[Sheepdog] [PATCH] collie: show better error message while node membership is changing

[MORITA Kazutaka]

While node membership is changing, some collie commands result in the
SD_RES_NEW/OLD_NODE_VER error and we need to retry the commands after
new membership is established.  This patch shows a bit more friendly
error message to explain it.

In future, it might be better to retry sending requests automatically
instead of showing errors.

Signed-off-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
---
Hi Chris,

It looks a bit difficult to handle collie commands gracefully during
node membership changes.  I think of showing an error message to force
users to retry the commands, and leaving this problem as a future work.

Thanks,

Kazutaka


 collie/common.c |   31 +++++++++++++++++++++++++------
 1 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/collie/common.c b/collie/common.c
index 0653b72..14dc915 100644
--- a/collie/common.c
+++ b/collie/common.c
@@ -79,13 +79,22 @@ int sd_read_object(uint64_t oid, void *data, unsigned int datalen,
 		return SD_RES_EIO;
 	}
 
-	if (rsp->result != SD_RES_SUCCESS) {
+	switch (rsp->result) {
+	case SD_RES_SUCCESS:
+		/* success */
+		break;
+	case SD_RES_OLD_NODE_VER:
+	case SD_RES_NEW_NODE_VER:
+		fprintf(stderr, "new node membership is not established yet, "
+			"try again later\n");
+		break;
+	default:
 		fprintf(stderr, "failed to read object, %lx %s\n", oid,
 			sd_strerror(rsp->result));
-		return rsp->result;
+		break;
 	}
 
-	return SD_RES_SUCCESS;
+	return rsp->result;
 }
 
 int sd_write_object(uint64_t oid, uint64_t cow_oid, void *data, unsigned int datalen,
@@ -122,13 +131,23 @@ int sd_write_object(uint64_t oid, uint64_t cow_oid, void *data, unsigned int dat
 		fprintf(stderr, "failed to write object, %lx\n", oid);
 		return SD_RES_EIO;
 	}
-	if (rsp->result != SD_RES_SUCCESS) {
+
+	switch (rsp->result) {
+	case SD_RES_SUCCESS:
+		/* success */
+		break;
+	case SD_RES_OLD_NODE_VER:
+	case SD_RES_NEW_NODE_VER:
+		fprintf(stderr, "new node membership is not established yet, "
+			"try again later\n");
+		break;
+	default:
 		fprintf(stderr, "failed to write object, %lx %s\n", oid,
 			sd_strerror(rsp->result));
-		return rsp->result;
+		break;
 	}
 
-	return SD_RES_SUCCESS;
+	return rsp->result;
 }
 
 int parse_vdi(vdi_parser_func_t func, size_t size, void *data)
-- 
1.7.2.5