Shard 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 index.search.slowlog.level: info
All of the above settings are dynamic and are set per-index.
By default, none are enabled (set to -1). Levels (warn, info,
debug, trace) allow to control under which logging level the log
will be logged. Not all are required to be configured (for example, only
warn threshold can be set). The benefit of several levels is the
ability to quickly "grep" for specific thresholds breached.
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 logging file is configured by default using the following
configuration (found in log4j2.properties):
appender.index_search_slowlog_rolling.type = RollingFile
appender.index_search_slowlog_rolling.name = index_search_slowlog_rolling
appender.index_search_slowlog_rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_index_search_slowlog.log
appender.index_search_slowlog_rolling.layout.type = PatternLayout
appender.index_search_slowlog_rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c] [%node_name]%marker %.-10000m%n
appender.index_search_slowlog_rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_index_search_slowlog-%i.log.gz
appender.index_search_slowlog_rolling.policies.type = Policies
appender.index_search_slowlog_rolling.policies.size.type = SizeBasedTriggeringPolicy
appender.index_search_slowlog_rolling.policies.size.size = 1GB
appender.index_search_slowlog_rolling.strategy.type = DefaultRolloverStrategy
appender.index_search_slowlog_rolling.strategy.max = 4
logger.index_search_slowlog_rolling.name = index.search.slowlog
logger.index_search_slowlog_rolling.level = trace
logger.index_search_slowlog_rolling.appenderRef.index_search_slowlog_rolling.ref = index_search_slowlog_rolling
logger.index_search_slowlog_rolling.additivity = falseThe indexing slow log, similar in functionality to the search slow
log. The log file name ends with _index_indexing_slowlog.log. 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.level: info index.indexing.slowlog.source: 1000
All of the above settings are dynamic and are set per-index.
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 an 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 by default in the log4j2.properties
file:
appender.index_indexing_slowlog_rolling.type = RollingFile
appender.index_indexing_slowlog_rolling.name = index_indexing_slowlog_rolling
appender.index_indexing_slowlog_rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_index_indexing_slowlog.log
appender.index_indexing_slowlog_rolling.layout.type = PatternLayout
appender.index_indexing_slowlog_rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c] [%node_name]%marker %.-10000m%n
appender.index_indexing_slowlog_rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}_index_indexing_slowlog-%i.log.gz
appender.index_indexing_slowlog_rolling.policies.type = Policies
appender.index_indexing_slowlog_rolling.policies.size.type = SizeBasedTriggeringPolicy
appender.index_indexing_slowlog_rolling.policies.size.size = 1GB
appender.index_indexing_slowlog_rolling.strategy.type = DefaultRolloverStrategy
appender.index_indexing_slowlog_rolling.strategy.max = 4
logger.index_indexing_slowlog.name = index.indexing.slowlog.index
logger.index_indexing_slowlog.level = trace
logger.index_indexing_slowlog.appenderRef.index_indexing_slowlog_rolling.ref = index_indexing_slowlog_rolling
logger.index_indexing_slowlog.additivity = false