The default value of logging level in Mixer is info. And the logs provided by you, confirms that you have this settings. Therefore, a lot of redundant information gathered in logs and it is possible to decrease logging level for some sources.

You can change it in two ways:

1. On working pod without restart.

   In your logs you can find the following line:

   2018-12-12T17:54:55.461261Z info    ControlZ available at 192.168.87.249:9876

   It means, that in the mixer container on 9876 port you can find Istio ControlZ web-interface. To get an access to it from a computer with installed kubectl, you need to run the following command:

   kubectl -n istio-system port-forward $(kubectl -n istio-system get pod -l istio=mixer,istio-mixer-type=telemetry -o jsonpath='{.items[0].metadata.name}') 9876:9876 &

   After that, in your browser go to the link http://localhost:9876/scopez/, and you will see the following dashboard, where you can change log levels:

   

2. Add --log_output_level flag to the istio-telemetry deployment for the mixer container.

   Here is the description for the flag from the mixer's documentation:

   --log_output_level string
   Comma-separated minimum per-scope logging level of messages to output, in the form of :,:,... where scope can be one of [adapters, api, attributes, default, grpcAdapter, loadshedding] and level can be one of [debug, info, warn, error, none] (default "default:info")

   Note, that for key --log_output_level attributes:warn,api:error in yaml file you need to use one of the following:

   • value - --log_output_level=attributes:warn,api:error or
   • values - --log_output_level and - attributes:warn,api:error on different lines

   The example of the deployment:

   apiVersion: extensions/v1beta1
   kind: Deployment
   metadata:
     annotations:
     labels:
       chart: mixer-1.0.4
       istio: mixer
       release: istio
     name: istio-telemetry
     namespace: istio-system
   spec:
     progressDeadlineSeconds: 600
     replicas: 2
     revisionHistoryLimit: 10
     selector:
       matchLabels:
         app: telemetry
         istio: mixer
         istio-mixer-type: telemetry
     strategy:
       rollingUpdate:
         maxSurge: 1
         maxUnavailable: 1
       type: RollingUpdate
     template:
       metadata:
         annotations:
           scheduler.alpha.kubernetes.io/critical-pod: ""
           sidecar.istio.io/inject: "false"
         creationTimestamp: null
         labels:
           app: telemetry
           istio: mixer
           istio-mixer-type: telemetry
       spec:
         containers:
         - args:                                                #Flags for the Mixer process
           - --address                                          #Flag on two different lines
           - unix:///sock/mixer.socket
           - --configStoreURL=k8s://                            #Flag with '='
           - --configDefaultNamespace=istio-system
           - --trace_zipkin_url=http://zipkin:9411/api/v1/spans
           - --log_output_level=attributes:warn,api:error       # <------ THIS LINE IS WHAT YOU ARE LOOKING FOR
           env:
           - name: GODEBUG
             value: gctrace=2
           image: docker.io/istio/mixer:1.0.4
           imagePullPolicy: IfNotPresent
           livenessProbe:
             failureThreshold: 3
             httpGet:
               path: /version
               port: 9093
               scheme: HTTP
             initialDelaySeconds: 5
             periodSeconds: 5
             successThreshold: 1
             timeoutSeconds: 1
           name: mixer
           ports:
           - containerPort: 9093
             protocol: TCP
           - containerPort: 42422
             protocol: TCP
           resources:
             requests:
               cpu: 10m
           terminationMessagePath: /dev/termination-log
           terminationMessagePolicy: File
           volumeMounts:
           - mountPath: /sock
             name: uds-socket
         - args:
           - proxy
           - --serviceCluster
           - istio-telemetry
           - --templateFile
           - /etc/istio/proxy/envoy_telemetry.yaml.tmpl
           - --controlPlaneAuthPolicy
           - MUTUAL_TLS
           env:
           - name: POD_NAME
             valueFrom:
               fieldRef:
                 apiVersion: v1
                 fieldPath: metadata.name
           - name: POD_NAMESPACE
             valueFrom:
               fieldRef:
                 apiVersion: v1
                 fieldPath: metadata.namespace
           - name: INSTANCE_IP
             valueFrom:
               fieldRef:
                 apiVersion: v1
                 fieldPath: status.podIP
           image: docker.io/istio/proxyv2:1.0.4
           imagePullPolicy: IfNotPresent
           name: istio-proxy
           ports:
           - containerPort: 15090
             name: http-envoy-prom
             protocol: TCP
           resources:
             requests:
               cpu: 10m
           terminationMessagePath: /dev/termination-log
           terminationMessagePolicy: File
           volumeMounts:
           - mountPath: /etc/certs
             name: istio-certs
             readOnly: true
           - mountPath: /sock
             name: uds-socket
         dnsPolicy: ClusterFirst
         restartPolicy: Always
         schedulerName: default-scheduler
         securityContext: {}
         serviceAccount: istio-mixer-service-account
         serviceAccountName: istio-mixer-service-account
         terminationGracePeriodSeconds: 30
         volumes:
         - name: istio-certs
           secret:
             defaultMode: 420
             optional: true
             secretName: istio.istio-mixer-service-account
         - emptyDir: {}
           name: uds-socket
   

Additionally, you can configure log rotation for mixer process using the following flags:

--log_rotate string The path for the optional rotating log file

--log_rotate_max_age int The maximum age in days of a log file beyond which the file is rotated (0 indicates no limit) (default 30)

--log_rotate_max_backups int The maximum number of log file backups to keep before older files are deleted (0 indicates no limit) (default 1000)

--log_rotate_max_size int The maximum size in megabytes of a log file beyond which the file is rotated (default 104857600)

However, I have no possibility to generate a huge amount of such logs and test how it works.

Links:

Unfortunately, the official documentation is not good, but maybe it helps somehow.

And as a bonus, here is the list of all mixer server flags.