feat: DTail fork — server/client feature development

Squashed development of the snonux/dtail fork's product code (internal/, cmd/)
since diverging from mimecast/dtail. Major areas:

- Read/output path: the former "turbo" channel-less path is now the single,
  default server-side read/output path for cat/grep/tail and MapReduce; the old
  channel-based path and its config/env toggles were removed.
- MapReduce: single aggregate implementation (server + serverless) fed directly
  by a processor pipeline, with input-exhausted finalization via the shutdown
  coordinator; high-concurrency and data-race fixes.
- Journal source reads (journal:unit.service) via journalctl, Linux-gated behind
  a journal-v1 capability.
- Auth-key fast reconnect: in-memory per-user public-key cache with TTL/max-keys,
  registered over an authenticated session (AUTHKEY), checked before
  authorized_keys.
- Interactive query reload (--interactive-query) with SESSION START/UPDATE
  generation boundaries and capability negotiation.
- Client-side deadlines: --timeout / --shutdownAfter as context deadlines;
  follow shutdown handling.
- Client logging: diagnostics-only daily log by default, opt-in payload tee via
  --log-payload.
- Numerous correctness fixes (buffer-pool double-recycle races, EOF-sentinel
  leaks, glob-expansion cap, TOCTOU in CSV parsing) with accompanying unit tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 76 insertions, 0 deletions

diff --git a/internal/io/dlog/rawlog_test.go b/internal/io/dlog/rawlog_test.go
new file mode 100644
index 0000000..7fb7a05
--- /dev/null
+++ b/internal/io/dlog/rawlog_test.go
@@ -0,0 +1,76 @@
+package dlog
+
+import (
+	"context"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/mimecast/dtail/internal/config"
+	"github.com/mimecast/dtail/internal/io/dlog/loggers"
+)
+
+// recordingLogger records whether a message arrived via the diagnostic (Log)
+// path or the payload (Raw) path, so the test can assert how RawLog vs Raw route
+// their messages. It reports SupportsColors()=false so the callers take their
+// non-color branch (logger.Log / logger.Raw), which is what the routing test
+// needs to observe.
+type recordingLogger struct {
+	mutex sync.Mutex
+	logs  []string
+	raws  []string
+}
+
+func (r *recordingLogger) Log(now time.Time, message string) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	r.logs = append(r.logs, message)
+}
+func (r *recordingLogger) LogWithColors(now time.Time, message, colored string) { r.Log(now, message) }
+func (r *recordingLogger) Raw(now time.Time, message string) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	r.raws = append(r.raws, message)
+}
+func (r *recordingLogger) RawWithColors(now time.Time, message, colored string) { r.Raw(now, message) }
+func (r *recordingLogger) Start(ctx context.Context, wg *sync.WaitGroup)        { wg.Done() }
+func (r *recordingLogger) Flush()                                               {}
+func (r *recordingLogger) Pause()                                               {}
+func (r *recordingLogger) Resume()                                              {}
+func (r *recordingLogger) Rotate()                                              {}
+func (r *recordingLogger) SupportsColors() bool                                 { return false }
+
+var _ loggers.Logger = (*recordingLogger)(nil)
+
+// TestRawLogUsesDiagnosticSink is the regression guard for the ReportServerError
+// footgun: a server-error audit line must go through the diagnostic (Log) sink,
+// not the payload (Raw) sink. Only the Log sink is written to the client log file
+// by default (Client.LogPayload=false gates the Raw/payload sink out of the file),
+// so a server error routed via Raw would silently vanish from the on-disk audit
+// trail. This asserts RawLog -> Log and, for contrast, Raw -> Raw.
+func TestRawLogUsesDiagnosticSink(t *testing.T) {
+	prevClient := config.Client
+	config.Client = &config.ClientConfig{TermColorsEnable: false}
+	t.Cleanup(func() { config.Client = prevClient })
+
+	rec := &recordingLogger{}
+	d := &DLog{logger: rec}
+
+	const serverError = "SERVER|srv1|ERROR|journal file targets require server capability journal-v1"
+	d.RawLog(serverError)
+
+	if len(rec.logs) != 1 || rec.logs[0] != serverError {
+		t.Fatalf("RawLog must reach the diagnostic (Log) sink verbatim; got logs=%v raws=%v",
+			rec.logs, rec.raws)
+	}
+	if len(rec.raws) != 0 {
+		t.Fatalf("RawLog must NOT use the payload (Raw) sink (it would be gated out of the file); got raws=%v",
+			rec.raws)
+	}
+
+	// Contrast: bulk payload still goes through the Raw/payload sink.
+	d.Raw("payload-line\n")
+	if len(rec.raws) != 1 || rec.raws[0] != "payload-line\n" {
+		t.Fatalf("Raw must reach the payload (Raw) sink; got raws=%v", rec.raws)
+	}
+}