Connecting services and hosts in Icinga2

To minimize overall configuration text it might be convenient to list all host services in the same block where the host is defined. The “apply for ” construct allows to di such thing. For example:   object Host “myhost.com” { import “generic-host-template” address = “myhost.com” vars.ipmi_address = “myhost-mgmt.com” vars.ipmi_config = “/usr/local/etc/freeipmi/ipmi_myhost.cfg” vars.service.https[“Myhost web”] = {port=8443} […]

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Battery learning on LSI controller

https://web.archive.org/web/20130729085738/http://inside.godaddy.com/learning-deal-learning/ Many RAID controllers, like our Dell PERC cards, go through a battery learning cycle which calibrates the capacity of the battery to ensure it does not unexpectedly fail. For us, this cycle occurs every 90 days. When a battery learning cycle begins, it fully charges, discharges, and then charges again, realigning the true capacity of the […]

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Working with local sendmail queue

https://www.cyberciti.biz/tips/howto-postfix-flush-mail-queue.html Under Postfix MTA, just enter the following command to flush the mail queue: # postfix flush OR # postfix -f To see mail queue, enter: # mailq OR #  sendmail -bp To remove all mail from the queue, enter: # postsuper -d ALL To remove all mails in the deferred queue, enter: # postsuper […]

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Spring inside Netty

http://findevelop.blogspot.ru/2014/02/netty.html Netty: делаем лёгкий сервер с блэкджеком и аннотациями Допустим вам нужно обрабатывать http-запросы в своём приложении… Пишем на servlet-ах! Spring!! ЕщёКакойТоФреймворк!!! A теперь нам нужно слушать websocket… Выбор сужается? А завтра потребуется добавить поддержку SMPP или какого-нибудь ещё “необычного” протокола? Рано или поздно вам прийдётся создать консольное java-приложение и начать изучать “встраиваемые” сервера. Встроить […]

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Java EL implicit objects

http://incepttechnologies.blogspot.ru/p/jsf-implicit-objects.html What are Expression Language Implicit Objects? JSF framework provides several objects related to current request being processed and/or execution environment. These objects aka Implicit Objects can be accessed at runtime in a facelet or backing bean using EL. Although you can access implicit objects using EL and JEE Servlet API as well, having predefined objects […]

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Latencies reference

https://gist.github.com/jboner/2841832 Latency Comparison Numbers ————————– L1 cache reference 0.5 ns Branch mispredict 5 ns L2 cache reference 7 ns 14x L1 cache Mutex lock/unlock 25 ns Main memory reference 100 ns 20x L2 cache, 200x L1 cache Compress 1K bytes with Zippy 3,000 ns 3 us Send 1K bytes over 1 Gbps network 10,000 ns […]

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InitV and systemd parctical notes

Nicely written reference https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sect-Managing_Services_with_systemd-Unit_Files.html Short cheat shit List services: # chkconfig –list # systemctl list-units This will show any unit that systemd loaded or attempted to load, regardless of its current state on the system. # systemctl list-units –all # systemctl list-units –all –state=inactive # systemctl list-units –type=service Since systemd will only read units that it […]

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Mutually recuresive type variable bounds

http://stackoverflow.com/questions/23248103/example-8-1-2-1-of-java-language-specificationmutually-recursive-type-variable http://www.javaadvent.com/2013/12/type-safing-the-observer-with-mutually-recursive-bounds.html A recursive type is a type that uses itself in its definition. The simplest example is the linked list: class List<T> { T value; List<T> next; } Here, List<T> is recursively defined because it uses a List<T> in its own definition. A type variable bound (Foo in <T> extends Foo) is recursive if […]

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Apache Shiro

https://shiro.apache.org http://meri-stuff.blogspot.ru/2011/03/apache-shiro-part-1-basics.html The following is a reprint from http://meri-stuff.blogspot.ru Apache Shiro, originally called JSecurity, is Java security framework. It was accepted and became Apache top level project in 2010. It aims to be powerful and easy to be used. The project is in active development with active both users and developers mailing lists. Most important areas are […]

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Running Spring application in WebLogic

http://pauldone.blogspot.ru/2010/02/weblogic-and-spring.html   WebLogic and Spring In this blog topic I describe some of the integration points that WebLogic provides for Spring based applications. I have mixed feelings about Spring. I definitely prefer its primary focus on the Dependency Injection pattern (DI) instead of the more typical JavaEE model of using the Service Locator pattern (think […]

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JDBC url format

In case of PostgreSQL it is documented here. With JDBC, a database is represented by a URL (Uniform Resource Locator). With PostgreSQL™, this takes one of the following forms: jdbc:postgresql:database jdbc:postgresql://host/database jdbc:postgresql://host:port/database In case of MySQL it is documented here. The general format for a JDBC URL for connecting to a MySQL server is as […]

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Functional data structures In Java

Also known as purely functional data structures, these are immutable and persistent. The methods of functional data structures are referential transparent. A persistent data structure does preserve the previous version of itself when being modified and is therefore effectively immutable. Fully persistent data structures allow both updates and queries on any version. Many operations perform […]

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Cipher suites in Java SE

http://www.techstacks.com/howto/j2se5_ssl_cipher_strength.html HOWTO: Distinguish the Good SSL Ciphers from the Bad in J2SE5 One of the things I am always forgetting with SSL in Java is the relationship between the names of the ssl ciphers and whether or not any particular cipher is weak, medium, strong, etc.  The tables below have been set up to provide […]

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How to check isolation level in hibernate session

import java.sql.Connection; import java.sql.SQLException; import javax.persistence.EntityManager; import javax.persistence.FlushModeType; import javax.persistence.LockModeType; import javax.persistence.Query; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import org.hibernate.cfg.Environment; import org.hibernate.jdbc.Work; import static org.junit.Assert.assertTrue; import org.junit.Test;   public class TestIsolation { @Test public void testIsolationLevel() { Connection cc = null; Session session = null; Transaction txn = null; EntityManager entityManager = entityManagerFactory.createEntityManager(); […]

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Spring contexts

Web Application context extended Application Context which is designed to work with the standard javax.servlet.ServletContext so it’s able to communicate with the container. public interface WebApplicationContext extends ApplicationContext { ServletContext getServletContext(); } Beans, instantiated in WebApplicationContext will also be able to use ServletContext if they implement ServletContextAware interface package org.springframework.web.context; public interface ServletContextAware extends Aware […]

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Basic map-filter-reduce pattern

??? JDK 7 way public interface Mapper<T, V> { public V map(T t) ; } public interface Predicate<T> { public boolean filter(T t) ; } public interface Reducer<T> { public T reduce(T t1, T t2) ; } List<Person> persons = … ; int sum = persons.map( new Mapper<Person, Integer>() { public Integer map(Person p) { […]

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