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Bobby HoandCian Johnston
511c3cddc0
## Summary Partial fix for the flake in [PLAT-251](https://linear.app/codercom/issue/PLAT-251/flake-test-go-pg-macos-job-timeoutcancelled) / [coder/internal#1365](https://github.com/coder/internal/issues/1365) (`test-go-pg (macos-latest)` timing out and getting cancelled after 25 minutes). ## Problem `testutil/expecter.Expecter` drains a command's stdout/stderr through `io.Copy` into an internal buffer, but it also teed every write through a **second, independent unbuffered `io.Pipe()`**, read by a `bufio.Scanner`, purely to produce human-readable debug logs: ```go logr, logw := io.Pipe() w := io.MultiWriter(logw, out) // out never blocks; logw is a second unbuffered pipe go func() { io.Copy(w, r) }() // drains the command's real stdout/stderr go func() { bufio.NewScanner(logr).Scan() ... }() // only reads when scheduled ``` `io.MultiWriter` only returns once **every** writer succeeds. If the scanner goroutine is ever delayed (GC pause, scheduler contention under CI's `-parallel=16` test config), the write into `logw` blocks, which blocks the `io.Copy` write, which stops it from reading the command's actual output pipe, which means the **command's own write can never complete either**, since nobody is left reading it. Nothing on this path has a timeout, so once wedged it stays wedged until `go test`'s own `-timeout 20m` kills the whole binary. This reproduced locally in `TestConfigSSH_FileWriteAndOptionsFlow` under the macOS CI job's exact parallelism, stuck writing a routine "executable not in `$PATH`" warning (`cli.currentBinPath`) that the test wasn't actively reading at that instant. It's a flake, not a deterministic failure, because under light load the scanner always keeps up trivially. ### Race condition ```mermaid sequenceDiagram participant TG as Test goroutine participant CmdG as Command goroutine<br/>(inv.Run) participant P1 as Pipe 1<br/>(inv.Stdout) participant Copy as io.Copy goroutine participant P2 as Pipe 2<br/>(logw/logr, debug logging only) participant Scan as Scanner goroutine participant Buf as stdbuf (out)<br/>unbounded, never blocks CmdG->>P1: Write(warning output) P1-->>Copy: Read() unblocks Copy->>P2: MultiWriter step 1: write to logw Copy->>Buf: MultiWriter step 2: write to out rect rgb(255, 230, 230) Note over Scan: Under heavy parallel test load,<br/>Scan()'s next Read() is delayed P2--xCopy: Write(logw) blocks: nobody reading yet end Copy--xP1: Read() no longer called: Copy is stuck writing to P2 CmdG--xP1: Write() can't complete either: nobody reads Pipe 1 Note over CmdG: Command write blocks FOREVER<br/>(confirmed: 17-18 min in a goroutine dump) TG->>TG: ExpectMatch times out (got ""), fails the test Note over TG,CmdG: Test goroutine exits, but CmdG is<br/>orphaned and permanently blocked until<br/>go test's own -timeout kills the binary ``` ## Fix Remove the second pipe. `io.Copy` now writes only to the unbounded, non-blocking `stdbuf`. Debug logging is forwarded via a **bounded, non-blocking channel** instead of a second unbuffered pipe: a full channel just drops the chunk rather than propagating backpressure. This works because the only thing the command's real output pipe depends on is `io.Copy(out, r)`, and `out.Write()` can never block, so `io.Copy` always keeps calling `Read()`, so the command's write always has an active reader. Debug logging becomes provably unable to backpressure the command under test, since losing an occasional log line under extreme load is an acceptable tradeoff, unlike losing a whole CI job to a silent deadlock. The fix lives in the shared harness rather than in `cli/configssh.go` because the warning it's tripping over is legitimate, unrelated product behavior; every other test using this harness that happens to emit output the test isn't actively matching at that instant was exposed to the same bug. **Note:** this addresses one of two distinct root causes bundled under PLAT-251. The other is a Depot `GOCACHEPROG` shutdown hang in CI infrastructure (outside this repo, previously diagnosed by a maintainer on the Feb 2026 incident), which this change cannot affect. Locally this fix measurably improves things, but a residual, load-dependent hang was still observed under extreme synthetic contention on a shared dev machine; watching several real CI runs is the next step before considering the flake fully resolved. --------- Co-authored-by: Cian Johnston <cian@coder.com>
Coder is a self-hosted platform for cloud development environments and AI coding agents. Workspaces are defined with Terraform, connected through a secure Wireguard® tunnel, and automatically shut down when not used. Coder Agents runs a native AI coding agent whose loop executes in the control plane on your infrastructure, with no API keys in workspaces.
