mimir-operations: Ensure integer auto-scaling thresholds

CHANGELOG.md

@@ -102,6 +102,7 @@
 * [ENHANCEMENT] Added `$._config.usageStatsConfig` to track the installation mode via the anonymous usage statistics. #3294
 * [ENHANCEMENT] The query-tee node port (`$._config.query_tee_node_port`) is now optional. #3272
 * [ENHANCEMENT] Add support for autoscaling distributors. #3378
+* [ENHANCEMENT] Make auto-scaling logic ensure integer KEDA thresholds. #3512
 * [BUGFIX] Fixed query-scheduler ring configuration for dedicated ruler's queries and query-frontends. #3237 #3239
 
 ### Mimirtool

operations/mimir-tests/test-autoscaling-generated.yaml

@@ -510,10 +510,10 @@ spec:
           timeoutSeconds: 1
         resources:
           limits:
-            memory: 4Gi
+            memory: 6Gi
           requests:
-            cpu: "2"
-            memory: 2Gi
+            cpu: 2
+            memory: 3.2Gi
         volumeMounts:
         - mountPath: /etc/mimir
           name: overrides
@@ -1760,7 +1760,7 @@ spec:
       metricName: cortex_distributor_memory_hpa_default
       query: max_over_time(sum(container_memory_working_set_bytes{container="distributor",namespace="default"})[15m:])
       serverAddress: http://prometheus.default:9090/prometheus
-      threshold: "2147483648"
+      threshold: "3435973836"
     type: prometheus
 ---
 apiVersion: keda.sh/v1alpha1

operations/mimir-tests/test-autoscaling.jsonnet

@@ -27,4 +27,11 @@ mimir {
     autoscaling_distributor_min_replicas: 3,
     autoscaling_distributor_max_replicas: 30,
   },
+
+  local k = import 'ksonnet-util/kausal.libsonnet',
+  distributor_container+::
+    // Test a non-integer memory request, to verify that this gets converted into an integer for
+    // the KEDA threshold
+    k.util.resourcesRequests(2, '3.2Gi') +
+    k.util.resourcesLimits(null, '6Gi'),
 }

operations/mimir/autoscaling.libsonnet

@@ -80,7 +80,9 @@
             //
             // Read more:
             // https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/#algorithm-details
-            threshold: trigger.threshold,
+            //
+            // We also have to ensure that the threshold is an integer (represented as a string)
+            threshold: std.toString(std.parseInt(trigger.threshold)),
           },
         }
         for trigger in config.triggers
@@ -141,17 +143,23 @@
     // Simple method to convert binary multiples.
     // Only works for limited set of SI prefixes (as below).
 
-    if std.endsWith(str, 'Ki') then (
-      std.parseJson(std.rstripChars(str, 'Ki')) * std.pow(2, 10)
-    ) else if std.endsWith(str, 'Mi') then (
-      std.parseJson(std.rstripChars(str, 'Mi')) * std.pow(2, 20)
-    ) else if std.endsWith(str, 'Gi') then (
-      std.parseJson(std.rstripChars(str, 'Gi')) * std.pow(2, 30)
-    ) else if std.endsWith(str, 'Ti') then (
-      std.parseJson(std.rstripChars(str, 'Ti')) * std.pow(2, 40)
-    ) else (
-      str
-    )
+    // Utility converting the input to a (potentially decimal) number of bytes
+    local siToBytesDecimal(str) = (
+      if std.endsWith(str, 'Ki') then (
+        std.parseJson(std.rstripChars(str, 'Ki')) * std.pow(2, 10)
+      ) else if std.endsWith(str, 'Mi') then (
+        std.parseJson(std.rstripChars(str, 'Mi')) * std.pow(2, 20)
+      ) else if std.endsWith(str, 'Gi') then (
+        std.parseJson(std.rstripChars(str, 'Gi')) * std.pow(2, 30)
+      ) else if std.endsWith(str, 'Ti') then (
+        std.parseJson(std.rstripChars(str, 'Ti')) * std.pow(2, 40)
+      ) else (
+        std.parseJson(str)
+      )
+    );
+
+    // Round down to nearest integer
+    std.floor(siToBytesDecimal(str))
   ),
 
   local cpuToMilliCPUInt(str) = (
@@ -256,8 +264,8 @@
         // To scale out relatively quickly, but scale in slower, we look at the max memory utilization across all distributors over 15m.
         query: 'max_over_time(sum(container_memory_working_set_bytes{container="%s",namespace="%s"})[15m:])' % [name, $._config.namespace],
 
-        // threshold is expected to be a string, so use '' to cast any ints returned by siToBytes.
-        threshold: siToBytes(distributor_memory_requests) + '',
+        // threshold is expected to be a string
+        threshold: std.toString(siToBytes(distributor_memory_requests)),
       },
     ],
   }),