feat: implement slog-based logging by ivokub · Pull Request #1769 · Consensys/gnark

ivokub · 2026-05-20T00:11:49Z

Description

Start migration to log/slog which is a structured logger in standard library. Currently still backwards compatible, but will remove the logger package in the future to only provide entry points during compile, solve, prove and verify to plug in custom handlers.

Type of change

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to not work as expected)
This change requires a documentation update

How has this been tested?

Test A
Test B

How has this been benchmarked?

Benchmark A, on Macbook pro M1, 32GB RAM
Benchmark B, on x86 Intel xxx, 16GB RAM

Checklist:

I have performed a self-review of my code
I have commented my code, particularly in hard-to-understand areas
I have made corresponding changes to the documentation
I have added tests that prove my fix is effective or that my feature works
I did not modify files generated from templates
golangci-lint does not output errors locally
New and existing unit tests pass locally with my changes
Any dependent changes have been merged and published in downstream modules

Note

Medium Risk
Wide mechanical logging refactor across prove/verify and GPU paths could change default log noise or miss wiring a custom logger, but behavior is intended to stay backward compatible via the legacy logger shim.

Overview
Migrates gnark from the deprecated zerolog-based logger package toward log/slog, with a new internal/logger layer (including GNARK_LOG_LEVEL, a custom trace level, and logger.Trace for verbose GPU/prover paths).

Prover and verifier configs now carry an *slog.Logger, with WithProverLogger / WithVerifierLogger and the solver receiving the same logger via solver.WithLogger. ICICLE Groth16 backends and generated templates are updated to slog-style calls and downshift many GPU lifecycle messages from info to debug/trace.

Lint and CI: enables sloglint in .golangci.yml (with a custom rule for logger.Trace) and bumps golangci-lint to v2.12.2 in workflows. README documents logging levels.

Observability elsewhere: Groth16 prove/verify paths add structured timing logs; key/proof marshal read/write paths log debug serialization metrics.

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Copilot

Pull request overview

This PR starts migrating gnark’s logging from the legacy github.com/consensys/gnark/logger (zerolog-based) to Go’s standard log/slog, introducing an internal slog logger with environment-based configuration and wiring logger instances through compile/solve/prove/verify entry points while keeping backward compatibility.

Changes:

Add internal/logger (slog-based) with GNARK_LOG_LEVEL configuration and a zerolog compatibility adapter.
Thread *slog.Logger through frontend compilation, constraint solving, and backend prover/verifier configs (including templates and accelerated/icicle paths).
Deprecate the public logger package and update docs/tests to reflect the new logging output and configuration.

