| // Copyright 2019 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| package syslog |
| |
| import ( |
| "context" |
| "io" |
| "time" |
| |
| "go.fuchsia.dev/fuchsia/tools/lib/logger" |
| "go.fuchsia.dev/fuchsia/tools/lib/retry" |
| "go.fuchsia.dev/fuchsia/tools/lib/syslog/constants" |
| "go.fuchsia.dev/fuchsia/tools/net/sshutil" |
| ) |
| |
| const ( |
| // The program on fuchsia used to stream system logs through a shell, not to |
| // be confused with the zircon host tool "loglistener" (no underscore) used |
| // to stream zircon-level logs to host. |
| LogListener = "/bin/log_listener" |
| |
| // Time to wait between attempts to reconnect after losing the connection. |
| defaultReconnectInterval = 5 * time.Second |
| ) |
| |
| // Syslogger streams systems logs from a Fuchsia instance. |
| type Syslogger struct { |
| client sshClient |
| } |
| |
| type sshClient interface { |
| Run(context.Context, []string, io.Writer, io.Writer) error |
| ReconnectWithBackoff(context.Context, retry.Backoff) error |
| } |
| |
| // NewSyslogger creates a new Syslogger, given an SSH session with a Fuchsia instance. |
| func NewSyslogger(client *sshutil.Client) *Syslogger { |
| return &Syslogger{ |
| client: client, |
| } |
| } |
| |
| // Stream writes system logs to a given writer, starting from the very beginning |
| // of the system's uptime. It blocks until the context is canceled or until an |
| // unexpected (not SSH-related) error occurs. |
| func (s *Syslogger) Stream(ctx context.Context, output io.Writer) error { |
| cmd := []string{LogListener} |
| for { |
| // Note: Fuchsia's log_listener does not write to stderr. |
| err := s.client.Run(ctx, cmd, output, nil) |
| if ctx.Err() == nil { |
| if err != nil { |
| logger.Debugf(ctx, "error streaming syslog: %s", err) |
| } else { |
| logger.Debugf(ctx, "log_listener exited successfully, will rerun") |
| // Don't stream from the beginning of the system's uptime, since |
| // that would include logs that we've already streamed. |
| cmd = []string{LogListener, "--since_now", "yes"} |
| continue |
| } |
| } |
| |
| // We need not attempt to reconnect if we hit an error unrelated to the |
| // connection (which is probably unrecoverable) or if the context was |
| // canceled (context cancellation is the only mechanism for stopping |
| // this method, so it generally indicates that the caller is exiting |
| // normally). |
| if ctx.Err() != nil || !sshutil.IsConnectionError(err) { |
| logger.Debugf(ctx, "syslog streaming complete: %s", err) |
| return err |
| } |
| |
| logger.Errorf(ctx, "syslog: SSH client unresponsive; will attempt to reconnect and continue streaming: %s", err) |
| if err := s.client.ReconnectWithBackoff(ctx, retry.NewConstantBackoff(defaultReconnectInterval)); err != nil { |
| // The context probably got cancelled before we were able to |
| // reconnect. |
| if ctx.Err() != nil { |
| logger.Errorf(ctx, "syslog: %s: %s", constants.CtxReconnectError, ctx.Err()) |
| } |
| return err |
| } |
| // Start streaming from the beginning of the system's uptime again now that |
| // we're rebooting. |
| cmd = []string{LogListener} |
| logger.Infof(ctx, "syslog: refreshed ssh connection") |
| io.WriteString(output, "\n\n<< SYSLOG STREAM INTERRUPTED; RECONNECTING NOW >>\n\n") |
| } |
| } |