83 lines
2.0 KiB
Go
83 lines
2.0 KiB
Go
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package internal
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import (
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"bytes"
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"path"
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"runtime"
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)
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// StackTrace is a stack trace.
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type StackTrace struct {
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callers []uintptr
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written int
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}
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// GetStackTrace returns a new StackTrace.
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func GetStackTrace(skipFrames int) *StackTrace {
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st := &StackTrace{}
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skip := 2 // skips runtime.Callers and this function
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skip += skipFrames
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st.callers = make([]uintptr, maxStackTraceFrames)
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st.written = runtime.Callers(skip, st.callers)
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st.callers = st.callers[0:st.written]
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return st
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}
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func pcToFunc(pc uintptr) (*runtime.Func, uintptr) {
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// The Golang runtime package documentation says "To look up the file
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// and line number of the call itself, use pc[i]-1. As an exception to
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// this rule, if pc[i-1] corresponds to the function runtime.sigpanic,
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// then pc[i] is the program counter of a faulting instruction and
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// should be used without any subtraction."
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//
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// TODO: Fully understand when this subtraction is necessary.
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place := pc - 1
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return runtime.FuncForPC(place), place
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}
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func topCallerNameBase(st *StackTrace) string {
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f, _ := pcToFunc(st.callers[0])
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if nil == f {
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return ""
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}
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return path.Base(f.Name())
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}
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// WriteJSON adds the stack trace to the buffer in the JSON form expected by the
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// collector.
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func (st *StackTrace) WriteJSON(buf *bytes.Buffer) {
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buf.WriteByte('[')
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for i, pc := range st.callers {
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if i > 0 {
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buf.WriteByte(',')
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}
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// Implements the format documented here:
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// https://source.datanerd.us/agents/agent-specs/blob/master/Stack-Traces.md
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buf.WriteByte('{')
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if f, place := pcToFunc(pc); nil != f {
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name := path.Base(f.Name())
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file, line := f.FileLine(place)
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w := jsonFieldsWriter{buf: buf}
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w.stringField("filepath", file)
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w.stringField("name", name)
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w.intField("line", int64(line))
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}
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buf.WriteByte('}')
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}
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buf.WriteByte(']')
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}
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// MarshalJSON prepares JSON in the format expected by the collector.
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func (st *StackTrace) MarshalJSON() ([]byte, error) {
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estimate := 256 * len(st.callers)
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buf := bytes.NewBuffer(make([]byte, 0, estimate))
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st.WriteJSON(buf)
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return buf.Bytes(), nil
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}
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