Exam 350-901 topic 1 question 43 discussion

A The message 'Connection Refused' has two main causes: Nothing is listening on the IP:Port you are trying to connect to. The port is blocked by a firewall. Source - https://serverfault.com/questions/725262/what-causes-the-connection-refused-message

Log coming from backend. Seen such issue many Times

The log message shows an error when the backend tries to add an item to the cart: MYSQLDB ERROR: Connection refused This indicates that the backend application cannot establish a connection to the database server. This error is commonly caused when the database server (in this case, likely running in its own container) is not available or has crashed. Thus, the correct answer is: A. The database server container has crashed.

correct A, the others are authorization and timeout errors.

B Not A because it would be a timeout and not refusal. Not C because it's connection that is refused and not transaction B is caused either by some limit on tcp concurrent connections or a db level limit.

A. The database server container has crashed. If the database server has crashed or is not running, any attempts to connect to it would be refused, which aligns with the "Connection refused" error message. B. The backend process is overwhelmed with too many transactions. If the backend were simply overwhelmed, you'd expect to see timeout errors or performance-related messages, not a "Connection refused" error. C. The backend is not authorized to commit to the database. Authorization issues typically result in error messages about invalid credentials or permissions, not connection refusals. D. The user is not authorized to add the item to their cart. This would typically generate an error message about authorization or access control, not a connection issue. Based on the error message "Connection refused," the most likely cause is A. The database server container has crashed. This would result in refusal of connection attempts from the backend service.

A has more sense, DB is not taking connections

Connection refused implies that the DB is UP, like a 403 error code, not like the 500 range(A)

A common reason for this error is that the database server is down or not responding, which could be due to a crash or some issue with the database server container.

A. The database server container has crashed. and C. The backend is not authorized to commit to the database. Are correct answers (and B also can be correct at certain circumstate ) If You troubleshoot Connection refused error - first step check the configuration and credentials But also important - is it works before? Yes it works fine before - "User report that they can no longer able" So question - what happened? And for this perspective A is more preferable. And finally from DevCore study guide 350-901 p 34 : If a log indicated “Connection refused” or “Connection timeout,” quite often Linux admins would blame the network (which could be true), but in reality (or highly likely), some service on a server did not start or some container crashed. Another possible reason could be a server overload.

It is C. Not A, since MySql will not reply in case of container failure. Not B, because this will be “Too many connections” error Not D, because this will be “Access denied for ..."

C Its not A. Connection refused means that the server was able to respond back to you. If you try to open a TCP connection to another host and see the error "Connection refused," it means that You sent a TCP SYN packet to the other host. Then you received a TCP RST packet in reply. RST is a bit on the TCP packet which indicates that the connection should be reset. Usually it means that the other host has received your connection attempt and is actively refusing your TCP connection, but sometimes an intervening firewall may block your TCP SYN packet and send a TCP RST back to you.

IF THE CONTAINER HAS CRASHED THE ERROR MESSAGE WOULD NOT SAY REFUSED

B. If the system is down you get request timeout, not 'Connection Refused'

A seems to be suitable.

I agree with A, but I really hate this kind of question

Strange question... the least terrible option is A indeed.