ngit-grasp/docs/learnings/nostr-sdk.md

nostr-sdk - Learnings and Patterns

Purpose: Document nostr-sdk usage patterns, upgrade notes, and gotchas
Last Updated: November 4, 2025

---

Current Version

We use nostr-sdk 0.43.x (latest stable)

[dependencies]
nostr-sdk = "0.43"

Upgraded from: 0.35.0 on November 4, 2025

---

Critical Breaking Changes (0.35 → 0.43)

1. EventBuilder API Changed

Before (0.35):

let event = EventBuilder::new(kind, content, tags)
    .to_event(keys)?;

After (0.43):

let event = EventBuilder::new(kind, content)
    .tags(tags)
    .sign_with_keys(keys)?;

Changes:

• ❌ Removed tags parameter from constructor
• ✅ Use .tags() builder method instead
• ❌ Removed .to_event() method
• ✅ Use .sign_with_keys() instead (more descriptive)

---

2. Client Ownership of Keys

Before (0.35):

let keys = Keys::generate();
let client = Client::new(&keys);  // Reference
// keys still available

After (0.43):

let keys = Keys::generate();
let client = Client::new(keys.clone());  // Ownership
// Need to clone if we want to keep keys

Why: Allows Client to own the signer, enabling more flexible signer types.

---

3. Relay Status Check No Longer Async

Before (0.35):

if relay.is_connected().await {
    // ...
}

After (0.43):

if relay.is_connected() {  // No await!
    // ...
}

Why: Status check doesn't require async operation.

---

4. Query API Redesigned

Before (0.35):

let events = client
    .get_events_of(vec![filter], EventSource::relays(Some(timeout)))
    .await?;
// Returns Vec<Event>

After (0.43):

let events = client
    .fetch_events(filter, timeout)
    .await?;
// Returns Events (iterable collection)

// Convert to Vec if needed
let vec: Vec<Event> = events.into_iter().collect();

Changes:

• ❌ Removed get_events_of() method
• ✅ Use fetch_events() instead
• ❌ Removed EventSource parameter (confusing)
• ✅ Direct timeout parameter
• ❌ Single filter instead of Vec<Filter>
• ✅ Returns Events type instead of Vec<Event>

---

5. Filter Custom Tags Simplified

Before (0.35):

filter.custom_tag(tag, ["value"])
filter.custom_tag(tag, [&string_ref])

After (0.43):

filter.custom_tag(tag, "value")
filter.custom_tag(tag, &string_ref)

Why: Simplified API for the common case of single tag value.

---

6. Send Event Takes Reference

Before (0.35):

let event_id = client.send_event(event).await?;

After (0.43):

let output = client.send_event(&event).await?;
let event_id = *output.id();

Changes:

• Takes &Event instead of Event (can reuse events)
• Returns SendEventOutput instead of EventId
• Need to call .id() to get the event ID

---

Common Patterns

Creating and Signing Events

use nostr_sdk::prelude::*;

// Generate keys
let keys = Keys::generate();

// Create event
let event = EventBuilder::new(Kind::TextNote, "Hello Nostr!")
    .tags(vec![
        Tag::custom(TagKind::SingleLetter(SingleLetterTag::lowercase(Alphabet::T)), 
                    vec!["nostr"]),
    ])
    .sign_with_keys(&keys)?;

// Send event
let output = client.send_event(&event).await?;
println!("Event ID: {}", output.id());

---

Creating Custom Tags

use nostr_sdk::prelude::*;

// Single letter tag (like "t" for topics)
let t_tag = SingleLetterTag::lowercase(Alphabet::T);
let tag = Tag::custom(
    TagKind::SingleLetter(t_tag),
    vec!["my-topic"]
);

// Custom multi-letter tag
let tag = Tag::custom(
    TagKind::Custom("custom-tag".to_string()),
    vec!["value1", "value2"]
);

// Hashtag (convenience method)
let tag = Tag::hashtag("nostr");  // Creates ["t", "nostr"]

---

Querying Events

use nostr_sdk::prelude::*;

// Build filter
let filter = Filter::new()
    .kind(Kind::TextNote)
    .custom_tag(
        SingleLetterTag::lowercase(Alphabet::T),
        "my-topic"
    )
    .since(Timestamp::now() - Duration::from_secs(3600));  // Last hour

