Add backchannel log replay for TUI support#14512
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mitchdenny merged 1 commit intorelease/13.2from Feb 25, 2026
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🚀 Dogfood this PR with:
curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 14512Or
iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 14512" |
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Pull request overview
Adds server-side backchannel plumbing needed for the upcoming aspire monitor TUI by extending AppHost backchannel APIs with repository-root discovery and log history replay.
Changes:
- Adds
RepositoryRoottoGetAppHostInfoResponseand populates it via.gitdiscovery. - Introduces a 1000-entry log replay buffer in
BackchannelLoggerProviderand replays it before live streaming. - Exposes AppHost log streaming via the auxiliary backchannel and adjusts DI to allow resolving
BackchannelLoggerProviderdirectly.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| src/Aspire.Hosting/DistributedApplicationBuilder.cs | Registers BackchannelLoggerProvider as a concrete singleton and forwards it to ILoggerProvider for shared instance resolution. |
| src/Aspire.Hosting/Backchannel/BackchannelLoggerProvider.cs | Adds replay buffer and updates logger creation/disposal behavior. |
| src/Aspire.Hosting/Backchannel/BackchannelDataTypes.cs | Extends AppHost info response contract with RepositoryRoot. |
| src/Aspire.Hosting/Backchannel/AuxiliaryBackchannelRpcTarget.cs | Populates RepositoryRoot and adds auxiliary RPC method to stream AppHost log entries. |
| src/Aspire.Hosting/Backchannel/AppHostRpcTarget.cs | Replays buffered log entries before reading from the live log channel. |
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| if (_replayBuffer.Count >= MaxReplayEntries) | ||
| { | ||
| _replayBuffer.RemoveAt(0); | ||
| } | ||
| _replayBuffer.Add(entry); |
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The replay buffer eviction uses List.RemoveAt(0), which is O(n) and will shift the remaining items on every log once the buffer reaches MaxReplayEntries. Under high log volume this can become a noticeable CPU hotspot. Consider switching to a ring buffer / circular array (or Queue<T> with a fixed-capacity policy) to make eviction O(1).
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| // Replay buffered entries first so late-connecting clients see history | ||
| var loggerProvider = serviceProvider.GetService<BackchannelLoggerProvider>(); | ||
| if (loggerProvider is not null) | ||
| { | ||
| foreach (var entry in loggerProvider.GetReplaySnapshot()) | ||
| { | ||
| yield return entry; | ||
| } | ||
| } |
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GetAppHostLogEntriesAsync reads from a single shared Channel<BackchannelLogEntry>. With the auxiliary backchannel supporting multiple concurrent connections, multiple callers can enumerate this method simultaneously; Channel semantics will then distribute entries across readers (each entry consumed by only one client), so clients will see partial/missing live logs. To support multiple clients, switch to a fan-out/broadcast approach (e.g., maintain per-subscriber channels/writers and write each log entry to all subscribers), or enforce a single active subscriber explicitly (reject additional subscribers).
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| // Replay buffered entries first so late-connecting clients see history | ||
| var loggerProvider = serviceProvider.GetService<BackchannelLoggerProvider>(); | ||
| if (loggerProvider is not null) | ||
| { | ||
| foreach (var entry in loggerProvider.GetReplaySnapshot()) | ||
| { | ||
| yield return entry; | ||
| } | ||
| } |
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The new log replay behavior isn’t covered by the existing backchannel test suite (there are tests for connection/state streaming, but none exercising GetAppHostLogEntriesAsync or verifying replay/broadcast semantics). Adding an integration test that logs a few messages, connects after the fact, and asserts the historical entries are received would help prevent regressions—especially once multiple auxiliary clients are supported.