Reviewed changes

Copilot reviewed 49 out of 76 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/unsafekzg/options.go	Switch unsafe-KZG cache logging to internal slog logger.
test/unsafekzg/kzgsrs.go	Convert KZG SRS cache logging to slog + trace helper.
test/solver_test.go	Disable solver logging via slog-based solver option in tests; skip tinyfield-incompatible circuits.
test/engine.go	Add slog logger plumbing to test engine and trace/debug timings/counters.
test/assert_solidity.go	Use slog logger for solidity checker execution logs.
test/assert_options.go	Add assertion logger option using slog/internal logger.
test/assert_checkcircuit.go	Use structured slog logging throughout circuit checks.
std/rangecheck/rangecheck_commit.go	Route rangechecker warning via compiler logger (slog).
std/math/emulated/field.go	Replace zerolog usage with slog logger and trace-level compile logging.
std/algebra/native/sw_grumpkin/g1.go	Migrate compile-time deprecation log to slog level.
std/algebra/native/sw_bls12377/g1.go	Migrate compile-time deprecation log to slog level.
std/algebra/emulated/sw_bls12381/g2.go	Migrate compile-time deprecation log to slog level.
README.md	Document `GNARK_LOG_LEVEL` and default behavior.
profile/profile.go	Replace zerolog-style calls with slog; adjust fatal paths to exit after error log.
logger/logger.go	Deprecate legacy logger package; back it with internal slog logger + one-time warning.
internal/widecommitter/widecommitter.go	Emit warning via compiler logger (slog).
internal/logger/zerolog.go	Add bidirectional slog↔zerolog adapters for compatibility.
internal/logger/logger.go	Add internal default slog logger with env-configured levels and runtime metadata.
internal/logger/logger_test.go	Add tests for env level parsing, output behavior, source inclusion, and quiet mode.
internal/generator/backend/template/zkpschemes/plonk/plonk.verify.go.tmpl	Template: use verifier config logger (slog) and structured duration logging.
internal/generator/backend/template/zkpschemes/plonk/plonk.prove.go.tmpl	Template: use prover config logger (slog) and pass logger into solver options.
internal/generator/backend/template/zkpschemes/groth16/groth16.verify.go.tmpl	Template: use verifier config logger (slog) and structured duration logging.
internal/generator/backend/template/zkpschemes/groth16/groth16.prove.go.tmpl	Template: use prover config logger (slog) and pass logger into solver options.
internal/generator/backend/template/representations/system.go.tmpl	Template: parse solver config once, use slog logger, pass config into solver ctor.
internal/generator/backend/template/representations/solver.go.tmpl	Template: switch solver logging to slog for api.Println replay.
internal/compilelogger/compilelogger.go	Switch compile-time logging to compiler slog logger.
internal/compilelogger/compilelogger_test.go	Update tests/examples to use slog loggers via `frontend.WithLogger`.
frontend/schema/walk.go	Convert schema warnings to structured slog calls.
frontend/schema/schema.go	Convert schema warnings to structured slog calls.
frontend/cs/scs/builder.go	Expose compiler logger and emit build warnings via slog.
frontend/cs/r1cs/builder.go	Expose compiler logger and emit build warnings via slog.
frontend/cs/commitment.go	Update commitment placeholder warning to slog/internal logger.
frontend/compile.go	Add compilation logger option and structured compile timing/metadata logs.
frontend/builder.go	Extend `frontend.Compiler` interface to expose `Logger() *slog.Logger`.
debug_test.go	Update expected println trace output to slog text handler format.
constraint/tinyfield/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/tinyfield/solver.go	Switch solver printLogs plumbing to slog.
constraint/solver/options.go	Migrate solver config logger to `*slog.Logger` and add adapter-based WithLogger.
constraint/solver/hint_registry.go	Use internal slog trace logging for duplicate hint registrations.
constraint/koalabear/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/koalabear/solver.go	Switch solver printLogs plumbing to slog.
constraint/grumpkin/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/grumpkin/solver.go	Switch solver printLogs plumbing to slog.
constraint/core.go	Convert serialization header warning to structured slog.
constraint/bw6-761/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/bw6-761/solver.go	Switch solver printLogs plumbing to slog.
constraint/bn254/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/bn254/solver.go	Switch solver printLogs plumbing to slog.
constraint/bls12-381/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/bls12-381/solver.go	Switch solver printLogs plumbing to slog.
constraint/bls12-377/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/bls12-377/solver.go	Switch solver printLogs plumbing to slog.
constraint/babybear/system.go	Use slog logger from solver config; pass config into solver ctor.
constraint/babybear/solver.go	Switch solver printLogs plumbing to slog.
backend/plonk/bw6-761/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/plonk/bw6-761/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/plonk/bn254/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/plonk/bn254/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/plonk/bls12-381/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/plonk/bls12-381/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/plonk/bls12-377/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/plonk/bls12-377/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/groth16/bw6-761/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/groth16/bw6-761/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/groth16/bn254/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/groth16/bn254/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/groth16/bls12-381/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/groth16/bls12-381/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/groth16/bls12-377/verify.go	Use verifier config logger (slog) and structured duration logging.
backend/groth16/bls12-377/prove.go	Use prover config logger (slog) and pass logger into solver options.
backend/backend.go	Add prover/verifier logger fields and options to inject slog logger.
backend/accelerated/icicle/internal/generator/templates/groth16.icicle.go.tmpl	Template: use slog logger and pass logger into solver options + trace GPU lifecycle logs.
backend/accelerated/icicle/groth16/bw6-761/icicle.go	Use internal slog logger and pass logger into solver options + trace GPU lifecycle logs.
backend/accelerated/icicle/groth16/bn254/icicle.go	Use internal slog logger and pass logger into solver options + trace GPU lifecycle logs.
backend/accelerated/icicle/groth16/bls12-381/icicle.go	Use internal slog logger and pass logger into solver options + trace GPU lifecycle logs.
backend/accelerated/icicle/groth16/bls12-377/icicle.go	Use internal slog logger and pass logger into solver options + trace GPU lifecycle logs.

