Computation reports for Cadence scripts & transactions

[m-Peter]

Completes: 1st milestone of onflow/developer-grants#178
Closes: #526

Description

Introduces a new endpoint under http://localhost:8080/emulator/computationReport, to display computation reports. For example:

---

For contributor use:

• Targeted PR against master branch
• Linked to GitHub issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the GitHub PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.27136% with 91 lines in your changes are missing coverage. Please review.

Project coverage is 50.93%. Comparing base (d9395dd) to head (c21ffd9).

Files	Patch %	Lines
emulator/computation_report.go	49.29%	72 Missing ⚠️
server/utils/emulator.go	0.00%	10 Missing ⚠️
server/server.go	0.00%	5 Missing and 1 partial ⚠️
emulator/blockchain.go	92.68%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #609      +/-   ##
==========================================
+ Coverage   50.80%   50.93%   +0.13%     
==========================================
  Files          32       33       +1     
  Lines        4224     4421     +197     
==========================================
+ Hits         2146     2252     +106     
- Misses       1907     1996      +89     
- Partials      171      173       +2     

Flag	Coverage Δ
unittests	50.93% <54.27%> (+0.13%)	⬆️

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[janezpodhostnik]

Looks good. Some comments:

• It might be good to link to this function as an example on how to get the computation from the intensities https://github.com/onflow/flow-go/blob/master/fvm/meter/computation_meter.go#L32
• The naming: "profiling" hints to the profiling where you can see results per line of code executed which is a bit misleading. However if I understand correctly you intend to work towards that. If that is the case I'm ok with the name.

[janezpodhostnik]

I wish flow-go already offered ComputationKind names.

[m-Peter]

Unfortunately, I think this is not possible. The main problem is that ComputationKind is defined in Cadence repository and it uses the string cmd tool to generate the String representation for the values defined there. See: https://github.com/onflow/cadence/blob/master/runtime/common/compositekind.go#L27
Only the ComputationKind values defined in Cadence offer a human-readable name: https://github.com/onflow/cadence/blob/master/runtime/common/computationkind_string.go.

[janezpodhostnik]

I would not compare all the values, as the test might become fragile.
I would maybe omit GetValue and perhaps GetOrLoadProgram as well.

[m-Peter]

Good point 👍
Updated in 5dc4699

[janezpodhostnik]

I would not check:

• EncodeValue
• GetValue
• SetValue
• AllocateStorageIndex
• GetOrLoadProgram

[m-Peter]

Good point 👍
Updated in 5dc4699

[m-Peter]

@janezpodhostnik I have updated the naming pattern to computation report in 7a259eb, for types / variables / flags etc. I have also linked the relevant flow-go function for getting the computation from intensities.

[sideninja]

Very nice work, this is an awesome feature! 🎉