logstash elasticsearch output插件的bulk提交

logstash的output设置为elasticsearch时，实际上logstash在向es中插入数据时也是bulk提交的，和指提交相关的设置有以下两个参数：

flush_size

Value type is number

Default value is 500

This plugin uses the bulk index API for improved indexing performance. To make efficient bulk API calls, we will buffer a certain number of events before flushing that out to Elasticsearch. This setting controls how many events will be buffered before sending a batch of events. Increasing the flush_size has an effect on Logstash’s heap size. Remember to also increase the heap size using LS_HEAP_SIZE if you are sending big documents or have increased the flush_size to a higher value.

表示多少条flush一起提交到es.

idle_flush_time

Value type is number

Default value is 1

The amount of time since last flush before a flush is forced.

This setting helps ensure slow event rates don’t get stuck in Logstash. For example, if your flush_size is 100, and you have received 10 events, and it has been more than idle_flush_time seconds since the last flush, Logstash will flush those 10 events automatically.

This helps keep both fast and slow log streams moving along in near-real-time.

表示距离上次flush的时间之后多少秒自动flush提交一次

这两个参数一起用的意思就是：

累计缓冲event条数达到flush_size值会flush一次

距离上次flush的时间之后idle_flush_time秒后也会flush一次

满足上面任意两个条件logstash都会flush提交到es