MongoDB replication issues

Ops and Admin Replication
6

Hi ,

With following read and write concerns,

db.adminCommand({
  "setDefaultRWConcern" : 1,
  "defaultWriteConcern" : {
    "w" : 2
  },
  "defaultReadConcern" : { "level" : "majority" }
})

And knowing little more on readConcerns, we come to conclusion that why I faced these issues. I just mentioned them below with their cause.

Issue 1 :
As I have mentioned my writeConcern as ==> {w:2} data might not have been durable by the time am reading it through readConcern of ==> “majority”,
May be because of that I was not getting data even from primary node

Issue 2 :
Same thing applies to Secondary as well, with writeConcern as ==> {w:2} and read concern as ==>. “majority” you are trying to read durable data from secondary.
By the time that you are trying to read, it might not have been durable in the secondary.

With this , readConcern also plays a major role while reading the data. In our case, as we are not using any Transaction for storing data, and speed is main concern,
{readConcern: ‘local’} makes more sense for us. With this we get data faster as we are not looking at any fail over cases.

Hope this helps.

Thanks
Gangadhar M