feat(logging): add spdlog backend behind ICEBERG_SPDLOG (5/6) by kamcheungting-db · Pull Request #726 · apache/iceberg-cpp

kamcheungting-db · 2026-06-11T01:24:13Z

Part 5 of the logging stack (builds on #725). Adds the spdlog backend and the build option that selects it — the default in production builds.

What's here

SpdLogger wraps spdlog::logger (synchronous), maps levels (fatal/critical → spdlog critical; the abort stays in the macro layer), and forwards source location. Default sink is a colored stderr sink.
New ICEBERG_SPDLOG CMake option (ON by default). When OFF, the build has no spdlog dependency at all and CerrLogger is the default.
pattern property is honored here via spdlog set_pattern (the cerr backend keeps its fixed layout); level works on both backends.
SpdLogger lives in logging/internal/ and is not installed — apps get it via the default logger or the "spdlog" registry type.

Tests — spdlog_logger_test (compiled only when spdlog is ON): level mapping incl. fatal→critical, source-location forwarding, and the pattern property. clang/libc++ with spdlog 1.15.3.

This pull request and its description were written by Isaac.

Fourth block: the application-facing macros, the only part most callers touch. - ICEBERG_LOG_{TRACE,DEBUG,INFO,WARN,ERROR,CRITICAL,FATAL} plus the generic ICEBERG_LOG(level, ...), ICEBERG_LOG_TO(logger, level, ...) for an explicit logger, and ICEBERG_LOG_RUNTIME_FMT for a runtime (non-literal) format string. - ICEBERG_LOG_ACTIVE_LEVEL is a compile-time severity floor: statements below it are removed entirely via `if constexpr` (no format call site, no source location emitted). ICEBERG_LOG_FATAL is never gated by the floor -- its abort is always compiled in; it emits, best-effort Flush()es the same logger it emitted to, then std::abort(). - Filtering is decided solely by Logger::ShouldLog(); formatting is wrapped in try/catch so logging never throws (a format failure routes to EmitFormatError). - Bare Java-style aliases (LOG_INFO, ...) are opt-in via ICEBERG_LOG_SHORT_MACROS to avoid polluting consumers / colliding with glog/abseil. Header-only addition to logger.h. macros_test covers injection, the guard-before-format short-circuit, never-throws, and FATAL aborts; macros_active_level_test verifies compile-time stripping in a kOff translation unit. Co-authored-by: Isaac

Note in FormatAndEmit and the ICEBERG_INTERNAL_LOG comment that the only throws are std::format_error/std::bad_alloc (same recovery), and that catching std::exception rather than (...) lets a non-std unwind such as abi::__forced_unwind (thread cancellation) propagate. Co-authored-by: Isaac

… docs, FATAL test) - Revert the 6 catch sites to catch(...) so the noexcept "logging never throws" guarantee holds even when a user-defined std::formatter throws a non-std type (catch(const std::exception&) would let it reach std::terminate). - Apply /Zc:preprocessor to the iceberg library targets PUBLICly on MSVC, not only to tests: logger.h is public and uses __VA_OPT__, so the library build and consumers need the conforming preprocessor too. - Soften the compile-time-floor doc: `if constexpr` discards the emit but the statement must still be well-formed (bad format string is still a compile error). - Add the missing opening '[' to the logger.h example output lines to match CerrLogger's [file:line] layout. - Add MacrosDeathTest.FatalRoutesThroughScopedLogger locking in that ICEBERG_LOG_FATAL routes through the active ScopedLogger (GetCurrentLogger). Co-authored-by: Isaac

Adopt the structure from the apache#824 prototype (keeping our if constexpr gating): - logger.h is now the C++ API only; ICEBERG_LOG_* macros move to log_macros.h, and the bare LOG_* aliases move behind an opt-in short_log_macros.h (replacing the ICEBERG_LOG_SHORT_MACROS define). - Dedup the five macro bodies onto shared internal helpers (EmitIfEnabled + LogToCurrent / LogToCurrentRuntime / LogToExplicitRuntime / LogFatal) that take a lazy [&]()->std::string message thunk invoked only past ShouldLog, so disabled logs still don't evaluate their args. Keeps catch(...), the GetCurrentLogger() fatal path, and if constexpr compile-time floor. - VFormat moves to log_macros.h (only ICEBERG_LOG_RUNTIME_FMT uses it). Co-authored-by: Isaac

