Redis主从复制(Master-Slave Replication)
案例測試：
1. Master新增網卡，修改server端配置
IP : 192.168.40.128/24
注釋： bind，支持網絡連接
2. 新建虛機slave，配置網絡，修改redis配置
#slaveof <masterip> <masterport>
slaveof 192.168.40.128 6379
# masterauth <master-password>
masterauth "zcy1991"
3. 啟動redis，打開日志
4. 查看Replication信息
Master:
Slave：
5.配置文件 “主從復制”部分 【翻譯+理解】 (Verion 3.2.8)
################################# REPLICATION (復制) #################################
-------------------------------------------
# Master-Slave replication. Use slaveof to make a Redis instance a copy of
# another Redis server. A few things to understand ASAP about Redis replication.
#主從復制。 使用slaveof使一個Redis實例成為另一個Redis服務器的拷貝（副本）。
關于Redis復制的幾個事情:
# 1) Redis replication is asynchronous, but you can configure a master to
# ? ?stop accepting writes if it appears to be not connected with at least
# ? ?a given number of slaves.
1) Redis復制是異步的，但是如果它看起來沒有與至少給定數量的slave連接，您可以配置一個主設備停止接受寫入。
# 2) Redis slaves are able to perform a partial resynchronization with the
# ? ?master if the replication link is lost for a relatively small amount of
# ? ?time. You may want to configure the replication backlog size (see the next
# ? ?sections of this file) with a sensible value depending on your needs.
2) 如果復制鏈路丟失相對較少的時間，Redis slave能夠與master執行部分重新同步。 您可能需要根據需要，使用合理的值配置replication backlog 大小（請參閱此文件的下一個操作）。
# 3) Replication is automatic and does not need user intervention. After a
# ? ?network partition slaves automatically try to reconnect to masters
# ? ?and resynchronize with them.
# 3) 復制是自動的，不需要用戶干預。 網絡分割后，slaves 自動嘗試重新連接到masters 并與它們重新同步。
# slaveof <masterip> <masterport>
# If the master is password protected (using the "requirepass" configuration
# directive below) it is possible to tell the slave to authenticate before
# starting the replication synchronization process, otherwise the master will
# refuse the slave request.
#如果master使用密碼保護（使用下面的“requirepass”配置指令），可以在開始復制同步過程之前，告訴slaves進行認證，否則master將拒絕slave連接請求。
# masterauth <master-password>
-------------------------------------------
# When a slave loses its connection with the master, or when the replication
# is still in progress, the slave can act in two different ways:
#當一個slave與master斷開連接或復制仍在進行時，slave可以采用兩種不同的方式：
# 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will
# ? ?still reply to client requests, possibly with out of date data, or the
# ? ?data set may just be empty if this is the first synchronization.
# 如果slave-serve-stale-data設置為“yes”（默認值），則slave仍將回復客戶端請求，可能使用過期數據，或者如果這是第一次同步，則數據集可能為空。
# 2) if slave-serve-stale-data is set to 'no' the slave will reply with
# ? ?an error "SYNC with master in progress" to all the kind of commands
# ? ?but to INFO and SLAVEOF.
#如果slave-serve-stale-data設置為“no”，除了INFO和SLAVEOF，slave將回復錯誤“SYNC with master in progress”給所有類型的命令。
slave-serve-stale-data yes
# You can configure a slave instance to accept writes or not. Writing against
# a slave instance may be useful to store some ephemeral data (because data
# written on a slave will be easily deleted after resync with the master) but
# may also cause problems if clients are writing to it because of a
# misconfiguration.
# 您可以配置slave實例接受寫入或不接受寫入。 對slave實例進行寫操作對存儲一些臨時數據可能是有用的（因為寫在slave上的數據將在與master重新同步后很容易被刪除），但是如果客戶端因為錯誤配置而寫入它，也會導致問題。
#
# Since Redis 2.6 by default slaves are read-only. 自2.6之后，slaves默認只讀（不可寫）
#
# Note: read only slaves are not designed to be exposed to untrusted clients
# on the internet. It's just a protection layer against misuse of the instance.
# Still a read only slave exports by default all the administrative commands
# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
# security of read only slaves using 'rename-command' to shadow all the
# administrative / dangerous commands.
# 注意：只讀slaves并不設計為了暴露給互聯網上的不受信任的客戶端。 它只是一個防止濫用實例的保護層。 Slaves默認情況下仍然可以導出所有管理命令，如CONFIG，DEBUG等。 在有限的程度上，您可以使用“rename-command”來提高只讀從設備的安全性，以隱藏所有管理/危險命令。
