Add slow-client backpressure regression

Makefile

@@ -34,7 +34,7 @@ MANDIR ?= $(PREFIX)/share/man
 SYSTEMD_UNIT_DIR ?= $(PREFIX)/lib/systemd/system
 CI_TEST_PORT ?= $(if $(PORT),$(PORT),2222)
 
-.PHONY: all clean install install-systemd uninstall uninstall-systemd debug release release-check release-check-strict asan valgrind check test test-advisory ci-test unit-test integration-test anonymous-access-test connection-limit-test security-test stress-test soak-test user-lifecycle-test info
+.PHONY: all clean install install-systemd uninstall uninstall-systemd debug release release-check release-check-strict asan valgrind check test test-advisory ci-test unit-test integration-test anonymous-access-test connection-limit-test security-test stress-test soak-test slow-client-test user-lifecycle-test info
 
 all: $(TARGETS)
 
@@ -148,6 +148,10 @@ soak-test: all
 	@echo "Running soak tests..."
 	@cd tests && PORT=$${PORT:-2222} ./test_soak.sh $${DURATION:-8} $${RECONNECTS:-5}
 
+slow-client-test: all
+	@echo "Running slow-client tests..."
+	@cd tests && PORT=$${PORT:-2222} ./test_slow_client.sh $${DURATION:-8} $${BURST_CHARS:-1600}
+
 user-lifecycle-test: all
 	@echo "Running user lifecycle tests..."
 	@cd tests && PORT=$${PORT:-2222} ./test_user_lifecycle.sh

README.md

@@ -238,6 +238,7 @@ make connection-limit-test # verify per-IP concurrency and rate limits
 make security-test # run security feature checks
 make stress-test   # run configurable concurrent-client stress test
 make soak-test     # run idle/reconnect/control-plane soak test
+make slow-client-test # run slow interactive-client backpressure test
 make user-lifecycle-test # run a two-user TUI lifecycle test
 make ci-test       # run the same checks as GitHub Actions
 
@@ -249,6 +250,7 @@ cd tests
 ./test_connection_limits.sh  # per-IP concurrency and rate limits
 ./test_stress.sh             # stress test
 ./test_soak.sh               # soak test
+./test_slow_client.sh        # slow-client backpressure
 ./test_user_lifecycle.sh     # two-user TUI lifecycle
 ```
 
@@ -257,6 +259,8 @@ cd tests
 - Anonymous access: 2 tests
 - Security features: 12 tests
 - Stress test: configurable concurrent clients (`CLIENTS=20 DURATION=60 make stress-test`)
+- Slow-client test: an unread interactive SSH client cannot block health,
+  stats, post, tail, or server survival checks
 
 ### Dependencies
 
@@ -361,6 +365,12 @@ Before preparing a release locally:
 make release-check
 ```
 
