Catalog
One . Case a
Two . Wechat accept message order
3、 … and . General instructions —key Basic operation
Four . General database operations
One . Case a
1. Baidu self-developed speech recognition service , Free for enterprises to use , Now speed limit for users , Limit Each user initiates at most per minute 10 Time call
Solution :
1. Design Counter , The number of calls is used for Control the number of business execution , as well as user id by key, The number of times of use is value
2. Get number of times before calling , Judge whether the limit is exceeded
No more than the times , Count per call +1
Business call failed , Count -1
Set the life cycle of the counter to the specified period , for example :1 second , 1 minute
As shown in the figure :
The case is as follows :
Realization 1 Growth in minutes
Solution improvements :
Cancel the determination of the maximum value , utilize incr Throw an exception if the maximum value is exceeded Every time, we should judge whether it is more than 10
Judge Is it nil
If it is , Set to MAX- Scheduled times
If not , Count +1
Business call failed , Count -1
An exception is encountered + operation Over the limit , It is considered that the usage has reached the upper limit
exceed ERR increment or decrement wouid overflow Catch the exception
Use the maximum , Make a trigger judgment
tips16:redis It is applied to time limited service settlement control
Two . Wechat accept message order
Business scenario :
After wechat receives the message , By default, the most recently received messages are set to the top , When multiple friends and followers send messages at the same time , This sort of sorting will continue to alternate
, Set repeat session settings to top . Once the user is offline , When you open wechat again , In what order should messages be displayed
Solution :
1. rely on list The data has The order To manage messages , take list Structure as a stack Use
2. Create the top and normal conversations separately independent list Manage separately
3. When a list After receiving the user message in , Send the message to the sender id from list Add… At one end list( This is set to the left )
4. Many are the same id The message is repeated Push There will be problems , Before being put on the stack, whether or not it has the current id The corresponding message , First delete the id
5. Push the top session first when pushing messages list, Then push the normal conversation list, Push finished list Clear all the data
6. The number of messages , In other words, the number of wechat users’ conversations is recorded separately with the idea of counter , Along with list Operation synchronization update
tips17:
redis be applied to Data manipulation based on time order Instead of focusing on the specific time
3、 … and . General instructions —key Basic operation
1.key General instructions and database general instructions
key features :
key It’s a character string , adopt key obtain redis Data stored in
key What operations should be designed
1. about key Operation related to its own effectiveness : Delete… For example , Determine the existence of , Get type, etc
2. Control the effectiveness of the relevant operations : For example, expiration date setting , Determine whether it is valid , Effective state switching, etc
3. about key Quick query operation , For example, query according to the specified policy key etc.
4. Delete the specified key del key
5. obtain key Whether there is exists key
6. obtain key The type of type key
key Extended operation ( timeliness )
1. by key Set expiration date
expire key seconds
pexpire key milliseconds millisecond
expireat key seconds Time stamp
pexpireat key milliseconds timestamp Time stamp
obtain key Effective time of
ttl key (time to live )
pttl key
Switch key From timeliness to permanence persist key
2.key Query operation
key Extended operation ( Query mode )
Inquire about key keys pattern
Rules for query mode
1.* Match any number of arbitrary symbols
? With an arbitrary symbol
[] Match a specified symbol
Example :
keys * Query all
keys it* Query all with it start
keys *heima Query all with heima ending
keys ??kong Query all the first two characters any , Behind heima ending
keys user? Query all with user The first and last character is arbitrary
keys u[st]1 Query all with u start , With 1 ending , Contains a middle letter ,s perhaps t
3.key Other operations of
by key Change of name
rename key newkey If there is a repetition, the result is still changed
renamenx key newkey There are repetitive results , Failed to rename without covering
sort For all key Sort
help@ generic Query the usage of related commands
Commands for viewing common groups include del,dump… Wait for the general command
Four . General database operations
1. database
key Value repetition problem
1.key It’s defined by the programmer
2.redis In use , With the increase of operation data, there will be a large number of data and corresponding bug
3. Data doesn’t differentiate between categories , Categories are mixed up , It’s easy to repeat or conflict
Solution :
1. According to business Canonical namespace
2.redis For every service Provide 16 A database , Number from 0 To 15
3. Every Data between databases are independent of each other
2.db Basic operation
Switch database
select index
Just enter the password
Data manipulation
move key db Move data warehouse to target data
Data clearing
dbsize The total amount of data in the library
flushdb eliminate db Data in the library , Default 0 Warehouse No
flushall Empty redis database
