Monitoring ELB

Question 1

3 Types of Load Balancers

Answer 1

Application Load Balancer
Network Load Balancer
Classic Load Balancer (Being deprecated)

Question 2

4 ways to monitor load balancers

Answer 2

CloudWatch Metric
Access Logs
Request Tracing - Application LB only
CloudTrail Logs

Question 3

Differences: CloudWatch vs CloudTrail

Answer 3

CloudWatch monitors performance
CloudTrail monitors API calls in the AWS platform.
Remember; CloudWatch for performance, CloudTrail for auditing.

Question 4

Name the types of access logs

Answer 4

Detailed logs for requests sent to the LB such as:
Client IP
Latency
request path
server responses (200, 500, etc.)

Question 5

True or false: Accessing logs can be disabled?

Answer 5

True.

Question 6

How are access logs stored?

Answer 6

Compressed files on an S3 bucket.

Question 7

If instance(s) experience 500 errors, however, the instances were deleted along with the apache logs, how can information about those responses be recovered?

Answer 7

By using access logs stored on an S3 bucket. The logs are retained after instances are deleted.

Question 8

What is request tracing?

Answer 8

Tracks HTTP requests from client to targets or other services. The X-Amzon-Trace-ID is amended for each hop a request takes inside AWS.

Question 9

True or False: Request Tracing is available to application load balancers only?

Answer 9

True.

Question 10

CloudTrail Logs

Answer 10

Used to capture detailed information about calls made to the ELB API including source IP, who made the call, when, etc. Stores log files on S3.

Question 11

True or False: CloudTrail metrics will provide information on healthy and unheatlhy hosts?

Answer 11

False: CloudTrail is for auditing API requests only. Use CloudWatch for performace metrics.

Question 12

ELB errors all start with

Answer 12

4xx or 5xx

Question 13

Successful ELB response code

Answer 13

200

Question 14

4xx error messages

Answer 14

client-side error

Question 15

5xx error messages

Answer 15

server-side error

Question 16

Error 400

Answer 16

Bad/Malformed request - Such as malformed header

Question 17

Error 401

Answer 17

Unauthorized access - user access denied

Question 18

Error 403

Answer 18

Forbidden - Request is blocked by ACL

Question 19

Error 460

Answer 19

Client closed the connection before ELB responded

Question 20

Error 463

Answer 20

X-Forwarded-For header contains >30 IP addresses

Question 21

Error 500

Answer 21

Internal to server e.g. error on the LB

Question 22

Error 502

Answer 22

Bad gateway - e.g. application load balancer closed the connection

Question 23

Error 503

Answer 23

Service unavailable - No registered targets

Question 24

Error 504

Answer 24

Gateway Timeout - Application is not responding

Question 25

Error 561

Answer 25

Unauthorized