我们在 ubuntu 14.04 上运行 Elasticsearch 1.7.2，系统有足够的内存，服务器上的其他服务运行良好。但有时 elastic 关闭时没有任何内容记录到其日志中，或任何内容记录到 syslog 中。我该如何调查此问题？这是显示其关闭时的部分日志：
[2015-11-24 02:10:54,121][DEBUG][index.shard ] [Keen Marlow] [haystack_backup][4] updating index_buffer_size from [64mb] to
[4mb]
[2015-11-24 02:10:54,121][DEBUG][index.shard ] [Keen Marlow] [product_index_backup][0] updating index_buffer_size from [64m
b] to [4mb]
[2015-11-24 02:10:54,121][DEBUG][index.shard ] [Keen Marlow] [product_index_backup][1] updating index_buffer_size from [64m
b] to [4mb]
[2015-11-24 02:10:54,121][DEBUG][index.shard ] [Keen Marlow] [product_index_backup][2] updating index_buffer_size from [64m
b] to [4mb]
[2015-11-24 02:10:54,121][DEBUG][index.shard ] [Keen Marlow] [product_index_backup][3] updating index_buffer_size from [64m
b] to [4mb]
[2015-11-24 02:10:54,121][DEBUG][index.shard ] [Keen Marlow] [product_index_backup][4] updating index_buffer_size from [64m
b] to [4mb]
[2015-11-24 02:11:24,015][INFO ][com.asquera.elasticsearch.plugins.http.HttpBasicServer] [Keen Marlow] Authorization:xx, Host:xx.xx.xx.xx:yy, Path:/, :null, Request-IP:xx.xx.xx.xx, Client-IP:null, X-Client-IPnull
[2015-11-24 02:12:15,416][INFO ][com.asquera.elasticsearch.plugins.http.HttpBasicServer] [Keen Marlow] Authorization:Basic xxxx, Host:xx.xx.xx.xx:yy, Path:/product_index/product/webservice.ProductPage.282933/, :null, Request-IP:xx.xx.xx.xx
, Client-IP:null, X-Client-IPnull
[2015-11-24 02:25:18,402][INFO ][node ] [Stakar] version[1.7.2], pid[16597], build[e43676b/2015-09-14T09:49:53Z]
[2015-11-24 02:25:18,402][INFO ][node ] [Stakar] initializing ...
[2015-11-24 02:25:18,403][DEBUG][node ] [Stakar] using home [/usr/share/elasticsearch], config [/etc/elasticsearch],
data [[/var/lib/elasticsearch]], logs [/var/log/elasticsearch], work [/tmp/elasticsearch], plugins [/usr/share/elasticsearch/plugins]
[2015-11-24 02:25:18,550][DEBUG][plugins ] [Stakar] lucene property is not set in plugin es-plugin.properties file. Ski
pping test.
[2015-11-24 02:25:18,551][DEBUG][plugins ] [Stakar] [/usr/share/elasticsearch/plugins/http-basic-server-plugin/_site] d
irectory does not exist.
[2015-11-24 02:25:18,552][DEBUG][plugins ] [Stakar] [/usr/share/elasticsearch/plugins/http-basic/_site] directory does
not exist.
[2015-11-24 02:25:18,553][INFO ][plugins ] [Stakar] loaded [http-basic-server-plugin], sites []
[2015-11-24 02:25:18,581][DEBUG][common.compress.lzf ] using encoder [VanillaChunkDecoder] and decoder[{}]
[2015-11-24 02:25:18,605][DEBUG][env ] [Stakar] using node location [[NodePath{path=/var/lib/elasticsearch/torob/no
des/0}]], local_node_id [0]
当我再次启动 elastic 时，请注意 2:12 和 2:25 之间有 13 分钟的间隔。syslog 或 auth.log 中没有任何相关信息。我应该怎么做才能进一步调查？
更新 正如我所说，系统日志中没有与此相关的内容。以下是涵盖该部分时间的内容：
Nov 24 01:19:01 hostname CRON[13408]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
Nov 24 02:19:01 hostname CRON[16223]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
Nov 24 03:19:01 hostname CRON[22518]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)