Lemmy Know

September 5, 2025 · View on GitHub

Lemmy Know (let me know) is a lightweight CLI application / Docker service that monitors Lemmy for reports on posts and comments and sends notification. These can be sent to a Discord channel with a webhook or as MQTT messages (schema), which is useful for more complex setups with e.g., Node-RED.

Reports sometimes don't federate with my main account's instance and I therefore had to check several sites manually each day. There were also some instance for which the reports didn't seem to federate at all. This tool is therefore made to check for reports using multiple accounts on multiple instances to avoid this problem.

The Docker image is ~10MB, and the container uses 6MB RAM and ~0.1% CPU on my server.

If you find bugs, have suggestions, or want to contribute features, feel free to open an issue or submit a pull request.

Usage

The application uses a Postgres database to store credentials, the ID's of the reports which have already been sent, and the full report as a JSONB column in case you want to check something later.

Start application to generate DB tables
Add Lemmy moderator account credentials to table

Options

When running as CLI application it will use a .env file in the current working directory if available.

Note: All notification methods are optional, you only need to supply the variables for the methods you want to use.

CLI Option	Environment variable	Description
`--db-host`	DB_HOST	Host of the PostgreSQL database.
`--db-port`	DB_PORT	Port of the PostgreSQL database.
`--db-user`	DB_USER	Username for the PostgreSQL database.
`--db-password`	DB_PASSWORD	Password for the PostgreSQL database.
`--db-name`	DB_NAME	Database name of the PostgreSQL database.
`-d`, `--discord-webhook`	DISCORD_WEBHOOK	Optional Discord webhook for notification.
`--ntfy-host`	NTFY_HOST	Host URL for ntfy notifications.
`--ntfy-topic`	NTFY_TOPIC	Topic for ntfy notifications. `lemmy-know` by default.
`--ntfy-username`	NTFY_USERNAME	Username for ntfy.
`--ntfy-password`	NTFY_PASSWORD	Password for ntfy.
`--mqtt-host`	MQTT_HOST	Host of the MQTT broker.
`--mqtt-port`	MQTT_PORT	Port of the MQTT broker.
`--mqtt-user`	MQTT_USER	Username for the MQTT broker.
`--mqtt-password`	MQTT_PASSWORD	Password for the MQTT broker.
`-i`, `--interval`	INTERVAL	Interval in seconds to send requests to check for reports.

Database Schema

classDiagram
direction BT
class comment_reports {
    🔑 text domain
    🔑 integer id
    jsonb data
}
class credentials {
    🔑 text domain
    🔑 text username
    text password
}
class post_reports {
    🔑 text domain
    🔑 integer id
    jsonb data
}

MQTT message schema

Comment

Topic: lemmy-know/comment

{
  "source_domain": STRING,
  "report": {
    "comment_report": {
      "id": NUMBER,
      "creator_id": NUMBER,
      "comment_id": NUMBER,
      "original_comment_text": STRING,
      "reason": STRING,
      "resolved": BOOLEAN,
      "published": TIMESTAMP
    },
    "comment": {
      "id": NUMBER,
      "creator_id": NUMBER,
      "post_id": NUMBER,
      "content": STRING,
      "removed": BOOLEAN,
      "published": TIMESTAMP,
      "deleted": BOOLEAN,
      "ap_id": STRING,
      "local": BOOLEAN,
      "path": STRING,
      "distinguished": BOOLEAN,
      "language_id": NUMBER
    },
    "post": {
      "id": NUMBER,
      "name": STRING,
      "url": STRING,
      "body": STRING,
      "creator_id": NUMBER,
      "community_id": NUMBER,
      "removed": BOOLEAN,
      "locked": BOOLEAN,
      "published": TIMESTAMP,
      "updated": TIMESTAMP,
      "deleted": BOOLEAN,
      "nsfw": BOOLEAN,
      "thumbnail_url": STRING,
      "ap_id": STRING,
      "local": BOOLEAN,
      "language_id": NUMBER,
      "featured_community": BOOLEAN,
      "featured_local": BOOLEAN,
      "url_content_type": STRING
    },
    "community": {
      "id": NUMBER,
      "name": STRING,
      "title": STRING,
      "description": STRING,
      "removed": BOOLEAN,
      "published": TIMESTAMP,
      "updated": TIMESTAMP,
      "deleted": BOOLEAN,
      "nsfw": BOOLEAN,
      "actor_id": STRING,
      "local": BOOLEAN,
      "icon": STRING,
      "banner": STRING,
      "hidden": BOOLEAN,
      "posting_restricted_to_mods": BOOLEAN,
      "instance_id": NUMBER,
      "visibility": STRING
    },
    "creator": {
      "id": NUMBER,
      "name": STRING,
      "display_name": STRING,
      "banned": BOOLEAN,
      "published": TIMESTAMP,
      "actor_id": STRING,
      "bio": STRING,
      "local": BOOLEAN,
      "deleted": BOOLEAN,
      "matrix_user_id": STRING,
      "bot_account": BOOLEAN,
      "instance_id": NUMBER
    },
    "comment_creator": {
      "id": NUMBER,
      "name": STRING,
      "banned": BOOLEAN,
      "published": TIMESTAMP,
      "actor_id": STRING,
      "local": BOOLEAN,
      "deleted": BOOLEAN,
      "bot_account": BOOLEAN,
      "instance_id": NUMBER
    },
    "counts": {
      "comment_id": NUMBER,
      "score": NUMBER,
      "upvotes": NUMBER,
      "downvotes": NUMBER,
      "published": TIMESTAMP,
      "child_count": NUMBER
    },
    "creator_banned_from_community": BOOLEAN,
    "creator_is_moderator": BOOLEAN,
    "creator_is_admin": BOOLEAN,
    "creator_blocked": BOOLEAN,
    "subscribed": STRING,
    "saved": BOOLEAN
  }
}

