node package manager
Don’t reinvent the wheel. Reuse code within your team. Create a free org »



A flowtrace is a persisted record of the execution of an Flow-based Programming (FBP) or dataflow program. It is used for retroactive (after-the-fact) debugging; to locate, understand and fix bugs.

The concept is analogous to a 'stacktrace' or 'core dump' for imperative code.

This project will define a data format to store traces in, and provide debugging tools for working with these traces.


Minimally useful

  • NoFlo has support for creating flowtraces, from noflo-nodejs 0.6 and noflo-runtime-msgflo 0.2.2
  • Several commandline tools exist for working with flowtraces
  • Note: File format not 100% finalized
  • Some not-yet-useful timeline UI prototypes exist

See braindump and UI notes for ideas/plans.


First make sure you have Node.js with NPM installed.

To install locally in a project. Recommended.

npm install flowtrace
export PATH=./node_modules/.bin:$PATH

To install globablly on your system

npm install -g flowtrace

Display flowtrace on commandline

flowtrace-show reads a flowtrace, and renders a human-friendly log output from it.

./bin/flowtrace-show mytrace.flowtrace.json

Example output:

-> IN repeat CONN
-> IN repeat DATA hello world
-> IN stdout CONN
-> IN stdout DATA hello world
-> IN repeat DISC
-> IN stdout DISC

When used in a terminal, supports colors.

Show a flowtrace in Flowhub

flowtrace-replay reads a flowtrace, and then acts as a live FBP runtime. That means it can be used with any FBP IDEs/client which support the FBP runtime protocol.

flowtrace-replay mytrace.flowtrace.json

By default this will open Flowhub in your browser, automatically connect and show you the graph. To replay the data press the play button. You should then see the data flowing through edges.

Flowtrace replayed in Flowhub

You can specify which --ide to use, and disable automatic opening of browser with -n.

flowtrace-replay --ide http://localhost:8888 -n

You can also set the --host and --port. See --help for all options.