': 'keep-alive',
'Cookie': this.identity!.cookies,
...content_type,
...extraHeaders
},
body: raw_body
});
break;
case 'PUT':
break;
case 'DELETE':
res = await fetch(this.url+route, {
method: 'DELETE', redirect: 'manual', agent: this.agent,
headers: {
'Connection': 'keep-alive',
'Cookie': this.identity!.cookies,
'X-Csrf-Token': this.identity!.csrfToken,
...extraHeaders
}
});
break;
};

if (res && (res.status===200 || res.status===204)) {
const _res = res.status===200 ? await res.text() : undefined;
const response = callback && callback(_res);
return {
type: 'success',
...response
} as ResponseSchema;
} else {
res = res || { status:'undefined', text:()=>'' };
return {
type: 'error',
message: `${res.status}: `+await res.text()
};
if (res && (res.status===200 || res.status===204)) {
const _res = res.status===200 ? await res.text() : undefined;
const response = callback && callback(_res);
return {
type: 'success',
...response
} as ResponseSchema;
} else if (res && this.isTransientError(res.status) && attempt < MAX_HTTP_RETRIES) {
// Transient error: retry with backoff
const delayMs = Math.min(1000 * Math.pow(2, attempt), 4000);
console.log(`HTTP ${res.status} on ${route}, retrying in ${delayMs}ms (attempt ${attempt + 1}/${MAX_HTTP_RETRIES})`);
lastError = {statusCode: res.status, message: await res.text().catch(() => '')};
await new Promise(r => setTimeout(r, delayMs));
continue;
} else {
const resOrFallback = res || { status:'undefined', text: async () => '' };
let errorBody = '';
try { errorBody = await resOrFallback.text(); } catch { errorBody = ''; }
return {
type: 'error',
message: `${resOrFallback.status}: ${errorBody}`
};
}
} catch (err: any) {
const errMsg = err?.message || String(err);
if (this.isTransientError(undefined, errMsg) && attempt < MAX_HTTP_RETRIES) {
const delayMs = Math.min(1000 * Math.pow(2, attempt), 4000);
console.log(`HTTP fetch error on ${route}: ${errMsg}, retrying in ${delayMs}ms (attempt ${attempt + 1}/${MAX_HTTP_RETRIES})`);
await new Promise(r => setTimeout(r, delayMs));
continue;
}
return {
type: 'error',
message: errMsg
};
}
}

// All retries exhausted
return {
type: 'error',
message: lastError.message || `Request failed after ${MAX_HTTP_RETRIES + 1} attempts`
};
}

protected async download(route:string) {
Expand Down
67 changes: 63 additions & 4 deletions src/api/socketio.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -78,9 +78,13 @@ export class SocketIOAPI {
private scheme: ConnectionScheme = 'v1';
private record?: Promise<ProjectEntity>;
private _handlers: Array<EventsHandler> = [];
/** Track EventBus listeners for cleanup to prevent MaxListenersExceededWarning */
private _eventBusCleanups: Array<()=>void> = [];

private socket?: any;
private emit: any;
/** Track the scheme used when the socket was last initialized */
private _socketInitScheme?: ConnectionScheme;

constructor(private url:string,
private readonly api:BaseAPI,
Expand All @@ -91,6 +95,29 @@ export class SocketIOAPI {
}

init() {
// Clean up old EventBus listeners before creating new socket
this._cleanupEventBusListeners();

// CRITICAL: Properly disconnect old socket before creating a new one.
// Without this, the old TCP connection is abandoned but still alive. When the
// server later sends data on it (out-of-order/late packets), the OS TCP stack
// responds with RST, which can cause the server to drop ALL connections from
// this client — explaining the "connection lost" loop reported in issue #309.
if (this.socket) {
try {
// Remove all listeners to prevent stale event handlers from firing
if (typeof this.socket.removeAllListeners === 'function') {
this.socket.removeAllListeners();
}
// Gracefully close the connection (sends FIN, not RST)
if (typeof this.socket.disconnect === 'function') {
this.socket.disconnect();
}
} catch {
// Best-effort cleanup; socket may already be in a bad state
}
}

// connect
switch(this.scheme) {
case 'Alt':
Expand Down Expand Up @@ -127,7 +154,23 @@ export class SocketIOAPI {
this.emit = require('util').promisify(this.socket.emit).bind(this.socket);
// resume handlers
this.initInternalHandlers();
// this.resumeEventHandlers(this._handlers);
// Re-register existing event handlers on the new socket
this.resumeEventHandlers(this._handlers);
// Track which scheme this socket was created with
this._socketInitScheme = this.scheme;
}

/** Returns true if the socket needs re-initialization (scheme changed, or socket was never init'd) */
get needsReinit(): boolean {
return this._socketInitScheme !== this.scheme || !this.socket;
}

/** Clean up any accumulated EventBus listeners */
private _cleanupEventBusListeners() {
for (const cleanup of this._eventBusCleanups) {
try { cleanup(); } catch {}
}
this._eventBusCleanups = [];
}

private initInternalHandlers() {
Expand All @@ -141,10 +184,22 @@ export class SocketIOAPI {
console.log('SocketIOAPI: forceDisconnect', message);
});
this.socket.on('connectionRejected', (err:any) => {
console.log('SocketIOAPI: connectionRejected.', err.message);
console.log('SocketIOAPI: connectionRejected.', err?.message || err);
// If v2 also gets rejected, fall back to v1 rather than staying stuck
if (this.scheme === 'v2') {
console.log('SocketIOAPI: v2 rejected, falling back to v1');
this.scheme = 'v1';
}
// Disable auto-reconnect on this socket: the server explicitly rejected
// our connection parameters. Reconnecting would just get rejected again,
// creating unnecessary TCP connection churn (and RST packets).
if (this.socket.io && typeof this.socket.io.reconnect === 'function') {
this.socket.io.reconnect(false);
}
});
this.socket.on('error', (err:any) => {
throw new Error(err);
// Log error instead of throwing to avoid crashing the extension
console.error('SocketIOAPI: socket error', err?.message || err);
});

if (this.scheme==='v2') {
Expand Down Expand Up @@ -230,9 +285,11 @@ export class SocketIOAPI {
this.socket.on('connectionAccepted', (_:any, publicId:any) => {
handler(publicId);
});
EventBus.on('socketioConnectedEvent', (arg:{publicId:string}) => {
// Track EventBus listener via Disposable for cleanup to prevent MaxListenersExceededWarning
const eventBusDisposable = EventBus.on('socketioConnectedEvent', (arg:{publicId:string}) => {
handler(arg.publicId);
});
this._eventBusCleanups.push(() => eventBusDisposable.dispose());
break;
case handlers.onClientUpdated:
this.socket.on('clientTracking.clientUpdated', (user:UpdateUserSchema) => {
Expand Down Expand Up @@ -306,6 +363,8 @@ export class SocketIOAPI {
});
const rejectPromise = new Promise((_, reject) => {
this.socket.on('connectionRejected', (err:any) => {
// Only fall back to v2 if we haven't already tried it;
// otherwise let the outer retry logic handle backoff
this.scheme = 'v2';
reject(err.message);
});
Expand Down
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