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Presented at
What every DBA needs to know
about JDBC connection pools
Bridging the language barrier between DBA and Middleware
Administrators
Jacco H. Landlust
Platform Architect Director
Oracle Consulting NL, Core Technology
October, 2014
Copyright © 2014 Oracle and/or its affiliates. All rights reserved. |
Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
3
Program Agenda
Terminology
Connection Pool configuration
Perhaps some other helpful topics
Q&A
4
Terminology
Ensure you are talking the same language as your middleware friends
5
WebLogic Terminology
Domain
Machine A
Machine B
AdminServer
Managed Server
Cluster
Node Manager
Managed Server
Managed Server
Node Manager
6
Resources and Services within a Domain
• Can be target at One or Multiple Managed Servers
• Examples:
– application components, such as EJBs
– security providers
– resource adapters
– diagnostics and monitoring services
– JDBC data sources
– JMS servers or other messaging resources
– persistent store
7
Data source
• A Data Source object is the representation of a data source in the Java
programming language. In basic terms, a data source is a facility for storing
data
• An object that implements the Data Source interface will typically be
registered with a naming service based on the Java Naming and Directory
Interface (JNDI) API
• The Data Source interface is implemented by a driver vendor (in this
presentation examples are based on Oracle’s driver)
8
Data source; 3 types of implementations
• Basic implementation — produces a standard Connection object
• Connection pooling implementation — produces a Connection object that
will automatically participate in connection pooling. This implementation
works with a middle-tier connection pooling manager
• Distributed transaction implementation — produces a Connection object
that may be used for distributed transactions and almost always
participates in connection pooling. This implementation works with a
middle-tier transaction manager and almost always with a connection
pooling manager.
9
Distributed transactions (XA)
• “eXtended Architecture”, An X/Open group standard
• For executing a "global transaction" that accesses more than one back-end
data-store, thus XA is a type of transaction coordination
• Two-phase commit (2PC)
10
Be alarmed if your developer calls every transaction distributed
11
Java Transaction API (JTA)
• Enables distributed transactions to be done across multiple XA resources
• Can even be cross domain (warning: complicated setup!)
• Configuration settings for JTA are applicable at the domain level. This
means that configuration attribute settings (e.g. timeout) apply to all
servers within a domain
• Monitoring and logging tasks for JTA are performed at the server level
• Configuration settings for participating resources (such as JDBC data
sources) are per configured object
12
Data sources in Oracle WebLogic Server
• Generic
• Multi-Data source
• Gridlink
13
Generic Data source
• Provide connection management
processes that help keep your
system running efficiently
WLS
• Connects to a specific database
(service)
Generic DS
• Contains a pool of database
connections that are created when
the data source is created and at
server startup
RDBMS
14
Multi-Data source
• Abstraction around a group of
generic data sources
• The multi data source determines
which data source to use to satisfy
the request depending on the
algorithm selected in the multi data
source configuration: load balancing
or failover
WLS
Multi DS
Generic DS
INST1
Generic DS
RAC
INST2
15
Gridlink Data source
• Event-based data source that
adaptively responds to state changes in
an Oracle RAC instance
WLS
• Key foundation for providing deeper
integration with Oracle RAC
Gridlink DS
• Responds to FAN events to provide Fast
Connection Failover (FCF), Runtime
Connection Load-Balancing (RCLB), and
RAC instance graceful shutdown
• XA affinity is supported at the global
transaction ID level
INST1
RAC
INST2
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A GridLink data source uses Fast Connection Failover to:
• Provides rapid failure detection
• Abort and remove invalid connections from the connection pool
• Perform graceful shutdown for planned and unplanned Oracle RAC node
outages
• Adapt to changes in topology, such as adding or removing a node
• Distribute runtime work requests to all active Oracle RAC instances,
including those rejoining a cluster
17
Runtime Connection Load Balancing allows WebLogic
Server to:
• Adjust the distribution of work based on back end node capacities such as
CPU, availability, and current workload
• React to changes in Oracle RAC topology
• Manage pooled connections for high performance and scalability
18
XA affinity
• Performance feature that ensures that all database operations performed
on a RAC cluster within the context of a global transaction are directed to
the same RAC instance.
• Do not confuse this with DTP services!
• Will be established based on the global transaction id, instead of by
individual data source, to ensure that connections obtained from different
data sources that are configured for the same RAC cluster are all associated
with the same RAC instance..
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Use Gridlink whenever using RAC*
20
Connection pools
Cache of database connections maintained so connections can be reused when future
requests to the database are required
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Connection properties: JDBC URL
jdbc:oracle:<drivertype>:@<connection data>
thin|oci
@host:port:instance
@host:port/service
@ldap://host:port/entry,cn=OracleContext,dc=com
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Connection properties: JDBC URL & SCAN usage
• Requires 11.2.0.2 JDBC Driver
• Included in WebLogic version 10.3.4 and newer
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Connection Pool: Capacity
• Settings are per managed server
• Available settings: Initial, Min, Max
• Direct link to processes parameter configured per database instance:
PROCESSES = ( #ManagedServers * MAX) + 30*
• Test what happens if your application runs out of connections!
