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// Copyright 2015 Matthew Holt and The Caddy Authors
//
// 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 logging
import (
"fmt"
"io"
"net"
"os"
"sync"
"time"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
)
func init() {
caddy.RegisterModule(NetWriter{})
}
// NetWriter implements a log writer that outputs to a network socket. If
// the socket goes down, it will dump logs to stderr while it attempts to
// reconnect.
type NetWriter struct {
// The address of the network socket to which to connect.
Address string `json:"address,omitempty"`
// The timeout to wait while connecting to the socket.
DialTimeout caddy.Duration `json:"dial_timeout,omitempty"`
addr caddy.NetworkAddress
}
// CaddyModule returns the Caddy module information.
func (NetWriter) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "caddy.logging.writers.net",
New: func() caddy.Module { return new(NetWriter) },
}
}
// Provision sets up the module.
func (nw *NetWriter) Provision(ctx caddy.Context) error {
repl := caddy.NewReplacer()
address, err := repl.ReplaceOrErr(nw.Address, true, true)
if err != nil {
return fmt.Errorf("invalid host in address: %v", err)
}
nw.addr, err = caddy.ParseNetworkAddress(address)
if err != nil {
return fmt.Errorf("parsing network address '%s': %v", address, err)
}
if nw.addr.PortRangeSize() != 1 {
return fmt.Errorf("multiple ports not supported")
}
if nw.DialTimeout < 0 {
return fmt.Errorf("timeout cannot be less than 0")
}
return nil
}
func (nw NetWriter) String() string {
return nw.addr.String()
}
// WriterKey returns a unique key representing this nw.
func (nw NetWriter) WriterKey() string {
return nw.addr.String()
}
// OpenWriter opens a new network connection.
func (nw NetWriter) OpenWriter() (io.WriteCloser, error) {
reconn := &redialerConn{
nw: nw,
timeout: time.Duration(nw.DialTimeout),
}
conn, err := reconn.dial()
if err != nil {
return nil, err
}
reconn.connMu.Lock()
reconn.Conn = conn
reconn.connMu.Unlock()
return reconn, nil
}
// UnmarshalCaddyfile sets up the handler from Caddyfile tokens. Syntax:
//
// net <address> {
// dial_timeout <duration>
// }
func (nw *NetWriter) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
for d.Next() {
if !d.NextArg() {
return d.ArgErr()
}
nw.Address = d.Val()
if d.NextArg() {
return d.ArgErr()
}
for nesting := d.Nesting(); d.NextBlock(nesting); {
switch d.Val() {
case "dial_timeout":
if !d.NextArg() {
return d.ArgErr()
}
timeout, err := caddy.ParseDuration(d.Val())
if err != nil {
return d.Errf("invalid duration: %s", d.Val())
}
if d.NextArg() {
return d.ArgErr()
}
nw.DialTimeout = caddy.Duration(timeout)
}
}
}
return nil
}
// redialerConn wraps an underlying Conn so that if any
// writes fail, the connection is redialed and the write
// is retried.
type redialerConn struct {
net.Conn
connMu sync.RWMutex
nw NetWriter
timeout time.Duration
lastRedial time.Time
}
// Write wraps the underlying Conn.Write method, but if that fails,
// it will re-dial the connection anew and try writing again.
func (reconn *redialerConn) Write(b []byte) (n int, err error) {
reconn.connMu.RLock()
conn := reconn.Conn
reconn.connMu.RUnlock()
if n, err = conn.Write(b); err == nil {
return
}
// problem with the connection - lock it and try to fix it
reconn.connMu.Lock()
defer reconn.connMu.Unlock()
// if multiple concurrent writes failed on the same broken conn, then
// one of them might have already re-dialed by now; try writing again
if n, err = reconn.Conn.Write(b); err == nil {
return
}
// there's still a problem, so try to re-attempt dialing the socket
// if some time has passed in which the issue could have potentially
// been resolved - we don't want to block at every single log
// emission (!) - see discussion in #4111
if time.Since(reconn.lastRedial) > 10*time.Second {
reconn.lastRedial = time.Now()
conn2, err2 := reconn.dial()
if err2 != nil {
// logger socket still offline; instead of discarding the log, dump it to stderr
os.Stderr.Write(b)
return
}
if n, err = conn2.Write(b); err == nil {
reconn.Conn.Close()
reconn.Conn = conn2
}
} else {
// last redial attempt was too recent; just dump to stderr for now
os.Stderr.Write(b)
}
return
}
func (reconn *redialerConn) dial() (net.Conn, error) {
return net.DialTimeout(reconn.nw.addr.Network, reconn.nw.addr.JoinHostPort(0), reconn.timeout)
}
// Interface guards
var (
_ caddy.Provisioner = (*NetWriter)(nil)
_ caddy.WriterOpener = (*NetWriter)(nil)
_ caddyfile.Unmarshaler = (*NetWriter)(nil)
)
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