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, 33 insertions, 11 deletions

diff --git a/cmd/dtailhealth/main.go b/cmd/dtailhealth/main.go
index a0ca84e..33e84db 100644
--- a/cmd/dtailhealth/main.go
+++ b/cmd/dtailhealth/main.go
@@ -3,13 +3,12 @@ package main
 import (
 	"context"
 	"flag"
+	"fmt"
 	"os"
 	"sync"
+	"time"
 
-	"net/http"
-	_ "net/http"
-	_ "net/http/pprof"
-
+	"github.com/mimecast/dtail/internal/cli"
 	"github.com/mimecast/dtail/internal/clients"
 	"github.com/mimecast/dtail/internal/config"
 	"github.com/mimecast/dtail/internal/io/dlog"
@@ -28,11 +27,12 @@ func main() {
 	flag.StringVar(&args.Logger, "logger", config.DefaultHealthCheckLogger, "Logger name")
 	flag.StringVar(&args.LogLevel, "logLevel", "none", "Log level")
 	flag.StringVar(&args.ServersStr, "server", "", "Remote server to connect")
+	flag.BoolVar(&args.NoAuthKey, "no-auth-key", false, "Disable auth-key fast reconnect feature")
 	flag.StringVar(&pprof, "pprof", "", "Start PProf server this address")
 	flag.Parse()
 
 	if displayVersion {
-		version.PrintAndExit()
+		version.PrintAndExit(false)
 	}
 
 	config.Setup(source.HealthCheck, &args, flag.Args())
@@ -43,13 +43,35 @@ func main() {
 	wg.Add(1)
 	dlog.Start(ctx, &wg, source.HealthCheck)
 
+	var pprofServer *cli.PProfServer
 	if pprof != "" {
-		dlog.Client.Info("Starting PProf", pprof)
-		go func() {
-			panic(http.ListenAndServe(pprof, nil))
-		}()
+		pprofServer, pprofErr := cli.NewPProfServer(pprof)
+		if pprofErr != nil {
+			dlog.Client.Error("Unable to start PProf", pprofErr)
+		} else {
+			dlog.Client.Info("Starting PProf", pprofServer.Address())
+			pprofServer.Start(nil)
+		}
+	}
+
+	healthClient, err := clients.NewHealthClient(args)
+	status := 0
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "CRITICAL: unable to create dtailhealth client: %v\n", err)
+		status = 2
+	} else {
+		status = healthClient.Start(ctx, signal.NoCh(ctx))
+	}
+
+	if pprofServer != nil {
+		shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 5*time.Second)
+		if err := pprofServer.Shutdown(shutdownCtx); err != nil {
+			dlog.Client.Error("Unable to stop PProf", err)
+		}
+		shutdownCancel()
 	}
 
-	healthClient, _ := clients.NewHealthClient(args)
-	os.Exit(healthClient.Start(ctx, signal.NoCh(ctx)))
+	cancel()
+	wg.Wait()
+	os.Exit(status)
 }