Observability Done Right: Best Practices and Anti-Patterns for Effective System Monitoring

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  WHAT Observability is a concept that refers to the ability to gain insights into the behavior and performance of complex systems. In the context of software engineering, observability involves the collection, analysis, and visualization of data from software applications, infrastructure, and other components of a system. In the animal kingdom, observability plays a critical role in survival, allowing animals to monitor their surroundings, detect threats, and find food. Dolphins use echolocation to observe their surroundings. They emit high-frequency sounds that bounce off objects, allowing them to create a 3D map of their environment. Thanks for reading Knowledge Cafe! Subscribe for free to receive new posts and support my work. Subscribed WHY In today's era, architectures are becoming increasingly large, complex, and fast-paced due to the faster development and deployment of software by distributed teams with the help of DevOps, continuous delivery, and agile development methodo...

IdentityHashMap in java

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IdentityHashMap class implements the Map interface with a hash table, using reference-equality in place of object-equality when comparing keys (and values). In other words, in an IdentityHashMap, two keys k1 and k2 are considered equal if and only if (k1==k2). (In normal Map implementations (like HashMap) two keys k1 and k2 are considered equal if and only if (k1==null ? k2==null : k1.equals(k2)).)



This class is not a general-purpose Map implementation! While this class implements the Map interface, it intentionally violates Map's general contract, which mandates the use of the equals method when comparing objects. This class is designed for use only in the rare cases wherein reference-equality semantics are required.

Difference between IdentityHashMap and HashMap


Though both HashMap and IdentityHashMap implements Map interface, have fail-fast Iterator and non synchronized collections, following are some key differences between HashMap and IdentityHashMap in Java.
  • Main difference between HashMap vs IdentityHashMap is that IdentityHashMap uses equality operator "==" for comparing keys and values inside Map while HashMap uses equals method for comparing keys and values. 

  • Unlike HashMap, who uses hashcode to find bucket location, IdentityHashMap also doesn't use hashCode() instead it uses System.identityHashCode(object). 

  • Another key difference between IdentityHashMap and HashMap in Java is Speed. Since IdentityHashMap doesn't use equals() its comparatively faster than HashMap for object with expensive equals() and hashCode(). 

  • One more difference between HashMap and IdentityHashMap is Immutability of key. One of the basic requirement to safely store Objects in HashMap is keys needs to be immutable, IdentityHashMap doesn't require keys to be immutable as it is not relied on equals and hashCode.



import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.Map;

public class IdentityMapDemo {

public static void main(String[] args) {
 Map identityHashMap = new IdentityHashMap();
 Map hashMap = new HashMap();
 identityHashMap.put("one", 1);
 identityHashMap.put(new String("one"), 2);
 identityHashMap.put("two", 3);

 hashMap.put("one", 1);
 hashMap.put(new String("one"), 2);
 hashMap.put("two", 3);

 System.out.println("Identity Map KeySet Size : " +  identityHashMap.keySet().size());
 System.out.println("Hash Map KeySet Size : " + hashMap.keySet().size());
  }
 }


Output:
Identity Map KeySet Size : 3
Hash Map KeySet Size : 2

 Important Point:


HashMap creates Entry objects every time you add an object, which can put a lot of stress on the GC when you've got lots of objects. In a HashMap with 1,000 objects or more, you'll end up using a good portion of your CPU just having the GC clean up entries (in situations like pathfinding or other one-shot collections that are created and then cleaned up). IdentityHashMap doesn't have this problem, so will end up being significantly faster.


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