// Query events
let timeout = Duration::from_secs(10);
let events = client.fetch_events(filter, timeout).await?;

// Process events
for event in events.into_iter() {
    println!("Event: {}", event.id());
}

---

Multiple Filters

Since fetch_events() takes a single filter, combine multiple queries:

// Option 1: Fetch separately and combine
let mut all_events = Vec::new();
for filter in filters {
    let events = client.fetch_events(filter, timeout).await?;
    all_events.extend(events.into_iter());
}

// Option 2: Use subscription (more efficient)
let subscription_id = SubscriptionId::new("my-sub");
client.subscribe(filters, None).await?;

// Handle events via notification handler
let mut notifications = client.notifications();
while let Ok(notification) = notifications.recv().await {
    if let RelayPoolNotification::Event { event, .. } = notification {
        println!("Event: {}", event.id());
    }
}

---

Client Setup with Relay

use nostr_sdk::prelude::*;

// Create keys
let keys = Keys::generate();

// Create client
let client = Client::new(keys.clone());

// Add relay
client.add_relay("wss://relay.example.com").await?;

// Connect
client.connect().await;

// Wait for connection
tokio::time::sleep(Duration::from_secs(2)).await;

// Check connection
if client.relay("wss://relay.example.com")
    .await?
    .is_connected() 
{
    println!("Connected!");
}

---

Testing Patterns

Unit Tests (No Relay Required)

#[cfg(test)]
mod tests {
    use super::*;
    use nostr_sdk::prelude::*;

    #[test]
    fn test_event_creation() {
        let keys = Keys::generate();
        let event = EventBuilder::new(Kind::TextNote, "test")
            .sign_with_keys(&keys)
            .unwrap();
        
        assert_eq!(event.kind(), Kind::TextNote);
        assert_eq!(event.content(), "test");
    }

    #[test]
    fn test_tag_creation() {
        let t_tag = SingleLetterTag::lowercase(Alphabet::T);
        let tag = Tag::custom(
            TagKind::SingleLetter(t_tag),
            vec!["test-topic"]
        );
        
        // Verify tag structure
        assert_eq!(tag.as_vec()[0], "t");
        assert_eq!(tag.as_vec()[1], "test-topic");
    }
}

---

Integration Tests (Relay Required)

#[cfg(test)]
mod tests {
    use super::*;
    use nostr_sdk::prelude::*;

    #[tokio::test]
    #[ignore]  // Requires running relay
    async fn test_send_and_receive() -> Result<()> {
        // Setup
        let keys = Keys::generate();
        let client = Client::new(keys.clone());
        client.add_relay("ws://localhost:7000").await?;
        client.connect().await;
        tokio::time::sleep(Duration::from_secs(2)).await;

        // Send event
        let event = EventBuilder::new(Kind::TextNote, "test")
            .sign_with_keys(&keys)?;
        let output = client.send_event(&event).await?;
        
        // Query it back
        let filter = Filter::new()
            .id(*output.id());
        let events = client.fetch_events(filter, Duration::from_secs(5)).await?;
        
        assert_eq!(events.len(), 1);
        Ok(())
    }
}

Running integration tests:

# Start relay first
docker run --rm -p 7000:7000 scsibug/nostr-rs-relay

# Run tests
cargo test -- --ignored

---

Common Gotchas

1. Event Validation Failures

Problem: Events fail validation with cryptic errors

Common Causes:

• Invalid signature (wrong keys used)
• Invalid event ID (content/tags changed after signing)
• Invalid timestamp (too far in future/past)

Solution:

// Always sign AFTER setting all fields
let event = EventBuilder::new(kind, content)
    .tags(tags)  // Set tags first
    .sign_with_keys(&keys)?;  // Sign last

// Don't modify event after signing!

---

2. Filter Not Matching Events

Problem: Query returns no events even though they exist

Common Causes:

• Tag kind mismatch (uppercase vs lowercase)
• Wrong filter field (using .author() when you need .authors())
• Timeout too short

Solution:

// Be explicit about tag kinds
let t_tag = SingleLetterTag::lowercase(Alphabet::T);  // Lowercase!

