fix(eBPF): Flush symbol cache after replay to avoid unsent data (#11743)

During replay, keep symbols cached in g_symbol_buffer.
After replay_callbacks(jvmti) completes, immediately flush g_cached_bytes under g_df_lock protection.
Once flush is done, set replay_finish = true.
df_send_symbol() now only sends the current symbol when replay_finish == true, and no longer flushes replay cache automatically.

This prevents cached data from being left unsent if no new symbol events occur after replay completes.

Author: yinjiping

agent/src/ebpf/Makefile

@@ -102,7 +102,7 @@ OBJS := user/elf.o \
 	user/profile/java/collect_symbol_files.o
 
 JAVA_TOOL := deepflow-jattach
-JAVA_AGENT_VERSION := 3
+JAVA_AGENT_VERSION := 4
 JAVA_AGENT_GNU_SO := df_java_agent_v$(JAVA_AGENT_VERSION).so
 JAVA_AGENT_MUSL_SO := df_java_agent_musl_v$(JAVA_AGENT_VERSION).so
 JAVA_AGENT_SO := $(JAVA_AGENT_GNU_SO) $(JAVA_AGENT_MUSL_SO)

agent/src/ebpf/user/profile/java/symbol_collect_agent.c

@@ -323,11 +323,6 @@ void df_send_symbol(enum event_type type, const void *code_addr,
 	send_bytes = meta->len + sizeof(*meta);
 	pthread_mutex_lock(&g_df_lock);
 	if (replay_finish) {
-		if (g_cached_bytes > 0) {
-			send_msg(perf_map_socket_fd, g_symbol_buffer,
-				 g_cached_bytes);
-			g_cached_bytes = 0;
-		}
 		send_msg(perf_map_socket_fd, symbol_str, send_bytes);
 	} else {
 		int buff_remain_bytes =
@@ -566,7 +561,16 @@ Agent_OnAttach(JavaVM * vm, char *options, void *reserved)
 	if (g_jvmti == NULL)
 		g_jvmti = jvmti;
 	_(replay_callbacks(jvmti));
+	pthread_mutex_lock(&g_df_lock);
+	if (g_cached_bytes > 0) {
+		if (perf_map_socket_fd >= 0) {
+			send_msg(perf_map_socket_fd, g_symbol_buffer,
+				 g_cached_bytes);
+		}
+		g_cached_bytes = 0;
+	}
 	replay_finish = true;
+	pthread_mutex_unlock(&g_df_lock);
 	df_log
 	    ("- JVMTI symbolization agent startup sequence complete. Replay count %d\n",
 	     replay_count);