github.com/m3db/m3@v1.5.0/src/query/api/v1/middleware/panic.go (about)

     1  // Copyright (c) 2021 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package middleware
    22  
    23  import (
    24  	"fmt"
    25  	"net/http"
    26  	"sync"
    27  
    28  	"github.com/gorilla/mux"
    29  	"go.uber.org/zap"
    30  	"go.uber.org/zap/zapcore"
    31  
    32  	"github.com/m3db/m3/src/query/util/logging"
    33  	"github.com/m3db/m3/src/x/instrument"
    34  	xhttp "github.com/m3db/m3/src/x/net/http"
    35  )
    36  
    37  var highPriority = zap.LevelEnablerFunc(func(lvl zapcore.Level) bool {
    38  	return lvl >= zapcore.ErrorLevel
    39  })
    40  
    41  // Panic recovers from panics and logs the error/stacktrace if possible.
    42  func Panic(iOpts instrument.Options) mux.MiddlewareFunc {
    43  	return func(base http.Handler) http.Handler {
    44  		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    45  			writeCheckWriter := &responseWrittenResponseWriter{writer: w}
    46  			w = writeCheckWriter
    47  
    48  			defer func() {
    49  				if err := recover(); err != nil {
    50  					logger := logging.WithContext(r.Context(), iOpts).
    51  						WithOptions(zap.AddStacktrace(highPriority))
    52  					logger.Error("panic captured", zap.Any("stack", err))
    53  
    54  					if !writeCheckWriter.Written() {
    55  						xhttp.WriteError(w, fmt.Errorf("caught panic: %v", err))
    56  						return
    57  					}
    58  
    59  					// cannot write the error back to the caller, some contents already written.
    60  					logger.Warn("cannot write error for request; already written")
    61  				}
    62  			}()
    63  
    64  			base.ServeHTTP(w, r)
    65  		})
    66  	}
    67  }
    68  
    69  type responseWrittenResponseWriter struct {
    70  	sync.RWMutex
    71  	writer  http.ResponseWriter
    72  	written bool
    73  }
    74  
    75  func (w *responseWrittenResponseWriter) Written() bool {
    76  	w.RLock()
    77  	v := w.written
    78  	w.RUnlock()
    79  	return v
    80  }
    81  
    82  func (w *responseWrittenResponseWriter) setWritten() {
    83  	w.RLock()
    84  	if w.written {
    85  		return
    86  	}
    87  	w.RUnlock()
    88  
    89  	w.Lock()
    90  	w.written = true
    91  	w.Unlock()
    92  }
    93  
    94  func (w *responseWrittenResponseWriter) Header() http.Header {
    95  	return w.writer.Header()
    96  }
    97  
    98  func (w *responseWrittenResponseWriter) Write(d []byte) (int, error) {
    99  	w.setWritten()
   100  	return w.writer.Write(d)
   101  }
   102  
   103  func (w *responseWrittenResponseWriter) WriteHeader(statusCode int) {
   104  	w.setWritten()
   105  	w.writer.WriteHeader(statusCode)
   106  }