…review ⑤) Address the extensibility comment: let an embedder (JNI, Python host, crash reporter) run a hook on the fatal path before std::abort() to flush resources or print a stack trace. - Add FatalHandler = std::function<void(const std::source_location&, std::string_view)> plus thread-safe SetFatalHandler/GetFatalHandler (leaked, teardown-safe slot in logger.cc). - Wire it into LogFatal: format the message once, emit-if-enabled + flush, run the handler (message passed even when the record is filtered out), then abort. A throwing handler cannot prevent the abort. - Death tests: handler runs with the formatted message, receives the call-site location, and still fires when the record is suppressed. Co-authored-by: Isaac

Copilot

Pull request overview

This PR adds a selectable spdlog-backed logging sink to Iceberg C++ (guarded by ICEBERG_SPDLOG in CMake), introduces the public logging macro headers (log_macros.h / short_log_macros.h), and extends the test/build wiring to cover macro behavior and the spdlog backend.

Changes:

Add internal::SpdLogger (spdlog backend) and route the process default logger to it when ICEBERG_HAS_SPDLOG is enabled.
Introduce installed logging macro headers (ICEBERG_LOG_*, plus opt-in bare LOG_* aliases) and MSVC preprocessor flags needed for __VA_OPT__.
Add unit tests for logging macros and the spdlog backend; update CMake/Meson build definitions accordingly.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/iceberg/test/spdlog_logger_test.cc	Adds unit tests for the spdlog-backed logger behavior.
src/iceberg/test/meson.build	Includes the new logging-related tests in the Meson test target.
src/iceberg/test/macros_test.cc	Adds tests for formatting, level gating, runtime-format safety, and fatal-abort behavior in macros.
src/iceberg/test/macros_active_level_test.cc	Adds tests for compile-time log stripping via `ICEBERG_LOG_ACTIVE_LEVEL`.
src/iceberg/test/CMakeLists.txt	Wires the new tests into CMake and adds MSVC `/Zc:preprocessor` for test compilation.
src/iceberg/meson.build	Compiles the spdlog backend source in the Meson build.
src/iceberg/logging/short_log_macros.h	Adds opt-in bare `LOG_*` aliases for the Iceberg-prefixed macros.
src/iceberg/logging/meson.build	Generates `logging/config.h` and installs the new public logging headers in Meson.
src/iceberg/logging/logger.h	Extends the logging API docs and adds the `FatalHandler` hook API.
src/iceberg/logging/logger.cc	Selects spdlog vs `CerrLogger` as the default logger based on `ICEBERG_HAS_SPDLOG` and implements fatal-handler storage.
src/iceberg/logging/log_macros.h	Introduces the public logging macros and internal helpers used by those macros.
src/iceberg/logging/internal/spdlog_logger.h	Declares the internal spdlog-backed `SpdLogger` sink (not installed).
src/iceberg/logging/internal/spdlog_logger.cc	Implements the spdlog-backed sink (pattern support, level mapping, forwarding).
src/iceberg/logging/config.h.in	Adds the build-generated backend selection header template (`ICEBERG_HAS_SPDLOG`).
src/iceberg/CMakeLists.txt	Generates `iceberg/logging/config.h`, gates spdlog linkage/compilation behind `ICEBERG_SPDLOG`, and exports `/Zc:preprocessor` on MSVC.
meson.build	Adds `/Zc:preprocessor` to MSVC project arguments for Meson builds.
CMakeLists.txt	Introduces the `ICEBERG_SPDLOG` option (default ON).
cmake_modules/IcebergThirdpartyToolchain.cmake	Avoids resolving the spdlog dependency when `ICEBERG_SPDLOG` is OFF.

