feat: Disable SIGTERM reporting by default

We added support for SIGTERM reporting in the last release and enabled
it by default. For some users, SIGTERM events were verbose and not
actionable. Therefore, we disable it per default.

Fixes GH-4013

CHANGELOG.md

@@ -8,6 +8,11 @@
 - Add start time to network request breadcrumbs (#4008)
 - Add C++ exception support for `__cxa_rethrow` (#3996)
 - Add beforeCaptureScreenshot callback (#4016)
+- Add option to enable SIGTERM reporting (#4025). We added support
+for SIGTERM reporting in the last release and enabled it by default.
+For some users, SIGTERM events were verbose and not actionable.
+Therefore, we disable it per default in this release. If you'd like
+to receive SIGTERM events, set the option `enableSigtermReporting = true`.
 
 ### Improvements
 

Samples/iOS-Swift/iOS-Swift/AppDelegate.swift

@@ -22,6 +22,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
             options.beforeSend = { event in
                 return event
             }
+            options.enableSigtermReporting = true
             options.beforeCaptureScreenshot = { _ in
                 return true
             }

Sources/Sentry/Public/SentryOptions.h

@@ -74,6 +74,19 @@ NS_SWIFT_NAME(Options)
  */
 @property (nonatomic, assign) BOOL enableCrashHandler;
 
+/**
+ * When enabled, the SDK reports SIGTERM signals to Sentry.
+ *
+ * It's crucial for developers to understand that the OS sends a SIGTERM to their app as a prelude
+ * to a graceful shutdown, before resorting to a SIGKILL. This SIGKILL, which your app can't catch
+ * or ignore, is a direct order to terminate your app's process immediately. Developers should be
+ * aware that their app can receive a SIGTERM in various scenarios, such as  CPU or disk overuse,
+ * watchdog terminations, or when the OS updates your app.
+ *
+ * @note The default value is @c NO.
+ */
+@property (nonatomic, assign) BOOL enableSigtermReporting;
+
 /**
  * How many breadcrumbs do you want to keep in memory?
  * @note Default is @c 100 .

Sources/Sentry/SentryCrashIntegration.m

@@ -1,5 +1,6 @@
 #import "SentryCrashIntegration.h"
 #import "SentryCrashInstallationReporter.h"
+#import "SentryCrashMonitor_Signal.h"
 #import "SentryCrashWrapper.h"
 #import "SentryDispatchQueueWrapper.h"
 #import "SentryEvent.h"
@@ -87,7 +88,8 @@ - (BOOL)installWithOptions:(nonnull SentryOptions *)options
     self.scopeObserver =
         [[SentryCrashScopeObserver alloc] initWithMaxBreadcrumbs:options.maxBreadcrumbs];
 
-    [self startCrashHandler:options.cacheDirectoryPath];
+    [self startCrashHandler:options.cacheDirectoryPath
+        enableSigtermReporting:options.enableSigtermReporting];
 
     [self configureScope];
 
@@ -100,6 +102,7 @@ - (SentryIntegrationOption)integrationOptions
 }
 
 - (void)startCrashHandler:(NSString *)cacheDirectory
+    enableSigtermReporting:(BOOL)enableSigtermReporting
 {
     void (^block)(void) = ^{
         BOOL canSendReports = NO;
@@ -116,6 +119,7 @@ - (void)startCrashHandler:(NSString *)cacheDirectory
             canSendReports = YES;
         }
 
+        setEnableSigtermReporting(enableSigtermReporting);
         [installation install:cacheDirectory];
 
         // We need to send the crashed event together with the crashed session in the same envelope

Sources/Sentry/SentryOptions.m

@@ -87,6 +87,7 @@ - (instancetype)init
         self.enabled = YES;
         self.shutdownTimeInterval = 2.0;
         self.enableCrashHandler = YES;
+        self.enableSigtermReporting = NO;
         self.diagnosticLevel = kSentryLevelDebug;
         self.debug = NO;
         self.maxBreadcrumbs = defaultMaxBreadcrumbs;
@@ -316,6 +317,9 @@ - (BOOL)validateOptions:(NSDictionary<NSString *, id> *)options
     [self setBool:options[@"enableCrashHandler"]
             block:^(BOOL value) { self->_enableCrashHandler = value; }];
 
+    [self setBool:options[@"enableSigtermReporting"]
+            block:^(BOOL value) { self->_enableSigtermReporting = value; }];
+
     if ([options[@"maxBreadcrumbs"] isKindOfClass:[NSNumber class]]) {
         self.maxBreadcrumbs = [options[@"maxBreadcrumbs"] unsignedIntValue];
     }

Sources/SentryCrash/Recording/Monitors/SentryCrashMonitor_Signal.c

@@ -49,6 +49,13 @@
 // ============================================================================
 
 static volatile bool g_isEnabled = false;
+static volatile bool g_isSigtermReportingEnabled = false;
+
+void
+setEnableSigtermReporting(bool enabled)
+{
+    g_isSigtermReportingEnabled = enabled;
+}
 
 static SentryCrash_MonitorContext g_monitorContext;
 static SentryCrashStackCursor g_stackCursor;
@@ -163,6 +170,11 @@ installSignalHandler(void)
     action.sa_sigaction = &handleSignal;
 
     for (int i = 0; i < fatalSignalsCount; i++) {
+        if (fatalSignals[i] == SIGTERM && !g_isSigtermReportingEnabled) {
+            SentryCrashLOG_DEBUG("SIGTERM handling disabled. Skipping assigning handler.");
+            continue;
+        }
+
         SentryCrashLOG_DEBUG("Assigning handler for signal %d", fatalSignals[i]);
         if (sigaction(fatalSignals[i], &action, &g_previousSignalHandlers[i]) != 0) {
             char sigNameBuff[30];

Sources/SentryCrash/Recording/Monitors/SentryCrashMonitor_Signal.h

@@ -37,6 +37,10 @@ extern "C" {
 
 #include "SentryCrashMonitor.h"
 
+/** Wether to assign the signal handler for SIGTERM or not.
+ */
+void setEnableSigtermReporting(bool enabled);
+
 /** Access the Monitor API.
  */
 SentryCrashMonitorAPI *sentrycrashcm_signal_getAPI(void);

Sources/SentryCrash/Recording/Tools/SentryCrashSignalInfo.c

@@ -126,7 +126,7 @@ static const int g_fatalSignals[] = {
     // SIGTERM can be caught and is usually sent by iOS and variants
     // when Apple wants to try and gracefully shutdown the app
     // before sending a SIGKILL (which can't be caught).
-    // Some areas I've seen this happen are:
+    // Some areas this might happen are:
     // - When the OS updates an app.
     // - In some circumstances for Watchdog Events.
     // - Resource overuse (CPU, Disk, ...).

Tests/SentryTests/SentryOptionsTest.m

@@ -155,6 +155,11 @@ - (void)testDiagnosticlevelWith:(NSObject *)level expected:(SentryLevel)expected
     XCTAssertEqual(expected, options.diagnosticLevel);
 }
 
+- (void)testEnableSigtermReporting
+{
+    [self testBooleanField:@"enableSigtermReporting" defaultValue:NO];
+}
+
 - (void)testValidEnabled
 {
     [self testEnabledWith:@YES expected:YES];