How to import the old event from file to es use logstash

Elastic Stack Logstash
1

start_position => "beginning"
ignore_older => 2592000 #7 day before ignore

I use this config ,but find data missing, and I am not sure ,when to use start_position => "beginning" and when to use start_position => "end" config

2

Well beginning means go from the start of the file, end means only look for new data in the file.

3

thanks ,
but I wond if I want to import the old data , and run as tail at the same time ,how can I do, set beginning and stop to set end,so restart ? but during these perid of I swtich the code ,I wonder if the data is missing or not

thank you