feat(transport): add HTTP retry with exponential backoff

CHANGELOG.md

@@ -1,6 +1,10 @@
 # Changelog
 
-## Unreleased:
+## Unreleased
+
+**Features**:
+
+- Add HTTP retry with exponential backoff. ([#1520](https://github.com/getsentry/sentry-native/pull/1520))
 
 **Fixes**:
 

examples/example.c

@@ -659,6 +659,9 @@ main(int argc, char **argv)
         sentry_options_set_cache_max_age(options, 5 * 24 * 60 * 60); // 5 days
         sentry_options_set_cache_max_items(options, 5);
     }
+    if (has_arg(argc, argv, "no-http-retry")) {
+        sentry_options_set_http_retry(options, false);
+    }
 
     if (has_arg(argc, argv, "enable-metrics")) {
         sentry_options_set_enable_metrics(options, true);
@@ -940,6 +943,10 @@ main(int argc, char **argv)
         sentry_reinstall_backend();
     }
 
+    if (has_arg(argc, argv, "flush")) {
+        sentry_flush(10000);
+    }
+
     if (has_arg(argc, argv, "sleep")) {
         sleep_s(10);
     }

include/sentry.h

@@ -946,6 +946,24 @@ SENTRY_API void sentry_transport_set_shutdown_func(
     sentry_transport_t *transport,
     int (*shutdown_func)(uint64_t timeout, void *state));
 
+/**
+ * Retries sending all pending envelopes in the transport's retry queue,
+ * e.g. when coming back online. Only applicable for HTTP transports.
+ *
+ * Note: The SDK automatically retries failed envelopes on next application
+ * startup. This function allows manual triggering of pending retries at
+ * runtime. Each envelope is retried up to 6 times. If all attempts are
+ * exhausted during intermittent connectivity, events will be discarded
+ * (or moved to cache if enabled via sentry_options_set_cache_keep).
+ *
+ * Warning: This function has no rate limiting - it will immediately
+ * attempt to send all pending envelopes. Calling this repeatedly during
+ * extended network outages may exhaust retry attempts that might have
+ * succeeded with the SDK's built-in exponential backoff.
+ */
+SENTRY_EXPERIMENTAL_API void sentry_transport_retry(
+    sentry_transport_t *transport);
+
 /**
  * Generic way to free transport.
  */
@@ -1476,12 +1494,13 @@ SENTRY_API int sentry_options_get_symbolize_stacktraces(
     const sentry_options_t *opts);
 
 /**
- * Enables or disables storing envelopes in a persistent cache.
+ * Enables or disables storing failed envelopes in a persistent cache.
+ *
+ * When enabled, envelopes that fail to send are written to a `cache/`
+ * subdirectory within the database directory. The cache is cleared on startup
+ * based on the cache_max_items, cache_max_size, and cache_max_age options.
  *
- * When enabled, envelopes are written to a `cache/` subdirectory within the
- * database directory and retained regardless of send success or failure.
- * The cache is cleared on startup based on the cache_max_items, cache_max_size,
- * and cache_max_age options.
+ * Only applicable for HTTP transports.
  *
  * Disabled by default.
  */
@@ -2258,6 +2277,18 @@ SENTRY_EXPERIMENTAL_API void sentry_options_set_enable_logs(
 SENTRY_EXPERIMENTAL_API int sentry_options_get_enable_logs(
     const sentry_options_t *opts);
 
+/**
+ * Enables or disables HTTP retry with exponential backoff for network failures.
+ *
+ * Only applicable for HTTP transports.
+ *
+ * Enabled by default.
+ */
+SENTRY_EXPERIMENTAL_API void sentry_options_set_http_retry(
+    sentry_options_t *opts, int enabled);
+SENTRY_EXPERIMENTAL_API int sentry_options_get_http_retry(
+    const sentry_options_t *opts);
+
 /**
  * Enables or disables custom attributes parsing for structured logging.
  *

src/CMakeLists.txt

@@ -34,6 +34,8 @@ sentry_target_sources_cwd(sentry
 	sentry_process.h
 	sentry_ratelimiter.c
 	sentry_ratelimiter.h
+	sentry_retry.c
+	sentry_retry.h
 	sentry_ringbuffer.c
 	sentry_ringbuffer.h
 	sentry_sampling_context.h

src/backends/sentry_backend_crashpad.cpp

@@ -565,11 +565,9 @@ process_completed_reports(
 
     SENTRY_DEBUGF("caching %zu completed reports", reports.size());
 
-    sentry_path_t *cache_dir
-        = sentry__path_join_str(options->database_path, "cache");
-    if (!cache_dir || sentry__path_create_dir_all(cache_dir) != 0) {
+    sentry_path_t *cache_dir = options->run->cache_path;
+    if (sentry__path_create_dir_all(cache_dir) != 0) {
         SENTRY_WARN("failed to create cache dir");
-        sentry__path_free(cache_dir);
         return;
     }
 
@@ -593,8 +591,6 @@ process_completed_reports(
         sentry__path_free(out_path);
         sentry_envelope_free(envelope);
     }
-
-    sentry__path_free(cache_dir);
 }
 
 static int

src/sentry_core.c

@@ -292,8 +292,10 @@ sentry_init(sentry_options_t *options)
         backend->prune_database_func(backend);
     }
 
-    if (options->cache_keep) {
-        sentry__cleanup_cache(options);
+    if (options->cache_keep || options->http_retry) {
+        if (!sentry__transport_submit_cleanup(options->transport, options)) {
+            sentry__cleanup_cache(options);
+        }
     }
 
     if (options->auto_session_tracking) {