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We're going on a bug hunt! Experts Talk Manchester 2018
1. Making Software. Better.
Simple solutions to big business problems.
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2. The network
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3. We’re going on a Bug Hunt
Gerald Benischke
Software Engineer
8. Talking to Oracle Checklist
! Speak with the DBAs to check that the database is up
! Check the DB proxy that traffic is passing through
! Check whether any firewall / VPN changes were made
! Check Logs
! Check Stacktraces
! Check Metrics - and hope we’ve got decent ones!
! Check Logs Again
10. Get sidetracked - What does JMS have to do with a DB Bug?
WAR
Spring
Jms
Template
Active
MQ
Client
ELB
Camel
MQ
Bridge
Active
MQ
VPN
11. Why would that be connected?
jms.brokerUrl: "failover:(tcp://activemq-1:61616,tcp://activemq-2:61616,tcp://activemq-3:61616)?
maxReconnectAttempts=1&startupMaxReconnectAttempts=1"
October 26th 2017, 10:40:39.681 Waiting 30000 ms before attempting connection
October 26th 2017, 10:40:31.470 Attempting 1088th connect to: tcp://ip-10-10-10-217:61616
October 26th 2017, 10:40:09.623 Attempting 1084th connect to: tcp://ip-10-10-10-217:61616
October 26th 2017, 10:40:01.469 Waiting 30000 ms before attempting connection
October 26th 2017, 10:39:39.592 Attempting 1084th connect to: tcp://ip-10-10-10-25:61616
October 26th 2017, 10:39:31.434 Attempting 1087th connect to: tcp://ip-10-10-10-25:61616
October 26th 2017, 10:39:09.592 Waiting 30000 ms before attempting connection
October 26th 2017, 10:39:01.407 Attempting 1087th connect to: tcp://ip-10-10-10-217:61616
12. NO timeout?
! ActiveMQ was restarted - but bound to different DHCP addresses
! App lost connection - and waits forever in sending
15. Work on Sunday
! It works locally - against a DB running in docker
! It is broken on the server
! The settings have not been changed
! The stored procedure is the same
! The server versions are the same
! The driver versions are the same
! What else could it be?
! The logs are definitely showing the production server is
returning wrong results!
17. Oracle JDBC driver
Sets NLS_TERRITORY based on client Locale
Developer workstation was British
Server used Default Locale (US)
Fix the Application Servers settings
-Duser.language: en
-Duser.country: GB
20. Retries out of nowhere
! Backend team reports duplicate submissions
! Looking at the code, we don’t retry submissions
! What could cause it?
WAR
Http
Client
ELB
App
Proxy
VPN
28. Memory Leak Solved
! Due to corrupt data meant duplicate identifiers in a list
! A loop tried to find the “next” item in the list by identifier
and always found the first one - thereby entering an
infinite loop
! As part of the loop a Java object was added to another list
! The infinite loop kept going and adding to the list
! Eventually the JVM would only GC
! Healthcheck would kill the JVM eventually and restart
31. Entropy isn’t what it used to be
! When we moved to AWS - we experienced a dramatic
slow down in performance for SSL
! It turned out that in the old cloud the images had installed
havged package - which was missing from the new
! /dev/random blocked….
35. Thank You
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