lc-core 0.21.0

Core abstractions for langchainrust — Runnable, BaseTool, BaseChatModel, etc.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79

// lc-core/src/observability/mod.rs
//! Unified, pluggable observability export.
//!
//! `TokenTrackingLLM` (token usage) and `AgentExecutor` (per-run metrics) both
//! write through the same [`MetricsSink`] interface with an [`ObsEvent`] payload.
//! The framework only provides the capability — no concrete sink is bundled here
//! (see the `lc-observability` crate for `JsonLinesSink`/`MongoSink`). Failures
//! are logged as `warn` and never interrupt the main flow.

mod agent_metrics;
mod error;

pub use agent_metrics::AgentMetrics;
pub use error::ObsError;

use crate::language_models::TokenUsage;
use serde::Serialize;

/// One observability record (the unified export payload).
#[derive(Debug, Clone, Serialize)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum ObsEvent {
    /// Token usage of a single LLM call (exported as it happens).
    TokenUsage(TokenUsage),
    /// Aggregated metrics of one agent run (exported once at the end).
    AgentMetrics(AgentMetrics),
}

/// Pluggable observability sink. The framework only provides the interface and
/// binds no concrete plugin.
#[async_trait::async_trait]
pub trait MetricsSink: Send + Sync {
    /// Pushes one record. Implementations must contain their own failures (or
    /// let the framework `warn` on `Err`) — errors never propagate to the caller.
    async fn export(&self, event: &ObsEvent) -> Result<(), ObsError>;
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::time::Duration;

    fn sample_usage() -> TokenUsage {
        TokenUsage {
            prompt_tokens: 10,
            completion_tokens: 5,
            total_tokens: 15,
        }
    }

    #[test]
    fn obs_event_token_usage_serializes_with_kind_tag() {
        let json = serde_json::to_string(&ObsEvent::TokenUsage(sample_usage())).unwrap();
        let v: serde_json::Value = serde_json::from_str(&json).unwrap();
        assert_eq!(v["kind"], "token_usage");
        assert_eq!(v["prompt_tokens"], 10);
        assert_eq!(v["completion_tokens"], 5);
        assert_eq!(v["total_tokens"], 15);
    }

    #[test]
    fn obs_event_agent_metrics_serializes_with_kind_tag() {
        let m = AgentMetrics {
            trace_id: Some("trace-x".to_string()),
            llm_calls: 2,
            cache_hits: 0,
            tool_calls: 1,
            compactions: 1,
            total_tokens: Some(30),
            duration: Duration::from_millis(100),
        };
        let json = serde_json::to_string(&ObsEvent::AgentMetrics(m)).unwrap();
        let v: serde_json::Value = serde_json::from_str(&json).unwrap();
        assert_eq!(v["kind"], "agent_metrics");
        assert_eq!(v["llm_calls"], 2);
        assert_eq!(v["tool_calls"], 1);
        assert_eq!(v["total_tokens"], 30);
    }
}