Intro and motivation

Slack Morphism is a modern client library for Slack Web/Events API/Sockets Mode and Block Kit.

Type-safety

All of the models, API and Block Kit support in Slack Morphism are well-typed.

Easy to use

The library depends only on familiar for Rust developers principles and libraries like Serde, futures, hyper.

Async

Using the latest Rust async/await language features and libraries, the library provides access to all of the functions in asynchronous manner.

Base crate to support frameworks-agnostic client and that doesn't have any dependency to any HTTP/async library itself, and you can implement binding to any library you want. Includes also all type/models definitions that used for Slack Web/Events APIs.

This library provided the following features:

hyper: Slack client support/binding for Hyper/Tokio/Tungstenite.
axum: Slack client support/binding for axum framework support.

Getting Started

Cargo.toml dependencies example:

[dependencies]
slack-morphism = { version = "2.10", features = ["hyper", "axum"] }

All imports you need:

use slack_morphism::prelude::*;

Ready to use examples

Slack Web API client and Block kit example
Events API server example using either pure hyper solution or axum
Slack Web API client with Socket Mode

You can find them on GitHub

Slack Web API client

Create a client instance

use slack_morphism::prelude::*;

let client = SlackClient::new( SlackClientHyperConnector::new()? );

Make Web API methods calls

For most of Slack Web API methods (except for OAuth methods, Incoming Webhooks and event replies) you need a Slack token to make a call. For simple bots you can have it in your config files, or you can obtain workspace tokens using Slack OAuth.

In the example below, we’re using a hardcoded Slack token, but don’t do that for your production bots and apps. You should securely and properly store all of Slack tokens.


use slack_morphism::prelude::*;

async fn example() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
   
    let client = SlackClient::new(SlackClientHyperConnector::new()?);
    
    // Create our Slack API token
    let token_value: SlackApiTokenValue = "xoxb-89.....".into();
    let token: SlackApiToken = SlackApiToken::new(token_value);
    
    // Create a Slack session with this token
    // A session is just a lightweight wrapper around your token
    // not to specify it all the time for series of calls.
    let session = client.open_session(&token);
    
    // Make your first API call (which is `api.test` here)
    let test: SlackApiTestResponse = session
            .api_test(&SlackApiTestRequest::new().with_foo("Test".into()))
            .await?;

    // Send a simple text message
    let post_chat_req =
        SlackApiChatPostMessageRequest::new("#general".into(),
               SlackMessageContent::new().with_text("Hey there!".into())
        );

    let post_chat_resp = session.chat_post_message(&post_chat_req).await?;

    Ok(())
}

Note that session is just an auxiliary lightweight structure that stores references to the token and the client to make easier to have series of calls for the same token. It doesn't make any network calls. There is no need to store it.

Another option is to use session is to use function run_in_session:

    // Sessions are lightweight and basically just a reference to client and token
    client
        .run_in_session(&token, |session| async move {
            let test: SlackApiTestResponse = session
                .api_test(&SlackApiTestRequest::new().with_foo("Test".into()))
                .await?;

            println!("{:#?}", test);

            let auth_test = session.auth_test().await?;
            println!("{:#?}", auth_test);

            Ok(())
        })
        .await?;

Pagination support

Some Web API methods defines cursors and pagination, to give you an ability to load a lot of data continually (using batching and continually making many requests).

Examples: conversations.history, conversations.list, users.list, ...

To help with those methods Slack Morphism provides additional a “scroller” implementation, which deal with all scrolling/batching requests for you.

For example for users.list:


use slack_morphism::prelude::*;

use std::time::Duration;

async fn example() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {

    let hyper_connector = SlackClientHyperConnector::new()?;
    let client = SlackClient::new(hyper_connector);
    
    let token_value: SlackApiTokenValue = "xoxb-89.....".into();
    let token: SlackApiToken = SlackApiToken::new(token_value);
    let session = client.open_session(&token);
    
    // Create a first request and specify a batch limit:
    let scroller_req: SlackApiUsersListRequest = SlackApiUsersListRequest::new().with_limit(5);
    
    // Create a scroller from this request
    let scroller = scroller_req.scroller();
    
