Print info about ability to rebalance

As suggested during offline discussion, this patch adds a new bash
variable and description field in hcheck, which informs if the
rebalance was possible. This is to determine if there are split
instances on the cluster, in which case rebalance is impossible.

Signed-off-by: Agata Murawska <agatamurawska@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

htools/Ganeti/HTools/Program/Hcheck.hs

@@ -113,12 +113,24 @@ groupData = commonData ++ [("SCORE", "Group score")]
 
 -- | Data showed per cluster.
 clusterData :: [(String, String)]
-clusterData = commonData ++ [("NEED_REBALANCE", "Cluster is not healthy")]
+clusterData = commonData ++
+              [ ("NEED_REBALANCE", "Cluster is not healthy")
+              , ("CAN_REBALANCE", "Possible to run rebalance")
+              ]
+
 
 -- | Format a list of key, value as a shell fragment.
 printKeysHTC :: [(String, String)] -> IO ()
 printKeysHTC = printKeys htcPrefix
 
+-- | Prepare string from boolean value.
+printBool :: Bool    -- ^ Whether the result should be machine readable
+          -> Bool    -- ^ Value to be converted to string
+          -> String
+printBool True True = "1"
+printBool True False = "0"
+printBool False b = show b
+
 -- | Print all the statistics on a group level.
 printGroupStats :: Int -> Bool -> Phase -> Gdx -> [Int] -> Double -> IO ()
 printGroupStats _ True phase gidx stats score = do
@@ -140,26 +152,27 @@ printGroupStats verbose False phase gidx stats score = do
           (zip groupData printstats)
 
 -- | Print all the statistics on a cluster (global) level.
-printClusterStats :: Int -> Bool -> Phase -> [Int] -> IO (Bool)
-printClusterStats _ True phase stats = do
-  let needrebal = sum stats
-      printstats = map (printf "%d") $ stats ++ [needrebal]
-                 :: [String]
+printClusterStats :: Int -> Bool -> Phase -> [Int] -> Bool -> IO (Bool)
+printClusterStats _ True phase stats canrebal = do
+  let needrebal = sum stats > 0
+      printstats = map (printf "%d") stats ++
+                   map (printBool True) [needrebal, canrebal]
       printkeys = map (printf "%s_%s_%s"
                               (phasePrefix phase)
                               (levelPrefix ClusterLvl))
                       (map fst clusterData) :: [String]
   printKeysHTC (zip printkeys printstats)
-  return $ needrebal > 0
+  return needrebal
 
-printClusterStats verbose False phase stats = do
-  let needrebal = sum stats
-      printstats = map (printf "%d") stats :: [String]
+printClusterStats verbose False phase stats canrebal = do
+  let needrebal = sum stats > 0
+      printstats = map (printf "%d") stats ++
+                   map (printBool False) [needrebal, canrebal]
   unless (verbose == 0) $ do
       printf "\nCluster statistics %s\n" (phaseDescription phase) :: IO ()
       mapM_ (\(a,b) -> printf "    %s: %s\n" (snd a) b :: IO ())
-            (zip clusterData (printstats ++ [show (needrebal>0)]))
-  return $ needrebal > 0
+            (zip clusterData printstats)
+  return needrebal
 
 {- | Check group for N+1 hapiness, conflicts of primaries on nodes and
 instances residing on offline nodes.
@@ -233,7 +246,8 @@ main opts args = do
 
   groupsstats <- mapM (perGroupChecks verbose machineread Initial) splitcluster
   let clusterstats = map sum (transpose groupsstats) :: [Int]
-  needrebalance <- printClusterStats verbose machineread Initial clusterstats
+      canrebalance = length splitinstances == 0
+  needrebalance <- printClusterStats verbose machineread Initial clusterstats canrebalance
 
   when nosimulation $ do
     unless (verbose == 0 || machineread) $
@@ -256,6 +270,6 @@ main opts args = do
   newgroupstats <- mapM (perGroupChecks verbose machineread Rebalanced)
                      rebalancedcluster
   let newclusterstats = map sum (transpose newgroupstats) :: [Int]
-  _ <- printClusterStats verbose machineread Rebalanced newclusterstats
+  _ <- printClusterStats verbose machineread Rebalanced newclusterstats canrebalance
 
   printFinalHTC machineread