fact-read-concern-write-timeline.rst

Consider the following timeline of a write operation Write₀ to a three member replica set:

Note

For simplification, the example assumes:

• All writes prior to Write₀ have been successfully replicated to all members.
• Write_prev is the previous write before Write₀.
• No other writes have occurred after Write₀.

Time	Event	Most Recent Write	Most Recent w: "majority" write
t0	Primary applies Write0	Primary: Write0 Secondary1: Writeprev Secondary2: Writeprev	Primary: Writeprev Secondary1: Writeprev Secondary2: Writeprev
t1	Secondary1 applies write0	Primary: Write0 Secondary1: Write0 Secondary2: Writeprev	Primary: Writeprev Secondary1: Writeprev Secondary2: Writeprev
t2	Secondary2 applies write0	Primary: Write0 Secondary1: Write0 Secondary2: Write0	Primary: Writeprev Secondary1: Writeprev Secondary2: Writeprev
t3	Primary is aware of successful replication to Secondary1 and sends acknowledgement to client	Primary: Write0 Secondary1: Write0 Secondary2: Write0	Primary: Write0 Secondary1: Writeprev Secondary2: Writeprev
t4	Primary is aware of successful replication to Secondary2	Primary: Write0 Secondary1: Write0 Secondary2: Write0	Primary: Write0 Secondary1: Writeprev Secondary2: Writeprev
t5	Secondary1 receives notice (through regular replication mechanism) to update its snapshot of its most recent w: "majority" write	Primary: Write0 Secondary1: Write0 Secondary2: Write0	Primary: Write0 Secondary1: Write0 Secondary2: Writeprev
t6	Secondary2 receives notice (through regular replication mechanism) to update its snapshot of its most recent w: "majority" write	Primary: Write0 Secondary1: Write0 Secondary2: Write0	Primary: Write0 Secondary1: Write0 Secondary2: Write0