”use CGI;” or “use CGI qw(:standard);”, what does it mean?

Modules are made as classes. “use” is a class definition declaration.
“CGI” is a very easy name, but it is actually a class(function set) that processes basic CGI parameters in the basics when creating CGIs.
Therefore, “use CGI” defines a class of CGI module.

“use CGI” is an object-oriented style, and “use CGI qw(:standard);” is a function style declaration. 

#!/usr/bin/perl --
use strict;
use warnings;
use CGI qw(:standard);

Soap

SOAP is a relatively simple protocol for computers on a network to exchange information. The main feature of SOAP is that all messages to been exchanged are summarized in XML.

<?xml version='1.0' encoding='UTF-8'?>
<SOAP-ENV:Envelope
	xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
	xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance"
	xmlns:xsd="http://www.w3.org/1999/XMLSchema">
	<SOAP-ENV:Body>
		<ns1:getRate
			xmlns:ns1="urn:demo1:exchange"
			>
			<country1 xsi:type="xsd:string">USA</country1>
			<country2 xsi:type="xsd:string">Japan</country2>
		</ns1:getRate>
	</SOAP-ENV:Body>
</SOAP-ENV:Envelop>

AWS subnet

A subnet is an address space that further divides the VPC. A subnet is always created in one AZ, and it is not possible to create a subnet that spans multiple AZs.

UnHealthyHostCount, Latency

UnHealthyHostCount
Number of healthy EC2 instances registered with the load balancer in the specified Availability Zone. Hosts that do not fail the health check beyond the unhealthy threshold are considered healthy. When evaluating this metric, the dimensions should be defined by LoadBalancerName and AvailabilityZone.
This metric represents the number of healthy instances in the specified Availability Zone. Instances may become unhealthy due to connection problems such as non-200 responses (for HTTP and HTTPS health checks) and timeouts when doing health checks. In order to get the total number of all healthy hosts, this metric needs to get each registered AvailabilityZone and add all metrics together.

Latency
The elapsed time from request leaving the load balancer to receiving the corresponding response.

Amazon ElastiCache

Amazon ElastiCache is a web service that makes it easy to deploy and run server nodes compliant with Memcached or Redis protocols in the cloud. Amazon ElastiCache improves web application performance by enabling the retrieval of information from a fast managed in-memory system without relying entirely on slod disk-based databases. This service simplifies the management, monitoring, and operation of the in-memory environment and reduces the load so that engineering resources can be concentrated on application development. With Amazon ElastiCache, you can improve the loading and response times of user actions and queries, as well as reduce the costs associated with scaling web applications.

AWS 0.0.0.0/0

VPC default security group
The VPC automatically uses the default security group. If you do not specify another security group when launching an instance, each EC2 instance launced in VPC is automatically associated with the security group named “launch-wizard-xx”. For example, the security group name of the first EC2 instance to launch is “launch-wizard-1”.

outpoud
Destination: 0.0.0.0/0
Protocol: all
Port: all
Range: Allow all outgoing IPv4 traffic

WhiteListing

Whitelisting is one of the methods used to filter email and websites.
While the blacklisting method creates a list of dangerous users and websites, the whitelisting method creates a list of targets for which safety has been confirmed and excludes others. While it is possible to cut off dangerous objects completely, the contents of the list is arbitrary and limited to a part of safe objects, and it has the disadvantage of losing the user’s convenience.

td agent execution log

$ /var/log/td-agent/td-agent.log
~ omission  ~
013-11-16 14:21:22 +0900 [info]: adding source type="forward"
2013-11-16 14:21:22 +0900 [info]: adding source type="http"
2013-11-16 14:21:22 +0900 [info]: adding source type="debug_agent"
2013-11-16 14:21:22 +0900 [info]: adding source type="tail"
2013-11-16 14:21:22 +0900 [warn]: 'pos_file PATH' parameter is not set to a 'tail' source.
2013-11-16 14:21:22 +0900 [warn]: this parameter is highly recommended to save the position to resume tailing.
2013-11-16 14:21:22 +0900 [info]: adding match pattern="td.*.*" type="tdlog"
2013-11-16 14:21:22 +0900 [info]: adding match pattern="debug.**" type="stdout"
2013-11-16 14:21:22 +0900 [info]: adding match pattern="mongo.**" type="mongo"
2013-11-16 14:21:22 +0900 [info]: adding match pattern="apache.access" type="file"
2013-11-16 14:21:22 +0900 [error]: unexpected error error_class=Mongo::ConnectionFailure error=#
  2013-11-16 14:21:22 +0900 [error]: /usr/lib64/fluent/ruby/lib/ruby/gems/1.9.1/gems/mongo-1.8.6/lib/mongo/networking.rb:167:in `receive_header'
~ omission  ~

/var/log/lsyncd/lsyncd.status

[vagrant@localhost ~]$ sudo tail -n 10 /var/log/lsyncd/lsyncd.status
Lsyncd status report at Tue Mar 12 00:44:51 2019

Sync1 source=/tmp/origin/
There are 0 delays
Excluding:
  nothing.


Inotify watching 1 directories
  1: /tmp/origin/

It doesn’t seem to be an lsync execution log.