FlareLog SDK

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@flarelog/sdk

@flarelog/sdk / FlareLogConfig

Interface: FlareLogConfig ​

Defined in: types.ts:63

Configuration options for the FlareLog client (v2 — OTel-native).

The biggest change from v1: apiKey is now OPTIONAL. With no API key and no OTLP endpoint configured, the SDK defaults to console output. This makes the SDK useful out-of-the-box with zero backend setup.

Properties ​

apiKey? ​

optional apiKey?: string

Defined in: types.ts:71

Flarelog API key (optional).

When provided, enables the Flarelog hosted backend transport. When omitted, the SDK still works — it just exports to console and/or any OTLP endpoint you configure via transports or env vars.

endpoint? ​

optional endpoint?: string

Defined in: types.ts:74

Flarelog endpoint. Defaults to https://flarelog.dev

allowInsecure? ​

optional allowInsecure?: boolean

Defined in: types.ts:77

Allow insecure HTTP endpoints (not recommended). Defaults to false

level? ​

optional level?: LogLevel

Defined in: types.ts:80

Minimum log level to send. Defaults to "DEBUG"

batchSize? ​

optional batchSize?: number

Defined in: types.ts:83

Number of logs to batch before sending. Defaults to 50 (Node), 1 (Worker)

flushIntervalMs? ​

optional flushIntervalMs?: number

Defined in: types.ts:86

Flush interval in milliseconds. Defaults to 5000 (Node), 0 (Worker)

debug? ​

optional debug?: boolean

Defined in: types.ts:89

Whether to enable debug logging (OTel diag logger + extra console output). Defaults to false

warnOnConsoleFallback? ​

optional warnOnConsoleFallback?: boolean

Defined in: types.ts:109

Warn to console.warn when the SDK falls back to ConsoleTransport because no backend is configured (i.e., FLARELOG_API_KEY and OTEL_EXPORTER_OTLP_ENDPOINT are both unset AND no explicit transports array was provided).

This catches the most common deployment bug: the user set an API key in their platform's dashboard (e.g. Cloudflare Workers, Lovable, Vercel) but the SDK can't see it from process.env at module load, so it silently falls back to console-only logging and nothing ships to the dashboard.

  • true (default): emit a one-time console.warn describing the fallback and how to fix it.
  • false: suppress the warning (for users who intentionally want console-only logging).

The warning is emitted at most once per FlareLog instance.

logToStderr? ​

optional logToStderr?: boolean

Defined in: types.ts:123

Send the SDK's own console output (the console transport used when no backend is configured, and the console transport in transports) to stderr only.

Set this in stdio MCP servers, where stdout carries the protocol: any extra line on stdout makes the client fail to parse the stream. Has no effect on logs shipped to FlareLog or an OTLP backend, which never touch stdout.

Defaults to false.

defaultSource? ​

optional defaultSource?: string

Defined in: types.ts:126

Default source tag for all logs

includeTimestamps? ​

optional includeTimestamps?: boolean

Defined in: types.ts:129

Whether to include timestamps automatically. Defaults to true

autoCapture? ​

optional autoCapture?: AutoCaptureConfig

Defined in: types.ts:132

Automatic error capture configuration

environment? ​

optional environment?: string

Defined in: types.ts:135

Environment name (e.g., "production", "staging", "development") — sets deployment.environment.name resource attr

release? ​

optional release?: string

Defined in: types.ts:138

Release version — sets service.version resource attr

serverName? ​

optional serverName?: string

Defined in: types.ts:141

Server hostname — sets host.name resource attr

serviceName? ​

optional serviceName?: string

Defined in: types.ts:144

Service name — sets service.name resource attr. Defaults to npm_package_name or "unknown_service"

serviceNamespace? ​

optional serviceNamespace?: string

Defined in: types.ts:147

Service namespace — sets service.namespace resource attr

resourceAttributes? ​

optional resourceAttributes?: Record<string, string>

Defined in: types.ts:150

Extra resource attributes (in addition to OTEL_RESOURCE_ATTRIBUTES env var)

beforeSend? ​

optional beforeSend?: (log) => false | LogEntry

Defined in: types.ts:153

Callback to modify or drop logs before sending. Return false to drop.

