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Version: 1.1

Model configuration

This part of configuration defines how to configure the Executor (e.g. Flink job) and its components for a given scenario type. It is processed not only at the Designer but also passed to the execution engine (e.g. Flink), that’s why it’s parsed and processed a bit differently:

  • Defaults can be defined in defaultModelConfig.conf. Standard deployment (e.g. with docker sample) has it here.
  • defaultModelConfig.conf is currently resolved both on designer (to extract information about types of data or during scenario testing) and on execution engine (e.g. on Flink). That’s why all environment variables used there have to be defined also on all Flink hosts (!). This is a technical limitation and may change in the future.
  • Some Components can use a special mechanism which resolves and adds additional configuration during deployment, which is then passed to the execution engine. Such configuration is read and resolved only at the designer. Example: OpenAPI enrichers need to read its definition from external sites - so e.g. Flink cluster does not have to have access to the site with the definition.

Look at configuration areas to understand where Model configuration should be placed in Nussknacker configuration.

Common settings settings

Parameter nameImportanceTypeDefault valueDescription
timeoutMediumduration10sTimeout for invocation of scenario part (including enrichers)
asyncExecutionConfig.bufferSizeLowint200Buffer size used for async I/O
asyncExecutionConfig.workersLowint8Number of workers for thread pool used with async I/O
asyncExecutionConfig.defaultUseAsyncInterpretationMediumbooleantrueShould async I/O be used by scenarios by default - if you don't use many enrichers etc. you may consider setting this flag to false
checkpointConfig.checkpointIntervalMediumduration10mHow often should checkpoints be performed by default
checkpointConfig.minPauseBetweenCheckpointsLowdurationcheckpointInterval / 2Minimal pause between checkpoints
checkpointConfig.maxConcurrentCheckpointsLowint1Maximum concurrent checkpoints setting
checkpointConfig.tolerableCheckpointFailureNumberLowintTolerable failed checkpoint setting
rocksDB.enableMediumbooleantrueEnable RocksDB state backend support
rocksDB.incrementalCheckpointsMediumbooleantrueShould incremental checkpoints be used
rocksDB.dbStoragePathLowstringAllows to override RocksDB local data storage
enableObjectReuseLowbooleantrueShould allow object reuse
nkGlobalParameters.explicitUidInStatefulOperatorsLowbooleantrueShould consistent operator uids be used
nkGlobalParameters.useTypingResultTypeInformationLowbooleantrueEnables using Nussknacker additional typing information for state serialization. It makes serialization much faster, currently consider it as experimental
eventTimeMetricSlideDurationLowduration10 secondsWe use sliding window reservoir sampling for some metrics, this configures slide length
componentsGroupMappingLowmapOverride default grouping of basic components in toolbox panels. Component names are keys, while values are toolbox panels name (e.g. sources, enrichers etc.)
componentActionsLowlist[{id: string, title: string, icon: string, url: option[string], supportedComponentTypes: option[List[string]]}][{id: "usages", title: "Usages of component", icon: "/assets/components/actions/usages.svg"}]Component's actions configuration which are displayed at list of components. Fields title, icon, url can contain templates: $componentId nad $componentName which are replaced by component data. Parameter url isn't required because some of actions like usages are build-in FE actions. Url is required when you want to do redirect to another page. Param supportedComponentTypes means component's types which can support actions.

Exception handling can be customized using provided EspExceptionConsumer. By default, there are two available:

  • BrieflyLogging
  • VerboselyLogging More of them can be added with custom extensions. By default, basic error metrics are collected. If for some reason it's not desirable, metrics collector can be turned off with withRateMeter: false setting.

Some handlers can have additional properties, e.g. built in logging handlers can add custom parameters to log. See example below.

exceptionHandler {
type: BrieflyLogging
withRateMeter: false
params: {
additional: "value1"

Out of the box, Nussknacker provides following ExceptionHandler types:

  • BrieflyLogging - log error to Flink logs (on info level, with stacktrace on debug level)
  • VerboselyLogging - log error to Flink logs on error level, together with all variables (should be used mainly for debugging)
  • Kafka - send errors to Kafka topic

Kafka exception handling

Errors can be sent to specified Kafka topic in following json format (see below for format configuration options):

"processName" : "Premium Customer Scenario",
"nodeId" : "filter premium customers",
"message" : "Unknown exception",
"exceptionInput" : "SpelExpressionEvaluationException:Expression [1/0 != 10] evaluation failed, message: / by zero",
"inputEvent" : "{ \" field1\": \"vaulue1\" }",
"stackTrace" : "pl.touk.nussknacker.engine.api.exception.NonTransientException: mess\n\tat pl.touk.nussknacker.engine.kafka.exception.KafkaExceptionConsumerSerializationSpec.<init>(KafkaExceptionConsumerSerializationSpec.scala:24)\n\tat java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)\n\tat java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(\n\tat java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(\n\tat java.base/java.lang.reflect.Constructor.newInstance(\n\tat java.base/java.lang.Class.newInstance(\n\tat$.genSuiteConfig(Runner.scala:1431)\n\tat$.$anonfun$doRunRunRunDaDoRunRun$8(Runner.scala:1239)\n\tat\n\tat$.doRunRunRunDaDoRunRun(Runner.scala:1238)\n\tat$.$anonfun$runOptionallyWithPassFailReporter$24(Runner.scala:1033)\n\tat$.$anonfun$runOptionallyWithPassFailReporter$24$adapted(Runner.scala:1011)\n\tat$.withClassLoaderAndDispatchReporter(Runner.scala:1509)\n\tat$.runOptionallyWithPassFailReporter(Runner.scala:1011)\n\tat$.run(Runner.scala:850)\n\tat\n\tat org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.runScalaTest2or3(\n\tat org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.main(",
"timestamp" : 1623758738000,
"host" : "",
"additionalData" : {
"scenarioCategory" : "Marketing"

