【原创】大数据基础之Logstash（6）mongo input

logstash input插件之mongodb是第三方的，配置如下：

input {
  mongodb {
    uri => 'mongodb://mongo_server:27017/db'
    placeholder_db_dir => '/path/to/db_dir/'
    placeholder_db_name => 'table.db'
    collection => 'table'
    batch_size => 5000
  }
}

安装

./logstash-plugin install logstash-input-mongodb

插件实现非常简单，就一个ruby文件，

https://github.com/phutchins/logstash-input-mongodb/blob/master/lib/logstash/inputs/mongodb.rb

使用sqlite来维护状态，db文件目录在 placeholder_db_dir，可以直接通过sqlite命令查看和修改

# sqlite3 /path/to/db_dir/table.db

db结构

sqlite> .schema
CREATE TABLE `since_table` (`table` varchar(255), `place` Int);
sqlite> select * from since_table order by place desc limit 1;
logstash_since_table|5d0b2c2682b7d74de069ce4d

插件中取place代码

  public
  def get_placeholder(sqlitedb, since_table, mongodb, mongo_collection_name)
    since = sqlitedb[SINCE_TABLE]
    x = since.where(:table => "#{since_table}_#{mongo_collection_name}")
    if x[:place].nil? || x[:place] == 0
      first_entry_id = init_placeholder(sqlitedb, since_table, mongodb, mongo_collection_name)
      @logger.debug("FIRST ENTRY ID for #{mongo_collection_name} is #{first_entry_id}")
      return first_entry_id
    else
      @logger.debug("placeholder already exists, it is #{x[:place]}")
      return x[:place][:place]
    end
  end

place取自mongo的_id

> db.table.find().limit(1).pretty()
{
        "_id" : ObjectId("5b48cd2382b7d752b802de31"),
...

可以手工通过sqlite的update命令来操作进度；

同步过程日志

D, [2019-06-20T16:21:31.938302 #28968] DEBUG -- : MONGODB | 47.92.149.159:27017 | db.find | STARTED | {"find"=>"table", "filter"=>{"_id"=>{"$gt"=>BSON::ObjectId('5d0b420782b7d74de069db7b')}}, "limit"=>10000}
D, [2019-06-20T16:21:31.941658 #28968] DEBUG -- : MONGODB | 47.92.149.159:27017 | db.find | SUCCEEDED | 0.002s

读place，从place开始取10000条，然后写place，如此往复

参考：https://github.com/phutchins/logstash-input-mongodb