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exec.go
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exec.go
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// Copyright 2018 Authors of Cilium
//
// 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 exec
import (
"bufio"
"bytes"
"context"
"fmt"
"os/exec"
"strings"
"time"
"github.com/sirupsen/logrus"
)
// combinedOutput is the core implementation of catching deadline exceeded
// options and logging errors, with an optional set of filtered outputs.
func combinedOutput(ctx context.Context, cmd *exec.Cmd, filters []string, scopedLog *logrus.Entry, verbose bool) ([]byte, error) {
out, err := cmd.CombinedOutput()
if ctx.Err() != nil {
scopedLog.WithError(err).WithField("cmd", cmd.Args).Error("Command execution failed")
return nil, fmt.Errorf("Command execution failed for %s: %s", cmd.Args, ctx.Err())
}
if err != nil {
if verbose {
scopedLog.WithError(err).WithField("cmd", cmd.Args).Error("Command execution failed")
scanner := bufio.NewScanner(bytes.NewReader(out))
scan:
for scanner.Scan() {
text := scanner.Text()
for _, filter := range filters {
if strings.Contains(text, filter) {
continue scan
}
}
scopedLog.Warn(text)
}
}
}
return out, err
}
// Cmd wraps exec.Cmd with a context to provide convenient execution of a
// command with nice checking of the context timeout in the form:
//
// err := exec.Prog().WithTimeout(5*time.Second, myprog, myargs...).CombinedOutput(log, verbose)
type Cmd struct {
*exec.Cmd
ctx context.Context
cancelFn func()
// filters is a slice of strings that should be omitted from logging.
filters []string
}
// CommandContext wraps exec.CommandContext to allow this package to be used as
// a drop-in replacement for the standard exec library.
func CommandContext(ctx context.Context, prog string, args ...string) *Cmd {
return &Cmd{
Cmd: exec.CommandContext(ctx, prog, args...),
ctx: ctx,
}
}
// WithTimeout creates a Cmd with a context that times out after the specified
// duration.
func WithTimeout(timeout time.Duration, prog string, args ...string) *Cmd {
ctx, cancel := context.WithTimeout(context.Background(), timeout)
cmd := CommandContext(ctx, prog, args...)
cmd.cancelFn = cancel
return cmd
}
// WithCancel creates a Cmd with a context that can be cancelled by calling the
// resulting Cancel() function.
func WithCancel(ctx context.Context, prog string, args ...string) (*Cmd, context.CancelFunc) {
newCtx, cancel := context.WithCancel(ctx)
cmd := CommandContext(newCtx, prog, args...)
return cmd, cancel
}
// WithFilters modifies the specified command to filter any output lines from
// logs if they contain any of the substrings specified as arguments to this
// function.
func (c *Cmd) WithFilters(filters ...string) *Cmd {
c.filters = append(c.filters, filters...)
return c
}
// CombinedOutput runs the command and returns its combined standard output and
// standard error. Unlike the standard library, if the context is exceeded, it
// will return an error indicating so.
//
// Logs any errors that occur to the specified logger.
func (c *Cmd) CombinedOutput(scopedLog *logrus.Entry, verbose bool) ([]byte, error) {
out, err := combinedOutput(c.ctx, c.Cmd, c.filters, scopedLog, verbose)
if c.cancelFn != nil {
c.cancelFn()
}
return out, err
}