Sentry Elixir SDK Skill

All Skills > SDK Setup > 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/ before implementing.

Phase 1: Detect

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

# 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:
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.

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

Option 2: Manual Setup

Install

Add to mix.exs dependencies:

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

mix deps.get

Configure

# 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):

# 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:

# 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:

# 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

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

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

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., "my-app@1.0.0"; env: SENTRY_RELEASE | | :sample_rate | float | 1.0 | Error event sample rate (0.0–1.0) | | :enable_source_code_context | boolean | false | Include source lines around errors | | :root_source_code_paths | [path] | [] | Required when source context is enabled | | :in_app_otp_apps | [atom] | [] | OTP apps whose modules are "in-app" in stacktraces | | :before_send | (event -> event \| nil) \| {m, f} | nil | Hook to mutate or drop error events | | :after_send_event | (event, result -> any) \| {m, f} | nil | Hook called after event is sent | | :filter | module | Sentry.DefaultEventFilter | Module implementing Sentry.EventFilter | | :max_breadcrumbs | integer | 100 | Max breadcrumbs per process | | :dedup_events | boolean | true | Deduplicate identical events within ~30 seconds | | :tags | map | %{} | Global tags sent with every event | | :traces_sample_rate | float \| nil | nil | Non-nil enables tracing (requires OTel setup) | | :traces_sampler | fn \| {m, f} \| nil | nil | Custom per-transaction sampling | | :enable_logs | boolean | false | Enable Sentry Logs Protocol (v12.0.0+) | | :test_mode | boolean | false | Capture events in-memory for testing |

Environment Variables

| Variable | Maps to | Purpose | |----------|---------|---------| | SENTRY_DSN | :dsn | Data Source Name | | SENTRY_RELEASE | :release | App version (e.g., my-app@1.0.0) | | SENTRY_ENVIRONMENT | :environment_name | Deployment environment |

Verification

Test that Sentry is receiving events:

# Send a test event from your project
MIX_ENV=dev mix sentry.send_test_event

Or add a temporary call in a controller action:

# Temporary test — remove after confirming
def index(conn, _params) do
  Sentry.capture_message("Sentry Elixir SDK test event")
  text(conn, "sent")
end

Check the Sentry dashboard within a few seconds. If nothing appears:

Set config :sentry, log_level: :debug for verbose SDK output
Verify SENTRY_DSN is set and the project exists
Confirm :environment_name is not set to a value Sentry filters in your alert rules

Phase 4: Cross-Link

After completing Elixir setup, check for a companion frontend missing Sentry coverage:

ls assets/ frontend/ web/ client/ ui/ 2>/dev/null
cat assets/package.json frontend/package.json 2>/dev/null | grep -E '"react"|"svelte"|"vue"|"next"'

If a frontend directory exists without Sentry configured, suggest the matching skill:

| Frontend detected | Suggest skill | |-------------------|--------------| | React / Next.js | sentry-react-sdk or sentry-nextjs-sdk | | Svelte / SvelteKit | sentry-svelte-sdk | | Vue | See docs.sentry.io/platforms/javascript/guides/vue/ | | Other JS/TS | sentry-browser-sdk |

Connecting Phoenix backend and JavaScript frontend with linked Sentry projects enables distributed tracing — stack traces that span the browser, Phoenix HTTP server, and downstream services in a single trace view.

Troubleshooting

| Issue | Solution | |-------|----------| | Events not appearing | Verify SENTRY_DSN is set; run mix sentry.send_test_event; set log_level: :debug | | Missing stack traces on captured exceptions | Pass stacktrace: __STACKTRACE__ in the rescue block: Sentry.capture_exception(e, stacktrace: __STACKTRACE__) | | PlugCapture not working on Bandit | Sentry.PlugCapture is Cowboy-only; with Bandit errors surface via LoggerHandler | | Source code context missing in production | Run mix sentry.package_source_code before building your OTP release | | Context not appearing on async events | Sentry.Context.* is process-scoped; pass values explicitly or propagate Logger metadata across processes | | Oban integration not reporting crons | Requires Oban v2.17.6+ or Oban Pro; cron jobs must have "cron" => true in job meta | | Duplicate events from Cowboy crashes | Set excluded_domains: [:cowboy] in LoggerHandler config (this is the default) | | finch not starting | Ensure {:finch, "~> 0.21"} is in deps; Finch is the default HTTP client since v12.0.0 | | JSON encoding error | Add {:jason, "~> 1.4"} and set json_library: Jason for Elixir < 1.18 |

Agent Skills: Sentry Elixir SDK

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