#作為從服務器，默認情況下是只讀的（yes），可以修改成NO，用于寫（不建議
slave-read-only yes
-------------------------------------------
# Replication SYNC strategy: disk or socket. ?復制同步策略： disk或socket
#
# -------------------------------------------------------
# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY ?警告：無磁盤的復制當前還處于試驗階段。
# -------------------------------------------------------
#
# New slaves and reconnecting slaves that are not able to continue the replication
# process just receiving differences, need to do what is called a "full
# synchronization". An RDB file is transmitted from the master to the slaves.
# The transmission can happen in two different ways:
#是否使用socket方式復制數據。目前redis復制提供兩種方式，disk和socket。如果新的slave連上來或者重連的slave無法部分同步，就會執行全量同步，master會生成rdb文件。有2種方式：disk方式是master創建一個新的進程把rdb文件保存到磁盤，再把磁盤上的rdb文件傳遞給slave。socket是master創建一個新的進程，直接把rdb文件以socket的方式發給slave。disk方式的時候，當一個rdb保存的過程中，多個slave都能共享這個rdb文件。socket的方式就的一個個slave順序復制。在磁盤速度緩慢，網速快的情況下推薦用socket方式。
#新的slaves和重新連接的slaves，不能繼續復制過程只是接收差異，需要做的就是所謂的“完全同步”。 一個RDB文件從master傳輸到slaves。
# 傳輸可以以兩種不同的方式發生：
# 1) Disk-backed: The Redis master creates a new process that writes the RDB
# ? ? ? ? ? ? ? ? file on disk. Later the file is transferred by the parent
# ? ? ? ? ? ? ? ? process to the slaves incrementally.
磁盤支持：Redis master創建一個新進程，負責將RDB文件寫入磁盤。 稍后，該文件由父進程以增量方式傳送到slaves。
# 2) Diskless: The Redis master creates a new process that directly writes the
# ? ? ? ? ? ? ?RDB file to slave sockets, without touching the disk at all.
#無盤：Redis master創建一個新的進程，直接將RDB文件寫入slaves sockets，而不觸及磁盤。
# With disk-backed replication, while the RDB file is generated, more slaves
# can be queued and served with the RDB file as soon as the current child producing
# the RDB file finishes its work. With diskless replication instead once
# the transfer starts, new slaves arriving will be queued and a new transfer
# will start when the current one terminates.
#使用"磁盤支持"的復制，在生成RDB文件時，只要生成RDB文件，當前子進程就完成了它的工作，更多的slaves就可以排隊并被提供這一份RDB文件。（可同時提供給多個slaves）
# 使用無盤復制，一旦傳輸開始，新slaves到達將排隊，并且當當前的一個終止時，新的傳輸將開始。（順序復制，一個接一個）
# When diskless replication is used, the master waits a configurable amount of
# time (in seconds) before starting the transfer in the hope that multiple slaves
# will arrive and the transfer can be parallelized.
#當使用“無盤復制”時，master在開始傳輸之前等待可配置的時間量（以秒為單位），希望多個slaves將到達并且傳輸可以并行化。
#
# With slow disks and fast (large bandwidth) networks, diskless replication
# works better. 使用慢磁盤和快速（大帶寬）網絡，無盤復制工作更好（建議socket）
repl-diskless-sync no
# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that transfers the RDB via socket
# to the slaves.
diskless復制的延遲時間，防止設置為0。一旦復制開始，節點不會再接收新slave的復制請求直到下一個rdb傳輸。所以最好等待一段時間，等更多的slave連上來。
