Slow Log
editSlow Log
editSearch Slow Log
editShard level slow search log allows to log slow search (query and fetch phases) into a dedicated log file.
Thresholds can be set for both the query phase of the execution, and fetch phase, here is a sample:
index.search.slowlog.threshold.query.warn: 10s index.search.slowlog.threshold.query.info: 5s index.search.slowlog.threshold.query.debug: 2s index.search.slowlog.threshold.query.trace: 500ms index.search.slowlog.threshold.fetch.warn: 1s index.search.slowlog.threshold.fetch.info: 800ms index.search.slowlog.threshold.fetch.debug: 500ms index.search.slowlog.threshold.fetch.trace: 200ms
All of the above settings are dynamic and can be set for each index using the update indices settings API. For example:
response = client.indices.put_settings( index: 'my-index-000001', body: { "index.search.slowlog.threshold.query.warn": '10s', "index.search.slowlog.threshold.query.info": '5s', "index.search.slowlog.threshold.query.debug": '2s', "index.search.slowlog.threshold.query.trace": '500ms', "index.search.slowlog.threshold.fetch.warn": '1s', "index.search.slowlog.threshold.fetch.info": '800ms', "index.search.slowlog.threshold.fetch.debug": '500ms', "index.search.slowlog.threshold.fetch.trace": '200ms' } ) puts response
PUT /my-index-000001/_settings { "index.search.slowlog.threshold.query.warn": "10s", "index.search.slowlog.threshold.query.info": "5s", "index.search.slowlog.threshold.query.debug": "2s", "index.search.slowlog.threshold.query.trace": "500ms", "index.search.slowlog.threshold.fetch.warn": "1s", "index.search.slowlog.threshold.fetch.info": "800ms", "index.search.slowlog.threshold.fetch.debug": "500ms", "index.search.slowlog.threshold.fetch.trace": "200ms" }
By default thresholds are disabled (set to -1
).
The logging is done on the shard level scope, meaning the execution of a search request within a specific shard. It does not encompass the whole search request, which can be broadcast to several shards in order to execute. Some of the benefits of shard level logging is the association of the actual execution on the specific machine, compared with request level.
The search slow log file is configured in the log4j2.properties
file.
Identifying search slow log origin
editIt is often useful to identify what triggered a slow running query. If a call was initiated with an X-Opaque-ID
header, then the user ID
is included in Search Slow logs as an additional id field
{ "type": "index_search_slowlog", "timestamp": "2030-08-30T11:59:37,786+02:00", "level": "WARN", "component": "i.s.s.query", "cluster.name": "distribution_run", "node.name": "node-0", "message": "[index6][0]", "took": "78.4micros", "took_millis": "0", "total_hits": "0 hits", "stats": "[]", "search_type": "QUERY_THEN_FETCH", "total_shards": "1", "source": "{\"query\":{\"match_all\":{\"boost\":1.0}}}", "id": "MY_USER_ID", "cluster.uuid": "Aq-c-PAeQiK3tfBYtig9Bw", "node.id": "D7fUYfnfTLa2D7y-xw6tZg" }
Index Slow log
editThe indexing slow log, similar in functionality to the search slow
log. The log file name ends with _index_indexing_slowlog.json
. Log and
the thresholds are configured in the same way as the search slowlog.
Index slowlog sample:
index.indexing.slowlog.threshold.index.warn: 10s index.indexing.slowlog.threshold.index.info: 5s index.indexing.slowlog.threshold.index.debug: 2s index.indexing.slowlog.threshold.index.trace: 500ms index.indexing.slowlog.source: 1000
All of the above settings are dynamic and can be set for each index using the update indices settings API. For example:
response = client.indices.put_settings( index: 'my-index-000001', body: { "index.indexing.slowlog.threshold.index.warn": '10s', "index.indexing.slowlog.threshold.index.info": '5s', "index.indexing.slowlog.threshold.index.debug": '2s', "index.indexing.slowlog.threshold.index.trace": '500ms', "index.indexing.slowlog.source": '1000' } ) puts response
PUT /my-index-000001/_settings { "index.indexing.slowlog.threshold.index.warn": "10s", "index.indexing.slowlog.threshold.index.info": "5s", "index.indexing.slowlog.threshold.index.debug": "2s", "index.indexing.slowlog.threshold.index.trace": "500ms", "index.indexing.slowlog.source": "1000" }
By default Elasticsearch will log the first 1000 characters of the _source in
the slowlog. You can change that with index.indexing.slowlog.source
. Setting
it to false
or 0
will skip logging the source entirely, while setting it to
true
will log the entire source regardless of size. The original _source
is
reformatted by default to make sure that it fits on a single log line. If preserving
the original document format is important, you can turn off reformatting by setting
index.indexing.slowlog.reformat
to false
, which will cause the source to be
logged "as is" and can potentially span multiple log lines.
The index slow log file is configured in the log4j2.properties
file.
Slow log levels
editYou can mimic the search or indexing slow log level by setting appropriate
threshold making "more verbose" loggers to be switched off.
If for instance we want to simulate index.indexing.slowlog.level: INFO
then all we need to do is to set
index.indexing.slowlog.threshold.index.debug
and index.indexing.slowlog.threshold.index.trace
to -1
.