Post

Topic: lemmy-know/post

{
  "source_domain": STRING,
  "report": {
    "post_report": {
      "id": NUMBER,
      "creator_id": NUMBER,
      "post_id": NUMBER,
      "original_post_name": STRING,
      "original_post_url": STRING,
      "reason": STRING,
      "resolved": BOOLEAN,
      "published": TIMESTAMP
    },
    "post": {
      "id": NUMBER,
      "name": STRING,
      "url": STRING,
      "creator_id": NUMBER,
      "community_id": NUMBER,
      "removed": BOOLEAN,
      "locked": BOOLEAN,
      "published": TIMESTAMP,
      "deleted": BOOLEAN,
      "nsfw": BOOLEAN,
      "thumbnail_url": STRING,
      "ap_id": STRING,
      "local": BOOLEAN,
      "language_id": NUMBER,
      "featured_community": BOOLEAN,
      "featured_local": BOOLEAN,
      "url_content_type": STRING
    },
    "community": {
      "id": NUMBER,
      "name": STRING,
      "title": STRING,
      "description": STRING,
      "removed": BOOLEAN,
      "published": TIMESTAMP,
      "updated": TIMESTAMP,
      "deleted": BOOLEAN,
      "nsfw": BOOLEAN,
      "actor_id": STRING,
      "local": BOOLEAN,
      "icon": STRING,
      "banner": STRING,
      "hidden": BOOLEAN,
      "posting_restricted_to_mods": BOOLEAN,
      "instance_id": NUMBER,
      "visibility": STRING
    },
    "creator": {
      "id": NUMBER,
      "name": STRING,
      "display_name": STRING,
      "banned": BOOLEAN,
      "published": TIMESTAMP,
      "actor_id": STRING,
      "bio": STRING,
      "local": BOOLEAN,
      "deleted": BOOLEAN,
      "matrix_user_id": STRING,
      "bot_account": BOOLEAN,
      "instance_id": NUMBER
    },
    "post_creator": {
      "id": NUMBER,
      "name": STRING,
      "banned": BOOLEAN,
      "published": TIMESTAMP,
      "actor_id": STRING,
      "local": BOOLEAN,
      "deleted": BOOLEAN,
      "bot_account": BOOLEAN,
      "instance_id": NUMBER
    },
    "creator_banned_from_community": BOOLEAN,
    "creator_is_moderator": BOOLEAN,
    "creator_is_admin": BOOLEAN,
    "subscribed": STRING,
    "saved": BOOLEAN,
    "read": BOOLEAN,
    "hidden": BOOLEAN,
    "creator_blocked": BOOLEAN,
    "unread_comments": NUMBER,
    "counts": {
      "post_id": NUMBER,
      "comments": NUMBER,
      "score": NUMBER,
      "upvotes": NUMBER,
      "downvotes": NUMBER,
      "published": TIMESTAMP,
      "newest_comment_time": TIMESTAMP
    }
  }
}