Pod Resources: Room Capacity and Limits
Pod resources are like room capacity. Requests are minimum. Limits are maximum. That's pod resources.
🎯 The Big Picture​
Think of pod resources like room capacity. Requests are minimum room size needed. Limits are maximum room size allowed. That's pod resources.
Pod resources define CPU and memory. Requests guarantee minimum. Limits prevent maximum. Essential for resource management.
The Room Capacity Analogy​
Think of pod resources like room capacity:
Requests: Minimum room size
- Guaranteed space
- Always available
- Scheduling consideration
Limits: Maximum room size
- Can't exceed
- Prevents overuse
- Hard limit
CPU: Processing power
- Room amenities
- How much power
- Processing capacity
Memory: Storage space
- Room storage
- How much space
- Memory capacity
Once you see it this way, pod resources make perfect sense.
Resource Requests​
What they are:
- Minimum resources needed
- Guaranteed resources
- Scheduling consideration
Why important:
- Ensures resources available
- Helps scheduling
- Prevents overcommitment
Think of it as: Minimum room size. Guaranteed. Always available.
Example:
resources:
requests:
memory: "256Mi"
cpu: "250m"
What this means:
- Guaranteed 256Mi memory
- Guaranteed 250m CPU
- Scheduler ensures available
Resource Limits​
What they are:
- Maximum resources allowed
- Hard limit
- Prevents overuse
Why important:
- Prevents resource exhaustion
- Protects other pods
- Ensures fairness
Think of it as: Maximum room size. Can't exceed. Hard limit.
Example:
resources:
limits:
memory: "512Mi"
cpu: "500m"
What this means:
- Can't use more than 512Mi
- Can't use more than 500m CPU
- Hard limit enforced
Complete Resource Definition​
Production-ready resources:
apiVersion: v1
kind: Pod
metadata:
name: resource-room
spec:
containers:
- name: app
image: my-app:1.0
resources:
requests:
memory: "256Mi"
cpu: "250m"
limits:
memory: "512Mi"
cpu: "500m"
What this provides:
- Guaranteed minimum
- Maximum limit
- Resource protection
- Fair scheduling
Think of it as: Complete room capacity. Minimum. Maximum. Protected.
CPU Resources​
CPU units:
1= 1 CPU core500m= 0.5 CPU core250m= 0.25 CPU core
Example:
resources:
requests:
cpu: "250m" # 0.25 CPU
limits:
cpu: "500m" # 0.5 CPU
Think of it as: Room processing power. Minimum. Maximum.
Memory Resources​
Memory units:
1Gi= 1024 MiB512Mi= 512 MiB256Mi= 256 MiB
Example:
resources:
requests:
memory: "256Mi"
limits:
memory: "512Mi"
Think of it as: Room storage. Minimum. Maximum.
Resource Requests and Scheduling​
How scheduler uses requests:
Scheduler considers:
- Node available resources
- Pod resource requests
- Finds suitable node
Example:
- Node has 2 CPU, 4Gi memory
- Pod requests 1 CPU, 2Gi memory
- Scheduler can place pod
Think of it as: Room assignment. Check available. Assign if fits.
Resource Limits and Enforcement​
How limits are enforced:
CPU limits:
- Throttled if exceeds
- Not killed
- Slowed down
Memory limits:
- Killed if exceeds
- OOMKilled
- Container restarted
Think of it as: Room capacity. CPU throttled. Memory killed.
Multi-Container Resources​
Resources per container:
Each container:
- Has own requests
- Has own limits
- Independent
Pod total:
- Sum of all containers
- Total pod resources
- Scheduler considers total
Example:
containers:
- name: app
resources:
requests:
memory: "256Mi"
cpu: "250m"
limits:
memory: "512Mi"
cpu: "500m"
- name: sidecar
resources:
requests:
memory: "64Mi"
cpu: "100m"
limits:
memory: "128Mi"
cpu: "200m"
Pod total:
- Requests: 320Mi memory, 350m CPU
- Limits: 640Mi memory, 700m CPU
Think of it as: Suite resources. Each guest. Total suite.
Real-World Example: Production Resources​
Complete production pod:
apiVersion: v1
kind: Pod
metadata:
name: production-room
spec:
containers:
- name: app
image: my-app:1.0.0
resources:
requests:
memory: "512Mi"
cpu: "500m"
limits:
memory: "1Gi"
cpu: "1000m"
livenessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 30
periodSeconds: 10
readinessProbe:
httpGet:
path: /ready
port: 8080
initialDelaySeconds: 5
periodSeconds: 5
That's production resources. Appropriate. Protected.
Best Practices​
Always Set Resources​
Why:
- Prevents overcommitment
- Helps scheduling
- Protects cluster
Always:
- Set requests
- Set limits
- Both important
Right-Size Resources​
How:
- Profile application
- Measure usage
- Set appropriately
Don't:
- Over-provision
- Under-provision
- Guess
Monitor Resource Usage​
Why:
- Know actual usage
- Adjust if needed
- Optimize
Monitor:
- CPU usage
- Memory usage
- Adjust resources
My Take: Resource Strategy​
Here's what I do:
Development:
- Lower resources
- Quick testing
- Basic limits
Production:
- Appropriate resources
- Based on profiling
- Protected limits
The key: Always set resources. Right-size. Monitor. Adjust.
Memory Tip: The Room Capacity Analogy​
Pod resources = Room capacity
Requests: Minimum size Limits: Maximum size CPU: Processing power Memory: Storage space
Once you see it this way, resources make perfect sense.
Common Mistakes​
- Not setting resources: Overcommitment, poor scheduling
- Wrong sizing: Over or under provisioned
- Only limits: Missing requests
- Only requests: Missing limits
- Not monitoring: Don't know actual usage
Key Takeaways​
- Always set resources - Requests and limits
- Requests guarantee minimum - Scheduling consideration
- Limits prevent maximum - Resource protection
- Right-size resources - Based on profiling
- Monitor usage - Adjust as needed
What's Next?​
Congratulations! You've completed the Pods module. Now let's learn about deployments. Next: Understanding Deployments.
Remember: Pod resources are like room capacity. Requests are minimum. Limits are maximum. Always set both. Right-size. Monitor. Essential for resource management.