louislam/dockge · error · Error

URL must be a string

Error message

URL must be a string

What it means

The 'removeAgent' socket event requires the agent's URL as a string, which is used as the instance identifier by instanceManager.remove(url). Since the argument is unknown, a typeof check throws this Error for any non-string value before attempting removal.

Source

Thrown at backend/socket-handlers/manage-agent-socket-handler.ts:51

                callbackResult({
                    ok: true,
                    msg: "agentAddedSuccessfully",
                    msgi18n: true,
                }, callback);

            } catch (e) {
                callbackError(e, callback);
            }
        });

        // removeAgent
        socket.on("removeAgent", async (url : unknown, callback : unknown) => {
            try {
                log.debug("manage-agent-socket-handler", "removeAgent");
                checkLogin(socket);

                if (typeof(url) !== "string") {
                    throw new Error("URL must be a string");
                }

                let manager = socket.instanceManager;
                await manager.remove(url);

                server.disconnectAllSocketClients(undefined, socket.id);
                manager.sendAgentList();

                callbackResult({
                    ok: true,
                    msg: "agentRemovedSuccessfully",
                    msgi18n: true,
                }, callback);
            } catch (e) {
                callbackError(e, callback);
            }
        });

View on GitHub (pinned to f809ae192b)

Solutions

1. Pass the agent URL string exactly as it was added, e.g. 'http://agent:5001'.
2. Extract from the object first: socket.emit('removeAgent', agent.url, cb).
3. Guard with typeof url === 'string' before emitting.

Example fix

// before
socket.emit('removeAgent', agent, cb); // agent is an object
// after
socket.emit('removeAgent', agent.url, cb);

function isAgentUrl(v) {
    return typeof v === 'string' && v.length > 0 && /^https?:\/\//.test(v);
}

function isString(v) { return typeof v === 'string'; }

if (typeof url !== 'string') {
    throw new Error('URL must be a string');
}
socket.emit('removeAgent', url, cb);

When it happens

Trigger: Emitting 'removeAgent' with undefined, null, a number, or an object (e.g. { url: ... }) instead of the URL string itself.

Common situations: Passing the whole agent object rather than its url property; undefined when the agent record lacks a url; automation scripts removing agents positionally with wrong args.

Understand the failure class

Background: "Wrong argument type", "must be a string", "expected Array or Prism::Scope": TypeError and ArgumentError when a library receives a value of the wrong type — this error's family across 28 libraries.

Related errors

• Data must be an object
• dockerRunCommand must be a string
• Name must be a string
• Stack name must be a string
• Stack name and service name must be strings

AI-assisted analysis of louislam/dockge@f809ae192b (2026-08-31). Data as JSON: /api/errors/8f3ca9f77024e17b. Report an issue: GitHub.