sentry-elixir-sdk

What this skill does

> [All Skills](../../SKILL_TREE.md) > [SDK Setup](../sentry-sdk-setup/SKILL.md) > Elixir SDK

# Sentry Elixir SDK

Opinionated wizard that scans your Elixir project and guides you through complete Sentry setup.

## Invoke This Skill When

- User asks to "add Sentry to Elixir" or "set up Sentry" in an Elixir or Phoenix app
- User wants error monitoring, tracing, logging, or crons in Elixir or Phoenix
- User mentions `sentry` hex package, `getsentry/sentry-elixir`, or Elixir Sentry SDK
- User wants to monitor exceptions, Plug errors, LiveView errors, or scheduled jobs

> **Note:** SDK versions and APIs below reflect Sentry docs at time of writing (sentry v12.0.2, requires Elixir ~> 1.13).
> Always verify against [docs.sentry.io/platforms/elixir/](https://docs.sentry.io/platforms/elixir/) before implementing.

---

## Phase 1: Detect

Run these commands to understand the project before making any recommendations:

```bash
# Check existing Sentry dependency
grep -i sentry mix.exs 2>/dev/null

# Detect Elixir version
cat .tool-versions 2>/dev/null | grep elixir
grep "elixir:" mix.exs 2>/dev/null

# Detect Phoenix or Plug
grep -E '"phoenix"|"plug"' mix.exs 2>/dev/null

# Detect Phoenix LiveView
grep "phoenix_live_view" mix.exs 2>/dev/null

# Detect Oban (job queue / crons)
grep "oban" mix.exs 2>/dev/null

# Detect Quantum (cron scheduler)
grep "quantum" mix.exs 2>/dev/null

# Detect OpenTelemetry usage
grep "opentelemetry" mix.exs 2>/dev/null

# Check for companion frontend
ls assets/ frontend/ web/ client/ 2>/dev/null
```

**What to note:**

| Signal | Impact |
|--------|--------|
| `sentry` already in `mix.exs`? | Skip install; go to Phase 2 (configure features) |
| Phoenix detected? | Add `Sentry.PlugCapture`, `Sentry.PlugContext`, optionally `Sentry.LiveViewHook` |
| LiveView detected? | Add `Sentry.LiveViewHook` to the `live_view` macro in `my_app_web.ex` |
| Oban detected? | Recommend Crons + error capture via Oban integration |
| Quantum detected? | Recommend Crons via Quantum integration |
| OpenTelemetry already present? | Tracing setup only needs `Sentry.OpenTelemetry.*` config |
| Frontend directory found? | Trigger Phase 4 cross-link suggestion |

---

## Phase 2: Recommend

Based on what you found, present a concrete recommendation. Don't ask open-ended questions — lead with a proposal:

**Recommended (core coverage):**
- ✅ **Error Monitoring** — always; captures exceptions and crash reports
- ✅ **Logging** — `Sentry.LoggerHandler` forwards crash reports and error logs to Sentry
- ✅ **Tracing** — if Phoenix, Plug, or Ecto detected (via OpenTelemetry)

**Optional (enhanced observability):**
- ⚡ **Crons** — detect silent failures in scheduled jobs (Oban, Quantum, or manual GenServer)
- ⚡ **Sentry Logs** — forward structured logs to Sentry Logs Protocol (sentry v12.0.0+)

**Recommendation logic:**

| Feature | Recommend when... |
|---------|------------------|
| Error Monitoring | **Always** — non-negotiable baseline |
| Logging | **Always** — `LoggerHandler` captures crashes that aren't explicit `capture_exception` calls |
| Tracing | Phoenix, Plug, Ecto, or OpenTelemetry imports detected |
| Crons | Oban, Quantum, or periodic `GenServer`/`Task` patterns detected |
| Sentry Logs | sentry v12.0.0+ in use and structured log search is needed |

Propose: *"I recommend setting up Error Monitoring + Logging [+ Tracing if Phoenix/Ecto detected]. Want me to also add Crons or Sentry Logs?"*

---

## Phase 3: Guide

### Option 1: Igniter Installer (Recommended)

> **You need to run this yourself** — the Igniter installer requires interactive terminal input that the agent can't handle. Copy-paste into your terminal:
>
> ```bash
> mix igniter.install sentry
> ```
>
> Available since sentry v11.0.0. It auto-configures `config/config.exs`, `config/prod.exs`, `config/runtime.exs`, and `lib/my_app/application.ex`.
>
> **Once it finishes, come back and skip to [Verification](#verification).**

If the user skips the Igniter installer, proceed with Option 2 (Manual Setup) below.

