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Eliminate Application Downtime with Oracle Database and .NET

Alex Keh Gairik ChakrabortySenior Principal Product Manager Senior DirectorServer Technologies Database Administration October 25, 2018 Epsilon


Program Agenda

Application Continuous Availability

Fast Application Notification

Planned Maintenance Outages

Unplanned Outages

Real World Oracle HA .NET Experience: Epsilon

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Application Continuous AvailabilityOracle .NET Applications

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From High Availability to Continuous Availability

•Minimizes downtime

•In-flight work is lost

•Rolling maintenance at DB

•Predictable runtime performance

•Errors may be visible

•Design for single failure

•Basic HA building blocks

• Removes user perspective downtime

• In-flight work is preserved

• Maintenance is hidden

• Predictable outage performance

• Errors only if unrecoverable

• Handles multiple concurrent failures

• Builds on top of HA

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High Availability Continuous Availability


Application Continuous Availability

• Goal: Make Oracle .NET applications continuously available

– Not just Oracle DB servers

• What does that mean?

– Applications handle recoverable errors, such as DB and network failures, transparently

– Developers add no to small amounts of code to handle failures gracefully

• Benefits

– Improved end user service levels

– Less administrative time spent handling failover

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.NET


Fast Application NotificationOracle .NET Applications

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FAN in a Nut Shell

• FAN events specify what changed, where, when

– Server initiated messages

– ODP.NET apps receive these messages

– Adjusts connection behavior automatically

• ODP.NET subscribers receive FAN over either

– Oracle Notification Service (ONS): ODP.NET 12c and higher• Except unmanaged ODP.NET 12c with Oracle DB 11.2 or earlier

– AQ: ODP.NET 11g and lower

• ONS is faster, more scalable, eliminates firewall issue, supports Active Data Guard, and consolidates publish/subscribe service


FAN• Rapid notification about DB and service state changes

• Event types

– Down• Received quickly to invoke failover

– Planned Down• Drains sessions for planned maintenance with no user interruption

– Up• Re-allocates sessions when services resume

– Load % • Advice to balance sessions for RAC locally and GDS globally

– Affinity• Advice when to keep conversation locality


Planned Maintenance OutagesOracle .NET Applications

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• FAN alerts ODP.NET of impending downtime or service relocation

–ODP.NET stops allocating new connections to that DB node

– Idle connections closed

– Connections returned to the pool are closed

• Pool draining feature– Part of Fast Connection Failover (FCF)

• Shutdown commences when all connections are closed– Optionally set a maximum timeout upon which shutdown occurs

• End user experience: Little to no disruption

Planned Maintenance OutageConnection Pool Scenarios


Pool Draining

• Relocate service example

srvctl relocate service –database <unique database name> –service <service name> –drain_timeout 120 –stopoption IMMEDIATE –oldinst <existing instance>

• ODP.NET settings

– “Pooling=true” (default)

– “HA Events = true” – connection pool attribute• In ODP.NET 12.2+, set to true by default

• Recommend using Oracle Database 11.2.0.4+ and ODP.NET 11.2.0.4+

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Settings


Pool Draining

• Data Guard 12.2 adds support for pool draining

– Ex. SWITCHOVER TO <database name> [WAIT <timeout in seconds> ];

• Switchovers require primary to shut down before standby comes up

– End users may request a connection during that time

–With no available DB to serve the request, users receive timeout errors

– But this can be prevented by “pausing” ODP.NET requests

Data Guard Switchovers

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Pool Draining

• ODP.NET ServiceRelocationConnectionTimeout setting blocks incoming connection requests until standby is up or timeout expires

– Eliminates/Reduces connection timeout errors

– Set in .NET config file or OracleConfiguration class

– Default = 90 seconds

• Oracle TNSNAMES settings complementary to blocking connection requests

– RETRY_COUNT• Number of times ADDRESS list traversed before connection attempt terminates

– RETRY_DELAY• Delay in seconds between subsequent retries for a connection

Data Guard Switchovers

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RETRY_COUNT and RETRY_DELAYTNSNAMES.ORA Sample File

alias =(DESCRIPTION_LIST =

(DESCRIPTION=

(RETRY_COUNT=10)(RETRY_DELAY=5)

(ADDRESS_LIST=(ADDRESS = . . .)(ADDRESS= . . .))

(CONNECT_DATA=(SERVICE_NAME=hr_svc))) .

