FAQ of M103: Basic Cluster Administration category

Discussion about M103: Basic Cluster Administration

Hi everybody :wave:, welcome to M103! I am @Kushagra_Kesav, your Curriculum Services Engineer for this course. As a CSE, I help in developing MongoDB University courses, support learners, and incorporate feedback into future curriculum development.

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Good luck and happy learning!

Thanks & Regards.
Kushagra Kesav,
Curriculum Services Engineer


How to troubleshoot common errors

:information_source: Child Process Failed, exited with error number 48

Basically, code 48 indicates that newly started MongoDB could not listen to incoming connections, due to an error.

STEP 1: Try to cross verify the configuration parameters in the MongoDB configuration file.

STEP 2: Check the bindIp and port values in the IDE environment, which should be:

net:
  bindIp: localhost
  port: 27000

:information_source: “errmsg” : “Either all hostnames in a replica set configuration must be localhost references, or none must be; found 1 out of 2”

This error raises due to the replica set configuration.

STEP 1: Run the rs.initiate() and check hostname and port in the output of the following command.

STEP 2: Check the syntax of rs.add(host:port).

STEP 3: In this lab localhost is considered to be the hostname in the IDE environment. The port number for the second member of the replica set is 27001.

For example:

rs.add(“localhost:27001”)


:information_source: “About to fork child process, waiting until server is ready for connections. forked process: 446”

This error states that newly started mongod or mongos could not start listening for incoming connections due to an error.

For example:

ERROR: child process failed, exited with error number 48

STEP 1: Check for an existing running mongod instance on the same port. If there is an existing instance of mongod, please stop the instance first by using db.adminCommand('shutdown') and re-start the process.

STEP 2: If the first approach did not resolve your issue, click on the Reset Workspace button and then refresh the page. After relaunching the IDE, try to execute the command again.


:information_source: “I think the IDE is unresponsive"

Try refreshing the page or click on Reset Workspace and try to re-run the command again. Also, make sure the IDE is not active in some other tab at the same time.


:information_source: “Error: couldn’t connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused”

A connection attempt will fail or be refused if a MongoDB server is not actively listening on the specified IP address and port.

Example error using the `mongo` shell
user@M103# mongo --username m103-admin --password m103-pass

MongoDB shell version v4.0.5

connecting to: mongodb://127.0.0.1:27017/?gssapiServiceName=mongodb
2022-04-13T09:23:26.924+0000 E QUERY [js] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused :
connect@src/mongo/shell/mongo.js:328:13
@(connect):1:6

exception: connect failed

Try to specify the port 27000 in the command line. For example:

 mongosh --port 27000 -u "m103-admin" -p "m103-pass" --authenticationDatabase "admin"
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