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Slack Postgres State Example

Overview

This example runs a tiny Slack bot with Postgres-backed runtime state. When the bot is mentioned in a channel, or messaged directly if you enable the DM event, it subscribes the thread and replies. Later messages in that subscribed thread are routed through Postgres-backed state.

Slack App Setup

Set up a Slack app as in the tutorial: Steps 2–3 create the app and collect credentials, and Use HTTP Instead Of Socket Mode exposes your machine and sets the request URL. This example also replies to follow-up messages in subscribed threads, so add the channels:history scope and message.channels event from Step 6 too.

Setting Value
Bot token scopes chat:write, app_mentions:read, channels:history (add im:history for direct messages)
Bot events app_mention, message.channels (add message.im for direct messages)
Request URL https://YOUR_PUBLIC_HOST/webhooks/slack
SLACK_BOT_TOKEN OAuth & Permissions → Bot User OAuth Token (xoxb-…)
SLACK_SIGNING_SECRET Basic Information → App Credentials → Signing Secret

Reinstall the app from OAuth & Permissions after changing scopes or events.

Run Postgres

From the repository root:

cd examples/slack-postgres-state
docker compose up -d postgres

Or let Pitchfork supervise the service:

cd examples/slack-postgres-state
pitchfork start postgres

The database URL for the local Compose service is:

postgres://chat_sdk_go:chat_sdk_go@127.0.0.1:54330/chat_sdk_go?sslmode=disable

To stop Postgres:

docker compose down

To delete the Postgres volume:

docker compose down -v

Run The Bot

From this example directory:

export SLACK_SIGNING_SECRET="..."
export SLACK_BOT_TOKEN="xoxb-..."
export DATABASE_URL="postgres://chat_sdk_go:chat_sdk_go@127.0.0.1:54330/chat_sdk_go?sslmode=disable"
export PORT=8080

go run .

In Slack, mention the bot in a channel where it is present:

@your-bot hello

The bot replies in the same thread with portable Markdown and subscribes the thread:

**hello** _world_ from Postgres state. This thread is now subscribed.

Send another message in the same Slack thread. The bot should route it as a subscribed message and reply:

Postgres remembered this subscribed thread.

Notes

  • Runtime state is stored in Postgres, so subscriptions, dedupe data, and locks can survive process restarts while Postgres is still running.
  • The Postgres state adapter creates its runtime coordination tables on startup.
  • Slack URL verification is handled by the Slack adapter at /webhooks/slack.
  • Slack request signatures are verified with SLACK_SIGNING_SECRET.
  • The bot token is used for auth.test during adapter startup and chat.postMessage when replying.

Interface

package main in its own module, github.com/coder/chat/examples/slack-postgres-state [go.mod:module]. It is built from main.go and takes no CLI flags. It imports github.com/coder/chat, github.com/coder/chat/adapters/slack, github.com/coder/chat/state/postgres (as chatpostgres), and github.com/jackc/pgx/v5/pgxpool [main.go:main].

Symbol Role Source
main() Connects to Postgres, builds the state, the Slack adapter, and the chat.Chat runtime, registers both handlers, and serves the webhook. [main.go:main]
OnNewMention handler Subscribes the thread, then posts chat.Markdown("**hello** _world_ from Postgres state. This thread is now subscribed."). [main.go:main]
OnSubscribedMessage handler Posts chat.Markdown("Postgres remembered this subscribed thread."). [main.go:main]
/webhooks/slack The only HTTP route, on http.DefaultServeMux. It serves bot.Webhook("slack"), which answers 405 to any method but POST. [main.go:main]
mustEnv Reads a required environment variable. [main.go:mustEnv]
compose.yaml Local postgres service and volume. [compose.yaml:services.postgres]
pitchfork.toml Pitchfork daemon postgres that wraps the Compose service. [pitchfork.toml:daemons.postgres]

Invariants

  • DATABASE_URL, SLACK_SIGNING_SECRET, and SLACK_BOT_TOKEN must be non-empty. Otherwise mustEnv panics with <NAME> is required [main.go:mustEnv].
  • An error from pgxpool.New, chatpostgres.New, slack.New, chat.New, bot.Webhook("slack"), or http.ListenAndServe panics [main.go:main].
  • The state keys use the slack-example namespace: chatpostgres.New with Pool and Namespace: "slack-example" [main.go:main].
  • The mention handler subscribes the thread before it posts the reply [main.go:main].
  • go.mod replaces github.com/coder/chat with ../.. and github.com/coder/chat/state/postgres with ../../state/postgres, so the example builds against the local tree [go.mod:replace].

Side Effects

Environment variable Default Use Source
DATABASE_URL none (required) Postgres connection [main.go:main]
SLACK_SIGNING_SECRET none (required) slack.Options.SigningSecret [main.go:main]
SLACK_BOT_TOKEN none (required) slack.Options.BotToken [main.go:main]
PORT 8080 Listen address ":" + PORT [main.go:main]
  • Network: pgxpool.New(ctx, DATABASE_URL) opens a connection pool [main.go:main]. main does not close it directly: the deferred bot.Shutdown calls State.Shutdown, which closes it [main.go:main], [state/postgres State.Shutdown].
  • Network: http.ListenAndServe on :$PORT with the default server, so no server timeouts are set [main.go:main].
  • Network: slack.New builds the Slack adapter, and each handler posts a reply with Thread.Post [main.go:main].
  • State: runtime state goes to Postgres through chatpostgres.New [main.go:main].
  • Logging: slog.Default() goes to the adapter and the runtime. main logs listening and chat shutdown failed [main.go:main].
  • Lifecycle: a deferred bot.Shutdown(context.Background()) runs when main returns or panics. main installs no signal handler [main.go:main].
  • Compose service postgres: image postgres:17-alpine, port 127.0.0.1:54330:5432, volume postgres-data at /var/lib/postgresql/data [compose.yaml:services.postgres].
  • The Compose environment sets POSTGRES_DB, POSTGRES_USER, and POSTGRES_PASSWORD to chat_sdk_go [compose.yaml:services.postgres].
  • Compose healthcheck: pg_isready -U chat_sdk_go -d chat_sdk_go every 2s, timeout 5s, 30 retries [compose.yaml:services.postgres.healthcheck].
  • Pitchfork daemon postgres in namespace chat-sdk-go-slack-postgres-state: runs docker compose up postgres, waits on docker compose exec -T postgres pg_isready -U chat_sdk_go -d chat_sdk_go, and has auto = ["start", "stop"] [pitchfork.toml:daemons.postgres].

Verification

This example is a separate Go module with no _test.go files, so go test only builds it. From the repository root:

  • Run: cd examples/slack-postgres-state && go test ./...
  • Run: cd examples/slack-postgres-state && go vet ./...