ScriptParameterParseException when upgrading from 1.4 -> 1.5.2

[aewhite]

After upgrading from 1.4 -> 1.5.2 shards fail to load due to ScriptParameterParseException.

Stacktrace:

org.elasticsearch.script.ScriptParameterParser$ScriptParameterParseException: Value must be of type String: [lang]
        at org.elasticsearch.script.ScriptParameterParser.parseConfig(ScriptParameterParser.java:111)
        at org.elasticsearch.index.mapper.DocumentMapperParser.parseTransform(DocumentMapperParser.java:307)
        at org.elasticsearch.index.mapper.DocumentMapperParser.parse(DocumentMapperParser.java:257)
        at org.elasticsearch.index.mapper.DocumentMapperParser.parseCompressed(DocumentMapperParser.java:192)
        at org.elasticsearch.index.mapper.MapperService.parse(MapperService.java:434)
        at org.elasticsearch.index.mapper.MapperService.merge(MapperService.java:307)
        at org.elasticsearch.indices.cluster.IndicesClusterStateService.processMapping(IndicesClusterStateService.java:430)
        at org.elasticsearch.indices.cluster.IndicesClusterStateService.applyMappings(IndicesClusterStateService.java:376)
        at org.elasticsearch.indices.cluster.IndicesClusterStateService.clusterChanged(IndicesClusterStateService.java:181)
        at org.elasticsearch.cluster.service.InternalClusterService$UpdateTask.run(InternalClusterService.java:467)
        at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:188)
        at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:158)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)

The cause as I can best understand is the lang property is getting set to null for some transform scripts. We do not explicitly set the lang so this was unexpected. Our process is to use a template...

"mappings": {
            "<type>": {                
                "transform": [
                    {"script": "<source>"},
...

However, the mapping produced after an index creation (in 1.4) is...

{
    "<index-name>": {
        "mappings": {
            "<type>": {
                "transform": [
                    {"script": "<source>","lang": null}
...

The above mapping works in 1.4 but not in 1.5 it seems.

[clintongormley]

@colings86 please could you take a look. probably related to #7977

[aewhite]

Note to others; the only workaround I have found that works is to recreate the index and set lang property on transform explicitly. Perhaps there is a way to update an existing transform but it is not mentioned in the Transform Documentation at this time.

[colings86]

@aewhite thanks for raising this. When the transform is written in the mapping the script language is written even if it is set to null (null meaning use the default). I have opened PR #10976 which lets the parser reading the stored mapping read null for the script language instead of throwing an error

[colings86]

@aewhite thanks again for raising this. The fix has now been merged in and should be available from 1.5.3