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observability.go
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observability.go
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package grpc
import (
"context"
"strings"
"time"
"github.com/beatlabs/patron/correlation"
"github.com/beatlabs/patron/log"
"github.com/beatlabs/patron/trace"
"github.com/google/uuid"
"github.com/opentracing/opentracing-go"
"github.com/prometheus/client_golang/prometheus"
"google.golang.org/grpc"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
)
const (
componentName = "gRPC-server"
unary = "unary"
stream = "stream"
service = "service"
method = "method"
)
var (
rpcHandledMetric *prometheus.CounterVec
rpcLatencyMetric *prometheus.HistogramVec
)
func init() {
rpcHandledMetric = prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: "component",
Subsystem: "grpc",
Name: "handled_total",
Help: "Total number of RPC completed on the server.",
},
[]string{"grpc_type", "grpc_service", "grpc_method", "grpc_code"},
)
prometheus.MustRegister(rpcHandledMetric)
rpcLatencyMetric = prometheus.NewHistogramVec(
prometheus.HistogramOpts{
Namespace: "component",
Subsystem: "grpc",
Name: "handled_seconds",
Help: "Latency of a completed RPC on the server.",
},
[]string{"grpc_type", "grpc_service", "grpc_method", "grpc_code"})
prometheus.MustRegister(rpcLatencyMetric)
}
type observer struct {
typ string
corID string
service string
method string
sp opentracing.Span
ctx context.Context
started time.Time
}
func newObserver(ctx context.Context, typ, fullMethodName string) *observer {
md := grpcMetadata(ctx)
corID := getCorrelationID(md)
sp, ctx := grpcSpan(ctx, fullMethodName, corID, md)
ctx = log.WithContext(ctx, log.Sub(map[string]interface{}{correlation.ID: corID}))
svc, meth := splitMethodName(fullMethodName)
return &observer{
typ: typ,
corID: corID,
ctx: ctx,
method: meth,
service: svc,
sp: sp,
started: time.Now(),
}
}
func (o *observer) observe(err error) {
dur := time.Since(o.started)
trace.SpanComplete(o.sp, err)
o.log(err)
o.messageHandled(err)
o.messageLatency(dur, err)
}
func (o *observer) log(err error) {
if !log.Enabled(log.ErrorLevel) {
return
}
fields := map[string]interface{}{
"server-type": "grpc",
service: o.service,
method: o.method,
correlation.ID: o.corID,
}
if err != nil {
fields["error"] = err.Error()
log.Sub(fields).Error()
return
}
log.Sub(fields).Debug()
}
func (o *observer) messageHandled(err error) {
st, _ := status.FromError(err)
rpcHandledCounter := trace.Counter{
Counter: rpcHandledMetric.WithLabelValues(o.typ, o.service, o.method, st.Code().String()),
}
rpcHandledCounter.Inc(o.ctx)
}
func (o *observer) messageLatency(dur time.Duration, err error) {
st, _ := status.FromError(err)
rpcLatencyMetricObserver := trace.Histogram{
Observer: rpcLatencyMetric.WithLabelValues(o.typ, o.service, o.method, st.Code().String()),
}
rpcLatencyMetricObserver.Observe(o.ctx, dur.Seconds())
}
func observableUnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
obs := newObserver(ctx, unary, info.FullMethod)
resp, err = handler(obs.ctx, req)
obs.observe(err)
return resp, err
}
func observableStreamInterceptor(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
obs := newObserver(ss.Context(), stream, info.FullMethod)
err := handler(srv, ss)
obs.observe(err)
return err
}
func splitMethodName(fullMethodName string) (string, string) {
fullMethodName = strings.TrimPrefix(fullMethodName, "/") // remove leading slash
if i := strings.Index(fullMethodName, "/"); i >= 0 {
return fullMethodName[:i], fullMethodName[i+1:]
}
return "unknown", "unknown"
}
func getCorrelationID(md metadata.MD) string {
values := md.Get(correlation.HeaderID)
if len(values) == 0 {
return uuid.New().String()
}
return values[0]
}
func mapHeader(md metadata.MD) map[string]string {
mp := make(map[string]string, md.Len())
for key, values := range md {
mp[key] = values[0]
}
return mp
}
func grpcSpan(ctx context.Context, fullName, corID string, md metadata.MD) (opentracing.Span, context.Context) {
return trace.ConsumerSpan(ctx, trace.ComponentOpName(componentName, fullName), componentName,
corID, mapHeader(md))
}
func grpcMetadata(ctx context.Context) metadata.MD {
md, ok := metadata.FromIncomingContext(ctx)
if !ok {
md = metadata.New(make(map[string]string))
}
return md
}