daml/ledger/sandbox

Overview

This document is to help internal engineers work with the Sandbox and the new ledger API. Note: If you encounter bugs. Please report issues you find in the #team-ledger-api channel.

DAML Sandbox

To build a fat JAR with the sandbox built from HEAD run

bazel build //ledger/sandbox:sandbox-binary_deploy.jar

Sandbox application can be run from command line with the following command:

java -jar bazel-bin/ledger/sandbox/sandbox-binary_deploy.jar [options] <archive>

as run from the main project root directory (adjust the location of the JAR according to your working directory).

Command line arguments

  -p, --port <value>       Sandbox service port. Defaults to 6865.
  -a, --address <value>    Sandbox service host. Defaults to binding on all addresses.
  --dalf                   Parse provided archives as DAML-LF Archives instead of DARs.
  --static-time            Use static time, configured with TimeService through gRPC.
  -w, --wall-clock-time    Use wall clock time (UTC). When not provided, static time is used.
  -o, --sim-time-offset <value>
                           Use simulated time with the given duration (ISO-8601 with optional `-` prefix) as offset relative to UTC. For example, supplying `-PT6M` will result in the server time lagging behind UTC by 6 minutes. When not provided, static time is used.
  --no-parity              Disables Ledger Server parity mode. Features which are not supported by the Platform become available.
  --scenario <value>       If set, the sandbox will execute the given scenario on startup and store all the contracts created by it.
  --daml-lf-archive-recursion-limit <value>
                           Set the recursion limit when decoding DAML-LF archives (.dalf files). Default is 1000
  <archive>...             Daml archives to load. Only DAML-LF v1 Archives are currently supported.
  --pem <value>            TLS: The pem file to be used as the private key
  --crt <value>            TLS: The crt file to be used as the cert chain. Required if any other TLS parameters are set.
  --cacrt <value>          TLS: The crt file to be used as the the trusted root CA.
  --help                   Print the usage text

Compatibility

Sandbox uses models compiled in to the DAR format.

Note that the new Ledger API only supports DAML 1.0 or above codebases compiled to DAML-LF v1. Again, using the DAML packaging as suggested above will ensure that you are generating dar files that the Sandbox can consume.

Ledger API

The new Ledger API uses gRPC. If you just want to create / exercise contracts, I suggest you start by looking at command_service.proto, which exposes a synchronous API to the DAML ledger.

Logging

You can enable debug logging in Sandbox with sandbox-log-level system property:

$ java -jar ./bazel-bin/ledger/sandbox/sandbox-binary_deploy.jar --log-level=DEBUG $PWD/bazel-bin/ledger/sandbox/Test.dar

Or when started from Bazel with:

$ bazel run //ledger/sandbox:sandbox-binary -- --log-level=DEBUG $PWD/bazel-bin/ledger/sandbox/Test.dar

Profiling

You can enable profiling in Sandbox by passing a directory where the profiling information should be written via the --profile-dir flag, e.g.

$ bazel run //ledger/sandbox:sandbox-binary -- --profile-dir=/write/profiles/here/ ...

DISCLAIMER: Profiling is not intended to be used in production setups since it slows down DAML execution significantly and writes a lot of profiling information to disk.

For every command submitted to the Sandbox, a JSON file named like <submission time>-<command description>-<seed>.json is written to the directory specified via --profile-dir. In this file name, <command description> is a string of the form create:TemplateName or exercise:TemplateName:ChoiceName.

These JSON files can be viewed using the speedscope flamegraph visualizer. The easiest way to install speedscope is to run

$ npm install -g speedscope

See the Offline usage section of its documentation for alternatives.

Once speedscope is installed, a specific profile can be viewed via

$ speedscope /path/to/profile.json