Hi, I'm Sandy 👋

Based in Tokyo. I work on the unglamorous parts of distributed systems — the parts that page someone at 3 AM.

Most of my open-source time goes into observability infrastructure (Prometheus-compatible storage, log shipping, OpenTelemetry SDKs) and transport security (mTLS for OTLP across SDKs). I like fixing the bug that's been "flaky for ages," the one nobody wants to bisect.

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🌍 OSS contributions

Observability — storage, query, shipping

• cortexproject/cortex — Ingester correctness (counter leaks, send-on-closed-channel panics, TSDB appender lifecycle on error paths), ring/backoff timer reuse to cut per-poll allocations, memberlist cluster-label safety against accidental cross-cluster joins, plus the in-flight integration_query_fuzz stabilisation series.
• grafana/loki — Azure Managed Identity for the blob backend; better fluent-bit output plugin startup error messages.
• grafana/grafana — Alerting (instance-wide UI disable setting, disable Grafana-managed alert creation) and Dashboards (N+1 query in GetDashboardsByPluginID).
• fluent/fluent-bit — in_tail file-watching: inotify reconciliation after missed events, append-cleanup on failure.
• fluent/fluent-operator — CRD validation preventing a fluent-bit crash on null logfmt parser values.

OpenTelemetry — mTLS for OTLP across languages

• open-telemetry/opentelemetry-dotnet — End-to-end mTLS for OTLP exporters: TLS HTTP client factory, custom-CA-only trust scope, helper renames, integration-test cert generation via MSBuild.
• open-telemetry/opentelemetry-dotnet-instrumentation — mTLS env-var documentation.
• open-telemetry/opentelemetry-go — Fail-closed when an HTTP endpoint is paired with TLS client config; async-callback unregister deadlock fix in the SDK metric path.
• open-telemetry/opentelemetry-go-contrib — otelconf client-key/cert symmetry validation for mTLS.
• open-telemetry/opentelemetry-python — Client key/cert file support for all OTLP exporters.
• open-telemetry/opentelemetry-specification — Proposal for mTLS client-key password & certificate-revocation config.

Auth, proxies, migration tooling

• oauth2-proxy/oauth2-proxy — cookie-secret-file support.
• openrewrite/rewrite-spring — OpenTelemetry migration recipes for Spring Boot.
• traefik/traefik — HRW hashring perf path + benchmark; dynamic log-level via API.

I also keep react-otel-observability as a working example of an OTel-instrumented frontend wired to Loki / Tempo / Cortex.

🧰 Languages I actually write

• Go — observability work, ring/gossip internals, gRPC services.
• TypeScript — day-to-day product work (React, Node, Tauri, WeChat mini-program).
• Python — research, data crunching, older trading / ML projects.
• C / C++ — fluent-bit patches and a few low-level toolkits.
• C# — OTel .NET SDK contributions.
• Java — OpenRewrite recipes, JSP-era projects.
• Rust — occasional; servers and CLI tools.
• Past lives: MATLAB / Verilog (a CNN on FPGA), GDScript, Vue, a goyacc calculator.