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, 111 insertions, 0 deletions

diff --git a/internal/regex/bench_test.go b/internal/regex/bench_test.go
new file mode 100644
index 0000000..16fd98e
--- /dev/null
+++ b/internal/regex/bench_test.go
@@ -0,0 +1,111 @@
+package regex
+
+import (
+	"bytes"
+	"testing"
+)
+
+func BenchmarkLiteralVsRegex(b *testing.B) {
+	// Test data - typical log lines
+	testLines := [][]byte{
+		[]byte("2024-01-01 10:00:00 INFO Starting application"),
+		[]byte("2024-01-01 10:00:01 DEBUG Loading configuration"),
+		[]byte("2024-01-01 10:00:02 ERROR Failed to connect to database"),
+		[]byte("2024-01-01 10:00:03 WARN Retrying connection"),
+		[]byte("2024-01-01 10:00:04 INFO Connection established"),
+		[]byte("2024-01-01 10:00:05 ERROR Timeout while processing request"),
+		[]byte("2024-01-01 10:00:06 DEBUG Processing request ID: 12345"),
+		[]byte("2024-01-01 10:00:07 INFO Request processed successfully"),
+		[]byte("2024-01-01 10:00:08 ERROR Invalid input parameters"),
+		[]byte("2024-01-01 10:00:09 WARN High memory usage detected"),
+	}
+	
+	// Benchmark literal pattern matching (our optimization)
+	b.Run("Literal_ERROR", func(b *testing.B) {
+		r, _ := New("ERROR", Default)
+		if !r.isLiteral {
+			b.Fatal("Pattern should be detected as literal")
+		}
+		
+		b.ResetTimer()
+		matches := 0
+		for i := 0; i < b.N; i++ {
+			for _, line := range testLines {
+				if r.Match(line) {
+					matches++
+				}
+			}
+		}
+		_ = matches
+	})
+	
+	// Force regex pattern matching for comparison
+	b.Run("Regex_ERROR", func(b *testing.B) {
+		// Add a harmless regex operator to force regex compilation
+		r, _ := New("(?:ERROR)", Default)
+		if r.isLiteral {
+			b.Fatal("Pattern should not be detected as literal")
+		}
+		
+		b.ResetTimer()
+		matches := 0
+		for i := 0; i < b.N; i++ {
+			for _, line := range testLines {
+				if r.Match(line) {
+					matches++
+				}
+			}
+		}
+		_ = matches
+	})
+	
+	// Direct bytes.Contains for reference
+	b.Run("BytesContains_ERROR", func(b *testing.B) {
+		pattern := []byte("ERROR")
+		
+		b.ResetTimer()
+		matches := 0
+		for i := 0; i < b.N; i++ {
+			for _, line := range testLines {
+				if bytes.Contains(line, pattern) {
+					matches++
+				}
+			}
+		}
+		_ = matches
+	})
+}
+
+func BenchmarkComplexPatterns(b *testing.B) {
+	testLine := []byte("2024-01-01 10:00:00 ERROR Failed to connect to database server at 192.168.1.100:5432")
+	
+	patterns := []struct {
+		name    string
+		pattern string
+	}{
+		{"Simple_ERROR", "ERROR"},
+		{"Simple_database", "database"},
+		{"Regex_ERROR.*database", "ERROR.*database"},
+		{"Regex_\\d+\\.\\d+\\.\\d+\\.\\d+", `\d+\.\d+\.\d+\.\d+`}, // IP address pattern
+		{"Regex_^2024", "^2024"},
+		{"Regex_5432$", "5432$"},
+	}
+	
+	for _, p := range patterns {
+		b.Run(p.name, func(b *testing.B) {
+			r, err := New(p.pattern, Default)
+			if err != nil {
+				b.Fatal(err)
+			}
+			
+			b.ResetTimer()
+			matches := 0
+			for i := 0; i < b.N; i++ {
+				if r.Match(testLine) {
+					matches++
+				}
+			}
+			_ = matches
+		})
+	}
+}
\ No newline at end of file