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datadog: Config (final) portion of new tracing library (envoyproxy#26284
) This is the final part of the work proposed in envoyproxy#23958. This PR additionally contains all of the changes from envoyproxy#26148. This diff will shrink when that PR is merged. This revision alters the DatadogTracerFactory in source/extensions/tracers/datadog/config.h to produce instances of the new dd-trace-cpp based implementation of the Datadog tracer, instead of the old dd-opentracing-cpp based one. This revision actually alters the implementation of the Datadog tracer. Previous pull requests have only added code for use here. This revision also moves some unit tests around: Two tests that were part of datadog_tracer_impl_test.cc have been moved into agent_http_client_test.cc, because they're about HTTP requests. One test that was part of datadog_tracer_impl_test.cc has been removed because its behavior is already covered by tests added in other PRs in this series. The remaining tests in datadog_tracer_impl_test_.cc were moved into config_test.cc, since they all now have to do with the configuration of the tracer and the resulting behavior. Finally, all references to dd-opentracing-cpp and msgpack have been removed from the repo, and the documentation (READMEs) and demo/ directory from envoyproxy#23958 have been added. Signed-off-by: David Goffredo <david.goffredo@datadoghq.com>
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| # Prevent the exclusion of the diagram used in the readme. | ||
| !diagram.svg |
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| Datadog Tracer | ||
| ============== | ||
| This directory contains the source code for distributed tracing using Datadog. | ||
| It is a wrapper around [dd-trace-cpp][2], Datadog's core tracing C++ library. | ||
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| The unit tests are under [../../../../test/extensions/tracers/datadog/][1]. | ||
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| Design | ||
| ------ | ||
| The following diagram illustrates the relationships among classes relevant to | ||
| this library. | ||
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| Each node denotes one of the following: | ||
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| - Hexagonal nodes are interfaces defined by Envoy. | ||
| - Nodes that mention the 🐶 namespace (`::datadog::tracing`) are | ||
| defined within the Datadog core C++ tracing library, [dd-trace-cpp][2]. | ||
| - Rectangular nodes are classes defined in this library. | ||
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| Each edge denotes one of the following relationships: | ||
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| - Edges labeled "has" indicate that the predecessor node contains an instance of (or | ||
| a pointer to) the successor node. | ||
| - Edges labeled "implemented by" indicate that the successor node is an | ||
| implementation of the predecessor node. | ||
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|  | ||
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| The design of [dd-trace-cpp][2] was informed by the anticipated integration with | ||
| Envoy, Nginx, and arbitrary C++ code. The integration-specific operations are: | ||
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| - Scheduling an event to happen periodically: sending batched traces to the | ||
| Datadog Agent. | ||
| - Sending an HTTP POST request to the Datadog Agent and handling the resulting | ||
| response. | ||
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| For event scheduling there is the [🐶::EventScheduler][4] interface, whose | ||
| Envoy-specific implementation is [EventScheduler](./event_scheduler.h). | ||
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| For HTTP requests there is the [🐶::HTTPClient][3] interface, whose | ||
| Envoy-specific implementation is [AgentHTTPClient](./agent_http_client.h). | ||
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| Directory Contents | ||
| ------------------ | ||
| #### `agent_http_client.{h,cc}` | ||
| Contains `class AgentHTTPClient`, which is an implementation of | ||
| [🐶::HTTPClient][3] in terms of `Http::AsyncClient::Callbacks`. | ||
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| The HTTP client is passed to the configuration of | ||
| [🐶::DatadogAgent][10], a [🐶::Collector][11] | ||
| implementation that uses the HTTP client to send traces to the Datadog Agent. | ||
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| #### `BUILD` | ||
| The Bazel build configuration for this library ("datadog_tracer_lib"). | ||
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| #### `config.{h,cc}` | ||
| Contains `class DatadogTracerFactory`, a type that is registered to produce | ||
| `Tracer` instances (see `tracer.{h,cc}` below). | ||
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| #### `dict_util.{h,cc}` | ||
| The Datadog core tracing library uses two interfaces, `DictReader` and | ||
| `DictWriter`, for reading and writing, respectively, string mappings for trace | ||
| context (e.g. HTTP headers). | ||
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| These files contain implementations of those interfaces used by this library. | ||
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| #### `event_scheduler.{h,cc}` | ||
| Contains `class EventScheduler`, which is an implementation of | ||
| [🐶::EventScheduler][4] in terms of `Event::Dispatcher`. | ||
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| The event scheduler is passed to the configuration of | ||
