BerriAI/litellm · error · ValueError

Missing SLACK_WEBHOOK_URL from environment

Error message

Missing SLACK_WEBHOOK_URL from environment

What it means

When an alert type is configured for digest mode (_atc.digest true), litellm resolves the webhook in priority order: self.alert_to_webhook_url[alert_type], then self.default_webhook_url, then os.getenv('SLACK_WEBHOOK_URL'). If all three are unset the digest bucket cannot record a target and a ValueError is raised mid-_async_send_alert (litellm/integrations/SlackAlerting/slack_alerting.py:1347-1361).

Solutions

  1. Set SLACK_WEBHOOK_URL in the proxy process environment and restart.
  2. Or configure general_settings.alerting: ["https://hooks.slack.com/services/..."] so default_webhook_url is populated.
  3. Or map the specific alert type in general_settings.alerting_to_webhook_url (litellm_settings.alert_to_webhook_url) so the per-type lookup hits.
  4. Verify inside the container: docker exec <proxy> printenv SLACK_WEBHOOK_URL.

Example fix

# before
# litellm_config.yaml
litellm_settings:
alerting: ["spend_alerts"]  # digest-mode type, no webhook anywhere
# ValueError: Missing SLACK_WEBHOOK_URL from environment

# after
export SLACK_WEBHOOK_URL=https://hooks.slack.com/services/T000/B000/XXXX
# or in config:
general_settings:
  alerting: ["https://hooks.slack.com/services/T000/B000/XXXX"]
Defensive patterns

Strategy: validation

Validate before calling

import os

webhook = (
    (alerting.alert_to_webhook_url or {}).get(alert_type)
    or alerting.default_webhook_url
    or os.getenv("SLACK_WEBHOOK_URL")
)
if webhook is None:
    raise RuntimeError("no webhook resolvable for digest alerts: set SLACK_WEBHOOK_URL or general_settings.alerting URLs")

Try / catch

try:
    await alerting._async_send_alert(alert_type=..., message=msg)
except ValueError as e:
    if "Missing SLACK_WEBHOOK_URL" in str(e):
        logger.warning("digest alert dropped: configure SLACK_WEBHOOK_URL or alerting webhook URLs")
    else:
        raise

Prevention

When it happens

Trigger: Enabling a digest-mode alert type (e.g. db_exceptions/services/region-outage digests) via only the SLACK_WEBHOOK_URL env var while that env var is missing from the proxy process; configuring alert types without providing alerting webhook URLs in general_settings and without default_webhook_url; docker/k8s deployments where the env var is set in one container but alerts fire in another.

Common situations: Proxy config lists alert types under alerting: [...] assuming webhooks come from env, but the env var name is misspelled or unset in the deployment; moving from per-alert URLs to digest alerts without carrying the webhook config over.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

Related errors

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/aecc297b688051bd. Report an issue: GitHub.

Appendix: source

Thrown at litellm/integrations/SlackAlerting/slack_alerting.py:1345

            return
        if alert_type not in self.alert_types:
            return

        from datetime import datetime

        # Check if digest mode is enabled for this alert type
        alert_type_name_str: Final = getattr(alert_type, "value", str(alert_type))
        _atc: Final = self.alert_type_config.get(alert_type_name_str)
        if _atc is not None and _atc.digest:
            # Resolve webhook URL for this alert type (needed for digest entry)
            if self.alert_to_webhook_url is not None and alert_type in self.alert_to_webhook_url:
                _digest_webhook: str | list[str] | None = self.alert_to_webhook_url[alert_type]
            elif self.default_webhook_url is not None:
                _digest_webhook = self.default_webhook_url
            else:
                _digest_webhook = os.getenv("SLACK_WEBHOOK_URL", None)
            if _digest_webhook is None:
                raise ValueError("Missing SLACK_WEBHOOK_URL from environment")

            digest_key: Final = f"{alert_type_name_str}:{request_model or ''}:{api_base or ''}"

            async with self.digest_lock:
                now: Final = datetime.now()
                if digest_key in self.digest_buckets:
                    self.digest_buckets[digest_key]["count"] += 1
                    self.digest_buckets[digest_key]["last_time"] = now
                else:
                    self.digest_buckets[digest_key] = DigestEntry(
                        alert_type=alert_type_name_str,
                        request_model=request_model or "",
                        api_base=api_base or "",
                        first_message=message,
                        level=level,
                        count=1,
                        start_time=now,
                        last_time=now,

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