Flink supports different restart strategies which control how the jobs are restarted in case of a failure. The cluster can be started with a default restart strategy which is always used when no job specific restart strategy has been defined. In case that the job is submitted with a restart strategy, this strategy overrides the cluster's default setting.
The default restart strategy is set via Flink's configuration file flink-conf.yaml. The configuration parameter restart-strategy defines which strategy is taken. If checkpointing is not enabled, the “no restart” strategy is used. If checkpointing is activated and the restart strategy has not been configured, the fixed-delay strategy is used with Integer.MAX_VALUE restart attempts. See the following list of available restart strategies to learn what values are supported.
Each restart strategy comes with its own set of parameters which control its behaviour. These values are also set in the configuration file. The description of each restart strategy contains more information about the respective configuration values.
Apart from defining a default restart strategy, it is possible to define for each Flink job a specific restart strategy. This restart strategy is set programmatically by calling the setRestartStrategy method on the ExecutionEnvironment. Note that this also works for the StreamExecutionEnvironment.
The following example shows how we can set a fixed delay restart strategy for our job. In case of a failure the system tries to restart the job 3 times and waits 10 seconds in-between successive restart attempts.
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The following sections describe restart strategy specific configuration options.
The fixed delay restart strategy attempts a given number of times to restart the job. If the maximum number of attempts is exceeded, the job eventually fails. In-between two consecutive restart attempts, the restart strategy waits a fixed amount of time.
This strategy is enabled as default by setting the following configuration parameter in flink-conf.yaml.
{% highlight yaml %} restart-strategy: fixed-delay {% endhighlight %}
For example:
{% highlight yaml %} restart-strategy.fixed-delay.attempts: 3 restart-strategy.fixed-delay.delay: 10 s {% endhighlight %}
The fixed delay restart strategy can also be set programmatically:
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The failure rate restart strategy restarts job after failure, but when failure rate (failures per time interval) is exceeded, the job eventually fails. In-between two consecutive restart attempts, the restart strategy waits a fixed amount of time.
This strategy is enabled as default by setting the following configuration parameter in flink-conf.yaml.
{% highlight yaml %} restart-strategy: failure-rate {% endhighlight %}
{% highlight yaml %} restart-strategy.failure-rate.max-failures-per-interval: 3 restart-strategy.failure-rate.failure-rate-interval: 5 min restart-strategy.failure-rate.delay: 10 s {% endhighlight %}
The failure rate restart strategy can also be set programmatically:
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The job fails directly and no restart is attempted.
{% highlight yaml %} restart-strategy: none {% endhighlight %}
The no restart strategy can also be set programmatically:
The cluster defined restart strategy is used. This helpful for streaming programs which enable checkpointing. Per default, a fixed delay restart strategy is chosen if there is no other restart strategy defined.
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