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fix panic risk in func Middleware #6

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fix panic risk in func Middleware #6

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8 changes: 5 additions & 3 deletions ginhttp/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -96,9 +96,11 @@ func Middleware(tr opentracing.Tracer, options ...MWOption) gin.HandlerFunc {
c.Request = c.Request.WithContext(
opentracing.ContextWithSpan(c.Request.Context(), sp))

c.Next()
defer func() {
ext.HTTPStatusCode.Set(sp, uint16(c.Writer.Status()))
sp.Finish()
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When there is is a panic "c.Writer.Status" will be equal to 200.

This change means we will successfully complete the trace (sp.Finish()), but the response code will be 200 -- indicating the operation was successful. I wonder if that could be a little misleading?

Looking at https://github.com/opentracing-contrib/go-stdlib (which this library is derived from), our current behaviour matches theirs. When there is a panic the span is not finished (sp.Finish() is not called).

How would you feel about proposing a change similar to this to opentracing-contrib/go-stdlib:

       defer func() {                                                          
            if recover() != nil {                                                                            
                ext.HTTPStatusCode.Set(                                         
                    sp, uint16(http.StatusInternalServerError))                 
            } else {                                                                                            
                ext.HTTPStatusCode.Set(sp, uint16(sct.status))           
            }                                                                                                       
            sp.Finish()                                                         
        }()

That would mean that they would complete the span with an error if there is a panic. If that (or something similar) was acceptable we could then "backport" the change here.

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Just noticed https://github.com/opentracing-contrib/go-stdlib !

}()

ext.HTTPStatusCode.Set(sp, uint16(c.Writer.Status()))
sp.Finish()
c.Next()
}
}
47 changes: 47 additions & 0 deletions ginhttp/server_test.go
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Expand Up @@ -153,3 +153,50 @@ func TestURLTagOption(t *testing.T) {
})
}
}

func TestPanic(t *testing.T) {

tests := []struct {
handler gin.HandlerFunc
spanFinishCount int
tag string
}{
{
func(c *gin.Context) {
c.String(http.StatusOK, "OK")
},
1,
"OK",
},
{
func(c *gin.Context) {
panic("panic test")
},
1,
"Panic",
},
}

for _, tt := range tests {
testCase := tt
t.Run(testCase.tag, func(t *testing.T) {
tr := &mocktracer.MockTracer{}
mw := Middleware(tr)
r := gin.New()
r.Use(gin.Recovery(), mw)
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If you reverse this to be
r.Use(mw, gin.Recover())

you can check for a status code of 500 in the panic case and 200 in the non-panic case.

See https://github.com/gin-gonic/gin/blob/master/recovery.go#L68

r.GET("/hello", testCase.handler)
srv := httptest.NewServer(r)
defer srv.Close()

_, err := http.Get(srv.URL + "/hello")
if err != nil {
t.Fatalf("server returned error: %v", err)
}

spans := tr.FinishedSpans()
if got, want := len(spans), testCase.spanFinishCount; got != want {
t.Fatalf("got %d spans, expected %d", got, want)
}
})
}
}