+Longer local preflight can opt into runtime soak and slow-client coverage:
+
+```sh
+RUN_SOAK=1 RUN_SLOW_CLIENT=1 make release-check
+```
+
 Before publishing package recipes, replace placeholder checksums and run:
 
 ```sh

docs/CHANGELOG.md

@@ -19,6 +19,9 @@
 - Added a VHS tape draft for recording the core TNT terminal-chat experience.
 - Added live `:inbox` refresh behavior: `r` refreshes the inbox manually, and
   an open inbox refreshes when a new private message arrives.
+- Added `make slow-client-test`, an opt-in regression for an unread
+  interactive SSH client under backpressure while health, stats, post, tail,
+  and server survival stay responsive.
 
 ### Changed
 - `make install-systemd` now rewrites the installed unit's `ExecStart` to match
@@ -51,6 +54,8 @@
   direct slow-reader blocking path.
 - `make release-check` can now run the soak test with `RUN_SOAK=1`, keeping
   longer runtime checks opt-in for local release validation.
+- `make release-check` can also run the slow-client backpressure test with
+  `RUN_SLOW_CLIENT=1`.
 - Room capacity and mention notification bookkeeping now follow
   `TNT_MAX_CONNECTIONS` instead of a hidden fixed 64-client array limit.
 - Updated the roadmap to reflect completed `tntctl`, stable exec contract, and

docs/CICD.md

@@ -41,6 +41,9 @@ Release policy:
 2. Run the local preflight:
    make release-check
 
+   For a longer local runtime gate before publishing or production rollout:
+   RUN_SOAK=1 RUN_SLOW_CLIENT=1 make release-check
+
 3. Commit the release changes and create a local tag.  Do not push the tag
    until strict checks pass:
    git tag v1.0.1

docs/QUICKREF.md

@@ -15,6 +15,9 @@ TEST
   make connection-limit-test per-IP concurrency/rate-limit checks
   make security-test        security feature checks
   make stress-test          concurrent-client stress test
+  make soak-test            idle/reconnect/control-plane soak test
+  make slow-client-test     slow interactive-client backpressure test
+  make user-lifecycle-test  two-user TUI lifecycle test
   make ci-test              same checks as GitHub Actions
 
 DEBUG

docs/ROADMAP.md

@@ -94,7 +94,7 @@ Goal: make regressions harder to introduce.
 - add sanitizer jobs and targeted fuzzing for UTF-8, log parsing, and command parsing
 - ✅ add a configurable soak test for idle sessions, reconnects, and control
   interface availability
-- add deeper slow-client soak coverage with a deliberately backpressured SSH
+- ✅ add deeper slow-client coverage with a deliberately backpressured SSH
   client
 - keep deployment and test docs aligned with actual runtime behavior
 - require every user-visible interface change to update docs and tests in the same change set
@@ -106,7 +106,5 @@ These are the next changes that should happen before new feature work expands th
 1. Decide the daemon naming path: keep `tnt` as the server binary for 1.x, or
    introduce `tntd` later with a compatibility plan.
 2. Finish untangling client-state ownership into a clearer release path.
-3. Add deeper slow-client soak coverage with a deliberately backpressured SSH
-   client.
-4. Replace remaining release placeholders with real maintainer metadata and
+3. Replace remaining release placeholders with real maintainer metadata and
    source-archive checksums when cutting a public package release.

scripts/release_check.sh

@@ -21,6 +21,7 @@ Default checks:
 Environment:
   RUN_INTEGRATION=1  also run full make test
   RUN_SOAK=1         also run the configurable soak test
+  RUN_SLOW_CLIENT=1  also run the slow-client backpressure test
   PORT=12720         base port for integration tests
 
 Strict checks additionally require a clean tree, a vX.Y.Z tag at HEAD, a
@@ -123,6 +124,13 @@ if [ "${RUN_SOAK:-0}" = "1" ]; then
         DURATION="${SOAK_DURATION:-8}" RECONNECTS="${SOAK_RECONNECTS:-5}"
 fi
 
+if [ "${RUN_SLOW_CLIENT:-0}" = "1" ]; then
+    step "running slow-client test"
+    make slow-client-test PORT="$((${PORT:-12720} + 40))" \
+        DURATION="${SLOW_CLIENT_DURATION:-8}" \
+        BURST_CHARS="${SLOW_CLIENT_BURST_CHARS:-1600}"
+fi
+
 tmpdir=$(mktemp -d "${TMPDIR:-/tmp}/tnt-release-check.XXXXXX")
 cleanup() {
     rm -rf "$tmpdir"

tests/test_slow_client.sh

@@ -0,0 +1,223 @@
+#!/bin/sh
+# Slow interactive-client regression test for TNT.
+# Usage: ./test_slow_client.sh [hold_seconds] [burst_chars]
+
+PORT=${PORT:-2222}
+HOLD_SECONDS=${1:-8}
+BURST_CHARS=${2:-1600}
+BIN="../tnt"
+PASS=0
+FAIL=0
+STATE_DIR=$(mktemp -d "${TMPDIR:-/tmp}/tnt-slow-client-test.XXXXXX")
+SERVER_PID=""
+SLOW_PID=""
+
+cleanup() {
+    if [ -n "$SLOW_PID" ]; then
+        kill "$SLOW_PID" 2>/dev/null || true
+        wait "$SLOW_PID" 2>/dev/null || true
+    fi
+    exec 3>&- 2>/dev/null || true
+    if [ -n "$SERVER_PID" ]; then
+        kill "$SERVER_PID" 2>/dev/null || true
+        wait "$SERVER_PID" 2>/dev/null || true
+    fi
+    rm -rf "$STATE_DIR"
+}
+
+trap cleanup EXIT
+
+case "$HOLD_SECONDS" in
+    ''|*[!0-9]*)
+        echo "Error: hold_seconds must be a positive integer"
+        exit 2
+        ;;
+esac
+
+case "$BURST_CHARS" in
+    ''|*[!0-9]*)
+        echo "Error: burst_chars must be a positive integer"
+        exit 2
+        ;;
+esac
+
+if [ "$HOLD_SECONDS" -lt 1 ] || [ "$BURST_CHARS" -lt 1 ]; then
+    echo "Error: hold_seconds and burst_chars must be positive"
+    exit 2
+fi
+
+if [ ! -f "$BIN" ]; then
+    echo "Error: Binary $BIN not found. Run make first."
+    exit 1
+fi
+
+SSH_EXEC_OPTS="-n -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o BatchMode=yes -o LogLevel=ERROR -o ConnectTimeout=5 -p $PORT"
+SSH_TTY_OPTS="-e none -tt -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -o ConnectTimeout=5 -p $PORT"
+
+run_ssh_timeout() {
+    seconds=$1
+    outfile=$2
+    shift 2
+
+    ssh $SSH_EXEC_OPTS "$@" >"$outfile" 2>&1 &
+    cmd_pid=$!
+    elapsed=0
+
+    while [ "$elapsed" -lt "$seconds" ]; do
+        if ! kill -0 "$cmd_pid" 2>/dev/null; then
+            wait "$cmd_pid"
+            return $?
+        fi
+        sleep 1
+        elapsed=$((elapsed + 1))
+    done
+
+    if kill -0 "$cmd_pid" 2>/dev/null; then
+        kill "$cmd_pid" 2>/dev/null || true
+        wait "$cmd_pid" 2>/dev/null || true
+    fi
+    return 124
+}
+
+wait_for_health() {
+    out=""
+    for _ in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15; do
+        if [ -n "$SERVER_PID" ] && ! kill -0 "$SERVER_PID" 2>/dev/null; then
+            return 1
+        fi
+        out=$(ssh $SSH_EXEC_OPTS localhost health 2>/dev/null || true)
+        [ "$out" = "ok" ] && return 0
+        sleep 1
+    done
+    return 1
+}
+
+wait_for_slow_user() {
+    out=""
+    for _ in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15; do
+        if [ -n "$SERVER_PID" ] && ! kill -0 "$SERVER_PID" 2>/dev/null; then
+            return 1
+        fi
+        out=$(ssh $SSH_EXEC_OPTS localhost users --json 2>/dev/null || true)
