Improving Reliability: ASN Proxy Routing, Incident State, and Heartbeat Watchdogs at AlterLab

TL;DR

AlterLab shipped a batch of reliability‑focused changes: ASN‑scoped proxy routing now depends only on vendor/challenge class, a new CentralStoreIncidentStateSource supplies real‑time incident completeness and staleness data, and a heartbeat watchdog with Discord alerting ensures periodic jobs are never silently dropped. These updates reduce flaky scrapes, improve precondition accuracy, and turn hidden failures into actionable signals.

ASN‑Scoped Proxy Routing: Deterministic Class‑Based Selection

Previously, the proxy router could override ASN reputation routing with domain‑specific tweaks, TLS settings, or header changes. This made it hard to reason about why a request chose a particular exit IP and led to inconsistent reputation scores across similar challenges.

The recent batch changes the routing key to vendor/challenge class only. The router now:

1. Extracts the challenge class (e.g., Cloudflare Turnbox, Akamai Bot Manager) from the response fingerprint.
2. Looks up the ASN reputation table for that class.
3. Selects the proxy with the best reputation score for the class, ignoring any domain‑level overrides.

Because the key no longer includes the target domain, two requests to different sites that trigger the same challenge class will see identical proxy selection logic. This simplifies capacity planning and makes ASN reputation improvements directly observable in scrape success rates.

Why This Matters for Scraping Pipelines

• Predictable costs – ASN‑based pricing tiers are applied uniformly for a given challenge class.
• Easier debugging – If a scrape fails due to IP reputation, the same class of challenges elsewhere will show the same pattern.
• Better automation – Retry logic can rely on class‑level reputation rather than per‑domain guesswork.

CentralStoreIncidentStateSource: Real‑Time Health Signals

The precondition evaluator in AlterLab’s API gateways previously used UnavailableIncidentStateSource, which always reported “no active incident” (fail‑closed). This caused preconditions like no_active_incident to incorrectly block valid requests whenever the evaluator started, even when the system was healthy.

The new CentralStoreIncidentStateSource reads from the central incident store via the query_state endpoint. It returns a struct with:

• complete – bool indicating whether all expected incident ingestors have reported.
• stale – duration since the latest incident update.
• active – list of ongoing incidents.

Preconditions now evaluate complete && !stale && !active.any() before proceeding. On any store failure, the source still fails closed, preserving the original safety guarantee.

Impact on Traffic Flow

When a backend degrada­tion occurs (e.g., a delayed scrape worker), the incident store receives a heartbeat‑miss event. The central store marks the incident as active and stale after a threshold. The precondition evaluator then returns false for no_active_incident, causing API gateways to shed load or return 503s until the incident clears. This prevents cascading overload and gives operators a clear signal to investigate.

Heartbeat Watchdog: Turning Silent Job Deaths into Alerts

The infra/monitoring/check-periodic-heartbeats.sh script validates that the periodic‑heartbeat consumer is lag‑free, but it was never installed or scheduled on production hosts. Consequently, if the consumer crashed, no alert fired and downstream monitoring (e.g., backup checks) could run on stale data.

The update adds:

• A systemd timer that runs the consumer every minute on both prod hosts.
• The script infra/monitoring/heartbeat-watchdog.sh which:
  1. Executes the consumer.
  2. Checks its exit code and output for expected metrics.
  3. Sends a Discord alert via webhook if the consumer is missing, non‑zero, or reports lag.
• A contract test in CI that validates the script’s alert format.
• Deploy‑time verification that the timer is active and the script is present.

Now, any failure in the periodic‑heartbeat pipeline surfaces as a PagerDuty‑equivalent Discord ping, prompting immediate operator review.

Putting It Together: A Reliability‑First Workflow

The three changes interlock to give AlterLab a more observable, self‑healing stack:

1. Proxy routing provides consistent, class‑based exit IPs, reducing random scrape failures due to IP reputation.
2. Incident state supplies the precondition evaluator with real‑time health data, allowing the API layer to shed load before overload spreads.
3. Heartbeat watchdog guarantees that the background jobs feeding the incident store and monitoring pipelines stay alive, so the health signals themselves are trustworthy.

Step Flow: From Incident Detection to API Response

Practical Examples

These improvements are transparent to users, but here’s how you interact with AlterLab’s core scraping API, which now benefits from the more reliable backend.

import alterlab
from alterlab.exceptions import ScrapeError

client = alterlab.Client(api_key="YOUR_ALTERLAB_KEY")

try:
    # The scrape request now uses class‑scoped ASN routing behind the scenes
    resp = client.scrape(
        url="https://example.com/product-list",
        params={"formats": ["json"], "min_tier": 3}
    )
    print(resp.json())
except ScrapeError as e:
    print(f"Scrape failed: {e}")

curl -X POST https://api.alterlab.io/v1/scrape \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "url": "https://example.com/product-list",
    "formats": ["json"],
    "min_tier": 3
  }'

Both snippets illustrate a standard scrape request; the routing, incident checks, and heartbeat guarantees all happen server‑side, leading to higher success rates and fewer mysterious timeouts.

Internal Resources

• For details on configuring scraping parameters, see the API documentation.
• The Python SDK provides a batteries‑included client for asynchronous workloads.
• Learn how AlterLab handles anti‑bot challenges without targeting specific vendors in the smart rendering API.

Takeaway

AlterLab’s latest updates move the platform from “it usually works”