    // Option 1: Create a Rust Futures Stream from this scroller and use it
    use futures::stream::BoxStream;
    use futures::TryStreamExt;
    
    let mut items_stream = scroller.to_items_stream(&session);
    while let Some(items) = items_stream.try_next().await? {
        println!("users batch: {:#?}", items);
    }
    
    // Option 2: Collect all of the data in a vector (which internally uses the same approach above)
    // Only for Tokio/Hyper for now
    let collected_members: Vec<SlackUser> = scroller
        .collect_items_stream(&session, Duration::from_millis(1000))
        .await?;

    // Option 3: Throttling scrolling with Tokio/Hyper:
    let mut items_throttled_stream =
        scroller.to_items_throttled_stream(&session, Duration::from_millis(500));
    while let Some(items) = items_throttled_stream.try_next().await? {
        println!("res: {:#?}", items);
    }

    Ok(())
}

Block Kit support

To support Slack Block Kit rich messages and views, the library provides:

Well-typed models
Macros to help build blocks, block elements

Let’s take some very simple block example:

{
  "blocks": [
      {
        "type": "section",
        "text": {
            "type": "mrkdwn",
            "text": "A message *with some bold text* and _some italicized text_."
        }
      }
  ]
}

Now, let’s look at how it looks with type-safe code using Slack Morphism Blocks macro support:

use slack_morphism::prelude::*;

let blocks : Vec<SlackBlock> = slack_blocks![
 some_into(
    SlackSectionBlock::new()
        .with_text(md!("A message *with some bold text* and _some italicized text_."))
 )
];

Let’s look at another more complex example for welcoming message:


use slack_morphism::prelude::*;

async fn example() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {

    use std::time::Duration;
    use rsb_derive::Builder;

    let hyper_connector = SlackClientHyperConnector::new();
    let client = SlackClient::new(hyper_connector);

    let token_value: SlackApiTokenValue = "xoxb-89.....".into();
    let token: SlackApiToken = SlackApiToken::new(token_value);
    let session = client.open_session(&token);

    // Our welcome message params as a struct
    #[derive(Debug, Clone, Builder)]
    pub struct WelcomeMessageTemplateParams {
        pub user_id: SlackUserId,
    }

    // Define our welcome message template using block macros, a trait and models from the library
    impl SlackMessageTemplate for WelcomeMessageTemplateParams {
        fn render_template(&self) -> SlackMessageContent {
            SlackMessageContent::new()
                .with_text(format!("Hey {}", self.user_id.to_slack_format()))
                .with_blocks(slack_blocks![
                    some_into(
                        SlackSectionBlock::new()
                            .with_text(md!("Hey {}", self.user_id.to_slack_format()))
                    ),
                    some_into(SlackDividerBlock::new()),
                    some_into(SlackImageBlock::new(
                        "https://www.gstatic.com/webp/gallery3/2_webp_ll.png".into(),
                        "Test Image".into()
                    )),
                    some_into(SlackHeaderBlock::new(
                        pt!("Simple header")
                    )),
                    some_into(SlackActionsBlock::new(slack_blocks![some_into(
                        SlackBlockButtonElement::new(
                            "simple-message-button".into(),
                            pt!("Simple button text")
                        )
                    )]))
                ])
        }
    }

    // Use it
    let message = WelcomeMessageTemplateParams::new("some-slack-uid".into());

    let post_chat_req =
        SlackApiChatPostMessageRequest::new("#general".into(), message.render_template());

    Ok(())
}

Look other examples in examples/templates.rs.

Send Slack Webhook Messages

You can use client..post_webhook_message to post Slack Incoming Webhook messages:


use slack_morphism::prelude::*;
use url::Url;

let client = SlackClient::new(SlackClientHyperConnector::new()?);

// Your incoming webhook url from config or OAuth/events (ResponseURL)
let webhook_url: Url = Url::parse("https://hooks.slack.com/services/...")?; 

client
    .post_webhook_message(
        &webhook_url,
        &SlackApiPostWebhookMessageRequest::new(
            SlackMessageContent::new()
                .with_text(format!("Hey")),
        ),
    )
    .await?;

Different hyper connection types and proxy support

In some cases you may need to configure hyper connection types.

Common examples:

Need to use a proxy server
Have different initialisation for certs/TLS

To do that there is additional initialisation method in SlackClientHyperConnector.

