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

use crate::{
    google::LogSeverity,
    serializers::{SerializableContext, SerializableSpan},
    visitor::Visitor,
    writer::WriteAdaptor,
};
use serde::ser::{SerializeMap, Serializer as _};
use std::fmt;
use time::{format_description::well_known::Rfc3339, OffsetDateTime};
use tracing_core::{Event, Subscriber};
use tracing_subscriber::{
    field::VisitOutput,
    fmt::{
        format::{self, JsonFields},
        FmtContext, FormatEvent,
    },
    registry::LookupSpan,
};

#[derive(Debug, thiserror::Error)]
enum Error {
    #[error(transparent)]
    Formatting(#[from] fmt::Error),
    #[error("JSON serialization error: {0}")]
    Serialization(#[from] serde_json::Error),
    #[error(transparent)]
    Io(#[from] std::io::Error),
    #[error("Time formatting error: {0}")]
    Time(#[from] time::error::Format),
}

impl From<Error> for fmt::Error {
    fn from(_: Error) -> Self {
        Self
    }
}

/// Tracing Event formatter for Stackdriver layers
#[derive(Default)]
pub struct EventFormatter {
    #[cfg(feature = "opentelemetry")]
    pub(crate) cloud_trace_configuration: Option<crate::CloudTraceConfiguration>,
}

impl EventFormatter {
    /// Internal event formatting for a given serializer
    fn format_event<S>(
        &self,
        context: &FmtContext<S, JsonFields>,
        mut serializer: serde_json::Serializer<WriteAdaptor>,
        event: &Event,
    ) -> Result<(), Error>
    where
        S: Subscriber + for<'span> LookupSpan<'span>,
    {
        let time = OffsetDateTime::now_utc().format(&Rfc3339)?;
        let meta = event.metadata();
        let severity = LogSeverity::from(meta.level());

        let span = event
            .parent()
            .and_then(|id| context.span(id))
            .or_else(|| context.lookup_current());

        // FIXME: derive an accurate entry count ahead of time
        let mut map = serializer.serialize_map(None)?;

        // serialize custom fields
        map.serialize_entry("time", &time)?;
        map.serialize_entry("target", &meta.target())?;

        // serialize the current span and its leaves
        if let Some(span) = span {
            map.serialize_entry("span", &SerializableSpan::new(&span))?;
            map.serialize_entry("spans", &SerializableContext::new(context))?;

            #[cfg(feature = "opentelemetry")]
            if let (Some(crate::CloudTraceConfiguration { project_id }), Some(otel_data)) = (
                self.cloud_trace_configuration.as_ref(),
                span.extensions().get::<tracing_opentelemetry::OtelData>(),
            ) {
                use opentelemetry::trace::TraceContextExt;

                let builder = &otel_data.builder;

                if let Some(span_id) = builder.span_id {
                    map.serialize_entry("logging.googleapis.com/spanId", &span_id.to_string())?;
                }

                let (trace_id, trace_sampled) = if otel_data.parent_cx.has_active_span() {
                    let span_ref = otel_data.parent_cx.span();
                    let span_context = span_ref.span_context();

                    (Some(span_context.trace_id()), span_context.is_sampled())
                } else {
                    (builder.trace_id, false)
                };

                if let Some(trace_id) = trace_id {
                    map.serialize_entry(
                        "logging.googleapis.com/trace",
                        &format!("projects/{project_id}/traces/{trace_id}",),
                    )?;
                }

                if trace_sampled {
                    map.serialize_entry("logging.googleapis.com/trace_sampled", &true)?;
                }
            }
        }

        // serialize the stackdriver-specific fields with a visitor
        let mut visitor = Visitor::new(severity, map);
        event.record(&mut visitor);
        visitor.finish().map_err(Error::from)?;
        Ok(())
    }
}

impl<S> FormatEvent<S, JsonFields> for EventFormatter
where
    S: Subscriber + for<'span> LookupSpan<'span>,
{
    fn format_event(
        &self,
        context: &FmtContext<S, JsonFields>,
        mut writer: format::Writer,
        event: &Event,
    ) -> fmt::Result
    where
        S: Subscriber + for<'span> LookupSpan<'span>,
    {
        let serializer = serde_json::Serializer::new(WriteAdaptor::new(&mut writer));
        self.format_event(context, serializer, event)?;
        writeln!(writer)
    }
}