Restore-time SLA tests

import subprocess, time
import pytest

@pytest.mark.benchmark
def test_postgres_restore_time_under_rto():
    # Setup: clean target DB
    subprocess.run(["psql", "-h", "test-db", "-c", "DROP DATABASE IF EXISTS db_test"])
    subprocess.run(["psql", "-h", "test-db", "-c", "CREATE DATABASE db_test"])

    backup = "postgres-prod-latest.sql.gz"

    start = time.time()
    subprocess.run(
        ["bash", "-c", f"gunzip -c {backup} | psql -h test-db -d db_test"],
        check=True,
    )
    elapsed = time.time() - start

    RTO_BUDGET_SECONDS = 4 * 3600  # 4 hours
    # The 0.5 split (restore gets half the RTO, the rest goes to provision +
    # verify + cutover) is a planning choice, NOT a standard. Set the fraction
    # from your own per-segment RTO budget (Step 1).
    RESTORE_SEGMENT_FRACTION = 0.5
    budget = RTO_BUDGET_SECONDS * RESTORE_SEGMENT_FRACTION
    assert elapsed < budget, f"Restore took {elapsed:.0f}s; budget {budget:.0f}s"

# pg_restore parallel
pg_restore -j 8 -d db_test backup.dump  # 8 parallel workers

# WAL-E / pgbackrest parallel restore
pgbackrest --stanza=prod --process-max=8 restore

def test_parallel_restore_faster_than_serial():
    serial = run_restore(parallel_jobs=1)
    parallel = run_restore(parallel_jobs=8)

    speedup = serial / parallel
    # 3.0x is an illustrative target; real speedup depends on I/O saturation,
    # CPU count, and backup format. Set the expected ratio from your own
    # measured serial-vs-parallel baseline rather than this placeholder.
    assert speedup > 3.0, f"Parallel restore only {speedup:.1f}x faster"

def test_pitr_to_5min_ago_under_30min():
    target_time = datetime.utcnow() - timedelta(minutes=5)

    # 1. Lay down the PRE-EXISTING base backup into a clean data dir
    #    (untar the retained base backup; do not take a fresh one here).
    restore_retained_base_backup(dest="/restore")

    # 2. PG12+ recovery config: restore_command pulls archived WAL,
    #    recovery_target_time is the stop point, and recovery.signal triggers
    #    targeted recovery (recovery.conf was removed in PG12).
    write_conf("/restore/postgresql.auto.conf", {
        "restore_command": "cp /wal_archive/%f %p",
        "recovery_target_time": f"'{target_time.isoformat()}'",
        "recovery_target_action": "promote",
    })
    Path("/restore/recovery.signal").touch()

    # 3. Time the restore + WAL replay: this is the real PITR latency.
    start = time.time()
    subprocess.run(["pg_ctl", "start", "-D", "/restore", "-w"], check=True)
    wait_for_recovery_complete(timeout=1800)
    elapsed = time.time() - start

    # 1800s is illustrative; set the budget from your service's RTO segment SLA.
    assert elapsed < 1800, f"PITR took {elapsed:.0f}s; budget 30min"

def test_partial_object_restore_under_5_min():
    keys_to_restore = sample_500_keys_from_inventory()

    start = time.time()
    for key in keys_to_restore:
        s3.copy_object(
            Bucket="restore-target",
            Key=key,
            CopySource={"Bucket": "backup-versioned", "Key": key, "VersionId": ...},
        )
    elapsed = time.time() - start

    assert elapsed < 300, f"500-object restore took {elapsed:.0f}s"

def emit_restore_time_metric(elapsed_seconds, backup_size_bytes):
    metrics_client.gauge("dr.restore_time_seconds", elapsed_seconds)
    metrics_client.gauge("dr.backup_size_bytes", backup_size_bytes)
    metrics_client.gauge("dr.restore_throughput_bytes_per_sec",
                          backup_size_bytes / elapsed_seconds)

def test_post_restore_smoke_under_5_min():
    do_restore()

    start = time.time()
    run_smoke_suite("dr-environment")
    elapsed = time.time() - start

    assert elapsed < 300, f"Smoke tests took {elapsed:.0f}s; budget 5min"

def test_cold_start_latency_within_sla():
    # Restore complete; app started; first requests
    latencies = []
    for _ in range(100):
        start = time.time()
        requests.get("https://dr-env.svc/api/products")
        latencies.append(time.time() - start)

    p99_cold = sorted(latencies)[99]
    # 2.0s is a placeholder; set the cold-start bound from your service's SLO.
    assert p99_cold < 2.0, f"Cold-start p99 {p99_cold:.2f}s exceeds 2s SLA"