| [🐶::DatadogAgent][10], a [🐶::Collector][11] | ||
| implementation that uses the event scheduler to periodically send batched traces | ||
| to the Datadog Agent. | ||
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| #### `logger.{h,cc}` | ||
| Contains `class Logger`, which is an implementation of | ||
| [🐶::Logger][5] in terms of `spdlog::logger`. | ||
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| The logger is used by the Datadog core C++ tracing library to print error | ||
| diagnostics in cases where an error cannot otherwise be reported, and to print | ||
| a banner of the library's configuration on startup. | ||
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| #### `span.{h,cc}` | ||
| Contains `class Span`, which is an implementation of `Tracing::Span` in terms | ||
| of [🐶::Span][6]. | ||
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| #### `time_util.{h,cc}` | ||
| Contains a conversion function that estimates the value of a [datadog::tracing::TimePoint][7] given a `SystemTime`. | ||
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| `🐶::TimePoint` contains both a system time point and a steady | ||
| (monotonic) time point. The system time is used to determine when a span | ||
| begins, while the steady time is used to determine a span's duration once it | ||
| has finished. | ||
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| Envoy's tracing interface exposes only the system time. However, the Datadog | ||
| core tracing library uses the steady (monotonic) component of the start time | ||
| to later calculate a span's duration. The conversion function estimates the | ||
| steady time when a span starts by examining the difference between the current | ||
| system time and the provided system time, and uses that difference as the offset | ||
| to the current steady time. | ||
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| #### `tracer_stats.h` | ||
| Contains `struct TracerStats`, which is used by this library to keep track of | ||
| certain events, such as when sending traces to the Datadog Agent fails. | ||
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| #### `tracer.{h,cc}` | ||
| Contains `class Tracer`, which is an implementation of `Tracing::Driver` in | ||
| terms of [🐶::Tracer][8]. | ||
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| Each instance of `Tracer` is local to a worker thread. | ||
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| `Tracer` is what is returned by `DatadogTracerFactory::createTracerDriverTyped`. | ||
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| Demo | ||
| ---- | ||
| [demo/](demo/) contains a [docker compose][9] setup and supporting | ||
| configuration that can be used to manually test Datadog tracing in a local | ||
| build of Envoy. | ||
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| The local build of Envoy runs on the host, while the Datadog Agent and an | ||
| upstream HTTP server are services within the [docker compose setup](demo/docker-compose.yaml). | ||
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| See [demo/envoy](demo/envoy) and | ||
| [demo/docker-compose.yaml](demo/docker-compose.yaml). | ||
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| ### Example Usage | ||
| In a command shell: | ||
| ```console | ||
| $ cd demo | ||
| $ DD_API_KEY=your_datadog_api_key_here docker compose up --build | ||
| [...] | ||
| demo-http-1 | http node.js web server is running | ||
| demo-dd-agent-1 | system-probe exited with code 0, disabling | ||
| ``` | ||
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| In another command shell: | ||
| ```console | ||
| $ cd demo | ||
| $ ./envoy | ||
| [...] | ||
| [2022-11-10 20:06:10.217][264507][info][main] [source/server/server.cc:907] starting main dispatch loop | ||
| ``` | ||
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| In a third command shell: | ||
| ```console | ||
| $ curl 'http://localhost:1337' | ||
| { | ||
| "service": "http", | ||
| "headers": { | ||
| "host": "localhost:1337", | ||
| "user-agent": "curl/7.81.0", | ||
| "accept": "*/*", | ||
| "x-forwarded-for": "172.16.14.142", | ||
| "x-forwarded-proto": "http", | ||
| "x-envoy-internal": "true", | ||
| "x-request-id": "cfa52b85-8660-9532-b347-bd484da76166", | ||
| "x-envoy-expected-rq-timeout-ms": "15000", | ||
| "x-foobar-banana": "", | ||
| "x-datadog-tags": "_dd.p.dm=-0", | ||
| "x-datadog-trace-id": "6487770461011569198", | ||
| "x-datadog-parent-id": "6487770461011569198", | ||
| "x-datadog-sampling-priority": "1" | ||
| } | ||
| } | ||
| ``` | ||
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| If all went well, then the resulting trace will be visible in Datadog's UI. The | ||
| service name is `envoy-demo`. See the [Envoy config](demo/envoy.yaml). | ||
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| [1]: ../../../../test/extensions/tracers/datadog/ | ||
| [2]: https://github.com/DataDog/dd-trace-cpp | ||
| [3]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/http_client.h | ||
| [4]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/event_scheduler.h | ||
| [5]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/logger.h | ||
| [6]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/span.h | ||
| [7]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/clock.h | ||
| [8]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/tracer.h | ||
| [9]: https://docs.docker.com/compose/ | ||
| [10]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/datadog_agent.h | ||
| [11]: https://github.com/DataDog/dd-trace-cpp/blob/main/src/datadog/collector.h |
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