@google-cloud/logging/build/src/middleware/express/make-middleware.js

Cloud Logging Client Library for Node.js

"use strict";
/*!
 * Copyright 2018 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
Object.defineProperty(exports, "__esModule", { value: true });
exports.makeMiddleware = makeMiddleware;
const onFinished = require("on-finished");
const context_1 = require("../../utils/context");
const http_request_1 = require("../../utils/http-request");
/**
 * Generates an express middleware that installs a request-specific logger on
 * the `request` 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 `req` as `req.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 `CloudLoggingHttpRequest` which can be emitted as
 * request log.
 */
function makeMiddleware(projectId, makeChildLogger, emitRequestLog) {
    return (req, res, next) => {
        // TODO(ofrobots): use high-resolution timer.
        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)(req, projectId, true);
        // Install a child logger on the request object, with detected trace and
        // span.
        req.log = makeChildLogger(traceContext.trace, traceContext.spanId, traceContext.traceSampled);
        // Emit a 'Request Log' on the parent logger, with detected trace and
        // span.
        if (emitRequestLog) {
            onFinished(res, () => {
                const latencyMs = Date.now() - requestStartMs;
                const httpRequest = (0, http_request_1.makeHttpRequestData)(req, res, latencyMs);
                emitRequestLog(httpRequest, traceContext.trace, traceContext.spanId, traceContext.traceSampled);
            });
        }
        next();
    };
}
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