A few days ago, some water friends asked questions :

Through message queuing (MsgQueue,MQ) Send tasks and messages , In case MQ What if you restart it ? Can it be guaranteed MQ Don't lose news ?

Let's talk about it today MQ Architecture and process of message delivery .

Don't lose news ,MQ What is the core direction of architecture design ?

MQ If you want information, you will get it , There are two core design points in the architecture :

(1) News landing ;

(2) Message timeout , Retransmission , confirm ;

In order to achieve the above two core points ,MQ What is the architecture ?

The image above is a MQ Core architecture of , It can be divided into three parts :

(1) Sender -> Pink part on the left ;

(2)MQ Core cluster -> Middle blue part ;

(3) Receiver -> The yellow part of the excrement on the right ;

The pink sender consists of two parts :

(1) Business caller ;

(2)MQ-client-sender;

The latter provides two cores for the former API:

(1)SendMsg(bytes[] msg);

(2)SendCallback();

blue MQ The core cluster is divided into four parts :

(1)MQ-server

(2)zk;

(3)db;

(4) Management backstage web;

The Yellow receiver also consists of two parts :

(1) Business receiver ;

(2)MQ-client-receiver;

The latter provides two cores for the former API:

(1)RecvCallback(bytes[] msg);

(2)SendAck();

MQ It is a powerful tool for decoupling between systems , It can decouple publishing subscribers , It decouples the upstream and downstream message delivery into two parts , As in the frame composition 1 Arrow and 2 arrow :

arrow 1: The sender delivers the message to MQ, first half ;

arrow 2:MQ Post message to receiver , second half ;

MQ What is the core process of reliable message delivery ?

MQ Since we split the delivery of the message into the first and second half , In order to ensure the reliable delivery of the message , In the first half and the second half, the news must be delivered .

MQ First half of message delivery ,MQ-client-sender reach MQ-server The process is shown in the figure above 1-3:

(1)MQ-client Send message to MQ-server;

Voice over : At this point, the business side calls API:SendMsg.

(2)MQ-server Drop the news , After landing, the system is sent successfully ;

(3)MQ-server Send response to MQ-client;

Voice over : At this time, call back the business API:SendCallback.

MQ Message delivery second half ,MQ-server reach MQ-client-receiver The process is shown in the figure above 4-6:

(4)MQ-server Send message to MQ-client;

Voice over : At this time, call back the business API:RecvCallback.

(5)MQ-client Reply to MQ-server;

Voice over : At this time, the business side calls the API:SendAck.

(6)MQ-server received ack, Delete the message that has landed before , Complete the reliable delivery of messages ;

What if the news is lost ?

MQ The first and second half of message delivery , Message loss can occur , To ensure message accessibility ,MQ Timeout and retransmission are required .

How to implement overtime and retransmission in the first half ?

MQ First half 1 perhaps 2 perhaps 3 If lost or timed out ,MQ-client-sender Internal timer The message will be retransmitted
, Until you expect it 3, If retransmission N I haven't received it yet , be SendCallback Callback send failed , It should be noted that , In the process MQ-server Multiple retransmissions of the same message may be received .

How to implement overtime and retransmission in the second half ?

MQ In the second half 4 perhaps 5 perhaps 6 If lost or timed out ,MQ-server Internal timer The message will be retransmitted , Until we get it 5 And it was successfully implemented 6, This process can be repeated many times .

Voice over : Generally, the strategy of exponential backoff is adopted , Septum propria x Second retransmission ,2x Second retransmission ,4x Second retransmission , and so on .

It should be noted that , In the process MQ-client-receiver You may also receive multiple retransmissions of the same message .

summary

MQ It is a powerful tool for decoupling between systems ,MQ In order to ensure that the news will arrive , The direction of architecture design is :

(1) When the message is received, it will land first ;

(2) Message timeout , Retransmission , Confirm to ensure that the message will arrive ;

remaining problems :

first half ,MQ-server Duplicate messages may be received ; second half ,MQ-client-receiver, That is, the message receiver may receive duplicate messages , What should I do? ?

Voice over : How to remove duplicate , How to design idempotent , Listen to the live broadcast of sister Xuan .

event :《RocketMQ Enterprise application and customized development practice 》

character : Naixue Education CEO, Sister Xuan

time :6.4,6.5,6.6 Three days ,20:00-22:00

Voice over : Two hours a day , Free Admission , Is there sincerity ?

How to participate ?

Scan code and add assistant , Get live address , Send architect growth map

What about the content outline ?

(1)MQ Analysis of enterprise application scenarios ;

(2) common MQ Selection comparison ;

(3)MQ High availability and horizontal expansion architecture ;

(4)MQ In depth analysis of storage principle ;

(5)MQ Deep analysis of service registration and service discovery ;

(6)MQ Deep analysis of load balancing architecture ;

(7)MQ Principle of transaction message implementation ;

(8)MQ Principle of delay message architecture ;

(9)RocketMQ Customized development practice ;

(10) Homework and explanation ;

continuity 3 day (6.4/6.5/6.6), Every day 2 hour (20:00-22:00), Free live broadcast of sister Xuan ,MQ, A lot of dry goods , Read the original , Get live address , I can only help you get here , Let's learn together .

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