Running in production

A production Graft application is one long-lived process: graft start, or your own program built on Graft.layer, run by a service manager that restarts it and stops it with SIGTERM.

Start without --watch

Run graft start graft.yml in production and keep --watch for development. Every option is on the command line page.

Concern	Without --watch	With --watch
Plugin code changes	Need a restart.	Hot reload, which is not for production.
Hand edits to graft.yml	Applied at the next restart or the next Loader edit.	Applied on save.
--env-file contents	Read once at startup.	Read again on save.
Invalid graft.yml at startup	The process exits nonzero, so the deploy fails visibly.	The process waits, running no entries.
Failed entries	Retried on change, on their retry schedule, or by loader.retry.	Also retried after each module reload.

Give every entry an id, or commit graft.yml after Graft writes the missing ones, so a read-only or freshly deployed file is not rewritten at startup.

Pass secrets

Read secrets with !env and decode them as Redacted, so neither the file nor the logs hold the value (Types and secrets). For secrets mounted as files, add --env-dir:

graft.yml

- id: database
  name: "@acme/graft-plugin-postgres"
  config:
    url: !env DATABASE_URL

import { Effect, Redacted, Schema } from "effect"

const config = Schema.Struct({
  url: Schema.RedactedFromValue(Schema.String),
})

const { url } = await Effect.runPromise(
  Schema.decodeEffect(config)({ url: "postgres://app:secret@db/app" }),
)
String(url) // => "<redacted>"
Redacted.value(url) // => "postgres://app:secret@db/app"

Rule	Pitfall it avoids
Set production variables in the process environment.	It wins over --env-file, so a stale .env beside the deploy cannot override it.
Keep .env out of Git.	graft create writes a .gitignore that ignores it; keep that line.
Never publish the fork tree’s input.	Graft.forks shows each fork’s input as resolved, before decoding, so !env values appear there in plain text.
Catch a missing variable with a health check.	It fails only its entry, and the process keeps running.

Retry flaky resources

A plugin without retry stays Failed until its config or dependencies change or loader.retry runs. Give plugins that depend on a network resource a schedule that never gives up, caps its delay and adds jitter, so forks that share a database do not reconnect in lockstep:

import { Effect, Ref, Schedule, Schema, Stream } from "effect"

import { Graft, Plugin } from "@graftland/graft"

class ConnectionRefused extends Schema.TaggedError<
  ConnectionRefused,
  { readonly brand: unique symbol }
>()("ConnectionRefused", {}) {}

// Stands in for a database that refuses the first connection.
const attempts = Ref.makeUnsafe(0)
const connect = Effect.flatMap(
  Ref.updateAndGet(attempts, (n) => n + 1),
  (n) => (n === 1 ? ConnectionRefused.make({}) : Effect.void),
)

const client = Plugin.make({
  name: "app/client",
  retry: Schedule.min([
    Schedule.exponential("1 second"),
    Schedule.spaced("1 minute"),
  ]).pipe(Schedule.jittered),
  apply: () => connect,
})

await Effect.runPromise(
  Effect.gen(function* () {
    const fork = yield* Graft.plugin(client)
    yield* fork.state.pipe(
      Stream.map((state) => state._tag),
      Stream.takeUntil((tag) => tag === "Active"),
      Stream.runCollect,
    ) // => ["Loading", "Failed", "Loading", "Active"]
  }).pipe(Effect.scoped, Effect.provide(Graft.layer)),
)

• When to retry one call inside a task instead of the whole fork is on Let the fork fail and retry.
• Entries have no retry field, so the schedule belongs to the plugin. For a name: remote entry, see Contain failures.

Contain failures

A failure stops one activation and restarts the consumers of its services (How withdrawal works). Choose the boundary by what can go wrong:

What can fail	Boundary
Two resources that fail independently	Separate plugins. One failing task fails its whole activation.
One tenant’s or instance’s dependencies	A realm per instance. Only consumers in that realm wait.
Crashes, leaks, process.exit or code that throws outside Effect	Remote local: a child process.
CPU-heavy work that blocks the event loop	Remote worker: a Node worker in the same process.
Hardware, data or a network on another machine	A runner.
What the code is allowed to do	A runner inside a container or a VM; Remote does not limit permissions.

An exception thrown outside Effect, such as in a raw callback, can end the whole process. Inside the process, only Effect failures are contained.

A name: remote YAML entry has no retry, so a crashed child stays Failed until the entry changes or loader.retry runs. To restart it, export a Remote.plugin with retry from a module and load that module instead:

src/greeterHost.ts

import { Schedule, Schema } from "effect"

import * as Remote from "@graftland/plugin-remote"

declare const contract: Remote.Contract.Contract<
  Schema.Struct<{ readonly greeting: typeof Schema.String }>
>

export default Remote.plugin(contract, {
  contractModule: new URL("./contract.js", import.meta.url).href,
  connect: { local: {} },
  retry: Schedule.spaced("5 seconds"),
})

graft.yml

- id: greeter
  name: ./dist/greeterHost.js
  config:
    greeting: Hello

Report health

A failed or pending entry does not stop the process, so a service manager that only watches the process sees a healthy application. Publish the fork states for a health endpoint:

health.ts

import { Array, Context, Effect, Ref, Stream } from "effect"

import { Fork, Graft, Plugin } from "@graftland/graft"

export class Health extends Context.Service<
  Health,
  { readonly unhealthy: Effect.Effect<ReadonlyArray<string>> }
>()("app/Health") {}

const unhealthy = (
  trees: ReadonlyArray<Fork.ForkTree>,
): ReadonlyArray<string> =>
  Array.flatMap(trees, (tree) => [
    ...(tree.state._tag === "Failed" || tree.state._tag === "Pending"
      ? [`${tree.name}: ${tree.state._tag}`]
      : []),
    ...unhealthy(tree.children),
  ])

export const health = Plugin.make({
  name: "app/health",
  apply: () =>
    Effect.gen(function* () {
      const latest = yield* Ref.make<ReadonlyArray<string>>([])
      yield* Graft.forks.pipe(
        Stream.runForEach((trees) => Ref.set(latest, unhealthy(trees))),
        Plugin.fork,
      )
      yield* Graft.provide(Health, { unhealthy: Ref.get(latest) })
    }),
})

