Unique order IDs

[brigoraoul]

Hi :)

What is the correct way to generate a unique order ID for each order object? If I simply create and place the order, I sometimes get a "Duplicate Order ID" error. All info I can find online is about the nextValidId callback from the underlying ibapi. Does ib_async provide a simpler to use abstraction of that?

[quiet-backtester]

You don't need to touch nextValidId — ib_async already handles it. At connect it snoops the server's nextValidId and seeds an internal counter, and when you place an order without setting order.orderId it assigns the next unique id for you. In ib.placeOrder it's literally orderId = order.orderId or self.client.getReqId().

So the simplest correct pattern is: build a fresh Order each time and just place it — don't set orderId yourself.

"Duplicate Order ID" almost always means one of:

1. Reusing the same Order object. After the first placeOrder, that object's orderId is now set, so the next placeOrder reuses it. Create a new order each time (LimitOrder(...), MarketOrder(...), etc.).
2. Manually assigning order.orderId to a fixed or stale value.
3. Two clients on the same clientId. Each seeds its own counter from the same nextValidId, so they hand out overlapping ids — give every connection a distinct clientId.

If you genuinely need the id up front (to log/track before placing), pull it from the same source ib_async uses: order.orderId = ib.client.getReqId().