retry for scan for leader change (vesoft-inc#605)

* retry for scan for leader change

* code fmt

* set storage address mapping for scan

* fix get leader

* update the default config for allow_read_follower to false

client/src/main/java/com/vesoft/nebula/client/meta/MetaClient.java

@@ -505,4 +505,38 @@ public synchronized Set<HostItem> getHostItems() {
  }
  return hostItems;
  }
+
+ /**
+ * get the leader parts for all storaged address
+ */
+ public synchronized Set<HostItem> getHostItems() {
+ int retry = RETRY_TIMES;
+ ListHostsReq request = new ListHostsReq();
+ request.setType(ListHostType.ALLOC);
+ ListHostsResp resp = null;
+ try {
+ while (retry-- >= 0) {
+ resp = client.listHosts(request);
+ if (resp.getCode() == ErrorCode.E_LEADER_CHANGED) {
+ freshClient(resp.getLeader());
+ } else {
+ break;
+ }
+ }
+ } catch (TException e) {
+ LOGGER.error("listHosts error", e);
+ return null;
+ }
+ if (resp.getCode() != ErrorCode.SUCCEEDED) {
+ LOGGER.error("listHosts execute failed, errorCode: " + resp.getCode());
+ return null;
+ }
+ Set<HostItem> hostItems = new HashSet<>();
+ for (HostItem hostItem : resp.hosts) {
+ if (hostItem.getStatus().getValue() == HostStatus.ONLINE.getValue()) {
+ hostItems.add(hostItem);
+ }
+ }
+ return hostItems;
+ }
 }