THIS IS PRE-RELEASE DOCUMENTATION
This is a minor release.
Market by Price
There are various scenarios which could lead to an internally cached order book ending up in a "bad state"
- Dropped messages (exchange or CDN, since all currently supported exchanges use TCP)
- Configuration mistakes (gateway)
- Bugs (exchange or gateway)
"Bad state" can be sometimes be detected by price inversion (if unexpected by the gateway) or by other means, e.g. detecting dropped sequence numbers or by validating the current snapshot of an order book.
What is new is that the gateways will auto-resubscribe the relevant symbol(s) whenever "bad state" has been detected.
On the client side, there is the
GatewaySettings event which includes the required information
to correctly mirror and maintain order books.
DepthBuilder interface has been updated to accept the
Applying this event is required for the client to maintain an order book that will exactly mirror
the order book maintained by the gateway.
Inversion and rounding errors may result from not applying
This change was prompted by FTX potentially dropping messages during fast market conditions.
FTX requires the client side (the gateway) to use a very expensive checksum validation (expectation is 10-20 microseconds per update).
Validation is only enabled by setting the
--ws_order_book_checksum_every command-line flag to
a positive value.
This is used to validate on every N'th update (of the symbol).
Clients can now broadcast custom calculations for other clients to consume or simply to be collected in the event-logs for offline analysis.
Caching and broadcasting is currently managed by the gateways. However, this is not ideal because a single client can now potentially spam a gateway thereby causing unnecessary latency, or worse. A dedicated pub/sub service will be introduced at a later point.
Rate Limit Triggers
Trading strategies should ideally back off when the gateway's rate-limiter has been triggered.
The immediate response is for the gateway to reject via
OrderAck to the client who triggered the
However, there are other concerns
OrderAckmessage contains no information about when the the ban expires.
- Several clients can potentially be affected by a ban, e.g. when there is a globally configured rate-limiter.
This can obviously not be captured by the
OrderAckevent since it's only sent to a single client.
The solution is to broadcast the
RateLimitTrigger event to all connected clients.
Each client must then decide if it is impacted by the ban.
- Allow price inversion (Gemini) (#67).
- New enum value: "delisted" (JSON) (Coinbase PRO) (#66).
- Subscribe to reference data changes (FIX) (Deribit) (#65).
MarketByPricewhen updates have been lost (#31).
- HTTP request tracking (#55).
- Added new JSON fields
marketTakeBound(Binance Futures) (#54).
string_buffernow has O(1)
- Move OMS interfaces to API (#51).
- Support client publication of custom metrics (#8).
- New error code (Rate limit exceeded, retry in 1 seconds.) (BitMEX) (#64).
- Add currency (15) to ExecutionReport (8) (FIX Bridge) (#63).
- Config file can be used to specify what "zero" means (FIX Bridge) (#62).
- Option to terminate on order-ack timeout (FIX Bridge) (#60).
- Reject (3) message with "rate_limit_exceeded" (Deribit) (#73).
- API exceptions should compile with C++14 (#69).
- Only subscribe products with status "online" (Coinbase PRO) (#68).
OrderAckwas filtered for missing
routing_id(FIX Bridge) (#61).
RequestStatuswas not managed correctly for timeout scenarios (#59).
- Order ack handlers were not protected by try-catch (Kraken Futures) (#58).