---

### Option 2: Manual Setup

#### Install

Add to `mix.exs` dependencies:

```elixir
# mix.exs
defp deps do
  [
    {:sentry, "~> 12.0"},
    {:finch, "~> 0.21"}
    # Add jason if using Elixir < 1.18:
    # {:jason, "~> 1.4"},
  ]
end
```

```bash
mix deps.get
```

#### Configure

```elixir
# config/config.exs
config :sentry,
  dsn: System.get_env("SENTRY_DSN"),
  environment_name: config_env(),
  enable_source_code_context: true,
  root_source_code_paths: [File.cwd!()],
  in_app_otp_apps: [:my_app]
```

For runtime configuration (recommended for DSN and release):

```elixir
# config/runtime.exs
import Config

config :sentry,
  dsn: System.fetch_env!("SENTRY_DSN"),
  release: System.get_env("SENTRY_RELEASE", "my-app@#{Application.spec(:my_app, :vsn)}")
```

#### Quick Start — Recommended Init Config

This config enables the most features with sensible defaults:

```elixir
# config/config.exs
config :sentry,
  dsn: System.get_env("SENTRY_DSN"),
  environment_name: config_env(),
  enable_source_code_context: true,
  root_source_code_paths: [File.cwd!()],
  in_app_otp_apps: [:my_app],
  # Logger handler config — captures crash reports
  logger: [
    {:handler, :sentry_handler, Sentry.LoggerHandler, %{
      config: %{
        metadata: [:request_id],
        capture_log_messages: true,
        level: :error
      }
    }}
  ]
```

#### Activate Logger Handler

Add `Logger.add_handlers/1` in `Application.start/2`:

```elixir
# lib/my_app/application.ex
def start(_type, _args) do
  Logger.add_handlers(:my_app)   # activates the :sentry_handler configured above

  children = [
    MyAppWeb.Endpoint
    # ... other children
  ]

  Supervisor.start_link(children, strategy: :one_for_one)
end
```

#### Phoenix Integration

**`lib/my_app_web/endpoint.ex`**

```elixir
defmodule MyAppWeb.Endpoint do
  use Sentry.PlugCapture          # Add ABOVE use Phoenix.Endpoint (Cowboy adapter only)
  use Phoenix.Endpoint, otp_app: :my_app

  # ...

  plug Plug.Parsers,
    parsers: [:urlencoded, :multipart, :json],
    pass: ["*/*"],
    json_decoder: Phoenix.json_library()

  plug Sentry.PlugContext          # Add BELOW Plug.Parsers
  # ...
end
```

> **Note:** `Sentry.PlugCapture` is only needed for the **Cowboy** adapter. Phoenix 1.7+ defaults to **Bandit**, where `PlugCapture` is harmless but unnecessary. `Sentry.PlugContext` is always recommended — it enriches events with HTTP request data.

**LiveView errors — `lib/my_app_web.ex`**

```elixir
def live_view do
  quote do
    use Phoenix.LiveView

    on_mount Sentry.LiveViewHook   # captures errors in mount/handle_event/handle_info
  end
end
```

#### Plain Plug Application

```elixir
defmodule MyApp.Router do
  use Plug.Router
  use Sentry.PlugCapture          # Cowboy only

  plug Plug.Parsers, parsers: [:urlencoded, :multipart]
  plug Sentry.PlugContext
  # ...
end
```

### For Each Agreed Feature

Walk through features one at a time. Load the reference file for each, follow its steps, and verify before moving to the next:

| Feature | Reference file | Load when... |
|---------|---------------|-------------|
| Error Monitoring | `${SKILL_ROOT}/references/error-monitoring.md` | Always (baseline) |
| Tracing | `${SKILL_ROOT}/references/tracing.md` | Phoenix / Ecto / OpenTelemetry detected |
| Logging | `${SKILL_ROOT}/references/logging.md` | `LoggerHandler` or Sentry Logs setup |
| Crons | `${SKILL_ROOT}/references/crons.md` | Oban, Quantum, or periodic jobs detected |

For each feature: `Read ${SKILL_ROOT}/references/<feature>.md`, follow steps exactly, verify it works.

---

## Configuration Reference

### Key Config Options

| Option | Type | Default | Purpose |
|--------|------|---------|---------|
| `:dsn` | `string \| nil` | `nil` | SDK disabled if nil; env: `SENTRY_DSN` |
| `:environment_name` | `atom \| string` | `"production"` | e.g., `:prod`; env: `SENTRY_ENVIRONMENT` |
| `:release` | `string \| nil` | `nil` | e.g., `"[email protected]"`; env: