Those who are looking for scaling their cache server horizontally (redis/memcached) can use twemproxy. It is created by twitter:

https://github.com/twitter/twemproxy

#cache #redis #memcached #twemproxy

If you are a python programmer tell me which return is actually returned? :D

def test():
         try:
                 return 'Inside try block'
         except:
                 return 'Inside Exception'
         finally:
                 return 'Finally block'

 print test()

#python #try #except #finally

How to monitor network cards on Icinga2? (part-1)

Yesterday I've been on a task of monitoring network cards of all our servers and infrastructure to check the bandwidth in/out and send alarms based on some criteria. In Icigna2 we have a library from nagios called check_nwc_health. Download the script from https:// labs.consol.de/nagios/check_nwc_health/index.html.

Move the script to /usr/lib/nagios/plugins on a server that you have installed Icinga2. If you run it all alone you will get some helps that you could be useful.

Some important usages of the script:

- list interfaces of a specific server (we assume snmp has been installed on the destination server):

./check_nwc_health --mode list-interfaces --hostname YOUR_TARGET_SERVER_IP  --community YOUR_COMMUNITY_STRING

The output would be something like below (it can be different in your case):

000001 lo
 000002 Device 1af4:0001 2
 000003 Device 1af4:0001 3
 000004 docker0
 OK - have fun

The interface name is given in front of serial numbers which is lo, Device 1af4:0001 2 or docker0. These interface names are important and will be used in icinga2 to add network card to hosts.


Another mode for the script is interface-usage that shows in/out bandwidth. The output can be something like follow:

OK - interface Device 1af4:0001 2 (alias eth0) usage is in:0.00% (7058.67bit/s) out:0.00% (5603.67bit/s) | 'Device 1af4:0001 2_usage_in'=0%;80;90;0;100 'Device 1af4:0001 2_usage_out'=0%;80;90;0;100 'Device 1af4:0001 2_traffic_in'=7058.67;0;0;0;0 'Device 1af4:0001         2_traffic_out'=5603.67;0;0;0;0

OK, the important part is over and we can list all server network interfaces plus the usage of a specific network interface. In the next part we will explain the Icinga2 part to add the command and the service to icinga2.


#icinga2 #icinga #nagios #check_nwc_health #network #monitor

How to monitor network cards on Icinga2? (part-2)

Ok for now we have added the plugin to nagios folder and ran some tests on target server's network interfaces. We need to add a command to Icinga2 to use it in service section of Icinga2. To create a new command create a new file in /etc/icinga2/conf.d/commands/check_nwc_command.conf and with the following content:

object CheckCommand "YOUR_COMMAND_NAME" {
     import "plugin-check-command"
     command = [ PluginDir + "/check_nwc_health", "--mode", "interface-usage" ]
     arguments = {
         "-H" = "$address$"
         "-C" = "$community$"
         "--name" = "$int$"
     }
 }

In brief it creates a new command called YOUR_COMMAND_NAME that calls the script check_nwc_health with interface-usage argument to get the bandwidth data.


Now we need to use this command in a service. We have to create a new service which will be used in our hosts configuration sections /etc/icinga2/conf.d/services/if_traffic.conf:

apply Service for (display_name => config in host.vars.int) {
     import "generic-service"
     check_command = "YOUR_COMMAND_NAME"
     vars += config
     assign where host.vars.int
 }

Again in brief the service will be applied on hosts that have a variable section of int in their configuration that we will see a little bit later. YOUR_COMMAND_NAME is the name that we have given in the first part when creating the command.


The final part is to add this service to your desired host. Go to /etc/icinga2/conf.d/hosts and open the file which relates to your host. Host files content start with:

object Host "host-54 (Infra)" {

Add the service like below into your host:

vars.int["YOUR DISPLAY NAME"] = {
     int = "Device 1af4:0001 2"
     community = "YOUR SERVER COMMUNITY STRING"
 }

int is the part that we give the interface name, this should be given from the output of list-interfaces in part-1.

You can go even further like me :) and add these data into Grafana dashboard to have a better understanding of what is happening around you.

#icinga2 #icinga #service #host #command #nagios #interface #network

#grafana #network #network_throughput

I can talk about Icinga2 for about a book! From memory, CPU, disk usage monitoring to even creating custom plugins with python or other languages to monitor your specific use case (Let's you want to monitor your microservice modules).

Maybe in the future I do so! :)

One of the greatest examples of Geospatial queries is MongoDB's tutorial about finding the nearest restaurant. This example can be applied to online taxis like Snapp, tap30 or some social networks. Read the below article if you are crazy as hell to learn new things like me :)


https://docs.mongodb.com/manual/tutorial/geospatial-tutorial/

#mongodb #mongo #geospatial #geoWithin #geoNear #geo #2dsphere #geoIntersects

در طول دوره کاری خود بارها با بحث تغییر نیازمندیهای بیزینس مواجه شده ام و در تمامی موارد به جرات می توانم بگویم که هر زمانی که تغییر نیازمندی باعث تغییر زیاد در ماژولها میشود و من از انجام تغییر از راه میانبر و به قولی کثیف پیش برده ام یکجا همون قضیه یقه من راه گرفته (bite in the ass) و هر بار که تغییر مورد نظر با اینکه زیاد هم بوده انجامش داده ام توانستم که به بهترین نحو مسئله را حل کنم و در آینده هم خودم از کارم راضی بودم.

