How to represent 64bit integers as attribute value?

[jmorrell-cloudflare]

The OpenTelemetry spec says valid attribute types include signed 64bit integers:

A primitive type: string, boolean, double precision floating point (IEEE 754-1985) or signed 64 bit integer.

However in opentelemetry-js attribute values are represented as number which has a max safe value of 2^53 – 1.

There was a previous request for supporting BigInt as an attribute value here though it was marked as not planned. This makes some sense to me since it could represent much larger numbers, but still leaves a gap between 2^53-1 and 2^63-1 IIUC.

If we need to attach a 64 bit integer (say, received from an external system) to an attribute today that exceeds Number.MAX_SAFE_INTEGER, what is the recommended approach? Serialize it to a string? Or is there maybe some alternative I am missing?

[dyladan]

That linked issue does not have a lot of context but to my memory we decided not to implement BigInt originally because it wasn't widely available. We were supporting all the way back to node 8 for quite a while. That is no longer the case in the SDK so it should be safe to allow BigInt. You're correct that it might contain numbers larger than 64 bits, but in that case I would expect an overflow the same as you would get if you had native fixed integers and incremented them too many times. I think this is a very reasonable request.

Alternative strategies:

1. Represent 64 bit int as a TypedArray. I don't like this because we'd have to implement a lot of stuff on our own
2. Use some fixed integer library. I don't like this because it would require us to bring in more external dependencies. We could probably just copy the types into the API but the SDK would require it and it would require our users to depend on it.
3. Use longjs. This is just (2) but I feel it deserves its own point because it is used by protobufjs which we already are using.
4. Use bigint. This is the native solution. As mentioned above we can expect that it is possible for bigint to be too large for a fixed integer.

Personally, I like the bigint version. It will need to be converted to longjs for export with protobufjs but we might actually switch to a different proto library like buf in the future with bigint support anyway

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