sentry-elixir-sdk

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:

1. Set config :sentry, log_level: :debug for verbose SDK output
2. Verify SENTRY_DSN is set and the project exists
3. 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