remove hardcoded replicationGroupId and generate from pod name

- Removed the hardcoded default value 'RG001' for replicationGroupId.
- replicationGroupId is now generated from the Kubernetes pod name by
taking the first 2 characters of the long hash and concatenating it with
the full short hash (e.g., cloudserver-7869f99955-nr984 → 78nr984).
- Ensures uniqueness across deployments within the same namespace while
keeping the ID short.
- Falls back to 'RG001' only if neither config nor HOSTNAME is available.

Issue: CLDSRV-665

Author: Kerkesni

lib/Config.js

@@ -906,6 +906,20 @@ class Config extends EventEmitter {
             assert(typeof config.replicationGroupId === 'string',
                 'bad config: replicationGroupId must be a string');
             this.replicationGroupId = config.replicationGroupId;
+        } else if (process.env.HOSTNAME) {
+            // Extract the hash part from the pod name (e.g., cloudserver-7869f99955-nr984)
+            const parts = process.env.HOSTNAME.split('-');
+            // Kubernetes pods typically have two UID parts:
+            // - A long hash (10 characters) that guarantees uniqueness within the namespace.
+            // - A short hash (5 characters) that is unique only within the current ReplicaSet/Deployment.
+            if (parts.length > 2) {
+                const longId = parts[parts.length - 2];
+                const shortId = parts[parts.length - 1];
+                this.replicationGroupId = longId.slice(0, 2) + shortId;
+            } else {
+                // fallback: just use the last part if format is unexpected
+                this.replicationGroupId = parts.pop();
+            }
         } else {
             this.replicationGroupId = 'RG001';
         }

tests/unit/Config.js

@@ -810,4 +810,47 @@ describe('Config', () => {
             assert.deepEqual(config.internalListenOn, [{ ip: '127.0.0.1', port: 9000 }]);
         });
     });
+
+    describe('replicationGroupId', () => {
+        let sandbox;
+        let readFileStub;
+        let previousHostname;
+
+        beforeEach(() => {
+            sandbox = sinon.createSandbox();
+            readFileStub = sandbox.stub(fs, 'readFileSync');
+            readFileStub.callThrough();
+            previousHostname = process.env.HOSTNAME;
+        });
+
+        afterEach(() => {
+            sandbox.restore();
+            if (previousHostname) {
+                process.env.HOSTNAME = previousHostname;
+            } else {
+                delete process.env.HOSTNAME;
+            }
+        });
+
+        it('should return the replicationGroupId from config', () => {
+            const config = new ConfigObject();
+            assert.strictEqual(config.replicationGroupId, 'RG001');
+        });
+        it('should genrate a new replicationGroupId if not set in config', () => {
+            process.env.HOSTNAME = 'cloudserver-7869f99955-nr984';
+
+            const modifiedConfig = { ...defaultConfig, replicationGroupId: null };
+            readFileStub.withArgs(sinon.match(/config.json$/)).returns(JSON.stringify(modifiedConfig));
+
+            const config = new ConfigObject();
+            assert.strictEqual(config.replicationGroupId, '78nr984');
+        });
+        it('should use default replicationGroupId if HOSTNAME is not set', () => {
+            const modifiedConfig = { ...defaultConfig, replicationGroupId: null };
+            readFileStub.withArgs(sinon.match(/config.json$/)).returns(JSON.stringify(modifiedConfig));
+
+            const config = new ConfigObject();
+            assert.strictEqual(config.replicationGroupId, 'RG001');
+        });
+    });
 });