Compute

• There are two types of instance BM [Bare metal / physical machine], VM[Virtual Machine]
• There are two template type
  • Fixed Shape [BM/VM] : Can not be resized
  • Flexible Shape [VM only] : Can be resized cpu and memory
• Shape Types
  • Standard Shapes : Designed for general purpose workloads and suitable for a wide range of applications and use cases. Standard shapes provide a balance of cores, memory, and network resources. Standard shapes are available with Intel or AMD processors.
  • Dense I/O Shapes : Designed for large databases, big data workloads, and applications that require high-performance local storage. DenseIO shapes include locally-attached NVMe-based SSDs.
  • GPU Shapes : Designed for hardware-accelerated workloads. GPU shapes include Intel CPUs and NVIDIA graphics processors.
  • HPC Shapes : Designed for high-performance computing workloads that require high frequency processor cores and cluster networking for massively parallel HPC workloads.
  • Optimized shapes
• Capacity Type
  • On-demand capacity
  • Preemptible capacity
  • Reserved capacity
  • Dedicated capacity
• You can launch console connections that can be connected from your local machine or cloud itself.
• Compute agent provides cpu/memory/io/read/write/network/load metric, which is genrally installed in available images
• Default os can also show OS management and top process
• Cloud-init script can be setup for executing at provison time
• Stop and start does not change the IP [epeheraml ip], however, terminating instance will free that.
• Custom Image from computing will  only include boot volume, region-specific. Maximum size is 300 GB. Instance will shut down for a few minutes while creating images.
• Custom Images can be exported to OS and can be imported
• You can move instances in different fault domains but SAME AD
• Console connection
  • Not booting/need to reset ssh key for the OPC user [default user in oracle linux], edit system configuration
  • Serial console connection / vnc console connection
  • Need private/public key pair
  • Stop / start [can choose boot option and can edit boot file]/ reboot logs will display
• 169.254.0.0/16 These addresses are used for iSCSI connections to the boot and block volumes, instance metadata, and other services.

OS Management Service

• To apply patches at operating system provided by OS provider
• Support oracle Linux and windows
• Yum is mirrored among regions so that patch download does not incur a regional transfer charge
• Need to create Dynamic group policy for IAM, allow instances to use OSMS
• Install osms-agent service if not installed already
• Create Instance group, add instance, and apply the patches on-demand or schedule

Instance Configuration

• A pre-configuration to launch the instance includes details such as the base image, shape, and metadata.

Instance Pool

• Instance pools let you create and manage multiple compute instances within the same region as a group
• After you have created an instance pool, you can update the size of the pool, add and remove existing instances from the pool, and attach or detach load balancers
• You can automatically adjust the number of instances in an instance pool based on performance metrics or a schedule
• When you delete an instance pool, all of its resources are permanently deleted, including associated instances, attached boot volumes, and block volumes
• You can use the same instance configuration for multiple instance pools. However, an instance pool can have only one instance configuration associated with it.

ASG [Auto Scaling]:

• 1-to-1 mapping for ASG and Instnace Pool
• Scaling is done on the basis of
  • Metric based
    • Cpu utilization
    • Memory utilization
  • Schedule based: cron expression
    • Scale pool size
    • Change in instance state[start or stop]
• In Event of Scale-In, instances are terminated first based on how many instances from the instance pool are in that availability domain and fault domain. Within a placement, the oldest instances are terminated first.

Load Balancer

• Application Loadbalancer / Network Loadbalancer
• Network-based load balancer works on TCP/UDP/ICMP
• App-Based load Balancer works on Application Layer [Http/Https]
• Load Balancer Public [Comes with Public IP] and Private [With private Ip]
• Task: service discovery, health check, Algorithm
• Flexible Shape  or Dynamic Shape
• Layer 4 or Layer 7 LB
• You can attach NSG, by default not enabled
• LB can be attached to only one subnet
• You can enable WAF at LB
• Listener  : [Same AWS target group]
  • Weighted round-robin [Round robin with weighted distribution]
  • Ip Hash  [Bound Ip to make a request to the same server]
  • Least request [Redirect Request to the server which has the least number of conenction]

• Up to 16 Listener, 4-state health checks, updated every 3 minute
• There can be downtime in change shape as the existing connection will be drained
• Health Check status
  • OK
  • INVALID_STATUS_CODE
  • TIMEOUT 
  • REGEX_MISMATCH
  • IO_ERROR
  • OFFLINE
  • UNKNOW
• Route based on Virtual Hostname or path-based routing

OCI Traffic Management and Health Checks

• A global Service, generally used in DR/HA to perform Request regional Request Routing

Traffic Management

• Policy
  • Load Balancer [weighted based load balancing]
  • Failover
  • Geolocation Steering
  • ASN Steering
  • IP Prefix Steering

Health check

• Health Check is available for any public ip available [LB, Compute etc]
• Check the target from different Vantage points
• HTTP based health check  or ping type monitors
• Performance monitoring from response time
• Failover detection
• Hybrid Monitoring