bug logging: do not ignore SIGUSR1 during boot

commit_hash:d1a54d592ce6084740c28c1b8c0289ff28594922

Author: segoon

core/src/logging/component.cpp

@@ -9,6 +9,7 @@
 
 #include <userver/alerts/source.hpp>
 #include <userver/components/component.hpp>
+#include <userver/components/scope.hpp>
 #include <userver/components/statistics_storage.hpp>
 #include <userver/engine/async.hpp>
 #include <userver/engine/sleep.hpp>
@@ -67,17 +68,25 @@ void ReportReopeningErrorAndThrow(
 
 }  // namespace
 
-/// [Signals sample - init]
 Logging::Logging(const ComponentConfig& config, const ComponentContext& context)
     : fs_task_processor_{GetFsTaskProcessor(config, context)},
-      metrics_storage_(context.FindComponent<components::StatisticsStorage>().GetMetricsStorage()),
-      signal_subscriber_(context.FindComponent<os_signals::ProcessorComponent>()
-                             .Get()
-                             .AddListener(this, kName, os_signals::kSigUsr1, &Logging::OnLogRotate))
-/// [Signals sample - init]
+      metrics_storage_(context.FindComponent<components::StatisticsStorage>().GetMetricsStorage())
 {
     try {
         Init(config, context);
+
+        /// [Signals sample - init]
+        auto& signals_processor = context.FindComponent<os_signals::ProcessorComponent>().Get();
+        context.RegisterScope(MakeScope([this, &signals_processor] {
+            auto holder = signals_processor.AddListener(this, kName, os_signals::kSigUsr1, &Logging::OnLogRotate);
+
+            // Force logrotate just after signal subscription to be sure we haven't lost signals during the loading.
+            // If there were no signals, it's OK to re-open log files one more time.
+            OnLogRotate();
+
+            return holder;
+        }));
+        /// [Signals sample - init]
     } catch (const std::exception&) {
         Stop();
         throw;
@@ -157,11 +166,6 @@ void Logging::Init(const ComponentConfig& config, const ComponentContext& contex
 Logging::~Logging() { Stop(); }
 
 void Logging::Stop() noexcept {
-    /// [Signals sample - destr]
-
-    signal_subscriber_.Unsubscribe();
-
-    /// [Signals sample - destr]
     flush_task_.Stop();
 
     // Loggers could be used from non coroutine environments and should be

scripts/docs/en/userver/os_signals.md

@@ -28,9 +28,6 @@ after executing [logrotate](https://github.com/logrotate/logrotate).
   components::Logging uses the following code:
   @snippet core/src/logging/component.cpp  Signals sample - init
 
-3. In the component's destructor, unsubscribe from the signal
-  @snippet core/src/logging/component.cpp  Signals sample - destr
-
 
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