No SDR prices available anymore

[StrathCole]

It seems, exchangerate.host changed their policy to closed usage. All (or at least most) oracle price servers who used the service, don't have an API key, but calling the api without key is no longer possible.

So the chain currently has no SDR price anymore. And as it's the core currency for the MM … 🤷‍♂️ It stopped working ~ Block 14723744. Which was ~2 days ago.

You can see that https://terra-classic-lcd.publicnode.com/terra/oracle/v1beta1/denoms/exchange_rates has no usdr in the exchange rates anymore. Also curl -s http://127.0.0.1:8532/latest | jq '.prices[] | select(.denom == "SDR")' on the oracle server returns an empty result.

It also means that stable-to-stable swaps are currently non-functional.

[StrathCole]

A possible solution to work around the common issue of only a single (or none) source for SDR, it would maybe be an idea to calculate a pseudo-SDR ourselves.

Regarding https://www.imf.org/en/News/Articles/2022/07/29/pr22281-press-release-imf-determines-new-currency-amounts-for-the-sdr-valuation-basket the basket only changes each 5 years, so next time in 2027.

The current formula would be: SDR value in USD=(0.57813⋅USD)+(0.37379⋅EUR)+(1.0993⋅CNY)+(13.452⋅JPY)+(0.080870⋅GBP)

So as we have values for EUR, CNY, JPY, GBP available, we could calculate the SDR value in USD with that formula in the price feeder. It may not be 100% the same value as published by the IMF daily, but it would represent the same factors of each currency.

[StrathCole]

curl -s http://127.0.0.1:8532/latest | jq '[.prices[] | 
        select(.denom == "GBP" or .denom == "EUR" or .denom == "CNY" or .denom == "JPY") | 
        {(.denom): (.price | tonumber)}] | 
        add | 
        (0.57813 + (.EUR * 0.37379) + (.CNY * 1.0993) + (.JPY * 13.452) + (.GBP * 0.080870))'

Result: 1.31140786

Which nearly matches yesterday's official IMF value of 1.311320 published on https://www.imf.org/external/np/fin/data/rms_sdrv.aspx

[aeuser999]

Comments: Just a note though that there are other SDR Providers (FastForex is $9 a month - was just added in 3 months back to help keep SDR pricing from a single source of failure, also the other fiat providers were also fixed to work for SDR pricing as well [although a bit higher than $9 a month]).

What is interesting is that many are still voting with SDR sources:

• See All Individual Exchange Rate Votes For Validators
  • For instance: blocks: 14747800 - 14747803

Yet, it is seeing 0.0 as an actual price rather than an abstain (so that probably needs to be fixed):

• Aggregate Vote Example With SDR showing 0.0000000000 currently
• Should see a non-positive integer as abstaining for that denomination:
  • https://github.com/classic-terra/core/blob/main/x/oracle/spec/03_end_block.md#tally-exchange-rate-votes
  • https://classic-docs.terra.money/docs/develop/module-specifications/spec-oracle.html#abstaining-from-voting
• For some reason it sees 0.0 as not abstaining - if they had, it would appear that the other positive value SDR pricing should have come through
• Somewhere in Code, Type, or sdk.Dec and IsPositive()?:
  • https://github.com/classic-terra/core/blob/main/x/oracle/abci.go#L55-L58
  • https://github.com/classic-terra/core/blob/main/x/oracle/keeper/ballot.go#L26-L30
  • https://github.com/classic-terra/core/blob/main/x/oracle/tally.go#L23-L32

A Potential Code Update Here is an adjustment to make ExchangeRate work (both non-API and API):

• Adjust ExchangeRate.tx and updated default-test.js
  • Note: just needs the testing comments removed (which have no indentation to make identification easier), and that along with the changes mentioned earlier here, and final testing on your side, and it should be good (feel free to use any of the code, and/or change it, or improve it).
  • tagging @nghuyenthevinh2000 , @inon-man and @StrathCole incase it looks helpful
    • New ExchangeRate API Docs W/API
    • New ExchangeRate API Docs W/Open-No-API-Key-Needed

I hope that helps out a little bit, and that you each have a great day today :)

[StrathCole]

Just a note though that there are other SDR Providers (FastForex is $9 a month - was just added in 3 months back to help keep SDR pricing from a single source of failure, also the other fiat providers were also fixed to work for SDR pricing as well [although a bit higher than $9 a month]).

The issue is that with high probability most are not using any price services that cost that much, especially not in the current LUNC price situation. And even with using FastForex now, it would be back at a single provider (exchangerate would now cost ~$40/m). So the question is if using external sources for SDR is necessary at all. After all it's only a combination of other currencies which we have more (free) sources for, I think.

[aeuser999]

@StrathCole : here is a fix that works with ExchangeRate both without api key and with api key (tested it), just did not create a pull request (although you can pull the whole repo and test with, just rename default-test.js to default.js):

• https://github.com/aeuser999/test_oracle_feeder/commit/141872a89fb5ddeb5b915c8d8b8380600eec02a5

[StrathCole]

@StrathCole : here is a fix that works with ExchangeRate both without api key and with api key (tested it), just did not create a pull request (although you can pull the whole repo and test with, just rename default-test.js to default.js):

* [aeuser999/test_oracle_feeder@141872a](https://github.com/aeuser999/test_oracle_feeder/commit/141872a89fb5ddeb5b915c8d8b8380600eec02a5)

Looks good and seems to return valid results. The question is, if it is necessary to use these SDR prices or if it is better to calculate it ourselve from the other fiat prices which we have more sources of I think? https://github.com/classic-terra/oracle-feeder/pull/30

From the values I would guess that the er-api doesn't match the IMF value either, but we still rely on the external SDR source(s) then.

IMF (official source) reports: 1.311320 currently for yesterday (28th), er-api reports 1,30979, the manual calculation from on-chain oracle rates (above PR) gives 1.31140786