24
Consider using a value of 5000 operating
system processes to be connected to
Oracle concurrently
Fusion Middleware Performance and Tuning Guide 11g Release 1
25
Connection Pool: Capacity Management
Set Shrink frequency to manage
aggressive capacity management
(default 900 seconds)
Set Inactive Connection Timeout to
return unused connections
(default 0 = disabled)
Set Login Delay to prevent logon
storm (default 0)
26
Connection Pool: Pinned to Thread
• Minimize the time it takes for an application to reserve a database
connection from a data source
• Eliminates contention between threads for a database connection
• Do not use in combination with Multi Data Sources
• Maximum Capacity is ignored
• Shrinking does not apply
• When you Reset a connection pool, the reset connections from the
connection pool are marked as Test Needed.
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Connection Pool: Row Prefetching
• Every time an application asks the driver to retrieve a row from the
database, several rows are prefetched with it and stored in client-side
memory. In this way, several subsequent requests do not have to execute
database calls to fetch data
• Default disabled at data source level
• Some memory structures are pre-initialise to hold the full prefetch size.
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Configure prefetch size at per-query basis
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Connection Pool: Statement Cache
• Size of cache is 1:1 related to OPEN_CURSORS database parameter
• Type [LRU|Fixed]:
– LRU: After the Statement Cache Size is met, the Least Recently Used statement is
removed when a new statement is used
– Fixed: The first Statement Cache Size number of statements is stored and stay fixed in
the cache. No new statements are cached unless the cache is manually cleared or the
cache size is increased.
30
Connection Pool: Test Connections on Reserve
• Test each connection before giving to a client
• Adds slight delay to the request
• Seconds to Trust an Idle Pool Connection setting to minimize delay
• Only use dual for test SQL table to minimize unnecessary LIO
31
Connection Pool: Statement Timeout
• The time after which a statement currently being executed will time out.
• A value of -1 disables this feature
• A value of 0 means that statements will not time out
• Statement Timeout <= JTA
• This will not kill the database session/transaction! So load on database
server will remain.
32
Connection Pool: XA transaction timeout
• Whenever the timeout has been reached, an error will be thrown at the
client starting the transaction. The actual transaction will be rolled back.
The actual error is:
ORA-02049 timeout: distributed transaction waiting for lock
• XA Transaction Timeout <= DISTRIBUTED_LOCK_TIMEOUT
• Extra privileges required for monitoring:
– dba_2pc_pending, dba_2pc_neighbors
– dba_pending_transactions
– v$global_transactions
33
Other helpful topics
Some semi-random topics that might be helpful when working with WebLogic and JDBC
34
Use jnettrace.jar to Debug Connectivity issues
• java -jar jnettrace.jar <Database Server Host> <Database Server Port>
<JavaNet_Port>
• http://www.oracle.com/technetwork/database/enterpriseedition/jnettrace.jar
35
JDBC persistent stores
You can configure a persistency store to use JDBC for TLOGs and JMS, which
provides the following benefits:
• Leverages replication and HA characteristics of the underlying database.
• Simplifies disaster recovery by allowing the easy synchronization of the
state of the database and JMS/TLOGs.
• Improved Transaction Recovery service migration as the JMS mssages /
Transaction Logs to do not need to be migrated (copied) to a new location.
36
Hints when configuring JDBC persistent stores
• Default store used long raw data type, have your MW admin configure
“Create Tables from DLL file” to oracle_blob_securefile.ddl
• Configure WorkerCount (a.k.a. I/O multithreading)
• Setup reverse index on primary key of persistent store
• Setup hash partition on persistent store table
• Persistent stores for JMS tables should use MDS instead of Gridlink.
37
WebLogic 10.3.6 and newer in HA scenario’s:
use JDBC based persistent stores
38
Rolling Upgrades at Database level
• Data source must run against service
• Failover service before shutdown of instance
• Let connection dry out (= wait)
• Stop instance, patch and start instance
• Repeat for other instances
39
Wrap data types
If something like this shows up in the log file of WebLogic:
java.lang.ClassCastException: WebLogic.jdbc.wrapper.Blob_oracle_sql_BLOB
at
oracle.ifs.server.S_LibrarySession.getTokenCredentialBlob(S_LibrarySess
ion.java:23888)
You do not have a database issue, you have a WebLogic issue:
Disable wrap data types
40
WLS provides the ability to disable wrapping which provides
the following benefits
• Although WLS generates a dynamic proxy for vendor methods that
implement an interface to show through the wrapper, some data types do
not implement an interface. For example, Oracle data types Array, Blob,
Clob, NClob, Ref, SQLXML, and Struct are classes that do not implement
interfaces. Disabling wrapping allows applications to use native driver
objects directly.
• Eliminating wrapping overhead can provide a significant performance
improvement.
41
Ignore in use connections upon shutdown
• Default enabled
• Can kill in-flight transactions, and therefore jeopardize RPO=0 theories
• When disabled shutdown can take (very) long time.
42
Currently, Oracle Fusion Middleware
does not support configuring Oracle
Active Data Guard for the database
repositories that are a part of the
Fusion Middleware topology.
From: Disaster Recovery for Oracle Exalogic Elastic Cloud
43
Oracle Fusion Middleware SOA does not
support Oracle Active Data Guard
because the SOA components execute
and update information regarding SOA
composite instances in the database as
soon as they are started.
From: Best Practices for Oracle Fusion Middleware SOA 11g Multi
Data Center Active-Active Deployment
44
Exadata / Exalogic
• Pass startup options to Managed Server:
-Djava.net.preferIPv4Stack=true
-Doracle.net.SDP=true
• Change protocol from TCP to SDP n JDBC_URL
• No SCAN on SDP
• Monitoring SDP Sockets Using sdpnetstat on Oracle Linux
45
Questions?
and hopefully also some answers
46
47

How to Use the PowerPoint Template

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