For example for proxy server config it might be used as:


    let proxy = {
        let https_connector = hyper_rustls::HttpsConnectorBuilder::new()
            .with_native_roots()?
            .https_only()
            .enable_http1()
            .build();

        let proxy_uri = "http://proxy.unfortunate.world.example.net:3128"
            .parse()
            .unwrap();
        let proxy = Proxy::new(Intercept::Https, proxy_uri);
        ProxyConnector::from_proxy(https_connector, proxy).unwrap()
    };

    let _client = SlackClient::new(
        SlackClientHyperConnector::with_connector(proxy)
    );

Please note that this configuration available only for Slack Client, and doesn't work for Socket Mode (WS) mode.

Rate control, throttling and retrying Slack API method requests

Enable rate control

Slack API defines rate limits to which all of your applications must follow.

By default, throttler isn't enabled, so you should enable it explicitly:

use slack_morphism::prelude::*;

let client = SlackClient::new(
    SlackClientHyperConnector::new()?
        .with_rate_control(
            SlackApiRateControlConfig::new()
        )
);

The example above creates a Slack API Client that follows the official rate limits from Slack. Because the Slack rate limits apply per workspaces (separately), to use throttling and limits properly you have to specify team id in tokens:

let token_value: SlackApiTokenValue = config_env_var("SLACK_TEST_TOKEN")?.into();
let team_id: SlackTeamId = config_env_var("SLACK_TEST_TEAM_ID")?.into();
let token: SlackApiToken = SlackApiToken::new(token_value).with_team_id(team_id);

let session = client.open_session(&token);

Rate control params

You can also customise rate control params using SlackApiRateControlConfig:

To global rate limit all APIs and for all teams use: SlackApiRateControlConfig.global_max_rate_limit. Default is not limited.
To rate limit all APIs and each team separately: SlackApiRateControlConfig.team_max_rate_limit. Default is not limited.
To change default tiers limits use SlackApiRateControlConfig.tiers_limits. Defaults are following the Slack recommendations (almost, there are slight differences to optimize bursting for Tier1).

Enable automatic retry for rate exceeded requests

To enable automatic retry of Slack Web API method requests, you need to specify max_retries in rate control params (default value is 0):


    let client = SlackClient::new(
        SlackClientHyperConnector::new()?
            .with_rate_control(
                SlackApiRateControlConfig::new().with_max_retries(5)
            ),
    );

Observability and tracing

The library uses popular tracing crate for logs and distributed traces (spans). To improve observability for your specific cases, additionally to the fields provided by library, you can inject your own trace fields:

use slack_morphism::prelude::*;
use tracing::*;

// While Team ID is optional but still useful for tracing and rate control purposes
let token: SlackApiToken =
    SlackApiToken::new(token_value).with_team_id(config_env_var("SLACK_TEST_TEAM_ID")?.into());

// Let's create our own user specific span first
let my_custom_span = span!(Level::DEBUG, "My scope", my_scope_attr = "my-scope-value");
debug!("Testing tracing abilities");

// Sessions are lightweight and basically just a reference to client and token
client
    .run_in_session(&token, |session| async move {
        let test: SlackApiTestResponse = session
            .api_test(&SlackApiTestRequest::new().with_foo("Test".into()))
            .await?;
        println!("{:#?}", test);

        let auth_test = session.auth_test().await?;
        println!("{:#?}", auth_test);

        Ok(())
    })
    .instrument(my_custom_span.or_current())
    .await

Events API and OAuth

The library provides two different ways to work with Slack Events API:

Using pure Hyper-based solution
Using more high-level solution for axum web framework

Testing with ngrok

For development/testing purposes you can use ngrok:

ngrok http 8080

and copy the URL it gives for you to the example parameters for SLACK_REDIRECT_HOST.

Example testing with ngrok:

SLACK_CLIENT_ID=<your-client-id> \
SLACK_CLIENT_SECRET=<your-client-secret> \
SLACK_BOT_SCOPE=app_mentions:read,incoming-webhook \
SLACK_REDIRECT_HOST=https://<your-ngrok-url>.ngrok.io \
SLACK_SIGNING_SECRET=<your-signing-secret> \
cargo run --example events_api_server --all-features

Slack Signature Verifier

The library provides Slack events signature verifier (SlackEventSignatureVerifier), which is already integrated in the OAuth routes implementation for you, and you don't need to use it directly. All you need is provide your client id and secret configuration to route implementation. Look at the complete example here.

