[BUG] Cron expression with list (comma) value causes fatal error Opensearch thread due to NoClassDefFoundError when creating snapshot management policy

[tomchlee]

Describe the bug
When creating snapshot management policy, I'm able to specify wildcard, range and step values in cron expression. However, when I specify cron expression with list (comma) value, it causes fatal error in Opensearch due to NoClassDefFoundError:

[2022-09-13T17:33:13,207][ERROR][o.o.b.OpenSearchUncaughtExceptionHandler] [node-1] fatal error in thread [Thread-3], exiting
java.lang.NoClassDefFoundError: org/opensearch/jobscheduler/repackage/org/slf4j/LoggerFactory
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.generator.AndFieldValueGenerator.<clinit>(AndFieldValueGenerator.java:27) ~[?:?]
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.generator.FieldValueGeneratorFactory.forCronField(FieldValueGeneratorFactory.java:31) ~[?:?]
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.ExecutionTimeBuilder.forMinutesMatching(ExecutionTimeBuilder.java:57) ~[?:?]
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.ExecutionTime.forCron(ExecutionTime.java:50) ~[?:?]
    at org.opensearch.jobscheduler.spi.schedule.CronSchedule.<init>(CronSchedule.java:48) ~[?:?]
    at org.opensearch.jobscheduler.spi.schedule.ScheduleParser.parse(ScheduleParser.java:50) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.model.SMPolicy$Creation$Companion.parse(SMPolicy.kt:271) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.model.SMPolicy$Companion.parse(SMPolicy.kt:151) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.api.resthandler.RestBaseIndexSMPolicyHandler.prepareIndexRequest(RestBaseIndexSMPolicyHandler.kt:38) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.api.resthandler.RestCreateSMPolicyHandler.prepareRequest(RestCreateSMPolicyHandler.kt:25) ~[?:?]
...

and another similar stacktrace:

Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.opensearch.jobscheduler.repackage.com.cronutils.model.time.generator.AndFieldValueGenerator
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.generator.FieldValueGeneratorFactory.forCronField(FieldValueGeneratorFactory.java:31) ~[?:?]
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.ExecutionTimeBuilder.forMinutesMatching(ExecutionTimeBuilder.java:57) ~[?:?]
    at org.opensearch.jobscheduler.repackage.com.cronutils.model.time.ExecutionTime.forCron(ExecutionTime.java:50) ~[?:?]
    at org.opensearch.jobscheduler.spi.schedule.CronSchedule.<init>(CronSchedule.java:48) ~[?:?]
    at org.opensearch.jobscheduler.spi.schedule.ScheduleParser.parse(ScheduleParser.java:50) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.model.SMPolicy$Creation$Companion.parse(SMPolicy.kt:271) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.model.SMPolicy$Companion.parse(SMPolicy.kt:151) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.api.resthandler.RestBaseIndexSMPolicyHandler.prepareIndexRequest(RestBaseIndexSMPolicyHandler.kt:38) ~[?:?]
    at org.opensearch.indexmanagement.snapshotmanagement.api.resthandler.RestCreateSMPolicyHandler.prepareRequest(RestCreateSMPolicyHandler.kt:25) ~[?:?]
...

To Reproduce
Steps to reproduce the behavior:

1. Try to create SM policy via SM api with list value in cron expression, e.g., "0,30 * * * *"
2. Opensearch process is killed and SM policy failed to be created

Expected behavior
SM policy is created successfully

Plugins
Index Management

Screenshots
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Host/Environment (please complete the following information):

• OS: Linux
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[bowenlan-amzn]

Pin down the problem to be the missing slf4j which is the runtime dep of cron-utils.
Fix: opensearch-project/job-scheduler#256

To fix this on your side immediately, please refer to the change in the above PR, build the job scheduler zip manually (./gradlew assemble), and re-install (uninstall & install) the job scheduler plugin to your cluster (install plugin doc)

[tomchlee]

Thanks for the fix!