Files not reviewed (27)

backend/accelerated/icicle/groth16/bls12-377/icicle.go: Language not supported
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constraint/babybear/solver.go: Language not supported
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constraint/bls12-377/solver.go: Language not supported
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constraint/bls12-381/solver.go: Language not supported
constraint/bls12-381/system.go: Language not supported
constraint/bn254/solver.go: Language not supported

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Copilot

Pull request overview

Copilot reviewed 83 out of 107 changed files in this pull request and generated 1 comment.

Files not reviewed (24)

backend/accelerated/icicle/groth16/bls12-377/icicle.go: Language not supported
backend/accelerated/icicle/groth16/bls12-381/icicle.go: Language not supported
backend/accelerated/icicle/groth16/bn254/icicle.go: Language not supported
backend/accelerated/icicle/groth16/bw6-761/icicle.go: Language not supported
backend/groth16/bls12-377/marshal.go: Language not supported
backend/groth16/bls12-377/mpcsetup/marshal.go: Language not supported
backend/groth16/bls12-377/prove.go: Language not supported
backend/groth16/bls12-377/verify.go: Language not supported
backend/groth16/bls12-381/marshal.go: Language not supported
backend/groth16/bls12-381/mpcsetup/marshal.go: Language not supported
backend/groth16/bls12-381/prove.go: Language not supported
backend/groth16/bls12-381/verify.go: Language not supported
backend/groth16/bn254/marshal.go: Language not supported
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backend/groth16/bn254/prove.go: Language not supported
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backend/plonk/bls12-381/marshal.go: Language not supported

Copilot

Pull request overview

Copilot reviewed 84 out of 107 changed files in this pull request and generated 2 comments.

Files not reviewed (23)

backend/accelerated/icicle/groth16/bls12-377/icicle.go: Language not supported
backend/accelerated/icicle/groth16/bls12-381/icicle.go: Language not supported
backend/accelerated/icicle/groth16/bn254/icicle.go: Language not supported
backend/accelerated/icicle/groth16/bw6-761/icicle.go: Language not supported
backend/groth16/bls12-377/marshal.go: Language not supported
backend/groth16/bls12-377/mpcsetup/marshal.go: Language not supported
backend/groth16/bls12-377/prove.go: Language not supported
backend/groth16/bls12-377/verify.go: Language not supported
backend/groth16/bls12-381/marshal.go: Language not supported
backend/groth16/bls12-381/mpcsetup/marshal.go: Language not supported
backend/groth16/bls12-381/prove.go: Language not supported
backend/groth16/bls12-381/verify.go: Language not supported
backend/groth16/bn254/marshal.go: Language not supported
backend/groth16/bn254/mpcsetup/marshal.go: Language not supported
backend/groth16/bn254/prove.go: Language not supported
backend/groth16/bn254/verify.go: Language not supported
backend/groth16/bw6-761/marshal.go: Language not supported
backend/groth16/bw6-761/mpcsetup/marshal.go: Language not supported
backend/groth16/bw6-761/prove.go: Language not supported
backend/groth16/bw6-761/verify.go: Language not supported
backend/plonk/bls12-377/marshal.go: Language not supported
backend/plonk/bls12-377/prove.go: Language not supported
backend/plonk/bls12-377/verify.go: Language not supported

ivokub · 2026-06-11T11:18:19Z

@gbotrel - ready for review now. It should be backwards compatible, but we dispatch a message indicating that the users should avoid using the old zerolog based implementation. And now the new logger is internal, used only internally inside gnark. If the user wants to provide their custom logger, then they can provide their own initialized slog into frontend/backend etc.

We also now print out some runtime status so that its easier to debug the capabilities of the system. I was thinking about also querying AWS instance info (i.e. the machine type etc), but postponed for now.

time=2026-06-11T10:56:22.969Z level=DEBUG source=/home/ubuntu/src/gnark/internal/logger/logger.go:123 msg="runtime configuration" gomaxprocs=8 gomemlimit=∞ goarch=amd64 goos=linux support_neon=false support_avx512=f
alse support_avx512ifma=false gnark_version=0.15.0 build_tags=icicle go_build_version=go1.25.7 vcs_tagged_version=(devel) vcs_modified=""

I would say biggest difference is that now api.Println doesn't have custom handling, so the printed lines are a la https://github.com/Consensys/gnark/pull/1769/changes#diff-cd33dcd5c0776ca721b2b7bde44cffa80109541b9cdb11c2fe35c5a9d6cac275L51-R55. In principle I could have a custom handler to avoid printing fields etc, but I wanted to keep compatible with native TextHandler.

