@azure/eventgrid/dist/browser/cloudEventDistrubtedTracingEnricherPolicy.js

An isomorphic client library for the Azure Event Grid service.

// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
export const CloudEventBatchContentType = "application/cloudevents-batch+json; charset=utf-8";
export const TraceParentHeaderName = "traceparent";
export const TraceStateHeaderName = "tracestate";
export const ContentTypeHeaderName = "Content-Type";
/**
 * The programmatic identifier of the cloudEventDistributedTracingEnricherPolicy.
 */
export const cloudEventDistributedTracingEnricherPolicyName = "cloudEventDistributedTracingEnricherPolicy";
/**
 * cloudEventDistributedTracingEnricherPolicy is a policy which adds distributed tracing information
 * to a batch of cloud events. It does so by copying the `traceparent` and `tracestate` properties
 * from the HTTP request into the individual events as extension properties.
 *
 * This will only happen in the case where an event does not have a `traceparent` defined already. This
 * allows events to explicitly set a traceparent and tracestate which would be respected during "multi-hop
 * transmition".
 *
 * See https://github.com/cloudevents/spec/blob/master/extensions/distributed-tracing.md
 * for more information on distributed tracing and cloud events.
 */
export function cloudEventDistributedTracingEnricherPolicy() {
    return {
        name: cloudEventDistributedTracingEnricherPolicyName,
        async sendRequest(request, next) {
            const traceparent = request.headers.get(TraceParentHeaderName);
            const tracestate = request.headers.get(TraceStateHeaderName);
            if (request.headers.get(ContentTypeHeaderName) === CloudEventBatchContentType &&
                typeof request.body === "string" &&
                traceparent) {
                // per the cloud event batched content type we know the body is an array encoded in JSON.
                const parsedBody = JSON.parse(request.body);
                for (const item of parsedBody) {
                    // When using the distributed tracing extension, the "traceparent" is a required property
                    // and "tracestate" is optional. This means if an item already has a "traceparent" property
                    // we should not stomp over it. Well formed events will not have a "tracestate" without
                    // also having a "traceparent" so there's no need to guard against that case.
                    if (typeof item !== "object" || item.traceparent) {
                        continue;
                    }
                    item.traceparent = traceparent;
                    if (tracestate) {
                        item.tracestate = tracestate;
                    }
                }
                request.body = JSON.stringify(parsedBody);
            }
            return next(request);
        },
    };
}
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