In case you're embedding the library into your own Web/routes-framework, you can use it separately.

Events API and OAuth for Hyper

The library provides routes and middleware implementation in SlackClientEventsListener for:

Push Events
Interaction Events
Command Events
OAuth v2 redirects and client functions nested router

You can chain all of the routes using chain_service_routes_fn from the library.

Hyper configuration

In order to use Events API/OAuth you need to configure Hyper HTTP server. There is nothing special about how to do that, and you can use the official hyper docs. This is just merely a quick example how to use it with Slack Morphism routes.

Example


use slack_morphism::prelude::*;

// Hyper imports
use hyper::service::{make_service_fn, service_fn};
use hyper::{Body, Request, Response};

// For logging
use log::*;

// For convinience there is an alias SlackHyperClient as SlackClient<SlackClientHyperConnector>

async fn create_slack_events_listener_server() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {

    let addr = std::net::SocketAddr::from(([127, 0, 0, 1], 8080));
    info!("Loading server: {}", addr);

    // This is our default HTTP route when Slack routes didn't handle incoming request (different/other path).
    async fn your_others_routes(
        _req: Request<Body>,
    ) -> Result<Response<Body>, Box<dyn std::error::Error + Send + Sync>> {
        Response::builder()
            .body("Hey, this is a default users route handler".into())
            .map_err(|e| e.into())
    }
   
    // Our error handler for Slack Events API
    fn slack_listener_error_handler(err: Box<dyn std::error::Error + Send + Sync>, 
       _client: Arc<SlackHyperClient>, 
       _states: SlackClientEventsUserState) -> http::StatusCode {
        error!("Slack Events error: {:#?}", err);
        
        // Defines what we return Slack server
        http::StatusCode::BAD_REQUEST
    }

    // We need also a client instance. `Arc` used here because we would like 
    // to share the the same client for all of the requests and all hyper threads    
    
    let client = Arc::new(SlackClient::new(SlackClientHyperConnector::new()?));
    

    // In this example we're going to use all of the events handlers, but
    // you don't have to.

    // Our Slack OAuth handler with a token response after installation
    async fn slack_oauth_install_function(
        resp: SlackOAuthV2AccessTokenResponse,
        _client: Arc<SlackHyperClient>,
        _states: SlackClientEventsUserState
    ) {
        println!("{:#?}", resp);
        Ok(())
    }

    // Push events handler
    async fn slack_push_events_function(event: SlackPushEvent, 
       _client: Arc<SlackHyperClient>, 
       _states: SlackClientEventsUserState
    ) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        println!("{:#?}", event);

        Ok(())
    }

    // Interaction events handler
    async fn slack_interaction_events_function(event: SlackInteractionEvent, 
        _client: Arc<SlackHyperClient>,
        _states: SlackClientEventsUserState
    ) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        println!("{:#?}", event);

        Ok(())
    }

    // Commands events handler
    async fn slack_command_events_function(
        event: SlackCommandEvent,
        _client: Arc<SlackHyperClient>,
        _states: SlackClientEventsUserState
    ) -> Result<SlackCommandEventResponse, Box<dyn std::error::Error + Send + Sync>> {
        println!("{:#?}", event);
        Ok(SlackCommandEventResponse::new(
            SlackMessageContent::new().with_text("Working on it".into()),
        ))
    }

    // Now we need some configuration for our Slack listener routes.
    // You can additionally configure HTTP route paths using theses configs,
    // but for simplicity we will skip that part here and configure only required parameters.
    let oauth_listener_config = Arc::new(SlackOAuthListenerConfig::new(
        config_env_var("SLACK_CLIENT_ID")?.into(),
        config_env_var("SLACK_CLIENT_SECRET")?.into(),
        config_env_var("SLACK_BOT_SCOPE")?,
        config_env_var("SLACK_REDIRECT_HOST")?,
    ));

    let push_events_config = Arc::new(SlackPushEventsListenerConfig::new(
        config_env_var("SLACK_SIGNING_SECRET")?.into(),
    ));

    let interactions_events_config = Arc::new(SlackInteractionEventsListenerConfig::new(
        config_env_var("SLACK_SIGNING_SECRET")?.into(),
    ));

    let command_events_config = Arc::new(SlackCommandEventsListenerConfig::new(
        config_env_var("SLACK_SIGNING_SECRET")?.into(),
    ));

