ewrap

ewrap

A lightweight, modern Go error library: rich context, stack traces, structured serialization, slog/fmt.Formatter integration, HTTP/retry classification, PII-safe logging, and an opt-in circuit breaker — all in a tight dependency footprint (yaml + a fast JSON encoder, nothing else).

Highlights

• Stdlib-first. Two direct deps in the core module: gopkg.in/yaml.v3 for YAML, github.com/goccy/go-json for the serialization hot path (~2.5× faster than encoding/json).
• Correct by default. errors.Is / errors.As work via Unwrap(); Newf honors %w; every wrap captures its own stack frames.
• Lazy & cached hot paths. Lazy metadata map; Error() and Stack() cached via sync.Once. After the first call, Stack() is ~1.7 ns/op, zero allocations.
• Modern Go integrations. (*Error).Format for %+v; (*Error).LogValue for slog; errors.Join-aware ErrorGroup.
• Operational features. HTTP status, retryable / Temporary() classification, safe (PII-redacted) messages, recovery suggestions, structured ErrorContext.
• Opt-in subpackages. Circuit breaker lives in ewrap/breaker; slog adapter in ewrap/slog. Importing ewrap alone pulls in only the core.

Install

go get github.com/hyp3rd/ewrap

Requires Go 1.25+ (uses maps.Clone, slices.Clone, range-over-int, b.Loop).

Quick tour

import "github.com/hyp3rd/ewrap"

// Plain error with stack trace
err := ewrap.New("database connection failed")

// %w-aware formatted constructor
err := ewrap.Newf("query %q failed: %w", q, ioErr) // errors.Is(err, ioErr) == true

// Wrap preserves the inner cause AND captures the wrap site
err := ewrap.Wrap(ioErr, "syncing replicas")

// Nil-safe
ewrap.Wrap(nil, "ignored") == nil
ewrap.Wrapf(nil, "ignored %d", 42) == nil

Rich context

err := ewrap.New("payment authorization rejected",
    ewrap.WithContext(ctx, ewrap.ErrorTypeExternal, ewrap.SeverityError),
    ewrap.WithHTTPStatus(http.StatusBadGateway),
    ewrap.WithRetryable(true),
    ewrap.WithSafeMessage("payment authorization rejected"), // omits PII
    ewrap.WithRecoverySuggestion(&ewrap.RecoverySuggestion{
        Message: "Inspect upstream provider's queue and retry after backoff.",
        Documentation: "https://runbooks.example.com/payments/timeout",
    }),
).
    WithMetadata("provider", "stripe").
    WithMetadata("attempt", 2)

err.Log() // emits structured fields via the configured Logger

Stack traces

fmt.Printf("%+v\n", err) // message + filtered stack via fmt.Formatter

// Or inspect frames programmatically
for it := err.GetStackIterator(); it.HasNext(); {
    f := it.Next()
    fmt.Printf("%s:%d %s\n", f.File, f.Line, f.Function)
}

Stack() is computed once and cached. WithStackDepth(n) tunes capture; pass 0 to disable. NewSkip / WrapSkip add caller-skip when wrapping New/Wrap in helpers.

Standard library compatibility

errors.Is(err, ioErr)  // walks the cause chain via Unwrap()
errors.As(err, &netErr)
errors.Unwrap(err)
fmt.Errorf("layered: %w", err) // also walks correctly

Operational classification

ewrap.HTTPStatus(err)   // walks chain; 0 if unset
ewrap.IsRetryable(err)  // checks ewrap classification, then stdlib Temporary()
err.SafeError()         // redacted variant for external sinks
err.Recovery()          // typed accessor for the recovery suggestion
err.Retry()             // typed accessor for retry metadata
err.GetErrorContext()   // typed ErrorContext or nil

slog integration

*Error implements slog.LogValuer, so slog.Error("boom", "err", err) emits the message, type, severity, component, request_id, metadata and cause as structured fields.

For drivers that want an ewrap.Logger, the slog subpackage provides a 3-line adapter:

import (
    stdslog "log/slog"
    ewrapslog "github.com/hyp3rd/ewrap/slog"
)

logger := ewrapslog.New(stdslog.New(stdslog.NewJSONHandler(os.Stdout, nil)))
err := ewrap.New("boom", ewrap.WithLogger(logger))

For zap, zerolog, logrus, glog, etc. — write a 5-line adapter against the ewrap.Logger interface (3 methods: Error, Debug, Info).

