stackdriver-logging-winston-koa/build/src/middleware/common/make-middleware.js

Koa middleware for Winston transport to Cloud Logging

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.makeMiddleware = makeMiddleware;
const context_1 = require("@google-cloud/logging/build/src/utils/context");
const http_request_1 = require("@google-cloud/logging/build/src/utils/http-request");
/**
 * Generates a Koa middleware that installs a request-specific logger on
 * the `context` object. It optionally can do HttpRequest timing that can be
 * used for generating request logs. This can be used to integrate with logging
 * libraries such as winston and bunyan.
 *
 * @param projectId Generated traceIds will be associated with this project.
 * @param makeChildLogger A function that generates logger instances that will
 * be installed onto `ctx` as `ctx.log`. The logger should include the trace in
 * each log entry's metadata (associated with the LOGGING_TRACE_KEY property.
 * @param emitRequestLog Optional. A function that will emit a parent request
 * log. While some environments like GAE and GCF emit parent request logs
 * automatically, other environments do not. When provided this function will be
 * called with a populated `HttpRequest` which can be emitted as
 * request log.
 */
function makeMiddleware(projectId, makeChildLogger, emitRequestLog) {
    return async (ctx, next) => {
        const requestStartMs = Date.now();
        // Detect & establish context if we were the first actor to detect lack of
        // context so traceContext is always available when using middleware.
        const traceContext = (0, context_1.getOrInjectContext)(ctx.req, projectId, true);
        // Install a child logger on the context object, with detected trace and
        // span.
        ctx.log = makeChildLogger(traceContext.trace, traceContext.spanId, traceContext.traceSampled);
        await next();
        if (emitRequestLog) {
            // Emit a 'Request Log' on the parent logger.
            const latencyMs = Date.now() - requestStartMs;
            const { req, res } = ctx;
            const httpRequest = (0, http_request_1.makeHttpRequestData)(req, res, latencyMs);
            emitRequestLog(httpRequest, traceContext.trace, traceContext.spanId, traceContext.traceSampled);
        }
    };
}
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