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javascript.go
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javascript.go
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// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package javascript implements a Javascript scripting engine.
package javascript
import (
"context"
"runtime/trace"
"time"
"github.com/dop251/goja"
"go.thethings.network/lorawan-stack/v3/pkg/errors"
"go.thethings.network/lorawan-stack/v3/pkg/scripting"
)
type js struct {
options scripting.Options
}
// New returns a new Javascript scripting engine.
func New(options scripting.Options) scripting.AheadOfTimeEngine {
return &js{options}
}
var (
errScriptTimeout = errors.DefineDeadlineExceeded("script_timeout", "script timeout")
errScriptInterrupt = errors.DefineAborted("script_interrupt", "script interrupt")
errScript = errors.DefineAborted("script", "{message}")
errNoScriptOutput = errors.DefineAborted("no_script_output", "no script output")
errRuntime = errors.DefineAborted("runtime", "{message}")
errEntrypointNotFound = errors.DefineNotFound("entrypoint_not_found", "entrypoint `{entrypoint}` not found")
)
func convertError(err error) error {
if err == nil {
return nil
}
switch gojaErr := err.(type) {
case *goja.InterruptedError:
if gojaErr.Value() == context.DeadlineExceeded {
return errScriptTimeout.WithCause(err)
}
return errScriptInterrupt.WithCause(err)
case *goja.Exception:
return errScript.WithAttributes("message", gojaErr.Error()).WithCause(err)
default:
return errRuntime.WithAttributes("message", err.Error()).WithCause(err)
}
}
// Run executes the Javascript script and returns the output.
func (j *js) Run(ctx context.Context, script, fn string, params ...any) (as func(target any) error, err error) {
run := func(vm *goja.Runtime) (goja.Value, error) {
return vm.RunString(script)
}
return j.run(ctx, run, fn, params...)
}
// Compile compiles the Javascript script and returns the compiled program.
func (j *js) Compile(ctx context.Context, script string) (run func(context.Context, string, ...any) (func(any) error, error), err error) {
defer trace.StartRegion(ctx, "compile javascript").End()
start := time.Now()
defer func() {
compilationsLatency.Observe(time.Since(start).Seconds())
if err != nil {
compilations.WithLabelValues("error").Inc()
} else {
compilations.WithLabelValues("ok").Inc()
}
}()
program, err := goja.Compile("", script, false)
if err != nil {
return nil, err
}
return func(ctx context.Context, fn string, params ...any) (func(any) error, error) {
run := func(vm *goja.Runtime) (goja.Value, error) {
return vm.RunProgram(program)
}
return j.run(ctx, run, fn, params...)
}, nil
}
func (j *js) run(ctx context.Context, f func(*goja.Runtime) (goja.Value, error), fn string, params ...any) (as func(target any) error, err error) {
defer trace.StartRegion(ctx, "run javascript").End()
start := time.Now()
defer func() {
runLatency.Observe(time.Since(start).Seconds())
if err != nil {
runs.WithLabelValues("error").Inc()
} else {
runs.WithLabelValues("ok").Inc()
}
}()
vm := goja.New()
vm.SetFieldNameMapper(goja.TagFieldNameMapper("json", true))
// TODO: Set memory limit (https://github.com/dop251/goja/issues/6)
interrupt := time.AfterFunc(j.options.Timeout, func() {
vm.Interrupt(context.DeadlineExceeded)
})
defer interrupt.Stop()
defer func() {
if caught := recover(); caught != nil {
switch val := caught.(type) {
case error:
err = errRuntime.WithAttributes("message", val.Error()).WithCause(val)
default:
err = errRuntime.WithAttributes("message", "runtime error")
}
}
}()
_, err = f(vm)
if err != nil {
return nil, convertError(err)
}
entrypoint, ok := goja.AssertFunction(vm.Get(fn))
if !ok {
return nil, errEntrypointNotFound.WithAttributes("entrypoint", fn)
}
args := make([]goja.Value, len(params))
for i, param := range params {
args[i] = vm.ToValue(param)
}
res, err := entrypoint(goja.Undefined(), args...)
if err != nil {
return nil, convertError(err)
}
return func(target any) (err error) {
defer func() {
if caught := recover(); caught != nil {
switch val := caught.(type) {
case error:
err = errRuntime.WithAttributes("message", val.Error()).WithCause(val)
default:
err = errRuntime.WithAttributes("message", "runtime error")
}
}
}()
if res == goja.Null() || res == goja.Undefined() {
return errNoScriptOutput.New()
}
return convertError(vm.ExportTo(res, target))
}, nil
}