error "temporarily failed to flush the buffer" in using fluentd-plugin-elasticsearch

[kakalo24]

td-agent version is 2.2.1
fluentd-plugin-elasticsearch version is 1.2.1
elasticsearch version is 2.1.0

td-agent and elasticsearch are in the same machine，
td-agent.conf was be configured like this :

type elasticsearch
host 127.0.0.1
port 9200
index_name fluentd
type_name nginx
ssl_verify false
logstash_format true

type tail
format json
path /var/lib/docker/containers//.log
pos_file /var/log/td-agent/queue_log.pos
tag docker.kk
but td-agent's log reported error:
[warn]: temporarily failed to flush the buffer. next_retry=2015-12-07 20:24:20 +0800 error_class="Elasticsearch::Transport::Transport::Errors::Found" error="[302] " plugin_id="object:3fcf5df04558"
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-transport-1.0.14/lib/elasticsearch/transport/transport/base.rb:136:in __raise_transport_error' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-transport-1.0.14/lib/elasticsearch/transport/transport/base.rb:228:inperform_request'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-transport-1.0.14/lib/elasticsearch/transport/transport/http/faraday.rb:20:in perform_request' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-transport-1.0.14/lib/elasticsearch/transport/client.rb:119:inperform_request'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-api-1.0.14/lib/elasticsearch/api/actions/ping.rb:20:in block in ping' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-api-1.0.14/lib/elasticsearch/api/utils.rb:191:in__rescue_from_not_found'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/elasticsearch-api-1.0.14/lib/elasticsearch/api/actions/ping.rb:19:in ping' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluent-plugin-elasticsearch-1.2.1/lib/fluent/plugin/out_elasticsearch.rb:71:inclient'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluent-plugin-elasticsearch-1.2.1/lib/fluent/plugin/out_elasticsearch.rb:178:in rescue in send' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluent-plugin-elasticsearch-1.2.1/lib/fluent/plugin/out_elasticsearch.rb:176:insend'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluent-plugin-elasticsearch-1.2.1/lib/fluent/plugin/out_elasticsearch.rb:170:in write' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.12.12/lib/fluent/buffer.rb:325:inwrite_chunk'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.12.12/lib/fluent/buffer.rb:304:in pop' 2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.12.12/lib/fluent/output.rb:321:intry_flush'
2015-12-07 20:24:05 +0800 [warn]: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/fluentd-0.12.12/lib/fluent/output.rb:140:in `run'
2015-12-07 20:24:20 +0800 [warn]: temporarily failed to flush the buffer. next_retry=2015-12-07 20:24:46 +0800 error_class="Elasticsearch::Transport::Transport::Errors::Found" error="[302] " plugin_id="object:3fcf5df04558"
2015-12-07 20:24:20 +0800 [warn]: suppressed same stacktrace

I don't know what problem with td-agent, please help me to solve the problem,thanks.