(DESCRIPTION=

(RETRY_COUNT=10)(RETRY_DELAY=5)

(ADDRESS_LIST=(ADDRESS = . . .)(ADDRESS=. . .))

(CONNECT_DATA=(SERVICE_NAME=hr_svc2))))

Retry while service is unavailable

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Unplanned OutagesOracle .NET Applications

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Fast Connection Failover

• FAN alerts ODP.NET of immediate DB node, service, etc. failure

–ODP.NET stops allocating new connections to failed entity

– Idle connections closed

– Active connections are closed

• Benefits (assuming another DB instance is available)

– New users do not pick up invalid connections

– No need to clear pools explicitly

Unplanned Outage

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Application Continuity (AC)

• Recover active queries and transactions seamlessly after unplanned DB outages from a recoverable error

• Masks hardware, software, network, storage errors, and timeouts

– Available with RAC, RAC One Node, and Active Data Guard

• Benefits

– AC replays in-flight work on recoverable errors

– No additional ODP.NET code required

– Transparent to end users (except for a slight delay)

Unplanned Outage


• Built in session state tracking

• Restores and enforces session state before replay

• Discovers and advances request boundaries

• Keeps mutables for SQL

• Disables side-effects

• Adapts as applications change: apps protected for the future

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DatabaseRequest

Errors/Timeouts hidden

TAC

Transparent Application Continuity (TAC)


TAC Explained

Normal Operation

• ODP.NET marks DB requests

• Server tracks session state, decides which calls to replay, disables side effects

• ODP.NET holds original calls, their inputs, and validation data

Failover Phase 1: Reconnect

• Checks replay is enabled

• Verifies timeliness

• Creates a new connection

• Checks target database is legal for replay

• Uses Transaction Guard to guarantee commit outcome

Failover Phase 2: Replay

• Restores and verifies the session state

• Replays held calls, restores mutablesautomatically

• Ensures results, states, messages match original

• On success, returns control to the application

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New with TAC


Application Continuity

• Set “Pooling=true” (default)

• “Application Continuity=true” (default) in the connection string

– New ODP.NET 12.2 attribute

• AC requires unmanaged ODP.NET and DB 12.2 or higher

• TAC requires unmanaged ODP.NET and DB 18c

ODP.NET Settings


Transaction Guard

• ODP.NET can determine whether transaction committed even upon a DB failure without custom coding

• Used by AC

• Benefit

– Ensures accurate knowledge of transaction outcome

• App can query transaction outcome

–OracleConnection properties return transaction status

–OracleLogicalTransaction class

• Requires Oracle Database 12c and ODP.NET 12c or higher


Transaction Guard Scenario

1. ODP.NET receives FAN down event or error

2. IsRecoverable=false roll backIsRecoverable=true re-submit

3. To re-submit, retrieve OracleConnection.OracleLogicalTransaction

4. Retrieve transaction status with OracleLogicalTransaction.GetOutcome

5. If committed and completed, done.If not committed nor completed, re-submit.


Transaction GuardODP.NET Catch Block Code Sample

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catch (Exception ex){

if (ex is OracleException){

// It's safe to re-submit the work if the error is // recoverable and the transaction has not been committed

if (ex.IsRecoverable && ex.OracleLogicalTransaction != null && !ex.OracleLogicalTransaction.Committed)

{// safe to re-submit work

}else{

// do not re-submit work}

}}

©2014 Epsilon. Private & Confidential

Real world experience

Eliminate application downtime using ODP.NET and Oracle Database

Gairik Chakraborty

Senior Director , Database Administration , Epsilon

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• Snapshot of Epsilon

• Real world experience of application high availability using ODP.NET and Oracle database

• Planned next steps

Agenda

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• Epsilon is all-encompassing global marketing company, we are global leader in turning data-driven marketing into personalized customer experience lasting relationships.

