langchainrust 0.7.0

A LangChain-inspired framework for building LLM applications in Rust. Supports OpenAI, Agents, Tools, Memory, Chains, RAG, BM25, Hybrid Retrieval, LangGraph, HyDE, Reranking, MultiQuery, and native Function Calling.
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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

use std::sync::Mutex;

use super::span::{build_tree, TraceSpan};
use super::TracingBackend;

// ---------------------------------------------------------------------------
// In-memory backend
// ---------------------------------------------------------------------------

/// In-memory tracing backend for development and testing.
pub struct InMemoryTracingBackend {
    spans: Mutex<Vec<TraceSpan>>,
}

impl InMemoryTracingBackend {
    /// Create a new empty in-memory backend.
    pub fn new() -> Self {
        Self {
            spans: Mutex::new(Vec::new()),
        }
    }

    /// Return a snapshot of all recorded spans.
    pub fn spans(&self) -> Vec<TraceSpan> {
        self.spans.lock().unwrap_or_else(|e| e.into_inner()).clone()
    }

    /// Remove all recorded spans.
    pub fn clear(&self) {
        self.spans.lock().unwrap_or_else(|e| e.into_inner()).clear();
    }

    /// Get the full trace tree rooted at `root_id`.
    ///
    /// Returns `None` if no span with that ID exists.
    pub fn trace_tree(&self, root_id: &str) -> Option<super::TraceNode> {
        let spans = self.spans.lock().unwrap_or_else(|e| e.into_inner());
        let root = spans.iter().find(|s| s.id == root_id)?;
        Some(build_tree(root, &spans))
    }
}

impl Default for InMemoryTracingBackend {
    fn default() -> Self {
        Self::new()
    }
}

impl TracingBackend for InMemoryTracingBackend {
    fn start_span(&self, span: &TraceSpan) {
        self.spans
            .lock()
            .unwrap_or_else(|e| e.into_inner())
            .push(span.clone());
    }

    fn end_span(&self, span: &TraceSpan) {
        let mut spans = self.spans.lock().unwrap_or_else(|e| e.into_inner());
        if let Some(existing) = spans.iter_mut().find(|s| s.id == span.id) {
            *existing = span.clone();
        }
    }

    fn flush(&self) {
        // In-memory backend has nothing to flush.
    }
}

// ---------------------------------------------------------------------------
// Console / logging backend
// ---------------------------------------------------------------------------

/// Console logging backend that prints span lifecycle events.
pub struct ConsoleTracingBackend;

impl TracingBackend for ConsoleTracingBackend {
    fn start_span(&self, span: &TraceSpan) {
        println!("[TRACE START] {} ({})", span.name, span.kind);
    }

    fn end_span(&self, span: &TraceSpan) {
        let latency = span.latency_ms.unwrap_or(0);
        let status_str = match &span.status {
            super::SpanStatus::Ok => "OK".to_string(),
            super::SpanStatus::Error(e) => format!("ERROR: {}", e),
        };
        println!(
            "[TRACE END]   {} latency={}ms status={}",
            span.name, latency, status_str
        );
    }

    fn flush(&self) {}
}

// ---------------------------------------------------------------------------
// OpenTelemetry backend (feature-gated)
// ---------------------------------------------------------------------------

/// OpenTelemetry tracing backend (requires `opentelemetry` feature).
///
/// Converts framework trace spans into OTel spans via the global tracer.
#[cfg(feature = "opentelemetry")]
pub struct OtelTracingBackend {
    tracer: opentelemetry::global::BoxedTracer,
    spans: Mutex<Vec<opentelemetry::global::BoxedSpan>>,
}

#[cfg(feature = "opentelemetry")]
impl OtelTracingBackend {
    /// Create a new backend with the given tracer.
    pub fn new(tracer: opentelemetry::global::BoxedTracer) -> Self {
        Self {
            tracer,
            spans: Mutex::new(Vec::new()),
        }
    }

    /// Create a backend using the global tracer provider.
    pub fn from_global(name: &str) -> Self {
        Self::new(opentelemetry::global::tracer(name.to_string()))
    }
}

#[cfg(feature = "opentelemetry")]
impl TracingBackend for OtelTracingBackend {
    fn start_span(&self, span: &TraceSpan) {
        use opentelemetry::trace::Tracer as OtelTracer;
        let otel_span = OtelTracer::start(&self.tracer, span.name.clone());
        self.spans
            .lock()
            .unwrap_or_else(|e| e.into_inner())
            .push(otel_span);
    }

    fn end_span(&self, _span: &TraceSpan) {
        use opentelemetry::trace::Span as OtelSpan;
        if let Some(mut s) = self.spans.lock().unwrap_or_else(|e| e.into_inner()).pop() {
            OtelSpan::end(&mut s);
        }
    }

    fn flush(&self) {}
}