+        printf '%s\n' "$out" | grep -q '"slow"' && return 0
+        sleep 1
+    done
+    return 1
+}
+
+echo "=== TNT Slow Client Test ==="
+echo "hold=${HOLD_SECONDS}s burst_chars=$BURST_CHARS port=$PORT"
+
+TNT_LANG=en "$BIN" \
+    --bind 127.0.0.1 \
+    --public-host slow.local \
+    --max-connections 32 \
+    --max-conn-per-ip 32 \
+    --max-conn-rate-per-ip 64 \
+    --rate-limit 0 \
+    --idle-timeout 0 \
+    --ssh-log-level 1 \
+    -p "$PORT" \
+    -d "$STATE_DIR" >"$STATE_DIR/server.log" 2>&1 &
+SERVER_PID=$!
+
+if wait_for_health; then
+    echo "✓ server started"
+    PASS=$((PASS + 1))
+else
+    echo "✗ server failed to start"
+    sed -n '1,160p' "$STATE_DIR/server.log"
+    exit 1
+fi
+
+SLOW_FIFO="$STATE_DIR/slow.out"
+mkfifo "$SLOW_FIFO"
+exec 3<>"$SLOW_FIFO"
+
+(
+    printf 'slow\n'
+    sleep 2
+    i=0
+    while [ "$i" -lt "$BURST_CHARS" ]; do
+        printf 'x'
+        i=$((i + 1))
+    done
+    sleep "$HOLD_SECONDS"
+) | ssh $SSH_TTY_OPTS slow@127.0.0.1 >"$SLOW_FIFO" 2>"$STATE_DIR/slow.err" &
+SLOW_PID=$!
+
+if wait_for_slow_user; then
+    echo "✓ deliberately unread interactive client reached chat"
+    PASS=$((PASS + 1))
+else
+    echo "✗ slow client did not reach chat"
+    sed -n '1,120p' "$STATE_DIR/slow.err"
+    FAIL=$((FAIL + 1))
+fi
+
+sleep 3
+
+if run_ssh_timeout 5 "$STATE_DIR/health.out" localhost health &&
+   grep -qx 'ok' "$STATE_DIR/health.out"; then
+    echo "✓ health stayed responsive while slow client was pressured"
+    PASS=$((PASS + 1))
+else
+    echo "✗ health blocked or returned unexpected output"
+    cat "$STATE_DIR/health.out" 2>/dev/null || true
+    FAIL=$((FAIL + 1))
+fi
+
+if run_ssh_timeout 5 "$STATE_DIR/stats.out" localhost stats --json &&
+   grep -q '"status":"ok"' "$STATE_DIR/stats.out"; then
+    echo "✓ stats stayed responsive while slow client was pressured"
+    PASS=$((PASS + 1))
+else
+    echo "✗ stats blocked or returned unexpected output"
+    cat "$STATE_DIR/stats.out" 2>/dev/null || true
+    FAIL=$((FAIL + 1))
+fi
+
+FLOOD_FAIL=0
+i=1
+while [ "$i" -le 8 ]; do
+    msg=$(printf 'slow-client responsive post %02d %0900d' "$i" 0)
+    if ! run_ssh_timeout 5 "$STATE_DIR/post-$i.out" probe@localhost post "$msg" ||
+       ! grep -qx 'posted' "$STATE_DIR/post-$i.out"; then
+        echo "✗ post blocked or failed during slow-client pressure at $i/8"
+        cat "$STATE_DIR/post-$i.out" 2>/dev/null || true
+        FAIL=$((FAIL + 1))
+        FLOOD_FAIL=1
+        break
+    fi
+    i=$((i + 1))
+done
+
+if [ "$FLOOD_FAIL" -eq 0 ]; then
+    echo "✓ post path stayed responsive during slow-client pressure"
+    PASS=$((PASS + 1))
+fi
+
+if run_ssh_timeout 5 "$STATE_DIR/tail.out" localhost "tail -n 5" &&
+   grep -q 'slow-client responsive post 08' "$STATE_DIR/tail.out"; then
+    echo "✓ tail sees messages posted during slow-client pressure"
+    PASS=$((PASS + 1))
+else
+    echo "✗ tail missing slow-client pressure messages"
+    cat "$STATE_DIR/tail.out" 2>/dev/null || true
+    FAIL=$((FAIL + 1))
+fi
+
+if kill -0 "$SERVER_PID" 2>/dev/null; then
+    echo "✓ server survived slow-client pressure"
+    PASS=$((PASS + 1))
+else
+    echo "✗ server exited during slow-client pressure"
+    sed -n '1,160p' "$STATE_DIR/server.log"
+    FAIL=$((FAIL + 1))
+fi
+
+echo ""
+echo "PASSED: $PASS"
+echo "FAILED: $FAIL"
+[ "$FAIL" -eq 0 ] && echo "All tests passed" || echo "Some tests failed"
+exit "$FAIL"