• More than 9000 associates and70 offices worldwide

• Largest permission-based e-mailer in the world, delivering over 75 billion emails annually

• World’s leading source of data with information covering over 1.5B individualrecords and 278M devices

• More than 2,000 global clients, including 26 of the Fortune 1009 out of 10 Top Banks8 out of 10 Top Retailers9 out of Top 10 Pharmaceutical

Companies

Epsilon at a Glance

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We deliver personalized connections, build loyalty and drive business for

brands around the world

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Application high availability using ODP.NET

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• Loyalty real time marketing solution with extreme availability , performance and scalability requirement

• Deployment should support any public cloud as well as on premises – product offering is cloud first

• Platform supports real time POS integration with average call time from 200-500ms average and each API call can have multiple ( 20 – 100 ) sql internally

• Maintenance needs to be performed while system is online

• Scalable , Reliable and highly available infrastructure along with industry standard security and auditing

High Level Business Requirements

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Challenges Before ODP.NET HA implementation

• No draining method available using dedicated connection model

• Planned maintenance required application service restart - major pain point

• No protection for application API calls during unplanned outages e.g. node failure

• Large number of dedicated connection uses higher amount of CPU and memory in application server

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Application Load Balancer

Web Servers – ODP.NET Connection Pool

Web Service Call

OLTP Batch Read only

OLTP

Service

Batch

Service

RAC Node 1 RAC Node 2

Site 1

Primary DB





Report

Service

RRAC Node 1 RRAC Node 2

Site 2

Standby DB

Scheduled maintenance: Application service placement ( RAC )


Active Data Guard

Web Service Call

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Handling Planned Maintenance

• Ensure port 6200 is open in firewall between database and application server for Fast application notification messages from ONS

• Use Connection pool with proper settings required for application

<add key="DefaultConnectionString" value="User ID=<APP_USER>;Password=<PASSWORD>;Data Source=<TNS_ALIAS>;Decr Pool Size=5;Incr Pool Size=5;Max Pool Size=200;Min Pool Size=10;HA Events=True; Load Balancing=True; Connection Timeout=40" />

• For batch workload ( which doesn’t run all the time ) , recommend to use Min Pool size 0 for complete connection draining

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• Ensure application connections are returned back to pool once work is done for smooth draining

• Set TraceOption=1 , TraceLevel=127 ( only during debugging)

for i in $( ls -l|awk '{print $9}' ); doecho filename: $icat "$i"|grep "OracleConnection"|grep -i Open|grep -i "(ENTRY)"|wc -lcat "$i"|grep "OracleConnection"|grep -i Close|grep -i "(ENTRY)"|wc -lcat "$i"|grep "OracleConnection"|grep -i Dispose|grep -i "(ENTRY)"|wc -l

done

• Disable trace before production implementation

• Resource utilization is much less while using connection pooling compared to dedicated connection

• Using ServiceRelocationConnectionTimeout along with fast connection failover ( HA events=true ) helps to hide errors during data guard switchover brownout period.

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srvctl relocate service -db t1fusn -service OLTP_SERVICE -oldinstt1fusn1 -newinst t1fusn2 -drain_timeout 20 -stopoption Immediate

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Handling Unplanned Outage

• Pre 12.2 , Transaction guard along with ODP.NET implementation can be used to handle unplanned outage

• Implementation is not out of the box and requires custom code in error handling section

• Application Continuity is out of the box solution to handle unplanned outage ( requires 12.2+ RDBMS and 12.2+ ODAC ) , uses transaction guard internally.

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Web Service Call


OLTP

Service

Batch

Service

RAC Node 1 RAC Node 2

Site 1

Primary DB




Report

Service

RRAC Node 1 RRAC Node 2

Site 2

Standby DB

Unplanned Outage: Application service placement

Active Data Guard

FAN

AC ( USES TG )

Web Service Call

FAN

AC ( USES TG )

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Handling Unplanned Outage• Connection Pool Settings

<add key="DefaultConnectionString" value="User ID=<APP_USER>;Password=<PASSWORD>;Data Source=<TNS_ALIAS>;Decr Pool Size=5;Incr Pool Size=5;Max Pool Size=200;Min Pool Size=10;HA Events=True;Load Balancing=True;Application Continuity=true;Connection Timeout=40" />

• Database Settings :

1. GRANT EXECUTE ON DBMS_APP_CONT TO <app_user>;2. GRANT KEEP SYSGUID to <app_user>;3. GRANT KEEP DATE TIME to <app_user>;4. SELECT 'grant KEEP SEQUENCE on '||sequence_owner||'.'||sequence_name||' to <app_user>;'

FROM dba_sequences WHERE sequence_owner LIKE '<schema_owner>';5. SELECT 'alter SEQUENCE '||sequence_owner||'.'||sequence_name||' KEEP;' FROM

dba_sequences WHERE sequence_owner LIKE '<schema_owner>‘;

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Handling Unplanned Outage[oracle@dc1uorclrac01 trace]$ srvctl config service -db t1fusn -service oltp_serviceService name: OLTP_SERVICE.AQ HA notifications: true.

