devserver

README

DevServer (Local Update Emulator)

This devserver is a tiny HTTP server for local development/testing of go-autoupdater.

It emulates your real update hosting by serving:

• manifest.json (at GET /manifest.json)
• update artifacts (binaries/exe) (at GET /files/<filename>)

So you can test update flows locally without uploading to a real server.

This is a development tool. Do not use it as a production update server.

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What you need

• Go 1.22+
• The repo checked out locally
• One or more built artifacts (example: agent.exe, agent_linux_arm64, etc.)

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Folder layout (recommended)

Put your artifacts and (optionally) a static manifest under a single folder.

Recommended structure:

<repo-root>/
  cmd/
    devserver/
      main.go
      README.md
  testdata/
    updates/
      manifest.json               (optional if you use --gen)
      agent_1.0.12_windows_amd64.exe
      agent_1.0.12_linux_amd64
      agent_1.0.12_linux_arm64
      agent_1.0.12_darwin_arm64

Why testdata/?

• It’s a common Go convention for sample/test resources.
• It keeps dev-only artifacts separate from library code.

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Two ways to run devserver

Mode A — Static manifest (you write manifest.json yourself)

Use this when you want full control over the manifest content.

1. Create testdata/updates/manifest.json
2. Put your artifacts in the same folder
3. Run:

go run ./cmd/devserver --root ./testdata/updates

Then open:

• Manifest: http://127.0.0.1:8089/manifest.json
• Files: http://127.0.0.1:8089/files/<filename>

Mode B — Auto-generate manifest (fastest)

Use this when you want devserver to generate a manifest automatically.

Requirement: artifact filenames must contain _<os>_<arch> at the end.

Examples that will be detected:

• agent_1.0.12_windows_amd64.exe
• agent_1.0.12_linux_amd64
• agent_1.0.12_linux_arm64
• agent_1.0.12_darwin_arm64

Run:

go run ./cmd/devserver --root ./testdata/updates --gen --version 1.0.12

devserver will:

• scan files in --root
• compute SHA256 for each detected artifact
• output a generated manifest at GET /manifest.json

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Flags

Flag	Default	Description
--addr	127.0.0.1:8089	Address to listen on
--root	./testdata/updates	Directory containing artifacts (+ optional manifest)
--manifest	manifest.json	Manifest filename under --root (Mode A)
--gen	false	Enable auto-generate manifest (Mode B)
--product	agent	Product name used in generated manifest
--channel	stable	Channel used in generated manifest
--version	0.0.0-dev	Version used in generated manifest
--notes	local dev build	Notes used in generated manifest

Example: change port

go run ./cmd/devserver --addr 127.0.0.1:9090 --root ./testdata/updates --gen --version 1.0.12

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Build devserver binary

You can also build it as a standalone binary.

macOS / Linux

go build -o devserver ./cmd/devserver
./devserver --root ./testdata/updates --gen --version 1.0.12

Windows (PowerShell)

go build -o devserver.exe .\cmd\devserver
.\devserver.exe --root .\testdata\updates --gen --version 1.0.12

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Using devserver with updaterctl

Once devserver is running, point your updater to the local manifest URL.

Example (standalone mode):

./updaterctl \
  --manifest "http://127.0.0.1:8089/manifest.json" \
  --dir "./" \
  --exe "agent" \
  --current "1.0.11"

Windows service update test (NSSM/SC)

• Place updater-helper.exe next to your agent.exe (same install dir)
• Run updaterctl.exe with:

updaterctl.exe `
  --manifest "http://127.0.0.1:8089/manifest.json" `
  --dir "C:\\fck\\agent" `
  --exe "agent.exe" `
  --current "1.0.11" `
  --service "FCKAgent" `
  --nssm "C:\\tools\\nssm.exe"

If you want to force Windows built-in sc.exe controller, use: --nssm SC

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What you may need to change

1) Your artifact filenames (for --gen mode)

If you want auto-generation, make sure your file name ends with:

• _<os>_<arch> (plus .exe for Windows)

Valid OS values (Go runtime):

• windows, linux, darwin

Common arch values:

• amd64, arm64, arm, 386

Examples:

• agent_1.0.12_windows_amd64.exe
• agent_1.0.12_linux_arm64
• agent_1.0.12_darwin_arm64

If you don’t want to rename files, use Mode A (static manifest) and write URLs manually.

2) The --root directory

If your artifacts live somewhere else, just point devserver to it:

go run ./cmd/devserver --root /path/to/your/artifacts --gen --version 1.0.12

3) Using localhost vs 127.0.0.1

If your updater runs in a VM/container/another device, 127.0.0.1 will refer to that device itself.

In that case:

• bind devserver on 0.0.0.0:<port>
• use your host IP address

Example:

go run ./cmd/devserver --addr 0.0.0.0:8089 --root ./testdata/updates --gen --version 1.0.12

Then access from another machine:

• http://<YOUR_HOST_IP>:8089/manifest.json

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Troubleshooting

“No artifacts detected” (when using --gen)

This means devserver can’t infer os/arch from filenames.

Fix:

• rename artifacts to include _<os>_<arch> near the end, e.g. agent_1.0.12_linux_amd64
• or use Mode A (static manifest.json)

404 for a file

• Ensure the artifact file exists inside the --root directory
• Ensure the URL in the manifest points to /files/<filename>

Updater says “sha256 mismatch”

• You changed the artifact file after manifest was created
• Regenerate manifest (--gen) or update the SHA256 in your static manifest.json

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Notes

• devserver sets Cache-Control: no-store to avoid caching during development.
• This server is intentionally simple and should not be used for production.

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License

This devserver is part of the main repository and follows the repository license.