// Use correct filter methods
let filter = Filter::new()
    .authors(vec![keys.public_key()])  // Note: plural
    .kinds(vec![Kind::TextNote]);      // Note: plural

// Increase timeout for slow relays
let timeout = Duration::from_secs(10);

---

3. Connection Timing Issues

Problem: Events fail to send or queries return empty

Cause: Client not fully connected to relay

Solution:

// Connect
client.connect().await;

// Wait for connection to establish
tokio::time::sleep(Duration::from_secs(2)).await;

// Verify connection
let relay = client.relay("wss://relay.example.com").await?;
if !relay.is_connected() {
    return Err("Not connected".into());
}

// Now safe to send/query

---

4. Clone Keys When Creating Client

Problem: Can't use keys after creating client

Cause: Client takes ownership in 0.43+

Solution:

// Clone keys if you need them later
let keys = Keys::generate();
let client = Client::new(keys.clone());  // Clone!

// Now can still use keys
let pubkey = keys.public_key();

---

Performance Tips

1. Reuse Clients

// ✅ Good - single client
let client = Client::new(keys);
client.add_relay("wss://relay1.com").await?;
client.add_relay("wss://relay2.com").await?;
client.connect().await;

// ❌ Bad - multiple clients
for relay in relays {
    let client = Client::new(keys.clone());  // Wasteful!
    client.add_relay(relay).await?;
}

---

2. Use Subscriptions for Live Updates

// ✅ Good for live updates - subscription
let filters = vec![Filter::new().kind(Kind::TextNote)];
client.subscribe(filters, None).await?;

let mut notifications = client.notifications();
while let Ok(notification) = notifications.recv().await {
    // Handle events as they arrive
}

// ❌ Bad for live updates - polling
loop {
    let events = client.fetch_events(filter, timeout).await?;
    tokio::time::sleep(Duration::from_secs(1)).await;
}

---

3. Batch Event Creation

// ✅ Good - reuse keys
let keys = Keys::generate();
let events: Vec<Event> = (0..100)
    .map(|i| {
        EventBuilder::new(Kind::TextNote, format!("Message {}", i))
            .sign_with_keys(&keys)
            .unwrap()
    })
    .collect();

// ❌ Bad - regenerate keys
let events: Vec<Event> = (0..100)
    .map(|i| {
        let keys = Keys::generate();  // Wasteful!
        EventBuilder::new(Kind::TextNote, format!("Message {}", i))
            .sign_with_keys(&keys)
            .unwrap()
    })
    .collect();

---

Migration Checklist (0.35 → 0.43)

When upgrading from 0.35 to 0.43:

• Update Cargo.toml: nostr-sdk = "0.43"
• Fix EventBuilder::new() - remove tags parameter
• Fix EventBuilder::to_event() → sign_with_keys()
• Fix Client::new() - clone keys instead of reference
• Fix Relay::is_connected() - remove .await
• Fix Client::get_events_of() → fetch_events()
• Remove EventSource::relays() usage
• Fix Filter::custom_tag() - single value instead of array
• Fix Client::send_event() - pass reference, handle SendEventOutput
• Update tests
• Verify all builds pass
• Run integration tests

---

Useful Resources

• nostr-sdk docs: https://docs.rs/nostr-sdk/0.43.0
• rust-nostr GitHub: https://github.com/rust-nostr/nostr
• NIPs: https://github.com/nostr-protocol/nips
• NIP-01 (Events): https://github.com/nostr-protocol/nips/blob/master/01.md
• NIP-34 (Git): https://github.com/nostr-protocol/nips/blob/master/34.md

---

Quick Reference

Task	Code
Create event	EventBuilder::new(kind, content).sign_with_keys(&keys)?
Add tags	.tags(vec![tag1, tag2])
Custom tag	Tag::custom(TagKind::SingleLetter(t), vec!["value"])
Create client	Client::new(keys.clone())
Add relay	client.add_relay("wss://...").await?
Connect	client.connect().await
Send event	client.send_event(&event).await?
Query events	client.fetch_events(filter, timeout).await?
Subscribe	client.subscribe(filters, None).await?

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Last updated: November 4, 2025
Status: Living document - update as nostr-sdk evolves