zeroshade commented on code in PR #1343: URL: https://github.com/apache/iceberg-go/pull/1343#discussion_r3494080785
########## metrics/reporters.go: ########## @@ -0,0 +1,131 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package metrics + +import ( + "context" + "log/slog" + "sync" +) + +// Nop is a [Reporter] that discards every report. It is the default when no +// reporter is configured, so that instrumentation is free unless a user opts +// in. The zero value is ready to use. +type Nop struct{} + +var _ Reporter = Nop{} + +// Report implements [Reporter] and does nothing. +func (Nop) Report(context.Context, Report) {} + +// LoggingReporter is a [Reporter] that logs each report via an [slog.Logger]. It +// is a convenient default for development and debugging. +type LoggingReporter struct { + logger *slog.Logger +} + +var _ Reporter = (*LoggingReporter)(nil) + +// NewLoggingReporter returns a [LoggingReporter] that logs to logger. If logger +// is nil, [slog.Default] is used. +func NewLoggingReporter(logger *slog.Logger) *LoggingReporter { + if logger == nil { + logger = slog.Default() + } + + return &LoggingReporter{logger: logger} +} + +// Report logs report at info level. +func (r *LoggingReporter) Report(ctx context.Context, report Report) { + if report == nil { + return + } + r.logger.InfoContext(ctx, "iceberg metrics report", "report", report) +} + +// InMemoryReporter is a [Reporter] that retains every report it receives. It is +// primarily intended for tests and inspection. It is safe for concurrent use. +type InMemoryReporter struct { + mu sync.Mutex + reports []Report +} + +var _ Reporter = (*InMemoryReporter)(nil) + +// Report appends report to the retained set. +func (r *InMemoryReporter) Report(_ context.Context, report Report) { + if report == nil { + return + } + r.mu.Lock() + defer r.mu.Unlock() + r.reports = append(r.reports, report) +} + +// Reports returns a copy of the reports received so far, in arrival order. +func (r *InMemoryReporter) Reports() []Report { + r.mu.Lock() + defer r.mu.Unlock() + + return append([]Report(nil), r.reports...) +} + +// Reset discards all retained reports. +func (r *InMemoryReporter) Reset() { + r.mu.Lock() + defer r.mu.Unlock() + r.reports = nil +} + +// Combine returns a [Reporter] that forwards each report to all of the given +// reporters in order. nil reporters are skipped. A panic in one reporter must +// not prevent the others from receiving the report, so each call is isolated; +// in keeping with the [Reporter] contract a misbehaving reporter never affects +// the observed operation. +// +// As a convenience, Combine with no reporters returns [Nop], and with a single +// non-nil reporter returns that reporter directly. +func Combine(reporters ...Reporter) Reporter { + nonNil := make([]Reporter, 0, len(reporters)) + for _, r := range reporters { + if r != nil { + nonNil = append(nonNil, r) + } + } + + switch len(nonNil) { + case 0: + return Nop{} + case 1: + return nonNil[0] Review Comment: A few minor notes here (all non-blocking): - **Isolation asymmetry:** `Combine(r)` returns `r` directly, so a *single* reporter is not panic-isolated, whereas the composite path below (L124-129) recovers per reporter. Fine as an optimization, but worth a doc line that the panic safety-net only applies with 2+ reporters (or always wrap for uniform behavior). - **Silent recover (L127):** `defer func() { _ = recover() }()` swallows a panicking reporter entirely. Per the `Reporter` contract that's intentional, but a fully-silent recover makes a broken reporter invisible — consider logging the recovered value at debug level. - **FYI (not a change):** this is Phase 1 scaffolding — no concrete `Report` types or scan/commit instrumentation yet, so nothing produces reports in-tree until the later phases of #1236. Noting for anyone reading the package in isolation. ########## metrics/reporters.go: ########## @@ -0,0 +1,131 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package metrics + +import ( + "context" + "log/slog" + "sync" +) + +// Nop is a [Reporter] that discards every report. It is the default when no +// reporter is configured, so that instrumentation is free unless a user opts +// in. The zero value is ready to use. +type Nop struct{} Review Comment: Tiny consistency nit: the other built-ins are `LoggingReporter` / `InMemoryReporter`, but this one is `Nop`. Consider `NopReporter` so the set reads uniformly — or keep `Nop` intentionally as the short form; just flagging the asymmetry. Non-blocking. ########## metrics/reporter.go: ########## @@ -0,0 +1,54 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +// Package metrics implements Iceberg's Metrics Reporting API for iceberg-go. +// +// A [Reporter] is a pluggable sink that receives a [Report] — a ScanReport +// after scan planning or a CommitReport after a commit — describing what the +// client did (files and manifests considered, scanned and skipped; bytes read; +// commit attempts and durations). Reporting gives operators a standard way to +// aggregate these otherwise-invisible client-side metrics across many clients. +// +// Reporting is strictly opt-in: with no reporter configured the instrumented +// code paths do no work. Reporters must never block or fail the scan/commit +// they observe — see [Reporter] for the contract. +// +// This package provides the contract and the built-in reporters ([Nop], +// [LoggingReporter], [InMemoryReporter], and [Combine]). The concrete report +// types and the scan/commit instrumentation are layered on top in later work. +package metrics + +import "context" + +// Report is the sealed marker interface implemented by the concrete report +// types (ScanReport and CommitReport). It is sealed to this package so the set +// of report types stays under the framework's control. +type Report interface { Review Comment: **Naming — the one thing worth settling before this public API ships.** The marker interface is `Report` while the contract method is `Reporter.Report(ctx, report Report)`, so signatures read as `Report(context.Context, Report)` — a method named like its own parameter type. Java/PyIceberg call the marker **`MetricsReport`**, with `ScanReport`/`CommitReport` implementing it and `MetricsReporter.report(MetricsReport)`. Suggest renaming this interface `Report` → `MetricsReport` (keep `Reporter.Report(...)` as the verb). That (a) disambiguates the type from the method, and (b) aligns the Go API with the rest of the Iceberg ecosystem, easing ports from Java. Since `ScanReport`/`CommitReport` arrive in later phases, settling the marker name now avoids a churny rename across those PRs. -- This is an automated message from the Apache Git Service. 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