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🎬 CLI E2E Test RecordingsThe following terminal recordings are available for commit
📹 Recordings uploaded automatically from CI run #22339787086 |
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/deployment-test |
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🚀 Deployment tests starting on PR #14512... This will deploy to real Azure infrastructure. Results will be posted here when complete. |
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✅ Deployment E2E Tests passed Summary: 19 passed, 0 failed, 0 cancelled Passed Tests
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This was referenced Feb 19, 2026
…riber support Add server-side plumbing for TUI monitor support (13.3 preparation): - BackchannelLoggerProvider: Add circular replay buffer (1000 entries) with pub-sub subscriber model. Subscribe() atomically returns a snapshot of buffered entries plus a per-subscriber channel for live entries, enabling multiple concurrent TUI clients without entry loss or draining. - AppHostRpcTarget: Add GetAppHostLogEntriesAsync() that replays buffered entries then streams live entries via per-subscriber channel. Uses subscribe/unsubscribe lifecycle with proper cleanup in finally block. - AuxiliaryBackchannelRpcTarget: Add GetAppHostLogEntriesAsync() delegate that forwards to AppHostRpcTarget for auxiliary backchannel clients. - DistributedApplicationBuilder: Register BackchannelLoggerProvider as concrete singleton with ILoggerProvider forwarding, enabling direct resolution by AppHostRpcTarget. - Tests: 4 new tests covering replay buffer fill, eviction at capacity, snapshot isolation, and concurrent subscriber fan-out. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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| private readonly object _channelRegisteredLock = new(); | ||
| private readonly CancellationTokenSource _backgroundChannelRegistrationCts = new(); | ||
| private Task? _backgroundChannelRegistrationTask; | ||
| private readonly Queue<BackchannelLogEntry> _replayBuffer = new(); |
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Why not use the circularbuffer?
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…riber support (#14512) Add server-side plumbing for TUI monitor support (13.3 preparation): - BackchannelLoggerProvider: Add circular replay buffer (1000 entries) with pub-sub subscriber model. Subscribe() atomically returns a snapshot of buffered entries plus a per-subscriber channel for live entries, enabling multiple concurrent TUI clients without entry loss or draining. - AppHostRpcTarget: Add GetAppHostLogEntriesAsync() that replays buffered entries then streams live entries via per-subscriber channel. Uses subscribe/unsubscribe lifecycle with proper cleanup in finally block. - AuxiliaryBackchannelRpcTarget: Add GetAppHostLogEntriesAsync() delegate that forwards to AppHostRpcTarget for auxiliary backchannel clients. - DistributedApplicationBuilder: Register BackchannelLoggerProvider as concrete singleton with ILoggerProvider forwarding, enabling direct resolution by AppHostRpcTarget. - Tests: 4 new tests covering replay buffer fill, eviction at capacity, snapshot isolation, and concurrent subscriber fan-out. Co-authored-by: Mitch Denny <mitch@mitchdeny.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
Adds server-side backchannel plumbing to support a rich TUI monitor experience in 13.3. These changes are purely additive — they add new RPC methods and enhance the log streaming infrastructure so that AppHosts built with 13.2 already expose the APIs the TUI will consume.
Changes
BackchannelLoggerProvider (enhanced)
Subscribe()atomically returns a snapshot of buffered entries plus a per-subscriber channel for live entriesDispose()usesTryComplete()to handle the DI forwarding double-disposal patternAppHostRpcTarget (new method)
GetAppHostLogEntriesAsync()— replays buffered entries then streams live entries via per-subscriber channelSubscribe()/Unsubscribe()lifecycle with proper cleanup infinallyblockAuxiliaryBackchannelRpcTarget (new method)
GetAppHostLogEntriesAsync()delegate that forwards toAppHostRpcTargetDistributedApplicationBuilder (DI registration)
AddSingleton<ILoggerProvider, BackchannelLoggerProvider>()to forwarding patternAppHostRpcTargetto resolveBackchannelLoggerProviderdirectly for subscriber managementTests (new file)
Risk Assessment
ILoggerProviderresolution5 files changed, +193 / -57 lines