xrpl-price-persist-oracle

Mainnet

💳: rEGGEgg9hQSHLxUwycGnmjW2GKX9thn2yH 🧭

▶️:

Testnet

💳: rayZw5nJmueB5ps2bfL85aJgiKub7FsVYN 🧭

▶️:

Prices via Oracle

These graphs are generated from the CloudWatch Metric data pushed in the contract, the code that generates these images is in the metrics repo

🚧 Gaps indicate the oracle didn't reliably publish during this time see #27 🚧

This shows the Testnet updates less frequently than the mainnet.

This is a XRPL Oracle that publishes external data into the XRPL.

This Oracle was inspired by XRPL-Labs/XRPL-Persist-Price-Oracle. Also see the DEV post.

This Oracle is coded in python and built as a Serverless Application Model (SAM).

Take a look at the handler() in contract.py — where it's expected to run on any FaaS, such as OpenFaaS.

Deploying to your AWS account

To deploy to your AWS Account use the aws-sam-cli. If you don't have aws-sam-cli installed, you can grab it from pip or follow the installation documentation.

pip install -U aws-sam-cli

After installing aws-sam-cli, you can Build and Deploy.

# zip our function along with it's requirements from requirements.txt
# this also makes a new template pointing at those zips
sam build 
# now it's built, you'll be prompted to deploy, do so interactively with:
sam deploy --guided

Don't feel like doing it yourself? Expand me to see termcasts.

New stack, accepting all the defaults, besides the wallet secret.

A current stack, getting updated and deployed to

This will walk you through the deployment of the Oracle, name the stack input the parameters (the wallet seed parameter is NoEcho)

You may generate a Testnet wallet at the Testnet faucet: https://xrpl.org/xrp-testnet-faucet.html Click "Generate Testnet Credentials" and use the Secret as the input to the WalletSecret parameter.

Besides the one required parameter without a default (the wallet secret seed), you can accept all the defaults (including the stack name) and you'll be persisting aggregate prices to the XRPL Testnet.

Tailing Logs

After deployment, you can tail the logs of the function like, where my-stack-name is what you chose to name your stack during the --guided deploy, if you chose the default it's sam-app:

sam logs --stack-name my-stack-name -n OracleFunction -t

Note on `NoEcho` Cloudformation Parameter for Wallet Secret Seed

The NoEcho parameter of the wallet secret seed ensures that the parameter may not be read or may not be logged during any cloudformation events.

The produced resource that !Ref's the parameter in use, the function with it's environment variable. Be aware that any other user able to access the AWS account used to stand this stack will be able to read the secret on the lambda function itself.

If you're in a trusted account, and don't provide access to tools or services that would have access to these things you'll be fine.

Otherwise, you'll have a couple options:

One option is to encrypt the Lambda environment vars in transit (they're encrypted at rest by default). This would then require decrypting it in the function using a KMS call. (see Securing Environment Variables)

Alternatively you might want to call some key management service / secrets management service independently. There is two other AWS services that you could use, for managing encrypted secrets in transit.

One is Simple Systems Manager (ssm, specifically ssm-encrypted parameter store type). This includes some additional costs if the function needs to cold start (assuming you're persisting the client in the outer scope for subsequent executions). (see Sharing Secrets with AWS Lambda Using AWS Systems Manager Parameter Store)

You'll want to attach a policy to the function like in 5603945 include a policy attached to the OracleFunction resource under the Properties dict.

    Properties:
      CodeUri: oracle/
      Handler: contract.handler
      Runtime: python3.8
      Policies:
        - SSMParameterReadPolicy:
            # this should be a path you decide, here's an example:
            ParameterName: xrpl-oracle/test/wallet/secret
            # you can also use `!Sub`:
            # ParameterName: !Sub "xrpl-oracle/${XRPLNodeEnvironment}/wallet/secret"

Another is Secrets Manager aws-secrets-manager, which is also an additional cost. (see secretsmanager_basics.py)

There are many options! This is just a minimal example :)

An abundance of JSONDecodeError

While using the JsonRPCClient; the oracle will see an abundance of JSONDecodeErrors that are coming as a result of the server saying it's too busy.

I was aware of this happening, and was swallowing, notifying and then raising FailedExecutionWillRetry

Got a JSONDecodeError of 'Expecting value: line 1 column 1 (char 0)'. Retrying the transaction by failing this execution.


JSONDecodeError: Expecting value: line 1 column 1 (char 0)
Traceback (most recent call last):
  File "/var/lang/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 850, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/var/task/contract.py", line 45, in <module>
    base_fee = get_fee(xrpl_client)
  File "/var/task/xrpl/ledger/main.py", line 54, in get_fee
    return asyncio.run(main.get_fee(client))
  File "/var/lang/lib/python3.9/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/var/lang/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete
    return future.result()
  File "/var/task/xrpl/asyncio/ledger/main.py", line 64, in get_fee
    response = await client.request_impl(Fee())
  File "/var/task/xrpl/asyncio/clients/json_rpc_base.py", line 46, in request_impl
    return json_to_response(response.json())
  File "/var/task/httpx/_models.py", line 1415, in json
    return jsonlib.loads(self.text, **kwargs)
  File "/var/lang/lib/python3.9/json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
  File "/var/lang/lib/python3.9/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/var/lang/lib/python3.9/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None

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