C100DBA · Question #119
Which of the following is a valid Replica Set configuration if you want: 1-Have 3 copies of everything 2- That RS3 is never primary 2- That RSI and RS2 can be primary? You had to see the different con
The correct answer is A. ORS1. RS1 is the only eligible candidate because it has up-to-date data (the write operations replicated to it) and no configuration restrictions preventing it from becoming primary. RS2 also received the data, but its hidden: true (or priority: 0) configuration explicitly disqualifies
Question
Which of the following is a valid Replica Set configuration if you want:
1-Have 3 copies of everything 2- That RS3 is never primary 2- That RSI and RS2 can be primary? You had to see the different configurations, RS3 could be hidden or priority 0 (But not a referee because we need 3 replicas), while RSI and RS2 could NOT have priority 0 or be hidden or anything like that In a 4-member RS RSO , RSI, RS2 and RS3 + Referee, RSO (primary) falls after some write operations that have replicated RSI and RS2 (but NOT RS3), who can get up as the new primary? The configuration comes and in it we see that RS2 has a hidden: true (or a priority: 0, (I don't remember)
Options
- AORS1
- BORS2
- CORS3
- DO arbiter
- ERSO
How the community answered
(28 responses)- A54% (15)
- B4% (1)
- C7% (2)
- D21% (6)
- E14% (4)
Explanation
RS1 is the only eligible candidate because it has up-to-date data (the write operations replicated to it) and no configuration restrictions preventing it from becoming primary. RS2 also received the data, but its hidden: true (or priority: 0) configuration explicitly disqualifies it from ever being elected primary - hidden/priority-0 nodes are invisible to clients and ineligible for election. RS3 cannot be elected because it never received the replicated writes, meaning it lacks the up-to-date oplog required to win an election. The arbiter has no data and exists solely to cast a vote - it can never hold the primary role. RS0 is the node that just went down, so it is offline and cannot participate.
Memory tip: Think of election eligibility as a two-gate test - a node must pass both the data gate (it has the latest writes) and the config gate (priority > 0 and not hidden). RS2 fails the config gate; RS3 fails the data gate; arbiters and downed nodes fail both.
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