Detect local emulator connectivity failures

[Mike Krüger (mkrueger)]

Summary

• distinguish interactive Ctrl+C from emulator operation timeouts so failures are no longer silently discarded
• enforce a deterministic timeout for local emulator connect and command operations
• report unavailable emulator errors and return stale emulator sessions to the disconnected state
• keep cloud sessions and ordinary command errors connected

Validation

• dotnet build CosmosDBShell/CosmosDBShell.csproj --no-restore
• dotnet build CosmosDBShell.Tests/CosmosDBShell.Tests.csproj --no-restore
• 71 focused connectivity, command exception, and MCP token-source tests passed
• manually verified that connecting to a stopped emulator reports the failure and returns to the offline prompt
• git diff --check

[Copilot]

Pull request overview

This PR improves the shell’s handling of local Cosmos DB emulator outages by making emulator connectivity failures observable and deterministic, and by ensuring the shell transitions back to a disconnected/offline state on emulator connectivity failures (without impacting cloud sessions).

Changes:

• Added deterministic timeouts for local emulator connect and command execution, and differentiated user Ctrl+C cancellation from emulator timeouts.
• Introduced connectivity-failure detection (CommandException.IsConnectivityFailure) and used it to disconnect only local emulator sessions after connectivity-related failures.
• Updated client options for emulator sessions (shorter request timeout) and added test coverage + changelog entry.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
CosmosDBShell/Azure.Data.Cosmos.Shell.Core/ShellInterpreter.cs	Adds emulator-specific operation timeout logic, emulator-only disconnect behavior after connectivity failures, and emulator-specific client request timeout.
CosmosDBShell/Azure.Data.Cosmos.Shell.Core/CommandException.cs	Adds IsConnectivityFailure helper to classify connectivity-related exceptions (including nested exceptions).
CosmosDBShell.Tests/Shell/ExecuteCommandExceptionTests.cs	Adds tests validating connectivity-failure classification for CosmosException statuses and nested HttpRequestException.
CosmosDBShell.Tests/CommandTests/ConnectCommandTests.cs	Adds tests for emulator request timeout configuration and emulator-only disconnect behavior after connectivity failures.
CHANGELOG.md	Documents the emulator outage detection and state transition behavior change.

Suppressed comments (1)

CosmosDBShell/Azure.Data.Cosmos.Shell.Core/ShellInterpreter.cs:953

• The ReadAccountAsync(...).WaitAsync(LocalEmulatorOperationTimeout, token) timeout path throws TimeoutException but does not cancel the underlying ReadAccountAsync operation. That leaves the request running in the background even after the client is disposed in the catch block, which can surface delayed failures and adds avoidable work. Use a linked CTS with CancelAfter(LocalEmulatorOperationTimeout) and pass that token into ReadAccountAsync instead of WaitAsync.

                var readAccountTask = ReadAccountAsync(client, token);
                keyProps = isEmulator
                    ? await readAccountTask.WaitAsync(LocalEmulatorOperationTimeout, token)
                    : await readAccountTask;

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[github-code-quality]

Code Coverage Overview

Languages: C#

C# / code-coverage/dotnet

The overall line coverage in commit 1be8b36 in the dev/mkrueger/fix-emu... branch remains at 62%, unchanged from commit 0d21834 in the main branch.

Show a line coverage summary of the most impacted files.

File	main 0d21834	dev/mkrueger/fix-emu... 1be8b36	+/-
D:\a\CosmosDBSh...s\PwdCommand.cs	100%	87%	-13%
D:\a\CosmosDBSh...hellLocation.cs	89%	79%	-10%
D:\a\CosmosDBSh...andException.cs	91%	91%	0%
D:\a\CosmosDBSh...lInterpreter.cs	62%	63%	+1%