I also added Trace level for tracing different steps and made DEBUG level less noisy. Now the log level can also be set using GNARK_LOG_LEVEL tag (by default we are INFO, unless build tag debug is set. But the env value always overrides even the build tag).

ivokub added 30 commits May 19, 2026 23:49

feat: add internal log/slog backed logger

7bd6f77

feat: passthrough old logger to new logger with deprecation

f360eb5

docs: add log level info to README

77faa02

feat: add zerolog adapter for compatibility

346243c

feat: add trace log level

efcf114

feat: use slog in icicle prover

851b923

feat: add backend options for providing logger

72b769b

fix: use provided logger for icicle backend

27db43e

feat: use provided logger in backend prove/verify

c0850ec

feat: add backwards-compatible logger override in solver

45d109f

chore: reduce log level for multiple hint registration

8f50df7

chore: use new logger for solver hint registration option

bad00b0

chore: use new logger in solver checkSerialization

7183d13

feat: use new logger in solver

9ff470d

chore: provide logger to solve in icicle

4486cd7

feat: add DisabledLogger option

fc54dad

feat: provide Logger() method in Compiler

d8159c7

chore: reduce override hint log level to trace (BSB hint)

e0993f5

feat: use compiler logger in widecommitter

f131215

feat: use compiler logger in std

527d6de

feat: use new logger in profile

6f8fa99

chore: only retrieve logger when needed

5df6cca

feat: support custom logger in test engine

010895c

feat: use new logger in unsafekzg

a601cb7

feat: suppress logs in fuzzing test

80035a2

fix: skip solver consistency for U64-only circuit

7810dcb

feat: provide logger in assert method

627ab0f

feat: add trace logs in assertions

c209e58

feat: use assert logger in Solidity logs

ee920c7

test: update debug test

d612a67

ivokub requested a review from Copilot May 20, 2026 00:11

Copilot started reviewing on behalf of ivokub May 20, 2026 00:12 View session

Copilot AI reviewed May 20, 2026

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Comment thread internal/logger/logger.go

Comment thread internal/compilelogger/compilelogger.go

Comment thread internal/compilelogger/compilelogger.go

Comment thread std/rangecheck/rangecheck_commit.go

ivokub added 12 commits May 20, 2026 07:39

feat: remove format declarations

022e644

docs: update compilelogger interface

b0aa058

feat: add slog linter

d1a9c12

chore: update golangci-lint to latest to have new slog linter

4ce496e

chore: run go fix

6f6a6b7

feat: use infinity for unset gomemlimit

164ec57

fix: ensure trace logs source line

adff367

feat: add tracing logs in backends

ea435c9

feat: add logs for serialization steps

1b71a18

feat: log constraint system serialization

7200b2e

feat: plonk serialization logs

99096ee

feat: mpcsetup log marshal with debug

548b79e

ivokub marked this pull request as ready for review May 21, 2026 09:44

ivokub requested a review from Copilot May 21, 2026 09:44

Copilot started reviewing on behalf of ivokub May 21, 2026 09:44 View session

cursor Bot reviewed May 21, 2026

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Comment thread backend/accelerated/icicle/internal/generator/templates/groth16.icicle.go.tmpl Outdated

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Comment thread constraint/solver/options.go

ivokub added 3 commits May 25, 2026 08:15

fix: avoid string formatting in slog

1a58d1f

Merge remote-tracking branch 'origin/master' into feat/slog-rebased

c84e602

chore: use new logger in ICICLE Groth16 dispatcher

f9db470

ivokub requested review from Copilot and gbotrel June 11, 2026 11:12

Copilot started reviewing on behalf of ivokub June 11, 2026 11:12 View session

Copilot AI reviewed Jun 11, 2026

View reviewed changes

Comment thread frontend/builder.go

Comment thread backend/backend.go

Merge branch 'master' into feat/slog-rebased

b94e1f2

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feat: implement slog-based logging#1769

feat: implement slog-based logging#1769
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ivokub commented Jun 11, 2026

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