Python Database connection Pool dbutils

Dbutils is a Python module that implements database connection pooling.

There are two modes of connection for this connection pool:

• Mode one: Creates a connection for each thread, and the thread does not close even if the Close method is called, but simply puts the connection back into the connection pool for its own thread to use again. When the thread terminates, the connection is automatically closed.

• POOL =Persistentdb (creator=pymysql,#modules that use linked databasesMaxusage=none,#the maximum number of times a link is reused, none means unlimitedSetsession=[],#a list of commands to execute before starting the session. such as: ["Set Datestyle to ...", "Set time zone ..."]ping=0,#Ping the MySQL server to check if the service is available. # for example: 0 = None = never, 1 = default = Whenever it is requested, 2 = When a cursor is created, 4 = When a query is executed, 7 = Alwayscloseable=False,#If False, Conn.close () is actually ignored for the next use, and the link is automatically closed when the thread is closed. If True, Conn.close () closes the link, and then calls Pool.connection again with an error, because the connection is actually closed (pool.steady_connection () can get a new link)Threadlocal=none,#This thread is exclusive to the object that holds the linked object, if the linked object is resethost='127.0.0.1', Port=3306, the user='Root', Password='123', Database='Pooldb', CharSet='UTF8')deffunc (): Conn= Pool.connection (shareable=False) Cursor=conn.cursor () cursor.execute ('SELECT * from TB1') Result=Cursor.fetchall () cursor.close () Conn.close () func ()

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• Mode two: Create a batch of connections to the connection pool for all threads to share with.
  PS: Because the threadsafety value of Pymysql, MYSQLDB, etc. is 1, the threads in this mode connection pool are shared by all threads.

• Import TimeImportPymysqlImportThreading fromDbutils.pooleddbImportPooleddb, Shareddbconnectionpool=Pooleddb (creator=pymysql,#modules that use linked databasesMaxconnections=6,#the maximum number of connections allowed for a connection pool, 0 and none means no limit on the number of connectionsmincached=2,#at least 0 of the free links created in the link pool are not created when initializingMaxcached=5,#most idle links in the link pool, 0 and none are not limitedMaxshared=3,#The maximum number of links shared in a linked pool, 0 and none means sharing all. PS: Useless, because Pymysql and mysqldb modules such as threadsafety are 1, all values regardless of set to how much, _maxcached forever is 0, so forever is all links are shared. Blocking=true,#If there are no available connections in the connection pool, wait is blocked. True, wait, False, not wait and then errorMaxusage=none,#the maximum number of times a link is reused, none means unlimitedSetsession=[],#a list of commands to execute before starting the session. such as: ["Set Datestyle to ...", "Set time zone ..."]ping=0,#Ping the MySQL server to check if the service is available. # for example: 0 = None = never, 1 = default = Whenever it is requested, 2 = When a cursor is created, 4 = When a query is executed, 7 = Alwayshost='127.0.0.1', Port=3306, the user='Root', Password='123', Database='Pooldb', CharSet='UTF8')deffunc ():#detects if the number of currently running connections is less than the maximum number of links, if not less than: Waits or reports raise Toomanyconnections exception    #otherwise    #gets the link steadydbconnection in the link created when the initialization is prioritized.     #The Steadydbconnection object is then encapsulated into the pooleddedicateddbconnection and returned.     #if the link you initially created is not linked, create a Steadydbconnection object and encapsulate it in pooleddedicateddbconnection and return.     #once the link is closed, the connection is returned to the connection pool for subsequent threads to continue to use. conn =pool.connection ()#print (th, ' link was taken away ', Conn1._con)    #print (Th, ' currently in the pool ', Pool._idle_cache, ' \ r \ n ')cursor=conn.cursor () cursor.execute ('SELECT * from TB1') Result=Cursor.fetchall () conn.close () func ()

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  If there is no connection pool, using Pymysql to connect to the database, single-threaded application is completely no problem, but if it involves multi-threaded application then need to lock, once the lock then the connection will be queued, when the request more time, performance will be reduced.

• #!/usr/bin/env python#-*-coding:utf-8-*-ImportPymysqlImportThreading fromThreadingImportRlocklock=rlock () CONN= Pymysql.connect (host='127.0.0.1', Port=3306, the user='Root', Password='123', Database='Pooldb', CharSet='UTF8')defTask (ARG): With Lock:cursor=conn.cursor () cursor.execute ('SELECT * from TB1') Result=Cursor.fetchall () cursor.close ( )Print(Result) forIinchRange (10): T= Threading. Thread (Target=task, args=(i,)) T.start () locking

  Locking

  #!/usr/bin/env python#-*-coding:utf-8-*-ImportPymysqlImportThreadingconn= Pymysql.connect (host='127.0.0.1', Port=3306, the user='Root', Password='123', Database='Pooldb', CharSet='UTF8')defTask (ARG): Cursor=conn.cursor () cursor.execute ('SELECT * from TB1') Result=Cursor.fetchall () cursor.close ( )Print(Result) forIinchRange (10): T= Threading. Thread (Target=task, args=(i,)) T.start () no Lock (Error)

  no Lock (Error)

Python Database connection Pool dbutils