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“Read Your Writes” Consistency: Pin to Primary After POST

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                  module ReadYourWrites
  TTL = 10

  def pin_primary!
    session[:pin_primary_until] = Time.current.to_i + TTL
  end

  def pinned_to_primary?
    session[:pin_primary_until].to_i > Time.current.to_i
  end
end

                  class SnipsController < ApplicationController
  include ReadYourWrites

  def create
    snip = current_member.snips.create!(snip_params)
    pin_primary!
    redirect_to snip
  end

  def show
    scope = pinned_to_primary? ? Snip.all : Replica.read { Snip.all }
    @snip = scope.find(params[:id])
  end
end

With replicas, a user can create a record then immediately not see it due to replication lag. A simple mitigation is to pin subsequent reads to primary for a short window after writes.

Sarah Chen

More from Sarah Chen

“Read Your Writes” Consistency: Pin to Primary After POST

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More from Sarah Chen