Armchair architecture

Armchair architecture anti-pattern, most common in organizations :(

From O'Reilly.

Oracle Traffic Director tuning

• Number of acceptor threads
  
  Acceptor threads receive client requests and put them in the connection queue. When an Oracle Traffic Director instance starts, it creates the specified number of acceptor threads for each listener. If the number of acceptor threads for a listener is not specified, Oracle Traffic Director creates one acceptor thread per CPU on the host.
  
  Too many idle acceptor threads place an unnecessary burden on the system, while having too few acceptor threads might result in client requests not being accepted. One acceptor thread per CPU, which is the default setting, is an acceptable trade-off in most situations.
  
  For HTTP 1.0 workloads, which necessitate opening and closing a relatively large number of connections, the default number of acceptor threads—1 per listener—would be suboptimal. Consider increasing the number of acceptor threads.
  

https://docs.oracle.com/middleware/1221/otd/admin/perf.htm#OTADG799

Description of ''Figure 14-1 Connection Handling in Oracle Traffic Director ''

Description of ''Figure 14-2 Connection Handling in Oracle Traffic Director with Keep Alive Enabled''

https://medium.com/wlsdmforweblogic/how-to-monitor-oracle-traffic-director-otd-components-and-instances-65e90c0cd3c3

inefable

inefable

 

Del lat. ineffabĭlis 'indecible'.

1. adj. Que no se puede explicar con palabras.

Stuck Threads summary

base_domain -> Environment -> Servers -> Server -> Configuration/Tuning:  Stuck Thread Max Time: 600

Stuck Thread Max Time
The number of seconds that a thread must be continually working before this server considers the thread stuck.
For example, if you set this to 600 seconds, WebLogic Server considers a thread to be "stuck" after 600 seconds of continuous use.
In Web Logic Server 9.x and later, it is recommended that you use the ServerFailureTriggerMBean in the OverloadProtectionMBean. The ServerFailureTriggerMBean transitions the server to a FAILED state after the specified number of stuck threads are detected. The OverloadProtectionMBean has options to suspend or shutdown a failed server.
MBean Attribute:
ServerMBean.StuckThreadMaxTime

base_domain -> Environment -> Servers -> Server -> Configuration/Overload:  Failure Action

Failure Action
Enable automatic forceshutdown of the server on failed state. The server self-health monitoring detects fatal failures and mark the server as failed. The server can be restarted using NodeManager or a HA agent.

base_domain -> Environment -> Servers -> Server -> Configuration/Overload:  Stuck Thread Count

Stuck Thread Count
The number of stuck threads after which the server is transitioned into FAILED state. There are options in OverloadProtectionMBean to suspend and shutdown a FAILED server. By default, the server continues to run in FAILED state.
If the StuckThreadCount value is set to zero then the server never transitions into FAILED server irrespective of the number of stuck threads.

base_domain -> Environment -> Servers -> Server -> Configuration/Overload:  Max Stuck Thread Time:

Max Stuck Thread Time
The number of seconds that a thread must be continually working before this server diagnoses the thread as being stuck.
For example, if you set this to 600 seconds, WebLogic Server considers a thread to be "stuck" after 600 seconds of continuous use.
MBean Attribute: ServerFailureTriggerMBean.MaxStuckThreadTime

-->   ServerFailureTriggerMBean.MaxStuckThreadTime >>  ServerMBean.StuckThreadMaxTime


more info:

http://www.munzandmore.com/2012/ora/weblogic-stuck-threads-howto

https://docs.oracle.com/cd/E14571_01/apirefs.1111/e13952/pagehelp/Corecoreserverservermonitorthreadstitle.html

Capacity Planning

from Thinking Architecturally by Nathaniel Schutta

Java String.intern()

Although it's an old method/behavior, this feature is not very popular.
Java String has .intern() that points directly to String constant pool (pool of pointers, as C pointer) and can be used == instead .equals()(and it's faster)

More info:
https://www.geeksforgeeks.org/interning-of-string/

XAER_NOTA - DISTRIBUTED_LOCK_TIMEOUT

Several XAER_NOTA messages seen in the logs could be caused by not honoring:

DISTRIBUTED_LOCK_TIMEOUT (set on DB) > XA Transaction (connection) Timeout > WebLogic Server JTA timeout

netstat cheat sheet

Para ver conexiones tcp:

netstat -s -P tcp

ver un puerto en específico:

netstat –anp | grep puerto_admin

Mac:

netstat -an | grep -i 7001


----

A number of useful tools which can be used are netstat (to determine the number of sockets in TIME_WAIT state, for example by using, netstat –a | grep TIME_WAIT | wc –l) or iostat (to determine disk I/O on the operating system, for example, iostat 5 5). Note that iostat is part of the sysstat package, which can be installed by using: yum -y install sysstat.  
Networking linux:

https://upcloud.com/community/tutorials/troubleshoot-network-connectivity-linux-server/
https://geekflare.com/linux-networking-commands/
https://likegeeks.com/linux-network-commands/


 

Klondike Returns

Since 90s from college I read the old article of Martin Gardner from Scientific American.
This problem probably has been one of the most famous I have seen through the years, it appears with its own frequency.

With the original problem there are hundreds of solutions, some of them are

1. W W W E SW E NW SW NE NE NE SW SW SW NW
2. NW SE W SE SE W NW SW NE NE NE SW SW SW NW
3. N W E SW S E NW SW NE NE NE SW SW SW SE
4. NE W S SW S E NW SW NE NE NE SW SW SW SE
5. E W S SE S NW NW SW NE NE NE SW SW SW NW
6. SE W NW SE W W NW SW NE NE NE SW SW SW NW
7. S W E SW W NW SW NE NE NE SW SW SW NW


And with the troublesome fixed there are only two solutions:

SW SW NE NE NE SW SW SW NW
SW SW NE NE NE SW SW SW SE


I made Yet Another Search Program for it. where the troublesome 2 from Gardner article is verified, but I found a if we change (besides of the 2 mentioned) number 4 at (x,y) then there will be only one solution.

But there is a new probable modification I found to make the puzzle with an unique solution, which would be

Turing secret number

The secret Turing number: 885205232

As century of Turing ... birthday ? there are several events and commemorations...

This was revealed by Professor Knuth in the lecture in the UK .... twitter.

https://www-cs-faculty.stanford.edu/~knuth/news12.html

For the secret of the Turing number 885205232, see pages 45 and 53 of Selected Papers on Fun and Games.