#當啟用無磁盤復制時，可以配置服務器等待的延遲，以便產生子進程，通過socket傳輸RDB給slaves。
# This is important since once the transfer starts, it is not possible to serve
# new slaves arriving, that will be queued for the next RDB transfer, so the server
# waits a delay in order to let more slaves arrive.
#這是很重要的，因為一旦傳輸開始，不可能服務新到達的slaves，它們將為下一個RDB傳輸排隊，所以服務器等待一段時間，以便讓更多的slaves到達。
-------------------------------------
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
# 延遲以秒為單位指定，默認值為5秒。要完全禁用它，僅僅設置為0秒即可，傳輸將盡快開始。
repl-diskless-sync-delay 5
# Slaves send PINGs to server in a predefined interval. It's possible to change
# this interval with the repl_ping_slave_period option. The default value is 10
# seconds.
#slaves以預定義的時間間隔向服務器發送PING。可以使用repl_ping_slave_period選項更改此時間間隔。默認值為10秒。
#
# repl-ping-slave-period 10
-------------------------------------------
復制連接超時時間。master和slave都有超時時間的設置。master檢測到slave上次發送的時間超過repl-timeout，即認為slave離線，清除該slave信息。slave檢測到上次和master交互的時間超過repl-timeout，則認為master離線。需要注意的是repl-timeout需要設置一個比repl-ping-slave-period更大的值，不然會經常檢測到超時。
# The following option sets the replication timeout for: 設置復制timeout
#
# 1) Bulk transfer I/O during SYNC, from the point of view of slave. 從slave角度看，批量傳輸I / O在SYNC期間。
# 2) Master timeout from the point of view of slaves (data, pings). ?從slave角度看，master 超時（data,pings）
# 3) Slave timeout from the point of view of masters (REPLCONF ACK pings). 從masters角度看，slave超時（REPLCONF ACK pings）
#
# It is important to make sure that this value is greater than the value
# specified for repl-ping-slave-period otherwise a timeout will be detected
# every time there is low traffic between the master and the slave.
#重要的是確保此值大于為repl-ping-slave-period指定的值，否則每次master和slave之間的流量低時都會檢測到超時。
#
# repl-timeout 60
-------------------------------------------
是否禁止復制tcp鏈接的tcp nodelay參數，可傳遞yes或者no。默認是no，即使用tcp nodelay。如果master設置了yes來禁止tcp nodelay設置，在把數據復制給slave的時候，會減少包的數量和更小的網絡帶寬。但是這也可能帶來數據的延遲。默認我們推薦更小的延遲，但是在數據量傳輸很大的場景下，建議選擇yes。
# Disable TCP_NODELAY on the slave socket after SYNC? SYNC之后在slave socket上禁用TCP_NODELAY？
#
# If you select "yes" Redis will use a smaller number of TCP packets and
# less bandwidth to send data to slaves. But this can add a delay for
# the data to appear on the slave side, up to 40 milliseconds with
# Linux kernels using a default configuration.
#如果選擇“是”，Redis將使用較少數量的TCP數據包和較少帶寬將數據發送到從站。但是這可能會增加數據出現在對端slave上的延遲，對于Linux內核，使用默認配置可以延遲40毫秒。
# If you select "no" the delay for data to appear on the slave side will
# be reduced but more bandwidth will be used for replication.
#如果選擇“否”，數據在slave端出現的延遲將減少，但更多的帶寬將用于復制
# By default we optimize for low latency, but in very high traffic conditions
# or when the master and slaves are many hops away, turning this to "yes" may
# be a good idea.
#默認情況下，我們針對低延遲進行優化，但在非常高的流量情況下，或者當master和slave相隔許多跳時，將其轉換為“yes”可能是個好主意。
repl-disable-tcp-nodelay no
---------------------------------------
復制緩沖區大小，這是一個環形復制緩沖區，用來保存最新復制的命令。這樣在slave離線的時候，不需要完全復制master的數據，如果可以執行部分同步，只需要把緩沖區的部分數據復制給slave，就能恢復正常復制狀態。緩沖區的大小越大，slave離線的時間可以更長，復制緩沖區只有在有slave連接的時候才分配內存。沒有slave的一段時間，內存會被釋放出來，默認1m。
# Set the replication backlog size. The backlog is a buffer that accumulates
# slave data when slaves are disconnected for some time, so that when a slave
# wants to reconnect again, often a full resync is not needed, but a partial
# resync is enough, just passing the portion of data the slave missed while
# disconnected.
#設置復制backlog大小。backlog是一個緩沖器(buffer)，當slave斷開一段時間時積累slave數據，以便當slave想要再次重新連接時，通常不需要再“完全同步（full resync）”，而是“部分再同步（partial resync）”就足夠了，僅僅傳輸slave在斷開連接時錯失的那部分數據（余下的）即可。
#
# The bigger the replication backlog, the longer the time the slave can be
# disconnected and later be able to perform a partial resynchronization.
#復制backlog越大，slave可以斷開連接的時間就越長，之后就可以執行”部分重新同步（partial resynchronization）“。
# The backlog is only allocated once there is at least a slave connected. 只有在至少有一個slave連接時才分配backlog。
#
# repl-backlog-size 1mb
# After a master has no longer connected slaves for some time, the backlog
# will be freed. The following option configures the amount of seconds that
# need to elapse, starting from the time the last slave disconnected, for
# the backlog buffer to be freed.
# master沒有slave一段時間會釋放復制緩沖區的內存，repl-backlog-ttl用來設置該時間長度。單位為秒。
#在master已經不再連接slave一段時間后，backlog將被釋放。 以下選項配置需要經過的秒數，從最后一個slave服務器斷開的時間開始，backlog緩沖區被釋放。