    // Creating a shared listener environment with an ability to share client and user state
    let listener_environment = Arc::new(
        SlackClientEventsListenerEnvironment::new(client.clone())
            .with_error_handler(test_error_handler)
    );
    
   
    let make_svc = make_service_fn(move |_| {
        // Because of threading model you have to create copies of configs.
        let thread_oauth_config = oauth_listener_config.clone();
        let thread_push_events_config = push_events_config.clone();
        let thread_interaction_events_config = interactions_events_config.clone();
        let thread_command_events_config = command_events_config.clone();
 
        // Creating listener
        let listener = SlackClientEventsHyperListener::new(listener_environment.clone());
        
        // Chaining all of the possible routes for Slack.
        // `chain_service_routes_fn` is an auxiliary function from Slack Morphism. 
        async move {
            let routes = chain_service_routes_fn(
                listener.oauth_service_fn(thread_oauth_config, test_oauth_install_function),
                chain_service_routes_fn(
                    listener.push_events_service_fn(
                        thread_push_events_config,
                        slack_push_events_function,
                    ),
                    chain_service_routes_fn(
                        listener.interaction_events_service_fn(
                            thread_interaction_events_config,
                            slack_interaction_events_function,
                        ),
                        chain_service_routes_fn(
                            listener.command_events_service_fn(
                                thread_command_events_config,
                                slack_command_events_function,
                            ),
                            your_others_routes,
                        ),
                    ),
                ),
            );

            Ok::<_, Box<dyn std::error::Error + Send + Sync>>(service_fn(routes))
        }

    )};

    // Starting a server with listener routes
    let server = hyper::server::Server::bind(&addr).serve(make_svc);
    server.await.map_err(|e| {
        error!("Server error: {}", e);
        e.into()
    })
}

Complete example look at github

Events API and OAuth for Axum

The library provides route implementation in SlackEventsAxumListener based on Hyper/Tokio for:

Push Events
Interaction Events
Command Events
OAuth v2 redirects and client functions

Example


use slack_morphism::prelude::*;

use hyper::{Body, Response};
use tracing::*;

use axum::Extension;
use std::sync::Arc;

async fn test_oauth_install_function(
    resp: SlackOAuthV2AccessTokenResponse,
    _client: Arc<SlackHyperClient>,
    _states: SlackClientEventsUserState,
) {
    println!("{:#?}", resp);
}

async fn test_push_event(
    Extension(_environment): Extension<Arc<SlackHyperListenerEnvironment>>,
    Extension(event): Extension<SlackPushEvent>,
) -> Response<Body> {
    println!("Received push event: {:?}", event);

    match event {
        SlackPushEvent::UrlVerification(url_ver) => Response::new(Body::from(url_ver.challenge)),
        _ => Response::new(Body::empty()),
    }
}

async fn test_command_event(
    Extension(_environment): Extension<Arc<SlackHyperListenerEnvironment>>,
    Extension(event): Extension<SlackCommandEvent>,
) -> axum::Json<SlackCommandEventResponse> {
    println!("Received command event: {:?}", event);
    axum::Json(SlackCommandEventResponse::new(
        SlackMessageContent::new().with_text("Working on it".into()),
    ))
}

async fn test_interaction_event(
    Extension(_environment): Extension<Arc<SlackHyperListenerEnvironment>>,
    Extension(event): Extension<SlackInteractionEvent>,
) {
    println!("Received interaction event: {:?}", event);
}

fn test_error_handler(
    err: Box<dyn std::error::Error + Send + Sync>,
    _client: Arc<SlackHyperClient>,
    _states: SlackClientEventsUserState,
) -> HttpStatusCode {
    println!("{:#?}", err);

