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Increasing application complexity has caused applications to be refactored into smaller components known as microservices that communicate with each other using RPCs. Distributed tracing has emerged as an important debugging tool for such microservice-based applications. Distributed tracing follows the journey of a user request from its starting point at the application's front-end, through RPC calls made by the front-end to different microservices recursively, all the way until a response is constructed and sent back to the user. To reduce storage costs, distributed tracing systems sample traces before collecting them for subsequent querying, affecting the accuracy of queries on the collected traces. We propose an alternative system, Snicket, that tightly integrates querying and collection of traces. Snicket takes as input a database-style streaming query that expresses the analysis the developer wants to perform on the trace data. This query is compiled into a distributed collection of microservice extensions that run as "bumps-in-the-wire," intercepting RPC requests and responses as they flow into and out of microservices. This collection of extensions implements the query, performing early filtering and computation on the traces to reduce the amount of stored data in a query-specific manner. We show that Snicket is expressive in the queries it can support and can update queries fast enough for interactive use. |
