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filter_lua.go
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filter_lua.go
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package logmunch
import (
"fmt"
"strconv"
"strings"
"github.com/shopify/go-lua"
)
func filterLineByLua(prog string, line *LogLine) (bool, error) {
l := lua.NewState() // new VM instance
//lua.OpenLibraries(l) // register standard libraries
//lua.BaseOpen(l)
// Push timestamp a few times
l.PushNumber(float64(line.Time.Unix()))
l.SetGlobal("_time")
l.PushNumber(float64(line.Time.UnixNano() / 1e6))
l.SetGlobal("_time_ms")
// Push name
l.PushString(line.Name)
l.SetGlobal("_name")
// Set key/values from line
for k, v := range line.Entries {
k = strings.Replace(k, ".", "_", -1)
// Can it be passed as a number?
f, err := strconv.ParseFloat(v, 64)
if err != nil {
l.PushString(v)
} else {
l.PushNumber(f)
}
l.SetGlobal(k)
}
// Make sure this is prefixed with "return", thus creating an anonymous
// function
err := lua.DoString(l, "return "+prog)
if err != nil {
return false, fmt.Errorf("Cannot parse LUA: `return %s`: %s", prog, err)
}
// Call the anonymous function, expecting one return value
l.ProtectedCall(0, 1, 0)
// Check that whatever is at top of the array is boolean and then
// read out it's value
stackTop := l.Top()
if typ := l.TypeOf(stackTop); typ != lua.TypeBoolean {
fmt.Errorf("Expected `%s` to return a boolean, got %s", prog, typ)
}
/* DEBUG * /
for i:=0; i< l.Top()+1; i+=1 {
fmt.Printf("TypeOf(%d) = %s\n", i, l.TypeOf(i))
fmt.Printf("ToValue(%d) = %+v\n", i, l.ToValue(i))
if v, ok := l.ToString(i); ok {
fmt.Printf("ToString(%d) = `%s`\n", i, v);
}
fmt.Printf("IsFunction(%d) = %t\n", i, l.IsFunction(i))
fmt.Printf("IsBoolean(%d) = %t\n", i, l.IsBoolean(i))
fmt.Printf("ToBoolean(%d) = %t\n", i, l.ToBoolean(i))
}
/*
if l.ToBoolean(stackTop) == true {
return line
} else {
return nil
}
*/
//fmt.Println(stackTop, l.ToBoolean(stackTop))
if !l.IsBoolean(stackTop) {
return false, fmt.Errorf("Program `return %s` returned non-boolean result %s", prog, l.TypeOf(stackTop))
}
return l.ToBoolean(stackTop), nil
}
func MakeLuaFilter(prog string) func(*LogLine) *LogLine {
// TODO(msiebuhr): Make canary run to see if we have valid lua
return func(line *LogLine) *LogLine {
keep, err := filterLineByLua(prog, line)
if err != nil {
fmt.Println("Error filtering:", err)
return nil
}
if keep {
return line
}
return nil
}
}