9162: Add replication level histogram

Ported from 00a8ece1580a894dbbf9f756685eefc134e4d0d6 by jrandall

diff --git a/services/keep-balance/balance.go b/services/keep-balance/balance.go
index 7471aa6cb06d084416615c8a9eb975d231098dc5..2a2480cc31b6a3eb9dedd6452e42e793c79e1c08 100644 (file)
--- a/services/keep-balance/balance.go
+++ b/services/keep-balance/balance.go
@@ -3,6 +3,7 @@ package main
 import (
        "fmt"
        "log"
+       "math"
        "os"
        "runtime"
        "strings"
@@ -447,9 +448,11 @@ type balancerStats struct {
        lost, overrep, unref, garbage, underrep, justright blocksNBytes
        desired, current                                   blocksNBytes
        pulls, trashes                                     int
+       replHistogram                                      []int
 }
 
 func (bal *Balancer) getStatistics() (s balancerStats) {
+       s.replHistogram = make([]int, 2)
        bal.BlockStateMap.Apply(func(blkid arvados.SizedDigest, blk *BlockState) {
                surplus := len(blk.Replicas) - blk.Desired
                bytes := blkid.Size()
@@ -493,6 +496,11 @@ func (bal *Balancer) getStatistics() (s balancerStats) {
                        s.current.blocks++
                        s.current.bytes += bytes * int64(len(blk.Replicas))
                }
+
+               for len(s.replHistogram) <= len(blk.Replicas) {
+                       s.replHistogram = append(s.replHistogram, 0)
+               }
+               s.replHistogram[len(blk.Replicas)]++
        })
        for _, srv := range bal.KeepServices {
                s.pulls += len(srv.ChangeSet.Pulls)
@@ -521,6 +529,25 @@ func (bal *Balancer) PrintStatistics() {
                bal.logf("%s: %v\n", srv, srv.ChangeSet)
        }
        bal.logf("===")
+       bal.printHistogram(s, 60)
+       bal.logf("===")
+}
+
+func (bal *Balancer) printHistogram(s balancerStats, hashColumns int) {
+       bal.logf("Replication level distribution (counting N replicas on a single server as N):")
+       maxCount := 0
+       for _, count := range s.replHistogram {
+               if maxCount < count {
+                       maxCount = count
+               }
+       }
+       hashes := strings.Repeat("#", hashColumns)
+       countWidth := 1 + int(math.Log10(float64(maxCount+1)))
+       scaleCount := 10 * float64(hashColumns) / math.Floor(1+10*math.Log10(float64(maxCount+1)))
+       for repl, count := range s.replHistogram {
+               nHashes := int(scaleCount * math.Log10(float64(count+1)))
+               bal.logf("%2d: %*d %s", repl, countWidth, count, hashes[:nHashes])
+       }
 }
 
 // CheckSanityLate checks for configuration and runtime errors after