Commit Outcome: true => Transaction Guard EnabledFailover type: TRANSACTION => Application continuity enabledFailover method:TAF failover retries: 30TAF failover delay: 5.Connection Load Balancing Goal: LONGRuntime Load Balancing Goal: SERVICE_TIME.Retention: 86400 secondsReplay Initiation Time: 300 secondsDrain timeout: 30 seconds => 12.2 and 18cStop option: immediate => 12.2 and 18c.Preferred instances: t1fusn1Available instances: t1fusn2.

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Handling Unplanned Outage

• Coverage Analysis :

Set trace : alter system set event='10602 trace name context forever, level 28:trace[progint_appcont_rdbms]:10702 trace name context forever, level 16' scope = spfile ;

Run odp.net application workload , initiate failure

Run orachk coverage analysis

./orachk -asmhome /home/oracle/jar/asm-all-5.0.3.jar -javahome /lfs/dba/java/jdk1.8.0_144 -apptrc/u01/app/oracle/diag/rdbms/t1fusn/t1fusn1/trace 1

Analyze output of orachk

Disable trace

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Special Considerations

• Kill session while Application Continuity is enabled at service level should use noreplay clause:

alter system kill session 'sid, serial#, @inst' noreplay;alter system disconnect session 'sid, serial#, @inst' noreplay;

• odp.net CONNECT_TIMEOUT must be > ((RETRY_COUNT+1) * RETRY_DELAY)

OLTP_SERVICE =(DESCRIPTION =(CONNECT_TIMEOUT= 60)(RETRY_COUNT=5)(RETRY_DELAY=5)(TRANSPORT_CONNECT_TIMEOUT=3)

(ADDRESS = (PROTOCOL = TCP)(HOST = dc1uorclrac-scan.res.prod.global)(PORT = 1521))(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = oltp_service.res.prod.global)

))

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Lessons learned

• Periodically apply Bundle Patch to avoid known issues• 12.1.0.2 => Patch 28563501 • 12.2.0.1 => Patch 28574555

• Encountered memory leak and crash from ODAC libraries. Issue was fixed after applying BP and following setting in web.config or app.config

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Lessons learned

• Observed higher resource utilization in Web Servers ( 5 – 10% , it can vary depending on workload ) after enabling application continuity

• Change in transaction guard API for 12.2c:

https://docs.oracle.com/database/122/ODPNT/release_changes.htm#GUID-2B9620E7-F8AB-47AA-935C-B6B9E4893DF6

• For Application Continuity setup, refer following :

http://www.oracle.com/technetwork/database/options/clustering/application-continuity-wp-12c-1966213.pdf

https://docs.oracle.com/database/122/ODPNT/release_changes.htm#GUID-2B9620E7-F8AB-47AA-935C-B6B9E4893DF6

http://www.oracle.com/technetwork/database/options/clustering/application-continuity-wp-12c-1966213.pdf

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Benefits after ODP.NET HA implementation

• Scheduled maintenance of Oracle technology stack can be done without disrupting business user experience. ( meet security compliance as well as uptime SLA )

• No longer application server restart required for planned maintenance or unplanned outage of oracle stack – a big relief

• CPU utilization reduced in application servers after connection pool implementation

• No application call failure even in case of unplanned outage improves user experience

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Future plans

• Plan to deploy Oracle sharding with ODP.NET driver to implement true horizontally scalable multiple cloud global solution across any region as part of Epsilons global loyalty platform deployment plan

• POC and Implementation of ODP.NET core as part of Epsilon loyalty program deployment plan using .NET core


Additional Oracle .NET Resources

OTNotn.oracle.com/dotnet

GitHubgithub.com/oracle/dotnet-db-samples/

Twittertwitter.com/OracleDOTNET

YouTubeyoutube.com/OracleDOTNETTeam

[email protected]

mailto:[email protected]


Upcoming .NET Sessions – ThursdayOnline schedule: https://bit.ly/2yXG8oQ

• Hands on Lab: Building .NET Applications with Oracle

– Thursday – 12:00 PM – 1:00 PM Marriott Marquis (Yerba Buena Level) – Salon 3 / 4

•


Questions and Answers

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eliminate application downtime with oracle …...©2014 epsilon. private & confidential real...

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