Exceded maximum insert size of 16,000,000 bytes

gistfile1.txt

installed version
----------------------
fluent-plugin-mongo (0.6.3)
fluent-plugin-td (0.10.2)

td-agent.conf
----------------
<match dak.app>
  type mongo
  database dak
  collection app
  host localhost
  port 27017
  ignore_invalid_record true
  buffer_chunk_limit 1M
  flush_interval 3s
</match>


log
----
2012-02-11 14:24:36 +0900: failed to flush the buffer, retrying. error="Exceded maximum insert size of 16,000,000 bytes" instance=41053780
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluent-plugin-mongo-0.6.3/lib/fluent/plugin/mongo_ext.rb:36:in `insert_documents'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/mongo-1.5.2/lib/mongo/collection.rb:343:in `insert'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluent-plugin-mongo-0.6.3/lib/fluent/plugin/out_mongo.rb:110:in `operate'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluent-plugin-mongo-0.6.3/lib/fluent/plugin/out_mongo.rb:100:in `write'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluentd-0.10.11/lib/fluent/buffer.rb:262:in `write_chunk'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluentd-0.10.11/lib/fluent/buffer.rb:246:in `pop'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluentd-0.10.11/lib/fluent/output.rb:299:in `try_flush'
  2012-02-11 14:24:36 +0900: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/fluentd-0.10.11/lib/fluent/output.rb:121:in `run'