hcheck: rework output mode

Looking at the output of hcheck, in human readable mode, it looks like
it always starts with a blank line. This is not nice, so I wanted to
redo this to start cleanly.

However, looking at the code, I realised that we need some internal
cleanup; 'perGroupChecks' was doing both pure computation (computing
the score/stats) and I/O work (printing the stats), which is ugly, so
I split that in two; this allows perGroupChecks to be simpler, and we
can therefore first compute the group stats, and start the output with
the mode in which we run.

So right now, hcheck will first output whether we need to run a
rebalance, or if no-simulation is selected, etc., and only then
display the actual stats, making the output a bit more consistent.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>

htools/Ganeti/HTools/Program/Hcheck.hs

@@ -180,7 +180,8 @@ printStats verbose False level phase values name = do
   let prefix = phaseLevelDescr phase level name
       descr = descrData level
   unless (verbose == 0) $ do
-    printf "\n%s" prefix :: IO ()
+    putStrLn ""
+    putStr prefix
     mapM_ (\(a,b) -> printf "    %s: %s\n" a b) (zip descr values)
 
 -- | Extract name or idx from group.
@@ -199,9 +200,9 @@ prepareClusterValues machineread stats bstats =
   map show stats ++ map (printBool machineread) bstats
 
 -- | Print all the statistics on a group level.
-printGroupStats :: Int -> Bool -> Phase -> Group.Group -> [Int] -> Double
+printGroupStats :: Int -> Bool -> Phase -> ((Group.Group, Double), [Int])
                 -> IO ()
-printGroupStats verbose machineread phase grp stats score = do
+printGroupStats verbose machineread phase ((grp, score), stats) = do
   let values = prepareGroupValues stats score
       extradata = extractGroupData machineread grp
   printStats verbose machineread GroupLvl phase values (Just extradata)
@@ -220,9 +221,10 @@ clusterNeedsRebalance stats = sum stats > 0
 instances residing on offline nodes.
 
 -}
-perGroupChecks :: Int -> Bool -> Phase -> Group.List
-               -> (Gdx, (Node.List, Instance.List)) -> IO ([Int])
-perGroupChecks verbose machineread phase gl (gidx, (nl, il)) = do
+perGroupChecks :: Group.List
+               -> (Gdx, (Node.List, Instance.List))
+               -> ((Group.Group, Double), [Int])
+perGroupChecks gl (gidx, (nl, il)) =
   let grp = Container.find gidx gl
       offnl = filter Node.offline (Container.elems nl)
       n1violated = length $ fst $ Cluster.computeBadItems nl il
@@ -236,8 +238,7 @@ perGroupChecks verbose machineread phase gl (gidx, (nl, il)) = do
                    , offline_pri
                    , offline_sec
                    ]
-  printGroupStats verbose machineread phase grp groupstats score
-  return groupstats
+  in ((grp, score), groupstats)
 
 -- | Use Hbal's iterateDepth to simulate group rebalance.
 executeSimulation :: Options -> Cluster.Table -> Double
@@ -300,19 +301,20 @@ main opts args = do
 
   when machineread $ printGroupsMappings gl
 
-  groupsstats <- mapM (perGroupChecks verbose machineread Initial gl)
-                 splitcluster
-  let clusterstats = map sum (transpose groupsstats) :: [Int]
+  let groupsstats = map (perGroupChecks gl) splitcluster
+      clusterstats = map sum . transpose . map snd $ groupsstats
       needrebalance = clusterNeedsRebalance clusterstats
-  printClusterStats verbose machineread Initial clusterstats needrebalance
 
-  when nosimulation $ do
-    unless (verbose == 0 || machineread) $
-      putStrLn "Running in no-simulation mode. Exiting."
+  unless (verbose == 0 || machineread) $
+    if nosimulation
+      then putStrLn "Running in no-simulation mode."
+      else if needrebalance
+             then putStrLn "Cluster needs rebalancing."
+             else putStrLn "No need to rebalance cluster, no problems found."
+
+  mapM_ (printGroupStats verbose machineread Initial) groupsstats
 
-  unless needrebalance $ do
-    unless (verbose == 0 || machineread) $
-      putStrLn "No need to rebalance cluster, no problems found. Exiting."
+  printClusterStats verbose machineread Initial clusterstats needrebalance
 
   let exitOK = nosimulation || not needrebalance
       simulate = not nosimulation && needrebalance
@@ -320,11 +322,12 @@ main opts args = do
   rebalancedcluster <- maybeSimulateRebalance simulate opts splitcluster
 
   when (simulate || machineread) $ do
-    newgroupstats <- mapM (perGroupChecks verbose machineread Rebalanced gl)
-                     rebalancedcluster
-    let newclusterstats = map sum (transpose newgroupstats) :: [Int]
+    let newgroupstats = map (perGroupChecks gl) rebalancedcluster
+        newclusterstats = map sum . transpose . map snd $ newgroupstats
         newneedrebalance = clusterNeedsRebalance clusterstats
 
+    mapM_ (printGroupStats verbose machineread Rebalanced) newgroupstats
+
     printClusterStats verbose machineread Rebalanced newclusterstats
                            newneedrebalance