Add E2E test for MCPServer cross-replica session routing with Redis

[jerm-dro]

Summary

• MCPServer supports horizontal scaling with Redis session storage, but the proxy runner never read the ScalingConfig.SessionRedis config — sessions always used in-memory LocalStorage, making cross-replica routing non-functional.
• Wire ScalingConfig.SessionRedis from RunConfig into the transport layer via types.Config.SessionStorage, so both StdioTransport and HTTPTransport (transparent proxy) use Redis-backed session storage when configured.
• Add an E2E test that deploys MCPServer with replicas=2 and Redis, initializes a session on pod A via mcp-go, then creates a second mcp-go client on pod B with transport.WithSession reusing the same session ID — proving sessions are shared via Redis across replicas.

Fixes #4531

Type of change

• New feature

Test plan

• Unit tests (task test)
• E2E tests (task test-e2e)
• Linting (task lint-fix)
• Manual testing (describe below)

Verified locally on a Kind cluster: deployed MCPServer with 2 replicas + Redis, confirmed cross-pod session routing via kubectl port-forward to each pod individually. Also validated with raw curl: Initialize on pod A, tools/list on pod B with same Mcp-Session-Id.

Changes

File	Change
pkg/transport/types/transport.go	Add SessionStorage field to Config
pkg/transport/factory.go	Pass Config.SessionStorage to transports during construction
pkg/transport/http.go	Add sessionStorage field, pass to transparent proxy in Start()
pkg/transport/session/redis_config.go	Add RedisPasswordEnvVar constant (moved from pkg/vmcp/config)
pkg/runner/runner.go	Build Redis session storage from ScalingConfig.SessionRedis and set on transport config
test/e2e/images/images.go	Add RedisImage constant
test/e2e/thv-operator/virtualmcp/mcpserver_scaling_test.go	New E2E test for cross-replica session routing

Special notes for reviewers

• StdioTransport.SetSessionStorage already existed but was never called. The factory now sets session storage directly on both StdioTransport and HTTPTransport during construction via Config.SessionStorage.
• The E2E test uses kubectl port-forward to deterministically target specific pods rather than relying on round-robin through a Service.
• The test uses transport.WithSession(sessionID) from mcp-go to create a client on pod B that reuses pod A's session — this is the cleanest way to prove cross-pod session access.
• HTTPTransport.Start gained a nolint:gocyclo — it's a candidate for refactoring but keeping this PR focused on the Redis wiring.
• RedisPasswordEnvVar was moved from pkg/vmcp/config to pkg/transport/session to avoid a proxy runner dependency on the vMCP config package. The vMCP side should be updated to use the shared constant in a follow-up.

Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 0% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.91%. Comparing base (2e8e487) to head (4d2ab58).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/runner/runner.go	0.00%	19 Missing ⚠️
pkg/transport/factory.go	0.00%	11 Missing ⚠️
pkg/transport/http.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4525      +/-   ##
==========================================
- Coverage   69.06%   68.91%   -0.16%     
==========================================
  Files         502      505       +3     
  Lines       51997    52382     +385     
==========================================
+ Hits        35913    36098     +185     
- Misses      13300    13494     +194     
- Partials     2784     2790       +6     

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[Copilot]

Pull request overview

This PR fixes cross-replica MCP session routing for horizontally scaled MCPServer deployments by ensuring the proxy runner honors ScalingConfig.SessionRedis and injects Redis-backed session storage into the transport/proxy layer. It also adds an E2E regression test that proves a session created on one pod can be used from another pod when Redis session storage is configured.

Changes:

• Add SessionStorage to pkg/transport/types.Config and plumb it through transport creation so HTTP and stdio paths can share sessions via Redis.
• Update the proxy runner to construct a Redis session store from ScalingConfig.SessionRedis and inject it into the transport config.
• Add a Kubernetes E2E test that deploys MCPServer with replicas=2 + Redis and validates session reuse across two distinct pods.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/e2e/thv-operator/virtualmcp/mcpserver_scaling_test.go	New E2E test deploying Redis + MCPServer(2 replicas) and validating cross-pod session reuse via port-forward.
pkg/transport/types/transport.go	Adds Config.SessionStorage to allow overriding the default in-memory session storage.
pkg/transport/http.go	Adds sessionStorage field and forwards it into the transparent proxy via transparent.WithSessionStorage(...).
pkg/transport/factory.go	Wires Config.SessionStorage into stdio and HTTP transports during factory creation.
pkg/runner/runner.go	Builds Redis session storage from ScalingConfig.SessionRedis and injects it into the transport config.
.codespellrc	Extends codespell ignore words list.

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[yrobla]

Implementation is correct — the Redis wiring, factory plumbing, and E2E test structure all look solid. Two nits worth a follow-up but nothing blocking.

[yrobla]

Nit: HTTPTransport wires session storage via direct unexported field assignment, while StdioTransport uses stdio.SetSessionStorage(...) (a method call). Consider adding a SetSessionStorage method to HTTPTransport to keep the two transports consistent and avoid the factory reaching into unexported fields.

[yrobla]

Nit: clientA had to be added to the global .codespellrc ignore list to silence a false positive. Renaming to something like podAClient removes the need for that global exception and keeps the spell-checker effective for the rest of the codebase.