Prevent changes above 10%

2 files changed, 12 insertions, 0 deletions

diff --git a/searchcore/src/tests/proton/matching/matching_stats_test.cpp b/searchcore/src/tests/proton/matching/matching_stats_test.cpp
index 26eaa127aa3..78a53fb668d 100644
--- a/searchcore/src/tests/proton/matching/matching_stats_test.cpp
+++ b/searchcore/src/tests/proton/matching/matching_stats_test.cpp
@@ -271,6 +271,10 @@ TEST("requireThatSoftDoomFacorIsComputedCorrectly") {
     stats.updatesoftDoomFactor(1.0, 0.0009, 2.0);   // soft limits less than 1ms should be ignored
     EXPECT_EQUAL(1ul, stats.softDoomed());
     EXPECT_EQUAL(0.44, stats.softDoomFactor());
+    stats.updatesoftDoomFactor(1.0, 0.5, 10.0);      // Prevent changes above 10%
+    EXPECT_EQUAL(1ul, stats.softDoomed());
+    EXPECT_EQUAL(0.396, stats.softDoomFactor());
+
 }
 
 TEST_MAIN() {
diff --git a/searchcore/src/vespa/searchcore/proton/matching/matching_stats.cpp b/searchcore/src/vespa/searchcore/proton/matching/matching_stats.cpp
index 2b4660adc11..90d0c05c349 100644
--- a/searchcore/src/vespa/searchcore/proton/matching/matching_stats.cpp
+++ b/searchcore/src/vespa/searchcore/proton/matching/matching_stats.cpp
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 
 #include "matching_stats.h"
+#include <cmath>
 
 namespace proton::matching {
 
@@ -14,6 +15,7 @@ MatchingStats::Partition &get_writable_partition(std::vector<MatchingStats::Part
 }
 
 constexpr double MIN_TIMEOUT = 0.001;
+constexpr double MAX_CHANGE_FACTOR = 5;
 
 } // namespace proton::matching::<unnamed>
 
@@ -78,11 +80,17 @@ MatchingStats::add(const MatchingStats &rhs)
 
 MatchingStats &
 MatchingStats::updatesoftDoomFactor(double hardLimit, double softLimit, double duration) {
+    // The safety capping here should normally not be necessary all input numbers
+    // will normally be within reasonable values.
+    // It is merely a safety measure to avoid overflow on bad input as can happend with time senstive stuff
+    // in any soft real time system.
     if ((hardLimit >= MIN_TIMEOUT) && (softLimit >= MIN_TIMEOUT)) {
         double diff = (softLimit - duration)/hardLimit;
         if (duration < softLimit) {
+            diff = std::min(diff, _softDoomFactor*MAX_CHANGE_FACTOR);
             _softDoomFactor += 0.01*diff;
         } else {
+            diff = std::max(diff, -_softDoomFactor*MAX_CHANGE_FACTOR);
             _softDoomFactor += 0.02*diff;
         }
     }