    // Defines what we return Slack server
    HttpStatusCode::BAD_REQUEST
}

async fn test_server() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let client: Arc<SlackHyperClient> =
        Arc::new(SlackClient::new(SlackClientHyperConnector::new()?));

    let addr = std::net::SocketAddr::from(([127, 0, 0, 1], 8080));
    info!("Loading server: {}", addr);

    let oauth_listener_config = SlackOAuthListenerConfig::new(
        config_env_var("SLACK_CLIENT_ID")?.into(),
        config_env_var("SLACK_CLIENT_SECRET")?.into(),
        config_env_var("SLACK_BOT_SCOPE")?,
        config_env_var("SLACK_REDIRECT_HOST")?,
    );

    let listener_environment: Arc<SlackHyperListenerEnvironment> = Arc::new(
        SlackClientEventsListenerEnvironment::new(client.clone())
            .with_error_handler(test_error_handler),
    );
    let signing_secret: SlackSigningSecret = config_env_var("SLACK_SIGNING_SECRET")?.into();

    let listener: SlackEventsAxumListener<SlackHyperHttpsConnector> =
        SlackEventsAxumListener::new(listener_environment.clone());

    // build our application route with OAuth nested router and Push/Command/Interaction events
    let app = axum::routing::Router::new()
        .nest(
            "/auth",
            listener.oauth_router("/auth", &oauth_listener_config, test_oauth_install_function),
        )
        .route(
            "/push",
            axum::routing::post(test_push_event).layer(
                listener
                    .events_layer(&signing_secret)
                    .with_event_extractor(SlackEventsExtractors::push_event()),
            ),
        )
        .route(
            "/command",
            axum::routing::post(test_command_event).layer(
                listener
                    .events_layer(&signing_secret)
                    .with_event_extractor(SlackEventsExtractors::command_event()),
            ),
        )
        .route(
            "/interaction",
            axum::routing::post(test_interaction_event).layer(
                listener
                    .events_layer(&signing_secret)
                    .with_event_extractor(SlackEventsExtractors::interaction_event()),
            ),
        );

    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();

    Ok(())
}

Complete example look at github

Slack Socket Mode support

Slack Morphism supports Slack Socket Mode starting with 0.10.x. Socket Mode allows your app to use the Events API and interactive components without exposing a public HTTP endpoint.

The mode is useful if you want to create an app that works with few workspaces and don't want to work with HTTP endpoints yourself.

Register your event callback functions

use slack_morphism::prelude::*;

async fn test_interaction_events_function(
    event: SlackInteractionEvent,
    _client: Arc<SlackHyperClient>,
    _states: SlackClientEventsUserState,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    println!("{:#?}", event);
    Ok(())
}

async fn test_command_events_function(
    event: SlackCommandEvent,
    _client: Arc<SlackHyperClient>,
    _states: SlackClientEventsUserState,
) -> Result<SlackCommandEventResponse, Box<dyn std::error::Error + Send + Sync>> {
    println!("{:#?}", event);
    Ok(SlackCommandEventResponse::new(
        SlackMessageContent::new().with_text("Working on it".into()),
    ))
}

async fn test_push_events_sm_function(
    event: SlackPushEventCallback,
    _client: Arc<SlackHyperClient>,
    _states: SlackClientEventsUserState,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    println!("{:#?}", event);
    Ok(())
}

let client = Arc::new(SlackClient::new(SlackClientHyperConnector::new()?));

let socket_mode_callbacks = SlackSocketModeListenerCallbacks::new()
    .with_command_events(test_command_events_function)
    .with_interaction_events(test_interaction_events_function)
    .with_push_events(test_push_events_sm_function);   

let listener_environment = Arc::new(
        SlackClientEventsListenerEnvironment::new(client.clone())
);

let socket_mode_listener = SlackClientSocketModeListener::new(
      &SlackClientSocketModeConfig::new(),
      listener_environment.clone(),
      socket_mode_callbacks,
);

Connect using socket mode to Slack

The following code initiates Web-sockets based connections to Slack endpoints using Slack Web methods and provided user token.