Following properties can be configured:

NameDefault valueDescription
topic-Topic where errors will be sent. It should be configured separately (or topic auto.create setting should be enabled on Kafka cluster)
stackTraceLengthLimit50Limit of stacktrace length that will be sent (0 to omit stacktrace at all)
includeHosttrueShould name of host where error occurred (e.g. TaskManager in case of Flink) be included. Can be misleading if there are many network interfaces or hostname is improperly configured)
includeInputEventfalseShould input event be serialized (can be large or contain sensitive data so use with care)
useSharedProducerfalseFor better performance shared Kafka producer can be used (by default it's created and closed for each error), shared Producer is kind of experimental feature and should be used with care
additionalParams{}Map of fixed parameters that can be added to Kafka message

We rely on Flink restart strategies described in documentation. It's also possible to configure restart strategies per scenario, using additional properties.

    restartStrategy {
//if scenarioProperty is configured, strategy name will be used from this category: restartType = for-important, etc.
//probably scenarioProperty should be configured with FixedValuesEditor
//scenarioProperty: restartType. For simple cases one needs to configure only default strategy
default: {
strategy: fixed-delay
attempts: 10
delay: 10s
for-important {
strategy: fixed-delay
attempts: 30
for-very-important {
strategy: fixed-delay
attempts: 50

Configuration of UI attributes of components

In model configuration you can also define some UI attributes of components. This can be useful for tweaking of appearance of generated components (like from OpenAPI), in most cases you should not need to defined these settings. The settings you can configure include:

  • icons - icon property
  • documentation - docsUrl property
  • should component be disabled - disabled property
  • in which toolbox panel the component should appear (componentGroup property)
  • params configuration (allows to override default component settings):
    • editor - BoolParameterEditor, StringParameterEditor, DateParameterEditor etc.
    • validators - MandatoryParameterValidator, NotBlankParameterValidator, RegexpParameterValidator
    • defaultValue
    • label

Example (see dev application config for more examples):

  componentsUiConfig {
customerService {
params {
serviceIdParameter {
defaultValue: "customerId-10"
editor: "StringParameterEditor"
validators: [
type: "RegExpParameterValidator"
pattern: "customerId-[0-9]*"
message: "has to match customer id format"
description: "really has to match..."
label: "Customer id (from CRM!)
docsUrl: ""
icon: "icon_file.svg"

Additional properties

It's possible to add additional properties for scenario. They can be used for allowing more detailed scenario information (e.g. pass information about marketing campaign target etc.), they can also be used in various Nussknacker extensions:

Example (see dev application config for more examples):

additionalPropertiesConfig {
campaignType: {
editor: { type: "StringParameterEditor" }
validators: [ { type: "MandatoryParameterValidator" } ]
label: "Campaign type"
defaultValue: "Generic campaign"

Configuration is similar to component configuration

Kafka configuration

Currently, it's only possible to use one Kafka cluster for one model configuration. This configuration is used for all Kafka based sources and sinks

Important thing to remember is that Kafka server addresses/schema registry addresses have to be resolvable from:

  • Nussknacker Designer host (to enable schema discovery and scenario testing)
  • Flink cluster (both jobmanagers and taskmanagers) hosts - to be able to run job
NameImportanceTypeDefault valueDescription
kafka.kafkaAddressHighstringComma separated list of bootstrap servers
kafka.kafkaProperties."schema.registry.url"HighstringComma separated list of schema registry
kafka.kafkaPropertiesMediummapAdditional configuration of producers or consumers
kafka.useStringForKeyMediumbooleantrueShould we assume that Kafka message keys are in plain string format (not in Avro)
kafka.kafkaEspProperties.forceLatestReadMediumbooleanfalseIf scenario is restarted without state (if started with non-empty Flink state, the offsets are always taken from Flink state), should offsets of source consumers be reset to latest (can be useful in test enrivonments)
kafka.kafkaEspProperties.defaultMaxOutOfOrdernessMillisMediumduration60sConfiguration of bounded of orderness watermark generator used by Kafka sources
kafka.consumerGroupNamingStrategyLowprocessId/processId-nodeIdprocessId-nodeIdHow consumer groups for sources should be named
kafka.avroKryoGenericRecordSchemaIdSerializationLowbooleantrueShould AVRO messages from topics registered in schema registry be serialized in optimized way, by serializing only schema id, not the whole schema
kafka.topicsExistenceValidationConfig.enabledLowbooleanfalseShould we validate existence of topics if no auto.create.topics.enable is false on Kafka cluster - note, that it may require permissions to access Kafka cluster settings
kafka.topicsExistenceValidationConfig.validatorConfig.autoCreateFlagFetchCacheTtlLowduration5 minutesTTL for checking Kafka cluster settings
kafka.topicsExistenceValidationConfig.validatorConfig.topicsFetchCacheTtlLowduration30 secondsTTL for caching list of existing topics
kafka.topicsExistenceValidationConfig.validatorConfig.adminClientTimeoutLowduration500 millisecondsTimeout for communicating with Kafka cluster

Additional components configuration

Configuration of component providers

  components {
sqlHsql {
providerType: sql
jdbcUrl: jdbc:hsql...//
sqlOracle {
providerType: sql
jdbcUrl: jdbc:oracle...//
prinzH20 {
providerType: prinzH20
prinzMlFlow {
//this is not needed, as configuration is named just as provider
//providerType: prinzMLFlow
//not needed in our domain
aggregation {
disabled: true

Extra components providers

You can read about list of extra components in Extra components section