Parameters ​

log ​

LogEntry

Returns ​

false | LogEntry

scrubFields? ​

optional scrubFields?: string[]

Defined in: types.ts:156

Fields to scrub from metadata (PII redaction). Defaults to common sensitive fields. Keys are matched by substring. SDK-instrumented attributes under the gen_ai.* and flarelog.* namespaces are exempt.

sampleRate? ​

optional sampleRate?: number

Defined in: types.ts:159

Sample rate for logs (0.0 to 1.0). Defaults to 1.0 (100%)

maxBatchSize? ​

optional maxBatchSize?: number

Defined in: types.ts:162

Max in-flight buffer size. Defaults to 100

onDrop? ​

optional onDrop?: (droppedCount) => void

Defined in: types.ts:165

Callback invoked when logs are dropped due to buffer overflow.

Parameters ​

droppedCount ​

number

Returns ​

void

workerMode? ​

optional workerMode?: boolean

Defined in: types.ts:168

Worker mode: auto-detects if not set. When true, uses SimpleProcessor (flush on every event).

transports? ​

optional transports?: TransportConfig[]

Defined in: types.ts:174

Explicit list of transports. Overrides env-var-based auto-detection. Use this when you want full control (e.g. fan-out to console + OTLP + Flarelog).

otlpEndpoint? ​

optional otlpEndpoint?: string

Defined in: types.ts:181

OTLP/HTTP endpoint for any OTel backend (Grafana Cloud, Honeycomb, Tempo, etc.). Shorthand for transports: [{ type: "otlp", endpoint }]. Can also be set via OTEL_EXPORTER_OTLP_ENDPOINT env var.

otlpHeaders? ​

optional otlpHeaders?: Record<string, string>

Defined in: types.ts:184

Headers for the OTLP transport (e.g. Authorization). Shorthand for transports[0].headers.

ignorePaths? ​

optional ignorePaths?: (string | RegExp | ((pathname) => boolean))[]

Defined in: types.ts:218

Request path patterns to skip when wrapping handlers with workerFetch(), pagesFunction(), or logger.withRequest().

When the incoming request's URL pathname matches any entry, the SDK bypasses span creation, log emission, and end-of-request flush entirely — the handler runs as if the SDK weren't installed. This is the recommended way to keep browser-driven noise (e.g. /favicon.ico, /robots.txt, static-asset prefixes) out of your dashboard without touching your handler code.

Each entry can be:

  • a string: matched if the pathname equals it (case-sensitive)
  • a RegExp: matched if pattern.test(pathname) returns true
  • a function: matched if (pathname) => boolean returns true

Matching happens against new URL(request.url).pathname only — query string and host are ignored.

Example ​

ts
const logger = flarelog({
  apiKey: env.FLARELOG_API_KEY,
  ignorePaths: ["/favicon.ico", "/robots.txt", /^/static//],
});

Bypass is also applied automatically to OPTIONS and HEAD requests (mirrors @sentry/cloudflare's behaviour) — those methods are almost always CORS preflight or cache-validation traffic and shouldn't generate telemetry.

ai? ​

optional ai?: boolean | AIInstrumentationConfig

Defined in: types.ts:247

Enable AI inference observability with zero config.

  • true: activates global fetch() interception for OpenAI, Anthropic, and other supported providers. Token usage, cost, latency, and errors are captured automatically.
  • false / omitted: no AI instrumentation (default).
  • Object: full AIInstrumentationConfig for fine-grained control (sample capture, price overrides, extra providers, etc.).

When enabled, call logger.disposeAI() to remove instrumentation, or logger.destroy() to clean up everything at once.

Examples ​

Zero-config

ts
const logger = flarelog({ apiKey, ai: true });
// any fetch() to OpenAI/Anthropic is now captured

Full config

ts
const logger = flarelog({
  apiKey,
  ai: { captureSamples: true, priceOverrides: { "gpt-4o": { input: 5, output: 15 } } },
});

Released under the MIT License.

Copyright (c) 2026 Chiheb Nabil / Remote Skills LTD