+template <typename MakeMessage>
+void LogToExplicitRuntime(Logger& logger, LogLevel level,
+                          const std::source_location& location,
+                          MakeMessage&& make_message) noexcept {
+  EmitIfEnabled(logger, level, location, std::forward<MakeMessage>(make_message));
+  if (level == LogLevel::kFatal) {
+    logger.Flush();
+    std::abort();
+  }
+}


+Status SpdLogger::Initialize(
+    const std::unordered_map<std::string, std::string>& properties) {
+  if (auto it = properties.find(std::string(kPatternProperty)); it != properties.end()) {
+    logger_->set_pattern(it->second);
+  }
+  // Apply "level" via the base implementation.
+  return Logger::Initialize(properties);
+}


+void SpdLogger::Log(LogMessage&& message) noexcept {
+  try {
+    spdlog::source_loc loc{message.location.file_name(),
+                           static_cast<int>(message.location.line()),
+                           message.location.function_name()};
+    // Pass the pre-formatted text as an argument ("{}") so any braces in the
+    // message are not re-interpreted as a format string.
+    logger_->log(loc, ToSpdLevel(message.level), "{}", message.message);
+  } catch (...) {
+    // Logging must never throw.
+  }
+}


+void SpdLogger::Flush() noexcept {
+  try {
+    logger_->flush();
+  } catch (...) {
+  }
+}


+/// INTERNAL, NOT INSTALLED. It is only included from .cc files (logger.cc and
+/// spdlog_logger.cc) after config.h, and only when the project is built with
+/// ICEBERG_SPDLOG=ON. SpdLogger is not a consumer-constructible public type --
+/// applications obtain it via the default logger or the "logger-impl"="spdlog"
+/// registry factory.
+
+#include "iceberg/logging/config.h"


+# Generate the logging backend config header. ALWAYS generated (not gated by
+# ICEBERG_SPDLOG) so logging/logger.cc can include it in both ON and OFF builds;
+# only the definedness of ICEBERG_HAS_SPDLOG varies. Generated into the build
+# tree (already on ICEBERG_INCLUDES), included as "iceberg/logging/config.h", and
+# NOT installed (it must never appear in a public/installed header).
+if(ICEBERG_SPDLOG)
+  set(ICEBERG_HAS_SPDLOG ON)
+endif()
+configure_file("${CMAKE_CURRENT_SOURCE_DIR}/logging/config.h.in"
+               "${CMAKE_CURRENT_BINARY_DIR}/logging/config.h")


+template <typename MakeMessage>
+void LogToCurrentRuntime(LogLevel level, const std::source_location& location,
+                         MakeMessage&& make_message) noexcept {
+  const std::shared_ptr<Logger>& logger = CurrentLogger();
+  if (logger) {
+    EmitIfEnabled(*logger, level, location, std::forward<MakeMessage>(make_message));
+  }
+  if (level == LogLevel::kFatal) {
+    if (logger) logger->Flush();
+    std::abort();
+  }
+}


wgtmac · 2026-07-23T06:21:15Z

It's time to rebase it :)

The FatalHandler only ran for fixed ICEBERG_LOG_FATAL; reaching kFatal via the runtime-level ICEBERG_LOG(kFatal, ...) or ICEBERG_LOG_TO(sink, kFatal, ...) aborted without invoking it (and only formatted when ShouldLog passed). Extract the fatal sequence into a shared DispatchFatal (format once -> emit-if-enabled -> flush -> run handler -> abort) and route LogFatal, LogToCurrentRuntime, and LogToExplicitRuntime through it. Adds death tests for the two runtime paths. Co-authored-by: Isaac

Fifth block: the default production backend and the build option that selects it. - SpdLogger wraps spdlog::logger (kCritical/kFatal -> spdlog critical, others 1:1), forwarding the pre-formatted message and source location. Synchronous only in v1 (spdlog's source_loc is a non-owning const char*, unsafe with async sinks). It lives in logging/internal/, is gated by #ifdef ICEBERG_HAS_SPDLOG, and is NOT installed -- consumers obtain it via the default logger or the registry, never by including spdlog headers. - New ICEBERG_SPDLOG CMake option (default ON). config.h is ALWAYS generated (only ICEBERG_HAS_SPDLOG's definedness varies) so logger.cc compiles in both configurations; MakeDefaultLogger() prefers SpdLogger when compiled in, else CerrLogger. - Critically, ICEBERG_SPDLOG=OFF now UNWIRES the previously-unconditional spdlog link (interface-lib lists + resolve_spdlog_dependency), not just the new source -- so an OFF build has no spdlog dependency at all. spdlog_logger_test (compiled only on the ON path) covers the level mapping including fatal->critical and source-location forwarding. Co-authored-by: Isaac

wgtmac · 2026-08-01T07:55:43Z

+                           message.location.function_name()};
+    // Pass the pre-formatted text as an argument ("{}") so any braces in the
+    // message are not re-interpreted as a format string.
+    logger_->log(loc, ToSpdLevel(message.level), "{}", message.message);


