DEBUG_WITH_DLV.md

Debugging with dlv

This document is a guide describing how to debug with dlv and VSCode.

There are two options:

1. You can start entire V E G A and tendermint and fire instructions at your node and debug the results.
2. You can attach the dlv debugger to the integration tests.

For both you'll need to

• Read and follow instructions in GETTING_STARTED.md first.
• Install dlv if you've not already done so. In VSCode you can do this by launching the "Command Palette" and running Go: Install/Update Tools, select dlv, press OK.

Entire V E G A with tendermint

Once you have successfully installed V E G A with tendermint these are the steps to let you debug.

• Build the debug version (with optimisations disabled) of all the binaries with:

  DEBUGVEGA=yes make build

  If you're on a Mac make build will fail. This is because Mac OS isn't updating bash beyond version 3.x (something to do with GPL). The easiest solution is to install a recent bash e.g. with https://brew.sh/ and then either run the above in the new bash instance or add your new bash to /etc/shells and then do chsh to change your default shell.

• Use "Command Palette" to run Debug: Open launch.json. If you didn't already have a launch.json file, this will create one with the below default configuration which can be used to debug the current package. Enter the following into launch.json (which will be by default created inside vega/.vscode/):

  {
      "version": "0.2.0",
      "configurations": [
          {
              "name": "Debug V E G A",
              "type": "go",
              "request": "attach",
              "mode": "remote",
              "remotePath": "/path/to/vega", // trading-core
              "port": 2345,
              "host": "127.0.0.1",
              "showLog":true,
              "trace":"log"
          }
      ]
  }

  Edit the "remotePath" appropriately to reflect where your trading-core source code lives.

• Now open ideally two terminal windows. In the first one launch tendermint as you normally would. To hard-reset the chain and start from scratch use

  tendermint unsafe_reset_all && tendermint init && tendermint node 2>./tendermint.stderr.out 1>./tendermint.stdout.out

  Now launch the dlv debugger with V E G A by running

  dlv exec /path/to/data-node/cmd/data-node/data-node-dbg --headless --listen=:2345 --log --api-version=2 -- node

  again replacing the path to match where your git copy of trading core lives. If all went well you'll see something like:

  API server listening at: [::]:2345
  2019-10-13T20:37:41+01:00 info layer=debugger launching process with args: [/path/to/data-node/cmd/data-node/data-node-dbg node]
  debugserver-@(#)PROGRAM:LLDB  PROJECT:lldb-1100.0.28..1
   for x86_64.
  Got a connection, launched process /path/to/data-node/cmd/data-node/data-node (pid = 35671).
  

• Finally in VSCode open the Debug panel and run the Debug V E G A configuration created in the 2nd step above. At this point V E G A should be running.

• Test that V E G A is running as expected by e.g. visiting http://localhost:3003/statistics or trying something in the GraphQL playground at http://localhost:3004/. If all is well you should be able to create users, place orders etc. as normal. More to the point breakpoints, call stack and variables should be usable as normal in VSCode.

Debugging integration tests

• Build a debug version of the godog test harness: from the root of the V E G A core repository

  DEBUGVEGA=yes go test -c ./integration/...

• Use "Command Palette" to run Debug: Open launch.json. If you didn't already have a launch.json file, this will create one with the below default configuration which can be used to debug the current package. Enter the following into launch.json (which will be by default created inside vega/.vscode/):

  {
      "version": "0.2.0",
      "configurations": [
          {
              "name": "Debug Test",
              "type": "go",
              "request": "attach",
              "mode": "remote",
              "port": 2345,
              "host": "127.0.0.1",
              "showLog":true,
              "trace":"log"
          }
      ]
  }

• Stick a breakpoint somewhere in the code that you know will be triggered by your integration test (this clearly has to be in a .go file, not .feature).

• Launch the feature test you care about (in the example below it's 2668-price-monitoring.feature)

  dlv exec ./integration.test  --headless --listen=:2345 --log --api-version=2    -- -godog.format=pretty --  $(pwd)/integration/features/2668-price-monitoring.feature

  The godog test harness is now running inside dlv and it has launched the integration test you chose.

• Finally in VSCode open the Debug panel and run the Debug Test.