[sheepdog] [PATCH] sheep: don't call farm_init() for gateway-only node

[Liu Yuan]

From: Liu Yuan <tailai.ly at taobao.com>

Gateway-only node doesn't need backend at all, and we can restart it as gateway
node (has backend) again.

Signed-off-by: Liu Yuan <tailai.ly at taobao.com>
---
 sheep/group.c      |    9 ++++++---
 sheep/sheep.c      |    2 ++
 sheep/sheep_priv.h |    1 +
 sheep/store.c      |    8 +++++---
 4 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/sheep/group.c b/sheep/group.c
index 4f9d196..f67600f 100644
--- a/sheep/group.c
+++ b/sheep/group.c
@@ -754,21 +754,24 @@ static void finish_join(struct join_message *msg, struct sd_node *joined,
 	if (msg->cluster_status != SD_STATUS_OK)
 		update_exceptional_node_list(get_latest_epoch(), msg);
 
-	if (!sd_store && strlen((char *)msg->store)) {
+	/* We don't need backend for gateway-only node */
+	if (!sys->gateway_only && !sd_store && strlen((char *)msg->store)) {
 		sd_store = find_store_driver((char *)msg->store);
 		if (sd_store) {
 			sd_store->init(obj_path);
 			if (set_cluster_store(sd_store->name) != SD_RES_SUCCESS)
 				panic("failed to store into config file\n");
 		} else
-				panic("backend store %s not supported\n", msg->store);
+				panic("backend store %s not supported\n",
+				      msg->store);
 	}
 
 	/* We need to purge the stale objects for sheep joining back
 	 * after crash
 	 */
 	if (msg->inc_epoch)
-		if (sd_store->purge_obj &&
+		if (!sys->gateway_only &&
+		    sd_store->purge_obj &&
 		    sd_store->purge_obj() != SD_RES_SUCCESS)
 			panic("can't remove stale objects\n");
 
diff --git a/sheep/sheep.c b/sheep/sheep.c
index b3a12e3..2e208de 100644
--- a/sheep/sheep.c
+++ b/sheep/sheep.c
@@ -243,6 +243,8 @@ int main(int argc, char **argv)
 			break;
 		}
 	}
+	if (nr_vnodes == 0)
+		sys->gateway_only = 1;
 
 	if (optind != argc)
 		dir = argv[optind];
diff --git a/sheep/sheep_priv.h b/sheep/sheep_priv.h
index 7e89d7b..116be97 100644
--- a/sheep/sheep_priv.h
+++ b/sheep/sheep_priv.h
@@ -115,6 +115,7 @@ struct cluster_info {
 	uint32_t recovered_epoch;
 
 	int use_directio;
+	uint8_t gateway_only;
 
 	struct work_queue *gateway_wqueue;
 	struct work_queue *io_wqueue;
diff --git a/sheep/store.c b/sheep/store.c
index 17c2933..a05822d 100644
--- a/sheep/store.c
+++ b/sheep/store.c
@@ -467,9 +467,11 @@ int init_store(const char *d, int enable_write_cache)
 	if (ret)
 		return ret;
 
-	ret = init_store_driver();
-	if (ret)
-		return ret;
+	if (!sys->gateway_only) {
+		ret = init_store_driver();
+		if (ret)
+			return ret;
+	}
 
 	if (enable_write_cache) {
 		sys->enable_write_cache = 1;
-- 
1.7.10.2