binlog-analysis

# Binlog Analysis (via the binlog-mcp MCP server) Boil a failed build down to root causes. This skill does two small things and delegates the heavy lifting to an MCP server: 1. **Fetch** the build's `*.binlog` — from your local build, or from a failed `fsharp-ci` Azure DevOps PR build (downloads the published artifact). 2. **Hand the path to the `binlog-mcp` MCP server** (`Microsoft.AITools.BinlogMcp`), which queries the binlog live (≈38 tools): structured errors, categorized root causes, and an MSBuild X-ray (target/task/analyzer timings, incrementality, double-writes, …). Because the analysis lives in the MCP server, this skill stays tiny — and gets better automatically as that server gains features. ## When to use - A local build (with `-bl`) or a failed `fsharp-ci` PR build broke and you need to know **why** — compile / restore / analyzer / WarnAsError errors, or build perf. ## When NOT to use - **Test** failures or **CheckCodeFormatting**. The build binlog has no errors in that case: `binlog_overview` will show the build succeeded / 0 errors — stop and use `pr-build-status` / `flaky-test-detector` instead. ## Step 1 — get the binlog path ```pwsh # Local: newest *.binlog under <repo>/artifacts/log (build first, e.g. ./build.sh --binaryLog) pwsh .github/skills/binlog-analysis/scripts/Get-Binlog.ps1 # Local: a specific file, directory, or glob pwsh .github/skills/binlog-analysis/scripts/Get-Binlog.ps1 -BinlogPath artifacts/log/Debug/Build.binlog # Azure DevOps: latest FAILED fsharp-ci build for a PR (downloads + keeps the binlog) pwsh .github/skills/binlog-analysis/scripts/Get-Binlog.ps1 -PrNumber 19941 # Azure DevOps: explicit build id; -AllLegs for every leg; -Json for a path list pwsh .github/skills/binlog-analysis/scripts/Get-Binlog.ps1 -BuildId 1462217 -Json ``` It prints the resolved `*.binlog` path(s) (Azure DevOps artifacts are downloaded to a temp folder and kept so the MCP can read them). ## Step 2 — analyze via the binlog-mcp MCP tools With each path, call the MCP server (the argument is `binlog_file`): - `binlog_overview` — build status + error/warning counts. **Call this first** to decide whether there's anything to analyze. - `binlog_diagnose` — categorized root causes + next-step hints. - `binlog_errors` / `binlog_warnings` — structured diagnostics (code / file / line / column / project). - `binlog_search` — free-form drill-down. - Perf: `binlog_expensive_targets` / `binlog_expensive_tasks` / `binlog_expensive_analyzers`, `binlog_incremental_analysis`, `binlog_double_writes`, `binlog_target_graph`. > **Multi-targeting note.** Today `binlog_errors` returns one row per target > framework, so a single source error in a multi-TFM project (e.g. > FSharp.Compiler.Service → `net10.0;netstandard2.0`) appears once per TFM. A > lossless dedup (`code,file,line` → set of TFMs) is proposed upstream in > `dotnet-microsoft/ai-tools`; when it lands, this skill gets the deduped view for > free — no change here. ## Prerequisites - The **binlog-mcp MCP server** registered with your agent. The tool is pinned in the repo's `.config/dotnet-tools.json` (`Microsoft.AITools.BinlogMcp`); run `dotnet tool restore` once, then register it as an MCP server. For example, Copilot CLI (`~/.copilot/mcp-config.json`): ```jsonc { "mcpServers": { "binlog-mcp": { "command": "dotnet", "args": ["tool", "run", "binlog-mcp"], "tools": ["*"], "deferTools": "auto" } } } ``` (gh-aw: a `mcp-servers:` block; VS Code: `.vscode/mcp.json`. Telemetry is on by default — opt out with `DOTNET_CLI_TELEMETRY_OPTOUT=1` if desired.) - PowerShell 7+ (`pwsh`) and a .NET 10 SDK (already required by the repo). - Azure DevOps modes need network access to `dev.azure.com`.