process.go

Documentation: golang.org/x/tools/internal/stack

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package stack
     6  
     7  import (
     8  	"bytes"
     9  	"fmt"
    10  	"io"
    11  	"runtime"
    12  	"sort"
    13  )
    14  
    15  // Capture get the current stack traces from the runtime.
    16  func Capture() Dump {
    17  	buf := make([]byte, 2<<20)
    18  	buf = buf[:runtime.Stack(buf, true)]
    19  	scanner := NewScanner(bytes.NewReader(buf))
    20  	dump, _ := Parse(scanner)
    21  	return dump
    22  }
    23  
    24  // Summarize a dump for easier consumption.
    25  // This collates goroutines with equivalent stacks.
    26  func Summarize(dump Dump) Summary {
    27  	s := Summary{
    28  		Total: len(dump),
    29  	}
    30  	for _, gr := range dump {
    31  		s.addGoroutine(gr)
    32  	}
    33  	return s
    34  }
    35  
    36  // Process and input stream to an output stream, summarizing any stacks that
    37  // are detected in place.
    38  func Process(out io.Writer, in io.Reader) error {
    39  	scanner := NewScanner(in)
    40  	for {
    41  		dump, err := Parse(scanner)
    42  		summary := Summarize(dump)
    43  		switch {
    44  		case len(dump) > 0:
    45  			fmt.Fprintf(out, "%+v\n\n", summary)
    46  		case err != nil:
    47  			return err
    48  		case scanner.Done():
    49  			return scanner.Err()
    50  		default:
    51  			// must have been a line that is not part of a dump
    52  			fmt.Fprintln(out, scanner.Next())
    53  		}
    54  	}
    55  }
    56  
    57  // Diff calculates the delta between two dumps.
    58  func Diff(before, after Dump) Delta {
    59  	result := Delta{}
    60  	processed := make(map[int]bool)
    61  	for _, gr := range before {
    62  		processed[gr.ID] = false
    63  	}
    64  	for _, gr := range after {
    65  		if _, found := processed[gr.ID]; found {
    66  			result.Shared = append(result.Shared, gr)
    67  		} else {
    68  			result.After = append(result.After, gr)
    69  		}
    70  		processed[gr.ID] = true
    71  	}
    72  	for _, gr := range before {
    73  		if done := processed[gr.ID]; !done {
    74  			result.Before = append(result.Before, gr)
    75  		}
    76  	}
    77  	return result
    78  }
    79  
    80  // TODO: do we want to allow contraction of stacks before comparison?
    81  func (s *Summary) addGoroutine(gr Goroutine) {
    82  	index := sort.Search(len(s.Calls), func(i int) bool {
    83  		return !s.Calls[i].Stack.less(gr.Stack)
    84  	})
    85  	if index >= len(s.Calls) || !s.Calls[index].Stack.equal(gr.Stack) {
    86  		// insert new stack, first increase the length
    87  		s.Calls = append(s.Calls, Call{})
    88  		// move the top part upward to make space
    89  		copy(s.Calls[index+1:], s.Calls[index:])
    90  		// insert the new call
    91  		s.Calls[index] = Call{
    92  			Stack: gr.Stack,
    93  		}
    94  	}
    95  	// merge the goroutine into the matched call
    96  	s.Calls[index].merge(gr)
    97  }
    98  
    99  // TODO: do we want other grouping strategies?
   100  func (c *Call) merge(gr Goroutine) {
   101  	for i := range c.Groups {
   102  		canditate := &c.Groups[i]
   103  		if canditate.State == gr.State {
   104  			canditate.Goroutines = append(canditate.Goroutines, gr)
   105  			return
   106  		}
   107  	}
   108  	c.Groups = append(c.Groups, Group{
   109  		State:      gr.State,
   110  		Goroutines: []Goroutine{gr},
   111  	})
   112  }
   113
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