# Command Replay

The replay tool is an investigation tool shipped in its own separate Docker image. It replays the engine state from a given command index or timestamp, and outputs the data that would have been sent on the websockets feeds at that time. To do this, it scans a given directory, typically the engine persistence directory or the deep storage directory.

It finds a suitable starting point, either from command file 0 or from the first available snapshot in the directory, and replays the commands from that point onwards into a separate instance of the engine.

It outputs the messages that would have been produced by the joined message feed, i.e

• executions
• transactions
• liquidations
• funding

The replay can be narrowed down to a subset of commands in the available range with --from-index and -to-index options. It can also be filtered by account (--account) or by symbol (--symbol).

docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current -a --directory persistence

Below is a breakdown of the example arguments used to run the replay tool:

• --rm
  ↪ Automatically remove the container and its associated anonymous volumes when it exits

• -v /path/to/command/files:/app/persistence
  ↪ Mounts the local directory /path/to/command/files to /app/persistence inside the Docker container.
  This is the location where the replay tool expects to find command files.

• -it
  ↪ Docker run in interactive mode with a pseudo-TTY

• -e MEMORY=24G
  ↪ Set the MEMORY environment variable to 24G

• replay:current
  ↪ Runs the current version of the replay image.

• -a
  ↪ Includes all available command files for processing.

• --directory persistence
  ↪ Optional. Specifies the subdirectory within /app from which command files should be loaded.

• -o /path/to/output/file
  ↪ Directs output to a file at the specified path rather than stdout.

• -b
  ↪ Query and output account positions and balances once index --to-index has been reached. Requires --to-index and --account to be set, does nothing otherwise.

docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --from-index 7245876 --directory persistence
docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --to-index 7245924 --directory persistence 
docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --from-index 7245876 --to-index 7245924 --directory persistence -o /path/to/output/file

docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --account 123 --directory persistence 
docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --from-index 7245876 --to-index 7245924 --account 123 --directory persistence -o /path/to/output/file

docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --symbol ETHUSDT --directory persistence
docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --from-index 7245876 --to-index 7245924 --symbol ETHUSDT --directory persistence
docker run --rm -v /path/to/command/files:/app/persistence -it -e MEMORY=24G replay:current --from-index 7245876 --to-index 7245924 --symbol ETHUSDT --account 123 --directory persistence -o /path/to/output/file