update backgroud read endpoint refresh flow (Azure#24969)

### Packages impacted by this PR
@azure/cosmos

### Issues associated with this PR
22726

### Describe the problem that is addressed by this PR

This pull request aims to correct the flow of the update read endpoint
within the background refresh thread. Previously, it was retrieving
results from the database write endpoint.

### What are the possible designs available to address the problem? If
there are more than one possible design, why was the one in this PR
chosen?


### Are there test cases added in this PR? _(If not, why?)_
Yes

### Provide a list of related PRs _(if any)_
Azure#24296

### Command used to generate this PR:**_(Applicable only to SDK release
request PRs)_

### Checklists
- [ ] Added impacted package name to the issue description
- [ ] Does this PR needs any fixes in the SDK Generator?** _(If so,
create an Issue in the
[Autorest/typescript](https://github.com/Azure/autorest.typescript)
repository and link it here)_
- [ ] Added a changelog (if necessary)

---------

Co-authored-by: Manik Khandelwal <mkhandelwal@microsoft.com>

Author: topshot99

sdk/cosmosdb/cosmos/src/globalEndpointManager.ts

@@ -3,7 +3,8 @@
 import { OperationType, ResourceType, isReadRequest } from "./common";
 import { CosmosClientOptions } from "./CosmosClientOptions";
 import { Location, DatabaseAccount } from "./documents";
-import { Constants, RequestOptions } from "./index";
+import { RequestOptions } from "./index";
+import { Constants } from "./common/constants";
 import { ResourceResponse } from "./request";
 
 /**
@@ -181,7 +182,7 @@ export class GlobalEndpointManager {
         this.writeableLocations.push(location);
       }
     }
-    for (const location of databaseAccount.writableLocations) {
+    for (const location of databaseAccount.readableLocations) {
       const existingLocation = this.readableLocations.find((loc) => loc.name === location.name);
       if (!existingLocation) {
         this.readableLocations.push(location);
@@ -229,8 +230,9 @@ export class GlobalEndpointManager {
         loc &&
         now - loc.lastUnavailabilityTimestampInMs >= Constants.LocationUnavailableExpirationTimeInMs
       ) {
-        return true;
+        return false;
       }
+      return true;
     });
   }
 

sdk/cosmosdb/cosmos/test/public/functional/globalEndpointManager.spec.ts

@@ -74,6 +74,7 @@ describe("GlobalEndpointManager", function () {
         "https://test-eastus2.documents.azure.com:443/"
       );
     });
+
     it("should allow you to pass a normalized preferred location", async function () {
       gem = new GlobalEndpointManager(
         {
@@ -99,6 +100,7 @@ describe("GlobalEndpointManager", function () {
         "https://test-eastus2.documents.azure.com:443/"
       );
     });
+
     it("should resolve to endpoint when call made after server unavailability time", async function () {
       const clock: fakeTimers.InstalledClock = fakeTimers.install();
 
@@ -119,25 +121,19 @@ describe("GlobalEndpointManager", function () {
           return response;
         }
       );
-
+      await gem.refreshEndpointList();
       await gem.markCurrentLocationUnavailableForRead(
         "https://test-westus2.documents.azure.com:443/"
       );
-      assert.equal(
-        await gem.resolveServiceEndpoint(ResourceType.item, OperationType.Read),
-        "https://test.documents.azure.com:443/"
-      );
+      assert.equal(await gem.getReadEndpoint(), "https://test-eastus2.documents.azure.com:443/");
       clock.tick(locationUnavailabilityExpiratationTime);
       await gem.refreshEndpointList();
-      assert.equal(
-        await gem.resolveServiceEndpoint(ResourceType.item, OperationType.Read),
-        "https://test-westus2.documents.azure.com:443/"
-      );
+      assert.equal(await gem.getReadEndpoint(), "https://test-westus2.documents.azure.com:443/");
       clock.uninstall();
     });
   });
 
-  describe("#markCurrentLocationUnavailableForRead", function () {
+  describe("#markCurrentLocationUnavailable", function () {
     const gem = new GlobalEndpointManager(
       {
         endpoint: "https://test.documents.azure.com:443/",
@@ -157,16 +153,19 @@ describe("GlobalEndpointManager", function () {
       }
     );
 
+    beforeEach(async () => {
+      await gem.refreshEndpointList();
+    });
+
     it("should mark the current location unavailable for read", async function () {
       // We don't block on init for database account calls
       await gem.markCurrentLocationUnavailableForRead(
-        "https://test-westus2.documents.azure.com:443/"
+        "https://test-eastus2.documents.azure.com:443/"
       );
-
       /* As we have marked current location unavailable for read,
         next read should go to the next location or default endpoint
       */
-      assert.equal(await gem.getReadEndpoint(), "https://test.documents.azure.com:443/");
+      assert.equal(await gem.getReadEndpoint(), "https://test-westus2.documents.azure.com:443/");
     });
     it("should mark the current location unavailable for write", async function () {
       // We don't block on init for database account calls