RPC Tracing

Hyperledger Besu integrates with the open-telemetry project to integrate tracing reporting.

This allows to report all JSON-RPC traffic as traces.

To try out this example, start the Open Telemetry Collector and the Zipkin service with:

$> docker-compose up

Start besu with:

$> OTEL_RESOURCE_ATTRIBUTES="service.name=besu-dev" OTEL_EXPORTER_OTLP_METRIC_INSECURE=true OTEL_EXPORTER_OTLP_SPAN_INSECURE=true ./gradlew run --args="--network=dev --rpc-http-enabled --metrics-enabled --metrics-protocol=opentelemetry"

Try interacting with the JSON-RPC API. Here is a simple example using cURL:

$> curl -X POST --data '{"jsonrpc":"2.0","method":"web3_clientVersion","params":[],"id":53}' http://localhost:8545

Open the Zipkin UI by browsing to http://localhost:9411/

You will be able to see the detail of your traces.

References:

• OpenTelemetry Environment Variable Specification

Trace RPC API Notes

This document outlines major differences for trace_replayBlockTransactions compared to other implementations.

stateDiff

No major differences were observed in the stateDiff field.

trace

Besu reports gasUsed after applying the effects of gas refunds. Future implementations of Besu might track gas refunds separately.

vmTrace

Returned Memory from Calls

In the vmTrace ope.ex.mem fields Besu only reports actual data returned from a RETURN opcode. Other implementations return the contents of the reserved output space for the call operations. Note two major differences:

1. Besu reports null when a call operation ends because of a STOP, HALT, REVERT, running out of instructions, or any exceptional halts.
2. When a RETURN operation returns data of a different length than the space reserved by the call only the data passed to the RETURN operation is reported. Other implementations will include pre-existing memory data or trim the returned data.

Precompiled Contracts Calls

Besu reports only the actual cost of the precompiled contract call in the cost field.

Out of Gas

Besu reports the operation that causes out fo gas exceptions, including calculated gas cost. The operation is not executed so no ex values are reported.