Load the health monitor and this route plugin with the HTTP server. The mount injects Health and answers 503 when the list is not empty:

import { Effect } from "effect"
import { HttpRouter, HttpServerResponse } from "effect/http"

import { Plugin } from "@graftland/graft"
import * as Http from "@graftland/plugin-http/Http"

import { Health } from "./health.ts"

export default Plugin.make({
  name: "app/health-route",
  inject: [Health],
  apply: () =>
    Http.mount(
      HttpRouter.add(
        "GET",
        "/health",
        Effect.gen(function* () {
          const health = yield* Health
          const unhealthy = yield* health.unhealthy
          return HttpServerResponse.empty({
            status: unhealthy.length === 0 ? 200 : 503,
          })
        }),
      ),
    ).pipe(Effect.asVoid),
})

To diagnose the tree, see Troubleshooting.

Set log levels per entry

Lower the level only on the entry you are diagnosing, for as long as the investigation lasts. How to set it is on Set the level per entry, and how to get JSON logs or traces is on Choose the output in your host.

Stop gracefully

On SIGTERM or Ctrl+C, graft start unloads every plugin. A plugin that publishes services waits for their consumers to stop before it closes, so the consumers’ finalizers can still use them; see How withdrawal works.

Rule	Why
Hold every resource with Effect.acquireRelease or Effect.addFinalizer in apply.	Only what apply acquires is released at shutdown.
Finish work in flight in a finalizer or an uninterruptible region.	Tasks are interrupted after consumers drain; an interrupted task loses its work.
Set the service manager’s stop timeout above your slowest finalizer.	graft start has no overall shutdown timeout. Only SIGKILL cuts a stuck stop short.
Raise shutdownTimeout on Remote.plugin when a remote plugin’s finalizers need more than the default 5 seconds.	A YAML remote entry keeps the fixed 5 s; export a Remote.plugin from a module, as in Contain failures, to change it. See Timeouts and defaults.

For a stop that hangs, see A stop that does not finish.

Reconfigure without a restart

Change a running application through the Loader API instead of restarting it. Only the changed entries reload; the rest keep their connections and state. Which field change updates and which reloads is on Changes while running; a remote entry always restarts its plugin process.

• Edits are written to graft.yml. A deployment that replaces the file discards them, so treat the deployed file as state or write the change back to your repository.
• A running process’s environment cannot change from outside. Rotating a secret set there needs a restart. loader.retry rereads !env values, which helps only when their source changed, such as --env-file or --env-dir under --watch.
• Support Update in place in plugins that hold connections or caches, so a config edit does not drop them.

Upgrade plugins

Changes in node_modules never trigger a reload, with or without --watch. Upgrade by installing and restarting:

1. Install with graft add <package>@<version>. If the install fails, the package files are restored; see Rollback.
2. Restart the process. A running process keeps the modules it already imported.
3. Roll back by installing the previous version the same way and restarting.

Rule	Pitfall it avoids
Disable or remove the entry before graft remove.	graft add <package> and graft remove change only dependencies; an entry for a removed package fails to load.
Do not install while other tools edit the project.	An install owns the package files until it finishes; see Installation ownership.
Upgrade all @graftland/* packages to the same version.	Graft releases every package with one version.
Keep a config change compatible, or ship it with the new version.	Config that no longer decodes fails that entry with SchemaError.

To swap plugin code without a restart, an embedding host can call Graft.replace; the checkout-upgrade sample does this under load.

Embed instead of the CLI

Run Graft from your own program when you need what graft start does not offer: JSON logs, a tracer, a fixed set of bundled plugins, or services that your existing server already owns. Build the environment yourself, including the intercepts your graft.yml uses; an embedded loader registers none:

import { Layer, Logger, LogLevel, References, Schema } from "effect"
import { NodeServices } from "@effect/platform-node"

import { Intercept, ModuleResolver } from "@graftland/loader"

const environment = Layer.mergeAll(
  NodeServices.layer,
  ModuleResolver.layer({
    base: process.cwd(),
    importer: (specifier) => import(specifier),
  }).pipe(Layer.provide(NodeServices.layer)),
  Intercept.layer([
    Intercept.make(
      References.MinimumLogLevel,
      Schema.Literals(LogLevel.values),
      (_, level) => level,
    ),
  ]),
  Logger.layer([Logger.consoleJson]),
)

Then run Include.Include in Layer.provideMerge(Graft.layer, environment), as in Load a config file.

Rule	Why
Put the server’s own services in environment.	Plugins inject them like any service, and they live as long as the program.
Run with NodeRuntime.runMain.	It turns SIGINT and SIGTERM into interruption, so the scope closes and plugins stop in order.
Add SecureRandom.layerWebCrypto if you load remote entries.	Remote needs it; graft start provides it for you.