Revert "Deprecate _source.mode in mappings (#116689)"

[martijnvg]

This reverts #116689. Bwc tests fail, because older nodes are killed with the following error:

[2024-11-20T10:54:58,600][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [v8.17.0-0] fatal error in thread [elasticsearch[v8.17.0-0
][clusterApplierService#updateTask][T#1]], exiting java.lang.AssertionError: provided source [{"_doc":{"_data_stream_timestamp":{"enabled":true},"_source":{},"properties":{"@timestamp":{"type":"date"},"k8s":{"properties":{"pod":{"properties":{"ip":{"type":"ip"},"name":{"type":"keyword"},"network":{"properties":{"rx":{"type":"long"},"tx":{"type":"long"}}},"uid":{"type":"keyword","time_series_dimension":true}}}}},"metricset":{"type":"keyword","time_series_dimension":true}}}}] differs from mapping [{"_doc":{"_data_stream_timestamp":{"enabled":true},"_source":{"mode":"synthetic"},"properties":{"@timestamp":{"type":"date"},"k8s":{"properties":{"pod":{"properties":{"ip":{"type":"ip"},"name":{"type":"keyword"},"network":{"properties":{"rx":{"type":"long"},"tx":{"type":"long"}}},"uid":{"type":"keyword","time_series_dimension":true}}}}},"metricset":{"type":"keyword","time_series_dimension":true}}}}]
        at [email protected]/org.elasticsearch.index.mapper.DocumentMapper.<init>(DocumentMapper.java:66)
        at [email protected]/org.elasticsearch.index.mapper.MapperService.newDocumentMapper(MapperService.java:588)
        at [email protected]/org.elasticsearch.index.mapper.MapperService.updateMapping(MapperService.java:346)
        at [email protected]/org.elasticsearch.index.IndexService.updateMapping(IndexService.java:840)
        at [email protected]/org.elasticsearch.indices.cluster.IndicesClusterStateService.createIndicesAndUpdateShards(IndicesClusterStateService.java:583)
        at [email protected]/org.elasticsearch.indices.cluster.IndicesClusterStateService.doApplyClusterState(IndicesClusterStateService.java:306)
        at [email protected]/org.elasticsearch.indices.cluster.IndicesClusterStateService.applyClusterState(IndicesClusterStateService.java:260)
        at [email protected]/org.elasticsearch.cluster.service.ClusterApplierService.callClusterStateAppliers(ClusterApplierService.java:544)
        at [email protected]/org.elasticsearch.cluster.service.ClusterApplierService.callClusterStateAppliers(ClusterApplierService.java:530)
        at [email protected]/org.elasticsearch.cluster.service.ClusterApplierService.applyChanges(ClusterApplierService.java:503)
        at [email protected]/org.elasticsearch.cluster.service.ClusterApplierService.runTask(ClusterApplierService.java:432)
        at [email protected]/org.elasticsearch.cluster.service.ClusterApplierService$UpdateTask.run(ClusterApplierService.java:157)
        at [email protected]/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:956)
        at [email protected]/org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:218)
        at [email protected]/org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:184)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
        at java.base/java.lang.Thread.run(Thread.java:1575)

The mode parameter no longer gets serialized for new indices. However on the older nodes still serialize the mode parameter, which caused the menioned assertion to fail. Reverting for now and see how best to address this bwc serialization issue.

We can only stop serializing mode, when all nodes are on the same version. Unfortunately we can't invoke c.clusterTransportVersion().get() from parser or builder, because that calling thread isn't allowed to call clusterService.state().

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)