- Define cloud development environments in Terraform
- EC2 VMs, Kubernetes Pods, Docker Containers, etc.
- Automatically shutdown idle resources to save on costs
- Onboard developers in seconds instead of days
- Delegate coding work to AI agents on your infrastructure
- Bring any model (Anthropic, OpenAI, Google, Bedrock, self-hosted)
- No LLM credentials in workspaces, user identity on every action
- Centralized model governance, cost tracking, and audit logging
Quickstart
The most convenient way to try Coder is to install it on your local machine and experiment with provisioning cloud development environments using Docker (works on Linux, macOS, and Windows).
# First, install Coder
curl -L https://coder.com/install.sh | sh
# Start the Coder server (caches data in ~/.cache/coder)
coder server
# Navigate to http://localhost:3000 to create your initial user,
# create a Docker template and provision a workspace
Install
The easiest way to install Coder is to use the
install script for Linux
and macOS. For Windows, use the latest ..._installer.exe file from GitHub
Releases.
curl -L https://coder.com/install.sh | sh
You can run the install script with --dry-run to see the commands that will be used to install without executing them. Run the install script with --help for additional flags.
See install for additional methods.
Once installed, you can start a production deployment with a single command:
# Automatically sets up an external access URL on *.try.coder.app
coder server
# Requires a PostgreSQL instance (version 13 or higher) and external access URL
coder server --postgres-url <url> --access-url <url>
Use coder --help to get a list of flags and environment variables. See the install guides for a complete tutorial.
Documentation
Browse the documentation or visit a specific section below:
- Workspaces: Workspaces contain the IDEs, dependencies, and configuration information needed for software development
- Templates: Templates are written in Terraform and describe the infrastructure for workspaces
- Coder Agents: Delegate coding work to AI agents running on your self-hosted infrastructure
- Administration: Learn how to operate Coder
- Premium: Learn about paid features built for large teams
- IDEs: Connect your existing editor to a workspace
Support
Feel free to open an issue if you have questions, run into bugs, or have a feature request.
Join our Discord to provide feedback on in-progress features and chat with the community using Coder!
Integrations
New integrations are always in progress. Open an issue to request one. Contributions are welcome in any official or community repository.
Official
- Coder Registry: Templates, modules, and integrations for common development environments
- VS Code Extension: Open any Coder workspace in VS Code with a single click
- JetBrains Toolbox Plugin: Open any Coder workspace from JetBrains Toolbox with a single click
- JetBrains Gateway Plugin: Open any Coder workspace in JetBrains Gateway with a single click
- Dev Containers: Build development environments using
devcontainer.jsonon Docker, Kubernetes, and OpenShift - Kubernetes Log Stream: Stream Kubernetes Pod events to the Coder startup logs
- Self-Hosted VS Code Extension Marketplace: A private extension marketplace that works in restricted or airgapped networks integrating with code-server.
- GitHub Actions: An action to set up the Coder CLI in GitHub workflows
Community
- Community Templates: Community-contributed workspace templates in the Coder Registry
- Community Modules: Community-contributed modules to extend Coder templates
- Provision Coder with Terraform: Provision Coder on Google GKE, Azure AKS, AWS EKS, DigitalOcean DOKS, IBMCloud K8s, OVHCloud K8s, and Scaleway K8s Kapsule with Terraform
- Coder Template GitHub Action: A GitHub Action that updates Coder templates
- Discord: Chat with the community and provide feedback on in-progress features
Contributing
New contributors are always welcome. If you are new to the Coder codebase, see the contribution guide to get started.
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Apply on the careers page if you are interested in joining the team.