1. Onkar kadam
onkarkadam@live.com

2. Cloud Environment.
Virtualization/Virtual machines.
Monitoring Multiple hosts.
Monitoring a Distributed environment.
Central Monitoring Server.
Real-time messaging.
Selecting the metrics.
Incident reports and notifications.

3. When the Monitoring server triggers the
check on a host then it is termed as active
monitoring.

4. In an active monitoring environment , the
central monitoring server performs periodic
checks on hosts and retrieves metrics related
to that service.
If the central monitoring server is within the
cloud then its easy to monitor the hosts.
If the central monitoring server is at a remote
location , ssh services are required to monitor
virtual hosts.

5. Scripts or programs on the virtual host
perform tests and send the results to the
central monitoring server.

6. Active monitoring doesn’t put the load on the
host to run monitoring scripts.
Passive monitoring is effective in case of
failures. Passive monitoring fit well in the
case of reporting problems to the central
monitoring server in real time.

7. The need of an efficient messaging protocol for
sending performance metrics to the central
monitoring server.
For Real Time Application performance
monitoring a fast messaging protocol is a must.
Leveraging already available messaging services
to be used in the architecture
RabbitMQ , ActiveMQ , Apache Kafka.

9. In the architecture, the monitoring agent will
calculate the performance metrics and
publish it on RabbitMQ.
The virtual hosts are the producers
application performance metrics and the
Central monitoring server is the consumer.
The Central monitoring server will fetch the
metrics from the queue of RabbitMQ.

11. Instead of point-to-point pipelines use of a
central data pipeline.
The producers, in our case the virtual
machines hosting the rails application,
produce metrics and publish data on the
kafka cluster with a key in the message which
specifies the source of the metric.
The consumer reads the messages from the
kafka cluster(commit log) and then
represents the data in graphs for the end
user.

12. Website activity tracking (page views,
searches , or other action users perform)
Real time processing and real time
monitoring.
Aggregating statistics from applications and
produce operational monitoring data.

13. Two ways: Ruby plug-in or a full-fledged rails
application’.
The main goal of the agent is to collect
critical metrics from the host and send it to
the central monitoring server, hence a plug-
in will be more suitable and lightweight.
In cloud environment it is necessary to have a
lightweight plug-in as the size of an instance
varies.

15. Monitoring web servers is important as it is
the front end of any web application.
We can monitor the web server by parsing the
log files.

16. Action Controller receives incoming requests
and hands off each request to a particular
action. It maps URL to specific actions.
Rails comes with a number of built-in logging
facilities.
Use of after_filter to invoke custom logging
method for each request.
It will help the monitor to inspect the request
cycle in real time.

17. Using “~/projects$ ruby script/console –s”
we can inspect the relationships between the
objects.
Giving the client a view of the these
relationships in the front end of the
application monitoring agent.

18. Use of “stats rake” task to generate statistics
about the Rails project.
A “Httperf” like tool can be used to generate
real time web server performance statistics
for a real world web traffic.
A front end abstraction can be used to
represent the statistics collected in an
graphical view.
Monitoring the web server cache.

19. The most important part of a rails application
is the database.
The most important thing to monitor is the
mapping between the database and Active
records.
To maintain the integrity of ORM, a change in
active record object should cause an
immediate change in the corresponding row
of a table in a database.

20. Periodically issue a MySql “Show status”
command and return.
Metrics such as Mysql traffic, No of
transactions between Controller and
database, no of queries ,no of update
queries, no of delete queries, no of times a
sql command is issued, query cache
statistics, etc

21. There are various methods an monitoring
application can be deployed in the cloud.
One is providing the source code and installing it
after a virtual instance with the web application is
up an running.
Creating a custom image with the monitoring
agent already installed, such that the users only
select the image and deploy their applications
and start monitoring their application.
(http://docs.aws.amazon.com/gettingstarted/latest/wah-
linux/getting-started-create-custom-ami.html)

22. The main important decision is to perform
active or passive monitoring or combination
of both.
To collect statistics about an application it is
necessary to dig deeper in the PAAS
technology used by the application, for eg. a
rails application will have a different set of
performance metrics than a java based web
application , but both applications will have a
default set of metrics which are valid for both
type of applications.

23. The agent should be as light as possible so
that it will not affect the web application
performance.
Real- time messaging so that the metrics
reflect in the monitor in real time
Real time data processing to generate the
statistics.

24. A self aware scaling tool for web applications
in cloud.
A performance metric predicting tool based
on the past performance metric and current
time of the day.