Elasticsearch scripted_metric null_pointer_exception - elasticsearch

Question

I'm trying to use the scripted_metric aggs of Elasticsearch and normally, it's working perfectly fine with my other scripts
However, with script below, I'm encountering an error called "null_pointer_exception" but they're just copy-pasted scripts and working for 6 modules already
$max = 10;
{
"query": {
"match_all": {}
//omitted some queries here, so I just turned it into match_all
}
},
"aggs": {
"ARTICLE_CNT_PDAY": {
"histogram": {
"field": "pub_date",
"interval": "86400"
},
"aggs": {
"LATEST": {
"nested": {
"path": "latest"
},
"aggs": {
"SUM_SVALUE": {
"scripted_metric": {
"init_script": "
state.te = [];
state.g = 0;
state.d = 0;
state.a = 0;
",
"map_script": "
if(state.d != doc['_id'].value){
state.d = doc['_id'].value;
state.te.add(state.a);
state.g = 0;
state.a = 0;
}
state.a = doc['latest.soc_mm_score'].value;
",
"combine_script": "
state.te.add(state.a);
double count = 0;
for (t in state.te) {
count += ((t*10)/$max)
}
return count;
",
"reduce_script": "
double count = 0;
for (a in states) {
count += a;
}
return count;
"
}
}
}
}
}
}
}
}
I tried running this script in Kibana, and here's the error message:
What I'm getting is, that there's something wrong with the reduce_script portion, tried to change this part:
FROM
for (a in states) {
count += a;
}
TO
for (a in states) {
count += 1;
}
And worked perfectly fine, I felt that the a variable isn't getting what it's supposed to hold
Any ideas here? Would appreciate your help, thank you very much!

Answer 1

The reason is explained here:
If a parent bucket of the scripted metric aggregation does not collect any documents an empty aggregation response will be returned from the shard with a null value. In this case the reduce_script's states variable will contain null as a response from that shard. reduce_script's should therefore expect and deal with null responses from shards.
So obviously one of your buckets is empty, and you need to deal with that null like this:
"reduce_script": "
double count = 0;
for (a in states) {
count += (a ?: 0);
}
return count;
"