Error groups

pool := ewrap.NewErrorGroupPool(4)
eg := pool.Get()
defer eg.Release()

eg.Add(validate(req))
eg.Add(persist(req))

if err := eg.Join(); err != nil { // errors.Join semantics
    return err
}

(*ErrorGroup).ToJSON() / ToYAML() recursively serialize the whole group, walking both *Error and standard wrapped chains so transport consumers keep full context.

Circuit breaker

The breaker is a sibling subpackage so consumers who only want errors don't pay for it.

import "github.com/hyp3rd/ewrap/breaker"

cb := breaker.New("payments", 5, 30*time.Second)

if !cb.CanExecute() {
    return ewrap.New("payments breaker open",
        ewrap.WithRetryable(true))
}

if err := charge(req); err != nil {
    cb.RecordFailure()

    return ewrap.Wrap(err, "charging customer",
        ewrap.WithHTTPStatus(http.StatusBadGateway))
}

cb.RecordSuccess()

Observers receive transitions synchronously after the lock is released:

type metrics struct{ /* ... */ }

func (m *metrics) RecordTransition(name string, from, to breaker.State) {
    m.gauge.WithLabelValues(name, to.String()).Inc()
}

cb := breaker.NewWithObserver("payments", 5, 30*time.Second, &metrics{})

Error types and severity

Pre-defined enums for categorization. Their String() form is what shows up in ErrorOutput.Type / Severity, JSON, and slog fields.

ErrorTypeUnknown        // -> "unknown"
ErrorTypeValidation     // -> "validation"
ErrorTypeNotFound       // -> "not_found"
ErrorTypePermission     // -> "permission"
ErrorTypeDatabase       // -> "database"
ErrorTypeNetwork        // -> "network"
ErrorTypeConfiguration  // -> "configuration"
ErrorTypeInternal       // -> "internal"
ErrorTypeExternal       // -> "external"

SeverityInfo            // -> "info"
SeverityWarning         // -> "warning"
SeverityError           // -> "error"
SeverityCritical        // -> "critical"

Logger interface

type Logger interface {
    Error(msg string, keysAndValues ...any)
    Debug(msg string, keysAndValues ...any)
    Info(msg string, keysAndValues ...any)
}

Three methods, key-value pairs after the message. Implementations stay goroutine-safe; (*Error).Log calls them synchronously.

Performance

Snapshot from go test -bench=. -benchmem ./test/... on Apple Silicon (Go 1.25+):

Notable design choices behind the numbers:

• Lazy metadata map — only allocated on the first WithMetadata call.
• Cached Error() / Stack() — sync.Once guards a one-shot computation; subsequent reads are lock-free.
• goccy/go-json for the serialization hot path: ~2.5× faster than stdlib encoding/json with ~half the allocations.
• runtime.Callers captures up to 32 PCs by default, configurable via WithStackDepth(n). The frame filter is function-prefix based, so the output starts at user code.
• Breaker is allocation-free in steady state; observer/callback dispatch happens outside the lock to avoid holding it across user code.

Project layout

.
├── attributes.go              # WithHTTPStatus, WithRetryable, WithSafeMessage
├── context.go                 # ErrorContext, WithContext option
├── errors.go                  # Error type, New/Wrap/Newf/Wrapf, lazy paths
├── error_group.go             # ErrorGroup, pool, serialization
├── format.go                  # ErrorOutput, ToJSON/ToYAML
├── format_verb.go             # fmt.Formatter, slog.LogValuer
├── logger.go                  # Logger interface
├── observability.go           # Observer interface (errors only)
├── retry.go                   # RetryInfo, WithRetry
├── stack.go                   # StackFrame, StackIterator
├── types.go                   # ErrorType, Severity, RecoverySuggestion
├── breaker/                   # opt-in circuit breaker
└── slog/                      # opt-in slog adapter

Development

git clone https://github.com/hyp3rd/ewrap.git
cd ewrap
make prepare-toolchain    # one-time: golangci-lint, gofumpt, govulncheck, gosec
make test                 # go test -v -timeout 5m -cover ./...
make test-race            # go test -race ./...
make benchmark            # go test -bench=. -benchmem ./test/...
make lint                 # gci + gofumpt + staticcheck + golangci-lint
make sec                  # govulncheck + gosec

License

MIT License

Contributing

See CONTRIBUTING. PRs welcome — please run make lint and make test-race before opening one.

Author

I'm a surfer, and a software architect with 15 years of experience designing highly available distributed production systems and developing cloud-native apps in public and private clouds. Feel free to connect with me on LinkedIn.