نکته مهم قضیه این هست که همیشه مدیران عامل به سریعترین وجه ممکن خروجی را از شما میخواهند، در این گونه مواقع سریع تسلیم نشوید و کار کثیف و میانبر که بد هست را انجام ندهید. مدیر عامل فردی ست مثل شما با آنها صحبت کنید و بگویید به این دلایل زمان بیشتری میخواهید و باید به این صورت انجام شود وگرنه در آینده به مشکل میخوریم، در اکثر موارد موفق می شوید که زمان بیشتری بخرید و کار را بصورت درست انجام دهید. در کنار زمان، این مسئله به اخلاق برنامه نویسی نیز بازمیگردد و برخی افراد حوصله کار زیاد والبته درست را ندارند!!! عجیب است ولی خود من هم تا چند سال پیش در همین دسته جای میگرفتم.

نکته اینجاست که اخلاقتون رو خوب کنید :)
و نکته بعد این هست که با مدیران خود صحبت کنید و آنها را در قبال کاری که میکنید توجیح کنید.

#دلنوشته

https://medium.com/@psamim/performance-tips-to-have-in-mind-while-writing-react-components-1f387adce7a5

#react #reactjs

https://askubuntu.com/questions/919054/how-do-i-run-a-single-command-at-startup-using-systemd

#linux #systemd #systemctl #service

Upgrade mongoDB from 3.4 to 3.6:

Here we persume you are on debian 8 jessie.

1- import public key:

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv                        2930ADAE8CAF5059EE73BB4B58712A2291FA4AD5

2- create apt sources file:

echo "deb http://repo.mongodb.org/apt/debian jessie/mongodb-org/3.6 main" | sudo tee /   etc/apt/sources.list.d/mongodb-org-3.6.list

3- update repo

sudo apt-get update

4- install the MongoDB packages

sudo apt-get install -y mongodb-org=3.6.2 mongodb-org-server=3.6.2 mongodb-org-shell=3.  6.2 mongodb-org-mongos=3.6.2 mongodb-org-tools=3.6.2

* it will ask for config overwrite, if you want to take backup take a backup from config and then overwrite it.


#mongodb #mongo #mongodb36 #database #upgrade #mongodb34

Read on more: https://docs.mongodb.com/manual/tutorial/install-mongodb-on-debian/

Check grants of a specific user on MySQL:

SELECT sql_grants FROM common_schema.sql_show_grants WHERE user='app';

Please make sure that you have permissions on getting grants list, otherwise permission denied will be returned back.

#mysql #grants #sql_grants #database

Did you know that the mongoDB shell is a full-featured JavaScript interpreter, capable of running arbitrary JavaScript programs? To illustrate this, let’s perform some basic math:

> x = 200
 200
 > x / 5;
 40

We can also leverage all of the standard JavaScript libraries:

> Math.sin(Math.PI / 2);
 1
 > new Date("2010/1/1");
 "Fri Jan 01 2010 00:00:00 GMT-0500 (EST)"
 > "Hello, World!".replace("World", "MongoDB"); Hello, MongoDB!

We can even define and call JavaScript functions. In previous posts we explained how to kill slow queries, there we explained how to define a function in MongoDB and store that function inside of MongoDB.


#mongodb #mongo #shell #javascript #js

You can read more about mongoDB functions here...

OperationalError: (2013, 'Lost connection to MySQL server during query')

Usually it indicates network connectivity trouble and you should check the condition of your network if this error occurs frequently. If the error message includes “during query,” this is probably the case you are experiencing.

Sometimes the “during query” form happens when millions of rows are being sent as part of one or more queries. If you know that this is happening, you should try increasing net_read_timeout from its default of 30 seconds to 60 seconds or longer, sufficient for the data transfer to complete.

More rarely, it can happen when the client is attempting the initial connection to the server. In this case, if your connect_timeout value is set to only a few seconds, you may be able to resolve the problem by increasing it to ten seconds, perhaps more if you have a very long distance or slow connection. You can determine whether you are experiencing this more uncommon cause by using SHOW GLOBAL STATUS LIKE 'Aborted_connects'. It will increase by one for each initial connection attempt that the server aborts. You may see “reading authorization packet” as part of the error message; if so, that also suggests that this is the solution that you need.

If the cause is none of those just described, you may be experiencing a problem with BLOB values that are larger than max_allowed_packet, which can cause this error with some clients. Sometime you may see an ER_NET_PACKET_TOO_LARGE error, and that confirms that you need to increase max_allowed_packet.

#database #mysql #OperationalError #connection

How to check MySQL version:

If you have local access to mySQL server you can check it by:

mysql -v

If you have remote access to MySQL you can first login to mysql using mysql -u USERNAME -p PASS -h REMOTE_HOST. And then after successful login issue the below command:

SELECT version();

#mysql #version

#programmer_jokes #fun

To get time in epoch in linux`/`OS X you can use date with formatting like below:

date +%s

The output of the command is similar to the following output:

1518517636

#linux #osx #date #epoch

دوستانی که در مورد تدریس خصوصی سوال کرده بودند، خدمتشون عارض هستم که تا آخر سال متاسفانه فرصتش وجود نداره و کمی برای آخر سال سرمون شلوغ هستش. ان شالله بعد از عید در صورتی که فشار کاری کمتر بشه خدمتتون میگم. ممنونم بابت پیام های امید بخشتون برای ادامه کار. 💐

#تدریس #خصوصی