I have 3 mongod instances located in 3 different location. Let's call them IDC A, B, C.
Now something wrong happened to IDC C. mongod instance in this IDC can't access other instances. It's still running as secondary though, which is expected behavior. However, when my application in IDC C tries to connect to this instance, I kept getting the following error:

/home/yaoxing/Workspace/image-server/node_modules/mongodb/lib/mongo_client.js:389
throw err
^
AssertionError: null ==

at /home/yaoxing/Workspace/image-server/lib/mongodb.js:28:24
at /home/yaoxing/Workspace/image-server/node_modules/mongodb/lib/mongo_client.js:386:11
at doNTCallback0 (node.js:408:9)
at process._tickCallback (node.js:337:13)
I have all the addresses of 3 instances in my connection string. although only one of them is accessible now, I don't think the error 'no valid seed servers in list' is expected behavior here. Instead, my application should connect to instance in IDC C and read whatever in this instance.