apache/seatunnel · error · IllegalArgumentException

PostHog option 'base_url' must not be blank

Error message

PostHog option 'base_url' must not be blank

What it means

PostHogSourceParameter.normalizeBaseUrl() first requires base_url to be non-blank via requireNonBlank, then strips trailing slashes. If stripping slashes leaves an empty string (input was only slashes, e.g. '///'), it throws IllegalArgumentException with this message, since an API host is mandatory to build the request URL.

Source

Thrown at seatunnel-connectors-v2/connector-http/connector-http-posthog/src/main/java/org/apache/seatunnel/connectors/seatunnel/posthog/source/config/PostHogSourceParameter.java:85

        body.put("query", queryRequest);
        body.put("refresh", "blocking");
        setBody(JsonUtils.toJsonString(body));

        setRetry(pluginConfig.getOptional(HttpCommonOptions.RETRY).orElse(0));
        setRetryBackoffMultiplierMillis(
                pluginConfig.get(HttpCommonOptions.RETRY_BACKOFF_MULTIPLIER_MS));
        setRetryBackoffMaxMillis(pluginConfig.get(HttpCommonOptions.RETRY_BACKOFF_MAX_MS));
        setConnectTimeoutMs(pluginConfig.get(HttpSourceOptions.CONNECT_TIMEOUT_MS));
        setSocketTimeoutMs(pluginConfig.get(HttpSourceOptions.SOCKET_TIMEOUT_MS));
    }

    private static String normalizeBaseUrl(String baseUrl) {
        String normalized = requireNonBlank(baseUrl, "base_url");
        while (normalized.endsWith("/")) {
            normalized = normalized.substring(0, normalized.length() - 1);
        }
        if (normalized.isEmpty()) {
            throw new IllegalArgumentException("PostHog option 'base_url' must not be blank");
        }
        return normalized;
    }

    private static String encodePathSegment(String value) {
        try {
            return URLEncoder.encode(value, "UTF-8").replace("+", "%20");
        } catch (UnsupportedEncodingException e) {
            throw new IllegalStateException("UTF-8 encoding is not available", e);
        }
    }

    private static void setHeader(Map<String, String> headers, String name, String value) {
        headers.keySet().removeIf(headerName -> headerName.equalsIgnoreCase(name));
        headers.put(name, value);
    }

    private static String requireNonBlank(String value, String optionName) {

View on GitHub (pinned to cf67b549a7)

Solutions

  1. Set base_url to a full PostHog API host, e.g. 'https://us.posthog.com' or 'https://eu.posthog.com'.
  2. Check the env variable or placeholder feeding base_url is actually populated at runtime.
  3. Ensure no trailing-slash-only value is passed; the connector only trims trailing slashes, it cannot infer a host.

Example fix

// before
base_url = "${POSTHOG_URL}"  // env var unset -> blank

// after
base_url = "https://us.posthog.com"
Defensive patterns

Strategy: validation

Validate before calling

String baseUrl = config.getString("base_url");
if (baseUrl == null || baseUrl.trim().replaceAll("/+", "").isEmpty()) {
    throw new IllegalArgumentException("base_url must be a full PostHog API host, e.g. https://us.posthog.com");
}

Prevention

When it happens

Trigger: Configuring base_url as null, empty, whitespace-only, or composed entirely of '/' characters in the PostHog source config; the check runs when the parameter object is built via buildWithConfig -> baseUrl().

Common situations: Placeholder config value never replaced ('' or '${BASE_URL}' resolved to empty), env-var interpolation yielding blank, or a config typo like base_url = "/".

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/9877b4a7d51c9713. Report an issue: GitHub.