OCI Compute Service : cheatsheet


  • 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
  • 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
    • TIMEOUT 
    • IO_ERROR
    • 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

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