1. Debugging and
Testing ES Systems
Chris Birchall
2013/8/29
Elasticsearch 勉強会 第１回
#elasticsearchjp

2. Elasticsearch and me
● At Infoscience, helped build a log
management product based on ES +
Hadoop
● At M3, ES evangelist (??)
○ Maintain ES cluster
○ Help dev teams integrate ES into their apps
Twitter: @cbirchall
Github: https://github.com/cb372

3. Search at M3
● Using ES for all new services
○ Search, recommendation (MoreLikeThis)
● Slowly migrating other services from Solr
● A few legacy services use Lucene directly
● Running all indices on one ES cluster
● Kuromoji for Japanese content

4. Debugging
Mostly debugging of queries
● “Why doesn’t doc X match query Y?”
● “Why does this search return no results?”
Operational issues are very rare
● ES’s clustering magic is surprisingly
stable!
● No performance issues so far

5. Debugging - Step 1
Check for typos!
ES will silently ignore many typos in
settings/mapping definitions

6. Typo - Example
$ curl -X PUT localhost:9200/myapp -d '{
"settings": {
"number_of_shards": 3
},
"mapping" : {
"article" : {
"_source": { "enabled": false },
"properties": {
"title": { "type": "string", "store": "true" },
"body": { "type": "string", "store": "true" },
...
}
},
...
}'
Let’s create a new index...

7. Typo - Example (cont’d)
{"ok":true,"acknowledged":true}
Response from ES:
OK, seems fine...

8. Typo - Example (cont’d)
$ curl localhost:9200/myapp/_mappings?pretty
Response from ES:
{
"myapp" : { }
}
Eh?
Where are my lovingly-crafted mappings?!
Now check the mappings...

9. Typo - Example (cont’d)
$ curl -X PUT localhost:9200/myapp -d '{
"settings": {
"number_of_shards": 3
},
"mappings" : {
"article" : {
"_source": { "enabled": false },
"properties": {
"title": { "type": "string", "store": "true" },
"body": { "type": "string", "store": "true" },
...
}
},
...
}'
Oops!

10. Debugging - Step 2
Set up a local environment
● Makes it easy to wipe & rebuild index

11. Setting up a local env (OSX)
# Install
$ brew install elasticsearch
# Kuromoji plugin (optional)
$ /usr/local/opt/elasticsearch/bin/plugin -install
elasticsearch/elasticsearch-analysis-kuromoji/1.5.0
# Start
$ elasticsearch
# Create index
$ curl -X PUT localhost:9200/my_app -d '{ ... }'
# Insert some documents
$ curl -X PUT localhost:9200/my_app/my_type/1 -d '{ ... }'
$ curl -X PUT localhost:9200/my_app/my_type/2 -d '{ ... }'
# Done!

12. Useful commands - Analyze
$ curl 'localhost:9200/myindex/_analyze?pretty' /
-d '東京特許許可局許可局長'
{
"tokens" : [ {
"token" : "東京",
"start_offset" : 0,
"end_offset" : 2,
"type" : "word",
"position" : 1
}, {
"token" : "特許",
"start_offset" : 2,
"end_offset" : 4,
"type" : "word",
...
How is my
document/query
being
tokenized?

13. Useful commands - Explain
$ curl 'localhost:9200/kuro/docs/123/_explain?pretty' /
-d '{ "query": { "term": { "body": "東京" } } }'
{
...
"matched" : true,
"explanation" : {
"value" : 0.375,
"description" : "weight(body:東京 in 0)
[PerFieldSimilarity], result of:",
"details" : [ {
"value" : 0.375,
"description" : "fieldWeight in 0, product of:",
"details" : [ {
"value" : 1.0,
"description" : "tf(freq=1.0), with freq of:",
"details" : [ {
"value" : 1.0,
"description" : "termFreq=1.0"
...
Why does this
document (not)
match this
query?
Specify document ID

14. Tuning queries
Parameters to tweak
● default_operator (AND/OR)
● auto_generate_phrase_queries
● minumum_should_match
● Stop words/tags
● Kuromoji
○ Segmentation mode
○ Reading form filter
○ Disable Kuromoji! (for some fields)

15. Why disable Kuromoji?
Problem: occasionally weird tokenization
● AND query will fail, because not all terms match
● OR query will match any document with 病院
→ low precision
Phrase Terms
特定医療法人財団 日本会 東日本病院
(document field)
特定、医療、法人、財団、
日本、会、東日本、病院
東日本 (query) 東日、東日本、本
東日本病院 (query) 東、東日本、日本、病院

16. Useful plugin - Head
$ bin/plugin -install mobz/elasticsearch-head
http://mobz.github.io/elasticsearch-head/

17. Testing
Main goal: Ensure that queries return the
results that we expect
● Test coverage of representative queries
○ Freedom to tune for a given query without
breaking other queries
Ideally, tests should:
● Run fast
● Run standalone (i.e. no need to have an
ES server running)

18. Testing - Java
elasticsearch-test is awesome
● DSL to set up/tear down ES
● Annotations + JUnit runner
● ES runs in-process
○ No need to start an external ES server
● Index is stored in-memory
○ Runs quickly
https://github.com/tlrx/elasticsearch-test

19. https://github.com/cb372/elasticsearch-test-example
Testing - Java
Simple elasticsearch-test example

20. Testing - Ruby
Simple Rails + Tire + RSpec example
https://github.com/cb372/elasticsearch-rspec-example

21. We’re hiring!
TODO We are hiring slide
http://bit.ly/m3jobs