Move collecting and flushing telemetry to after final request flush

Signed-off-by: Bob Weinand <bob.weinand@datadoghq.com>

ext/ddtrace.c

@@ -1017,6 +1017,8 @@ static void dd_disable_if_incompatible_sapi_detected(void) {
     }
 }
 
+static void dd_post_sapi_deactivate_minit(void);
+
 static PHP_MINIT_FUNCTION(ddtrace) {
     UNUSED(type);
 
@@ -1109,6 +1111,7 @@ static PHP_MINIT_FUNCTION(ddtrace) {
     ddtrace_dogstatsd_client_minit();
 #endif
     ddshared_minit();
+    dd_post_sapi_deactivate_minit();
 
     dd_register_span_data_ce();
     dd_register_fatal_error_ce();
@@ -1401,16 +1404,6 @@ static PHP_RSHUTDOWN_FUNCTION(ddtrace) {
         DDTRACE_G(active_stack) = NULL;
     }
 
-    dd_finalize_telemetry();
-    if (DDTRACE_G(last_flushed_root_service_name)) {
-        zend_string_release(DDTRACE_G(last_flushed_root_service_name));
-        DDTRACE_G(last_flushed_root_service_name) = NULL;
-    }
-    if (DDTRACE_G(last_flushed_root_env_name)) {
-        zend_string_release(DDTRACE_G(last_flushed_root_env_name));
-        DDTRACE_G(last_flushed_root_env_name) = NULL;
-    }
-
     return SUCCESS;
 }
 
@@ -1430,6 +1423,75 @@ zend_result ddtrace_post_deactivate(void) {
     return SUCCESS;
 }
 
+static void dd_post_sapi_deactivate_do(void) {
+    dd_finalize_telemetry();
+    if (DDTRACE_G(last_flushed_root_service_name)) {
+        zend_string_release(DDTRACE_G(last_flushed_root_service_name));
+        DDTRACE_G(last_flushed_root_service_name) = NULL;
+    }
+    if (DDTRACE_G(last_flushed_root_env_name)) {
+        zend_string_release(DDTRACE_G(last_flushed_root_env_name));
+        DDTRACE_G(last_flushed_root_env_name) = NULL;
+    }
+}
+
+static int (*dd_prev_sapi_deactivate)(void);
+
+// Start of request_rec from httpd.h, this has been unchanged forever, so we can just use this.
+struct apache_request_rec {
+    void *pool;
+    void *connection;
+    void *server;
+    void *next;
+    void *prev;
+    void *main;
+};
+static void (*dd_ap_finalize_request_protocol)(struct apache_request_rec *r);
+
+static int dd_post_apache_deactivate(void) {
+    int result = dd_prev_sapi_deactivate();
+
+    struct apache_request_rec *r = ((struct {
+        int state;
+        struct apache_request_rec *r;
+    } *) SG(server_context))->r;
+    // Check whether this is not an apache sub-request, otherwise we may not alter the state of the connection, i.e. here we don't gain any latency benefit
+    if (!r->main) {
+        dd_ap_finalize_request_protocol(r);
+    }
+
+    dd_post_sapi_deactivate_do();
+
+    return result;
+}
+
+static int dd_post_sapi_deactivate(void) {
+    int result = dd_prev_sapi_deactivate();
+    dd_post_sapi_deactivate_do();
+    return result;
+}
+
+static void dd_post_sapi_deactivate_minit(void) {
+    dd_prev_sapi_deactivate = sapi_module.deactivate;
+
+    if (ddtrace_active_sapi == DATADOG_PHP_SAPI_APACHE2HANDLER) {
+#ifndef _WIN32
+        void *handle = dlopen(NULL, RTLD_LAZY);
+#else
+        void *handle = GetModuleHandle(NULL); // not refcounted, must not be closed
+#endif
+        dd_ap_finalize_request_protocol = DL_FETCH_SYMBOL(handle, "ap_finalize_request_protocol");
+#ifndef _WIN32
+        dlclose(handle);
+#endif
+        if (dd_ap_finalize_request_protocol) {
+            sapi_module.deactivate = dd_post_apache_deactivate;
+            return;
+        }
+    }
+    sapi_module.deactivate = dd_post_sapi_deactivate;
+}
+
 void ddtrace_disable_tracing_in_current_request(void) {
     // PHP 8 has ZSTR_CHAR('0') which is nicer...
     zend_string *zero = zend_string_init("0", 1, 0);