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Connecting services and hosts in Icinga2

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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} […]

Unix

Battery learning on LSI controller

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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 […]

Linux

Working with local sendmail queue

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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 […]

Java

Spring inside Netty

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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 […]

Java

Java EL implicit objects

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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 […]

General programming

Source code control for database schema

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http://www.liquibase.org The easiest way to run Liquibase is to set it to run automatically on startup. Once set up, your database state always matches what your code expects and you have no manual steps to forget. This method works best in environments where you have less control over the deployment process or if you want […]

General programming

Latencies reference

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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 […]

Linux

InitV and systemd parctical notes

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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 […]