How i can increase the thread_pool.index.size in 6.6.1

Hi

With the reference to Elasticsearch document forv6.6.1, i am trying to increase the thread_pool index/write size to number of cores times 5 (4*5=20)in elasticsearch.yml file and but getting exceptions during startup. Can you please help me out to increase threads size.

[2019-10-04T05:05:55,882][WARN ][o.e.b.ElasticsearchUncaughtExceptionHandler] [es1] uncaught exception in thread [main]
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalArgumentException: Failed to parse value [20] for setting [thread_pool.write.size] must be <= 5
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:163) ~[elasticsearch-6.6.1.jar:6.6.1]

Elasticsearch yml config:-
thread_pool:
index:
size: 20
queue_size: 1000
write:
size: 20
queue_size: 2000

Thanks,
Kamal

Hi @Kamal_Ambati,

From the docs, the write and index thread pools are of type fixed and the maximum size for this pool is 1 + # of available processors . So Elasticsearch won't start when using 20 as you only have 4 processors.

As a side comment, changing thread pools are the last resort when it comes to performance optimization.