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, 96 insertions, 0 deletions

diff --git a/internal/mapr/client/aggregate_test.go b/internal/mapr/client/aggregate_test.go
new file mode 100644
index 0000000..3387a63
--- /dev/null
+++ b/internal/mapr/client/aggregate_test.go
@@ -0,0 +1,96 @@
+package client
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mimecast/dtail/internal/mapr"
+	"github.com/mimecast/dtail/internal/protocol"
+)
+
+func TestAggregateResetsPendingLocalStateOnGenerationChange(t *testing.T) {
+	query := mustSessionStateQuery(t, "select status,count(status) from stats group by status")
+	state := NewSessionState(query)
+	aggregate := NewAggregate("srv1", state)
+	countStorage := aggregateCountStorage(t, query)
+
+	oldSet := aggregate.group.GetSet("ERROR")
+	oldSet.Samples = 1
+	oldSet.FValues[countStorage] = 1
+
+	rawQuery := "select status,count(status) from warnings group by status"
+	if _, err := state.CommitQuery(rawQuery, 2); err != nil {
+		t.Fatalf("CommitQuery() error = %v", err)
+	}
+
+	snapshot := state.Snapshot()
+	message := strings.Join([]string{
+		"WARN",
+		"1",
+		aggregateCountStorage(t, snapshot.Query) + protocol.AggregateKVDelimiter + "1",
+		"",
+	}, protocol.AggregateDelimiter)
+
+	if err := aggregate.Aggregate(message); err != nil {
+		t.Fatalf("Aggregate() error = %v", err)
+	}
+
+	result, numRows, err := snapshot.GlobalGroup.Result(snapshot.Query, 10, nil)
+	if err != nil {
+		t.Fatalf("Result() error = %v", err)
+	}
+	if numRows != 1 {
+		t.Fatalf("numRows = %d, want 1", numRows)
+	}
+	if !strings.Contains(result, "1") {
+		t.Fatalf("expected one new-generation aggregate row, got %q", result)
+	}
+}
+
+func TestAggregateRejectsMalformedMessage(t *testing.T) {
+	query := mustSessionStateQuery(t, "select count(status) from stats group by status")
+	state := NewSessionState(query)
+	aggregate := NewAggregate("srv1", state)
+
+	if err := aggregate.Aggregate("broken"); err == nil {
+		t.Fatalf("expected Aggregate() to reject malformed messages")
+	}
+}
+
+func TestAggregateFlushMergesPendingLocalState(t *testing.T) {
+	query := mustSessionStateQuery(t, "select status,count(status) from stats group by status")
+	state := NewSessionState(query)
+	aggregate := NewAggregate("srv1", state)
+	countStorage := aggregateCountStorage(t, query)
+
+	set := aggregate.group.GetSet("ERROR")
+	set.Samples = 3
+	set.FValues[countStorage] = 3
+
+	if err := aggregate.Flush(); err != nil {
+		t.Fatalf("Flush() error = %v", err)
+	}
+
+	result, numRows, err := state.Snapshot().GlobalGroup.Result(query, 10, nil)
+	if err != nil {
+		t.Fatalf("Result() error = %v", err)
+	}
+	if numRows != 1 {
+		t.Fatalf("numRows = %d, want 1", numRows)
+	}
+	if !strings.Contains(result, "3") {
+		t.Fatalf("expected flushed aggregate row, got %q", result)
+	}
+}
+
+func aggregateCountStorage(t *testing.T, query *mapr.Query) string {
+	t.Helper()
+
+	for _, selectCondition := range query.Select {
+		if selectCondition.Operation == mapr.Count {
+			return selectCondition.FieldStorage
+		}
+	}
+	t.Fatalf("query %q does not contain count() storage", query.RawQuery)
+	return ""
+}