Stream API - SUM_IMAGE not received for all subscription

[gsteinert]

Evening all,

I'm having some trouble with the Stream API not returning an initial image for some of my subscriptions.

I'm connecting to the API with the below function:


async connect() {
const APIKey = betfairAPIClient.getAPIKey();
const sessionToken = await betfairAPIClient.getSessionToken();

/* Socket connection options */
const options = { host: 'stream-api.betfair.com', port: 443 }
/* Establish connection to the socket */
this.client = tls.connect(options);
/* Send authentication message */
this.client.write('{"op": "authentication", "appKey": "' + APIKey + '", "session": "' + sessionToken + '"}\r\n');

this.client.on('data', this.onData.bind(this));
this.client.on('close', this.onClose.bind(this));
this.client.on('error', this.onError.bind(this));
}

And subscribing with this:

const marketSub = {
op: "marketSubscription",
id: id,
marketFilter: { marketIds: [market] },
marketDataFilter: { fields: ["EX_ALL_OFFERS"], ladderLevels: 3 },
};

this.client.write(JSON.stringify(marketSub) + '\r\n');


This works fine when subscribing to just one market, but when subscribing to multiple markets (currently 6) by sending 6 different subscription messages I receive success messages for all 6, but SUB_IMAGE messages for only a few.

The SUM_IMAGEs received vary, but are commonly just numbers 5 and 6, and I rarely if ever receive number 1.

I receive no errors and have confirmed that every message is being acted on with Wireshark.

Is there some kind of rate limit for subscriptions that I'm violating?

[LiamP]

As per the docs:

It is possible to subscribe multiple times - each replaces the previous (each will send a new initial image and deltas) - they are not additive.

https://docs.developer.betfair.com/d...riptionMessage

[gsteinert]

Hi Liam,

Thank you for the response.

That's all understood (and quite useful in my context), but I don't think it's related to the issue I'm having.

I subscribe to 6 different markets and receive 6 confirmations, but then only receive initial images for a few of them.

The below is example output - onData, onClose and onBind just output to console for now.

[0] {"op":"status","statusCode":"SUCCESS","connecti onC losed":false,"connectionsAvailable":1}
[0]
[0] {"op":"status","id":1,"statusCode":"SUCCESS","c onn ectionClosed":false}
[0]
[0] {"op":"status","id":2,"statusCode":"SUCCESS","c onn ectionClosed":false}
[0]
[0] {"op":"status","id":3,"statusCode":"SUCCESS","c onn ectionClosed":false}
[0]
[0] {"op":"status","id":4,"statusCode":"SUCCESS","c onn ectionClosed":false}
[0]
[0] {"op":"status","id":5,"statusCode":"SUCCESS","c onn ectionClosed":false}
[0]
[0] {"op":"status","id":6,"statusCode":"SUCCESS","c onn ectionClosed":false}
[0]
[0] {"op":"mcm","id":6,"initialClk":"whqYyLqQB8wa2o GOl gfFGsn7vJcH","clk":"AAAAAAAA","conflateMs":180000, "heartbeatMs":5000,"pt":1599761145870,"ct":"SU B_IM AGE","mc":[{"id":"1.172884531","rc":[{"atb":[[50,4.88],[48
,9.37],[1.03,1220].....

See the initial SUCCESS messages for ids 1-6, but an initial image is only received for id 6. The six markets subscribed to all have different IDs.

[LiamP]

You are seeing exactly as described in the docs, not sure there is a better way to explain it:

..each replaces the previous (each will send a new initial image and deltas) - they are not additive.

You need to take advantage of the market filter (list) if you want to subscribe to multiple markets.

[gsteinert]

Ah okay I think I get it.

If I subscribe to market 123, then subscribe separately to market 456 before I receive the initial image, the second subscription replaces the first.

If the subscription to 123 completes and I get the inital image, then i subscribe to 456 I'll get both images.

Does that sound about right?


I think I just need to queue and batch subscriptions so I don't send a scond before the first completes.

Thanks for your help, that gives me something to work on.

[LiamP]

No it’s one subscription per stream/socket, if you want multiple markets:

... marketFilter: { marketIds: [market, market, market, market] },

[gsteinert]

Third time lucky then!

To subscribe to one market, then later add another I'd need to do:

subscribe( { marketFilter: { marketIds: [ 123 ] } } )

...then later...

subscribe( { marketFilter: { marketIds: [ 123, 456 ] } } )

At which point I'd receive a new inital image for market 123, then deltas for them both?

[LiamP]

Sort of, they are not additive so the second subscribe would be a new subscription for both. You have to be coarse, for example subscribing to all UK racing markets, streaming is lightweight so just ignore the markets you don’t need.

[gsteinert]

Sounds good to me.

Thank you for your help!