Deployment & Provisioning Flashcards
InstanceLimitExceeded error
You have reached the limit on the number of instances you can launch in a region.
- 20 by default
InsufficientInstanceCapacity error
AWS does not currently have enough available On-Demand capacity to service your request.
- Wait a few minutes and try again - Request fewer instances - Select a different instance type - Purchase Reserved Instances instead - Submit a new request without specifying the AZ
What happens when you hit the IOPS limit of your volume? How to fix it?
App becomes to slow down and I/O request starts queuing
- gp2: increase the size of your volume (only if volume is < 5.2TB)
- if you have already reached 16,000 IOPS, chage storage class to Provisioned IOPS
Bastion Host
It’s a host located in a Public subnet
- Allows you to connect to your EC2 instances using SSH or RDP.
- Used to securely connect to instances in a Private Subnet, without exposing them to the internet.
- Does not enable outgoing requests, internet access for your instances in the private subnet.
Application Load Balancers
Layer 7
- Inspect packets
- Make routing or routing decisions based on the contents of the network packet.
- acloudguru/sales → goes to one server
- acloudguru/marketing → goes to another server.
- It can read HTTP, HTTPS headers.
Network Load Balancers
- Layer 4
- Load balancing TCP traffic
- Millions of requests per second, while maintaining ultra-low latencies.
Classic Load Balancers
Layer 4 and 7
- X-Forwarded-For, which simply allows you to determine the originating IP address for the device which sent the request.
- Allows Sticky sessions: simply binds a user’s session to a specific instance.
When should you Pre-Warm your Load Balancers?
Needed when there will be a crazy increase in your traffic
- Contact AWS and request them Pre-Warm ELB.
- It will configure the ELB to the appropriate level of capacity based on the traffic you expect.
What does AWS need to know in order to Pre-warm your load balancers? (3 things)
Start and end dates
Expected request rate per second
Total size of a typical request
Which ELB type should you use if there is a need for static IP addresses?
NLB
- It attaches 1 static ip address per subnet
400 ELB error
Bad or malformed request
- e.g. Request header malformed. - doesn't conform with HTTP or HTTPS standard.
401 ELB error
Unauthorized - user access denied.
- The user trying to request the web page, they don’t have access to the web page or the website that they’re trying to access.
403 ELB error
Forbidden
- Request is blocked by WAF access control list
460 ELB error
Client closed connection before the load balancer could respond.
- client timeout period may be too short. - it doesn't give the LB sufficient time to actually respond to your request
463 ELB error
LB has received an X-Forwarded-For request header, with more than 30 IP addresses.
- X-Forwarded-For request header allows you to identify the IP address of the originating requester. - Limit is 30 IPs per request - More than 30 you get a 463 error message.
500 ELB error
Internal server error
- e.g. Error with the LB
- Wrong configuration of the ELB
502 ELB Error
- bad gateway
- e.g. Your application server, it closed the connection or it sent back a malformed request to the load balancer.
503 ELB Error
Service unavailable
- No registered targets - it simply refers to the web servers themselves that are registered with the load balancer
504 ELB Error
Gateway timeout
- e.g. if the application is not responding.
- Maybe you've got a problem with your web server, your application server or database
561 Error Code
Unauthorized
- if your load balancer is using an identity provider to authorize or authenticate users. - if you don't receive a response from the identity provider - something's gone wrong with the identity provider - you can't reach it for whatever reason
What does BackendConnectionErrors shows?
Number of unsuccessful connections to backend instances.
HealthyHostCount
Number of healthy instances registered
UnHealthyHostCount
Number of unhealthy instances
Latency
number of seconds taken for registered instance to respond/connect.
RequestCount
number of request completed / connectiond made during the specified interval (1 or 5 minutes)
SurgeQueueLength
number of pending requests, max queue size is 1024, additional requests will be rejected (CLB only)
SpillOverCount
number of requests rejected because the surge queue is full (CLB only)
Allows you to centralize operational data from multiple AWS services and automate tasks across your AWS resources.
- Allows you to organize your inventory, grouping resources together.
- e.g. by application, by environment, or team.
Which Service is that?
Systems Manager
Run Command
It is a feature which automates operational tasks across your resources.
- security patching
- package installs
- E.g. stop, start, resize, terminate instances, without having to log in to each one.
Placement grOUPS
Allow you to control how your instances are deployed on physical hardware on AWS.
- Great for low latency
- High network throughput
- High performance computing applications
Instances are all created in a single AZ.
- Low latency, high network throughput.
Which kind of Placement group is that?
Cluster Placement Group
Instances are created in logical segments called partitions, each located in separate rack(s), with independent power & network.
- It can be multi-AZ
- HDF, HBase, and Cassandra
Partition Placement Group
Each instance is created in a separate rack, with independent power & network.
- used for maximum availability.
- Great for small number of critical instances that you need to segregate for resilience.
Spread Placement Group
ELB CloudWatch Metrics:
3 Types of Metrics for General Health.
HealthyHostCount
UnHealthyHostCount
HTTPCode_Backend_2XX
ELB CloudWatch Metrics:
4 Types of Metrics for Perfomance.
Latency
RequestCount
SurgeQueueLength - CLB Only
SpilloverCount - High numbers can indicate a performance issue, need to scale infra, etc. CLB Only.
By default, how frequently are ELB metrics published to CloudWatch?
60 seconds.