This re-formats an already formatted message through fmt for every emitted record, adding another full copy and possibly an allocation for long messages. Please call the raw-message overload with spdlog::string_view_t{message.message.data(), message.message.size()} instead.

wgtmac · 2026-08-01T07:55:45Z

+  // logger_ is a hard precondition: SpdLogger is not consumer-constructible (it is
+  // obtained via the default logger or the "spdlog" registry factory, both of which
+  // pass a real logger), so Initialize/Log/Flush may dereference it unconditionally.
+  ICEBERG_DCHECK(logger_ != nullptr, "SpdLogger requires a non-null spdlog::logger");


ICEBERG_DCHECK disappears under NDEBUG, and the constructor dereferences logger_ immediately afterwards. Since shared_ptr is nullable and the header only documents the synchronous requirement, an empty input becomes a release crash. Please reject null in a factory or encode the non-null requirement in the API.

wgtmac · 2026-08-01T07:55:46Z

+# build/src/iceberg/logging/config.h (resolved via include_directories('..'),
+# which exposes both the source and build trees); not installed.
+logging_config_data = configuration_data()
+logging_config_data.set('ICEBERG_HAS_SPDLOG', 1)


CMake supports ICEBERG_SPDLOG=OFF, but Meson always enables this backend and unconditionally links spdlog. Please add a matching Meson feature option so the no-spdlog/Cerr configuration is available in both supported build systems.

wgtmac · 2026-08-01T07:55:48Z

+  EXPECT_TRUE(logger.ShouldLog(LogLevel::kError));
+}
+
+TEST(SpdLoggerTest, ForwardsMessageToSink) {


This only verifies the payload, so the advertised source-location forwarding is untested. Please use a %s:%# %! %v pattern and assert the file, line, and function fields.

kamcheungting-db changed the title ~~feat: [Iceberg Logger] [Part-5] spdlog backend (ICEBERG_SPDLOG)~~ feat(logging): add spdlog backend behind ICEBERG_SPDLOG Jun 11, 2026

kamcheungting-db changed the title ~~feat(logging): add spdlog backend behind ICEBERG_SPDLOG~~ feat(logging): add spdlog backend behind ICEBERG_SPDLOG (5/6) Jun 11, 2026

kamcheungting-db force-pushed the logging-block5-spdlog branch 2 times, most recently from c6831cb to 2b80ee1 Compare June 14, 2026 06:16

kamcheungting-db mentioned this pull request Jun 14, 2026

feat(logging): add Loggers registry (6/6) #737

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kamcheungting-db force-pushed the logging-block5-spdlog branch 14 times, most recently from dd50f86 to 17a616e Compare June 22, 2026 10:24

kamcheungting-db force-pushed the logging-block5-spdlog branch 6 times, most recently from 7e81c6d to 2684d7c Compare June 24, 2026 18:39

kamcheungting-db force-pushed the logging-block5-spdlog branch 2 times, most recently from 289b0fb to ef127cd Compare June 30, 2026 20:36

kamcheungting-db mentioned this pull request Jun 30, 2026

feat(logging): zero-allocation format->dispatch path (LogRecord view) #795

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kamcheungting-db force-pushed the logging-block5-spdlog branch from ef127cd to b337dd0 Compare July 16, 2026 06:15

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manuzhang requested a review from Copilot July 20, 2026 07:27

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feat(logging): add spdlog backend behind ICEBERG_SPDLOG (5/6) - #726

feat(logging): add spdlog backend behind ICEBERG_SPDLOG (5/6)#726
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kamcheungting-db commented Jun 11, 2026 •

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