No primary_preferred server is available in cluster

[jerko-culina]

Hi,

sorry if this is not right place for this kind of question, but as I am getting NoServerAvaiable error I decided to ask here.

I have ruby on rails project that uses DocumentDB database. It uses:

• Ruby 3.2.2
• Rails 7.0.8.4
• MongoID 8.1.9
• Mongo 2.21.0

and everything works fine.

After upgrading rails to version 8.0 (everything else is same) I started to get next error:

Mongo::Error::NoServerAvailable · No primary_preferred server is available in cluster: 
#<Cluster topology=ReplicaSetNoPrimary
[projectname.cluster-abc.us-west-2.docdb.amazonaws.com:27017,name=rs0] 
servers=[#<Server address=projectname.cluster-abc.us-west-2.docdb.amazonaws.com:27017 UNKNOWN>]> 
with timeout=30, LT=0.015

Any idea what could be an issue.
I tried bunch of different things but nothing worked.
Thing that confuses me the most is that I am not sure how it is related to rails gem. I can not figure it out especially because the same version of mongoid and mongo-ruby-driver works on older rails.

here is connection uri:

qa:
  clients:
    default:
      uri: "\
        mongodb://\
        <%= db_user %>\
        :<%= db_password %>\
        @<%= db_host %>\
        /<%= db_database %>\
        ?ssl=true\
        &retryWrites=false\
        &maxPoolSize=50\
        &connectTimeoutMS=200000\
        &waitQueueTimeoutMS=50000\
        &connect=direct\
        &replicaSet=rs0\
        &readPreference=secondaryPreferred\
      "

If any other info would be useful feel free to ask.

[jamis]

@jerko-culina -- I'm sorry to hear you're running into issues. Sadly, MongoDB does not guarantee any compatibility with DocumentDB; AWS has developed DocumentDB without full functional parity with our database and drivers, and does not document those differences thoroughly. We can't generally help much with DocumentDB issues, since we do not test our drivers against DocumentDB and have no experience with that database.

That said, if rediscovery of the primary is not successful when connected to DocumentDB, that could indicate a problem with DocumentDB not emitting the expected responses to heartbeats. If you can reproduce this issue when connected to MongoDB (either self-hosted, or via MongoDB Atlas), we'll be happy to take a closer look. Otherwise, you will probably have better luck reaching out to Amazon technical support.

[jerko-culina]

Thanks for reply @jamis
Yeah, I am aware that you do not test any compatibility with DocumentDB.

Thing that confuses me the most, is that same version of driver works on older rails, and I do not see how it is connected to rails itself. Especially as it is about connecting to database, which should not have any connection with rails.

[jerko-culina]

Hi @jamis, I am getting same error with MongoDB Atlas
Here is copy paste from Bugsnag:

No primary_preferred server is available in cluster: #<Cluster topology=Unknown[osnonprod.depsp.mongodb.net:27017] servers=[#<Server address=osnonprod.depsp.mongodb.net:27017 UNKNOWN>]> with timeout=30, LT=0.015

[comandeo-mongo]

@jerko-culina Do you follow our "Usage with Forking Servers" guidelines?

• Mongoid: https://www.mongodb.com/docs/mongoid/current/configuration/forking-server-config/
• Driver: https://www.mongodb.com/docs/ruby-driver/current/reference/create-client/#usage-with-forking-servers

[jerko-culina]

Hi @comandeo-mongo , thanks for answering. I am using MongoID and puma server, so I have before_fork, on_refork and on_worker_boot hooks in config/puma.rb, but still I am getting same error

[jerko-culina]

I am getting same error in Thread Pool mode. Current version of puma is 6.6.0, downgraded on version 6.5.0 (version from rails 7.0) but still getting same error.

[jerko-culina]

The problem was in ssl_ca_cert file.

• Tried to connect to MongoDB Atlas, directly using mongo-ruby-driver and it worked.
• Tried again with MongoID and it failed. On bugsnag was getting no primary prefered server available. On server in rails console was getting ssl error.
• removed ssl=true from URI but still getting error
• removed ssl_ca_cert from options and it worked.
• Not sure if it is bug or feature, but not matter if ssl=true is in URI is ssl_ca_cerf options is present, MongoID will try to connect using SSL
• Anyway, at the end it was ssl error with MongoDB Atlas, but error that was in bugsnag in fact is not real error, and that caused confusion.
• will mention this in MongoID repo.