Replica Sets

High Availability

💡 Replica, set, EK, "BACKUP, TEAM" jaisa, hai — EK, PRIMARY, MEMBER, SAARE, WRITES, HANDLE, karta hai, aur, SECONDARY, MEMBERS, CONTINUOUSLY, SYNC, rehte, HAIN — AGAR, PRIMARY, "SICK" (DOWN) ho, jaaye, EK, SECONDARY, AUTOMATICALLY, "PROMOTE" ho, jaata hai.

Replica, set, EK, GROUP, OF, mongod, PROCESSES, hai, JO, SAME, DATA, SET, MAINTAIN, karte, HAIN — EK, PRIMARY, (WRITES, ACCEPT, karta hai) aur, MULTIPLE, SECONDARIES, (PRIMARY, se, DATA, REPLICATE, karte, HAIN).

AGAR, PRIMARY, FAIL, hota hai, AUTOMATIC, "ELECTION" hoti hai — SECONDARIES, mein, se, EK, NAYA, PRIMARY, BAN, jaata hai. YE, HIGH, AVAILABILITY, ENSURE, karta hai, MANUAL, INTERVENTION, ke, BINA.

// Replica set initiate karна (mongod instances, PEHLE, se, running):
rs.initiate({
  _id: "myReplicaSet",
  members: [
    { _id: 0, host: "mongo1:27017" },
    { _id: 1, host: "mongo2:27017" },
    { _id: 2, host: "mongo3:27017" }
  ]
});

// Status check:
rs.status();

👥

Replica, set, EK, "BACKUP, TEAM" jaisa, hai — EK, PRIMARY, MEMBER, SAARE, WRITES, HANDLE, karta hai, aur, SECONDARY, MEMBERS, CONTINUOUSLY, SYNC, rehte, HAIN — AGAR, PRIMARY, "SICK" (DOWN) ho, jaaye, EK, SECONDARY, AUTOMATICALLY, "PROMOTE" ho, jaata hai.

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⚡ झट से Recap

Replica set = mongod processes ka, group, jo, same, data, maintain, karte, hain
Primary, writes, accept, karta, hai. Secondaries, data, replicate, karte, hain
Primary, fail, hone, par, automatic, election, se, naya, primary, ban, jaata, hai

इस page में (2 subtopics)

Jab, PRIMARY, unavailable, ho, jaata hai, remaining, members, EK, "election" hold, karte, hain — MAJORITY, (jaise, 3, mein, se, 2) members, ka, VOTE, chahiye, EK, NAYA, primary, choose, karne, ke, liye. Isi, wajah, se, ODD, number, of, members, (3, 5, 7) RECOMMENDED, hai.

💡Tip: Ek, EVEN, number, of, members, (jaise, 4) se, "split, vote" scenarios, ho, sakte, hain — arbiter, (voting-only, member, without, data) add, karके, ODD, count, maintain, kiya, ja, sakta hai.

primary (default), primaryPreferred, secondary, secondaryPreferred, aur, nearest — DIFFERENT, read, preference, modes, hain, jo, decide, karte, HAIN, ki, reads, KAHAN, se, jaayenge, latency, aur, consistency, ke, trade-offs, ke, saath.

db.collection.find().readPref("secondaryPreferred");

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Code10x

Replica Sets

Election Process Details

Read Preference Modes