Slack Morphism supports multiple web-socket connections per one token to gracefully handle disconnects. By default it uses 2 connections to one token. To configure it see SlackClientSocketModeConfig;


// Need to specify App token for Socket Mode:
let app_token_value: SlackApiTokenValue = 
    config_env_var("SLACK_TEST_APP_TOKEN")?.into();
let app_token: SlackApiToken = SlackApiToken::new(app_token_value);

// Register an app token to listen for events, 
socket_mode_listener.listen_for(&app_token).await?;

// Start WS connections calling Slack API to get WS url for the token, 
// and wait for Ctrl-C to shutdown
// There are also `.start()`/`.shutdown()` available to manage manually 
socket_mode_listener.serve().await;

Important caveats

The time blocking of the SM listener callbacks is important

If your app blocks callbacks more than 2-3 seconds Slack server may decide to repeat requests again and also to inform users with errors and timeouts. So, if you have something complex and time-consuming in your callbacks you should spawn your own future, e.g:

    async fn test_push_events_sm_function(
        event: SlackPushEventCallback,
        _client: Arc<SlackHyperClient>,
        _states: SlackClientEventsUserState,
    ) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        tokio::spawn(async move { process_message(client, event).await; });
        Ok(())
    }

Error handling function

It is highly recommended implementing your own error handling function:


fn test_error_handler(
    err: Box<dyn std::error::Error + Send + Sync>,
    _client: Arc<SlackHyperClient>,
    _states: SlackClientEventsUserState,
) -> http::StatusCode {
    println!("{:#?}", err);

    // This return value should be OK if we want to return successful ack
    // to the Slack server using Web-sockets
    // https://api.slack.com/apis/connections/socket-implement#acknowledge
    // so that Slack knows whether to retry
    http::StatusCode::OK
}

// Register it:
    let listener_environment = Arc::new(
        SlackClientEventsListenerEnvironment::new(client.clone())
            .with_error_handler(test_error_handler),
    );

The implementation allows you:

Return positive ack using http::StatusCode result / implement complex logic related to it. https://api.slack.com/apis/connections/socket-implement#acknowledge
Increase visibility and observability in general when errors happen in your app and from Slack/library.

User state propagation for event listeners and callback functions

It is very common to have some user specific context and state in event handler functions. So, all listener handlers has access to it using SlackClientEventsUserStateStorage.

This needs for Hyper or Socket Mode. For Axum use its own support for user state management.

Defining user state


// Defining your state as a struct
struct UserStateExample(u64);

// Initializing it in listener environment:
let listener_environment = Arc::new(
    SlackClientEventsListenerEnvironment::new(client.clone())
        .with_error_handler(test_error_handler)
        .with_user_state(UserStateExample(555)),
);

Reading user state in listeners for Hyper/Socket Mode

async fn test_push_events_function(
    event: SlackPushEvent,
    client: Arc<SlackHyperClient>,
    user_state_storage: SlackClientEventsUserState,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {

    let states = user_state_storage.read().await;

    let user_state: Option<&UserStateExample> = 
        states.get_user_state::<UserStateExample>();

    Ok(())
}

Updating user state in listeners for Hyper/Socket Mode

async fn test_push_events_function(
    event: SlackPushEvent,
    client: Arc<SlackHyperClient>,
    user_state_storage: SlackClientEventsUserState,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {

    let states = user_state_storage.write().await;

    states.set_user_state(UserStateExample(555));

    Ok(())
}

Limitations

Slack Morphism doesn't provide:

RTM API (the usage of which is slowly declining in favour of Events API)
Legacy Web/Events API methods and models (like Slack Message attachments, which should be replaced with Slack Blocks)

Slack Morphism for Rust

Intro and motivation

Type-safety

Easy to use

Async

Modular design

Getting Started

Ready to use examples

Slack Web API client

Create a client instance

Make Web API methods calls

Block Kit support

Send Slack Webhook Messages

Different hyper connection types and proxy support

Rate control, throttling and retrying Slack API method requests

Enable rate control

Rate control params

Enable automatic retry for rate exceeded requests

Observability and tracing

Events API and OAuth

Testing with ngrok

Slack Signature Verifier

Events API and OAuth for Hyper

Hyper configuration

Example

Events API and OAuth for Axum

Example

Slack Socket Mode support

Register your event callback functions

Connect using socket mode to Slack

Important caveats

The time blocking of the SM listener callbacks is important

Error handling function

User state propagation for event listeners and callback functions

Defining user state

Reading user state in listeners for Hyper/Socket Mode

Updating user state in listeners for Hyper/Socket Mode

Limitations

Keyboard shortcuts

Slack Morphism for Rust