# A value of 0 means to never release the backlog. 值為0表示永不釋放backlog
#
# repl-backlog-ttl 3600
---------------------------------
# 當master不可用，Sentinel會根據slave的優先級選舉一個master。最低的優先級的slave，當選master。而配置成0，永遠不會被選舉。
# The slave priority is an integer number published by Redis in the INFO output.
# It is used by Redis Sentinel in order to select a slave to promote into a
# master if the master is no longer working correctly.
#slave優先級是由Redis在INFO輸出中發布的整數。 它由Redis Sentinel使用，以便選擇slave，如果master不再正常工作，則升級為主設備。
# A slave with a low priority number is considered better for promotion, so
# for instance if there are three slaves with priority 10, 100, 25 Sentinel will
# pick the one with priority 10, that is the lowest.
#具有低優先級編號的slave被認為更好地用于提升，因此例如如果存在具有優先級10,100,25的三個從設備，則哨兵將選擇具有優先級10，即最低的那個。
# However a special priority of 0 marks the slave as not able to perform the
# role of master, so a slave with priority of 0 will never be selected by
# Redis Sentinel for promotion.
#然而，0的特殊優先級標志著slave不能執行主設備的角色，因此優先級為0的從設備將不會被Redis Sentinel選擇用于升級。
# By default the priority is 100.
slave-priority 100
-----------------------------------------
#
# It is possible for a master to stop accepting writes if there are less than
# N slaves connected, having a lag less or equal than M seconds.
#如果連接少于N個slave，具有小于或等于M秒的滯后，則master可以停止接受寫入。
# The N slaves need to be in "online" state.
#
# The lag in seconds, that must be <= the specified value, is calculated from
# the last ping received from the slave, that is usually sent every second.
#以秒為單位的滯后，必須小于指定值，根據從slave接收的最后一次ping計算，通常每秒發送一次。
# This option does not GUARANTEE that N replicas will accept the write, but
# will limit the window of exposure for lost writes in case not enough slaves
# are available, to the specified number of seconds.
#此選項不保證N個副本將接受寫入，但會在沒有足夠的slave可用的情況下,將丟失寫入的曝光窗口限制為指定的秒數。
# For example to require at least 3 slaves with a lag <= 10 seconds use: ?例如，至少需要3個slave，lag小于10s
#
#redis提供了可以讓master停止寫入的方式，如果配置了min-slaves-to-write，健康的slave的個數小于N，mater就禁止寫入。master最少得有多少個健康的slave存活才能執行寫命令。這個配置雖然不能保證N個slave都一定能接收到master的寫操作，但是能避免沒有足夠健康的slave的時候，master不能寫入來避免數據丟失。設置為0是關閉該功能。
# min-slaves-to-write 3
# 延遲小于min-slaves-max-lag秒的slave才認為是健康的slave
# min-slaves-max-lag 10
#設置1或另一個設置為0禁用這個特性。
# Setting one or the other to 0 disables the feature.
#
# By default min-slaves-to-write is set to 0 (feature disabled) and
# min-slaves-max-lag is set to 10. ?默認配置
# A Redis master is able to list the address and port of the attached
# slaves in different ways. For example the "INFO replication" section
# offers this information, which is used, among other tools, by
# Redis Sentinel in order to discover slave instances.
# Another place where this info is available is in the output of the
# "ROLE" command of a masteer.
# Redis master能夠以不同的方式列出所連接slave的地址和端口。 例如，“INFO replication”部分提供此信息，除了其他工具之外，Redis Sentinel還使用該信息來發現slave實例。 此信息可用的另一個地方在masterser的“ROLE”命令的輸出中。
#
# The listed IP and address normally reported by a slave is obtained
# in the following way:
#通常由slave報告的列出的IP和地址,通過以下方式獲得：
# ? IP: The address is auto detected by checking the peer address
# ? of the socket used by the slave to connect with the master.
#IP：通過檢查slave與master連接使用的套接字的對等體地址自動檢測地址。
# ? Port: The port is communicated by the slave during the replication
# ? handshake, and is normally the port that the slave is using to
# ? list for connections.
#端口：端口在復制握手期間由slavet通信，并且通常是slave正在使用列出連接的端口。
# However when port forwarding or Network Address Translation (NAT) is
# used, the slave may be actually reachable via different IP and port
# pairs. The following two options can be used by a slave in order to
# report to its master a specific set of IP and port, so that both INFO
# and ROLE will report those values.
#然而，當使用端口轉發或網絡地址轉換（NAT）時，slave實際上可以通過(不同的IP和端口對)來到達。 slave可以使用以下兩個選項，以便向master報告一組特定的IP和端口，以便INFO和ROLE將報告這些值。
# There is no need to use both the options if you need to override just
# the port or the IP address. 如果你需要僅覆蓋端口或IP地址，則沒必要使用這兩個選項。
#
# slave-announce-ip 5.5.5.5
# slave-announce-port 1234
參考資源：
? 1.redis3.0配置文件詳解?
轉載于:https://blog.51cto.com/zcyns/1903276
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