add some mete.thrift comment

src/interface/meta.thrift

@@ -225,6 +225,7 @@ enum AdminJobOp {
     SHOW_All    = 0x02,
     SHOW        = 0x03,
     STOP        = 0x04,
+    //recover a stopped, failed, queued job
     RECOVER     = 0x05,
 } (cpp.enum_strict)
 
@@ -261,6 +262,11 @@ enum JobStatus {
 struct JobDesc {
     1: i32              id,
     2: AdminCmd         cmd,
+    // when submit a job, some infomation would push into paras
+    // for compact,flush and stats job, it's [job_concurrency, space_name] or [space_name]
+    // for balance
+    // e.g balance in zone remove ip1:port1, ip2:port2, it's ["ip1":port1,"ip2":port2,space_name]
+    // balance across zone remove zone1,zone2, it's [zone1,zone2,space_name]
     3: list<string>     paras,
     4: JobStatus        status,
     5: i64              start_time,