proxy: fix segfault, improve error messages

Give a bit more details in the "No service replied" error messages.

core/internals.h

@@ -46,6 +46,9 @@ extern "C" {
 #define ON_ENUM(P,E) case P##E: return #E
 
 #define CODE_IS_NETWORK_ERROR(C) ((C) > ERRCODE_PARAM && (C) <= CODE_NETWORK_ERROR)
+/* Tell if the error is a network error and appears after
+ * the connection has been established. */
+#define CODE_IS_ERR_AFTER_START(C) ((C) >= ERRCODE_CONN_RESET && (C) <= ERRCODE_CONN_TIMEOUT)
 
 #define CODE_IS_OK(C)       (((C) >= CODE_FINAL_OK) && ((C) < CODE_BEACON_REDIRECT))
 #define CODE_IS_TEMP(C)     (((C) >= CODE_TEMPORARY) && ((C) < CODE_FINAL_OK))
@@ -104,6 +107,8 @@ extern "C" {
 	period_reload = CLAMP(period_reload,2,(P)); \
 	tick_reload = 1
 
+/* Some macros make assumptions about the ordering of these error codes.
+ * Be careful if you plan to change them. */
 enum {
 	ERRCODE_UNKNOWN_ERROR = 0,
 	ERRCODE_PARAM = 1,

proxy/common.c

@@ -441,30 +441,35 @@ gridd_request_replicated (struct req_args_s *args, struct client_ctx_s *ctx,
 				 * the subsequent requests. */
 				service_invalidate(url);
 
-				/* TODO(jfs): should we let the client retry or occupy a
-				 * thread in the proxy to make all the necessary retries ? */
+				/* JFS: should we let the client retry or occupy a
+				 * thread in the proxy to make all the necessary retries?
+				 * FVE: in some cases where we are not sure the request
+				 * actually failed, we will let the client retry. */
 
 				/* that error is not strong enough to stop the iteration, we
 				 * just try with another service */
-				g_clear_error (&err);
+				GError *last_err = err;
+				err = NULL;
 
 				/* But if we expected at least one service to respond,
 				 * and we still encounter that error with the last URL of the
 				 * array (!pu[1]), then this is an overall error that we should return. */
 				if ((ctx->which != CLIENT_RUN_ALL
 						&& ctx->which != CLIENT_SPECIFIED) && !next_url) {
-					err = BUSY("No service replied");
+					err = BUSY("No service replied (last error: (%d) %s)",
+							last_err->code, last_err->message);
 					stop = TRUE;
 				} else if (ctx->which == CLIENT_PREFER_MASTER &&
-						(err->code == ERRCODE_CONN_CLOSED
-						|| err->code == ERRCODE_READ_TIMEOUT)) {
+						CODE_IS_ERR_AFTER_START(last_err->code)) {
 					/* Maybe the request is running in the background.
 					 * For requests on master, let the client decide to try again.
 					 * Retrying may trigger an error (such as a conflict),
 					 * if the request has already been executed. */
-					err = BUSY("No service replied");
+					err = BUSY("No service replied (last error: (%d) %s)",
+							last_err->code, last_err->message);
 					stop = TRUE;
 				}
+				g_clear_error(&last_err);
 			} else if (CODE_IS_RETRY(err->code)) {
 				/* the target service is in bad shape, let's avoid it for
 				 * the subsequent requests. And we currently we choose to