ce1ceeb257
Metrics collectors generally don't need the daemon to prime the stats with something to compare since they already have something to compare with. Before this change, the API does 2 collection cycles (which takes roughly 2s) in order to provide comparison for CPU usage over 1s. This was primarily added so that `docker stats --no-stream` had something to compare against. Really the CLI should have just made a 2nd call and done the comparison itself rather than forcing it on all API consumers. That ship has long sailed, though. With this change, clients can set an option to just pull a single stat, which is *at least* a full second faster: Old: ``` time curl --unix-socket /go/src/github.com/docker/docker/bundles/test-integration-shell/docker.sock http://./containers/test/stats?stream=false\&one-shot=false > /dev/null 2>&1 real0m1.864s user0m0.005s sys0m0.007s time curl --unix-socket /go/src/github.com/docker/docker/bundles/test-integration-shell/docker.sock http://./containers/test/stats?stream=false\&one-shot=false > /dev/null 2>&1 real0m1.173s user0m0.010s sys0m0.006s ``` New: ``` time curl --unix-socket /go/src/github.com/docker/docker/bundles/test-integration-shell/docker.sock http://./containers/test/stats?stream=false\&one-shot=true > /dev/null 2>&1 real0m0.680s user0m0.008s sys0m0.004s time curl --unix-socket /go/src/github.com/docker/docker/bundles/test-integration-shell/docker.sock http://./containers/test/stats?stream=false\&one-shot=true > /dev/null 2>&1 real0m0.156s user0m0.007s sys0m0.007s ``` This fixes issues with downstreams ability to use the stats API to collect metrics. Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Working on the Engine API
The Engine API is an HTTP API used by the command-line client to communicate with the daemon. It can also be used by third-party software to control the daemon.
It consists of various components in this repository:
api/swagger.yamlA Swagger definition of the API.api/types/Types shared by both the client and server, representing various objects, options, responses, etc. Most are written manually, but some are automatically generated from the Swagger definition. See #27919 for progress on this.cli/The command-line client.client/The Go client used by the command-line client. It can also be used by third-party Go programs.daemon/The daemon, which serves the API.
Swagger definition
The API is defined by the Swagger definition in api/swagger.yaml. This definition can be used to:
- Automatically generate documentation.
- Automatically generate the Go server and client. (A work-in-progress.)
- Provide a machine readable version of the API for introspecting what it can do, automatically generating clients for other languages, etc.
Updating the API documentation
The API documentation is generated entirely from api/swagger.yaml. If you make updates to the API, edit this file to represent the change in the documentation.
The file is split into two main sections:
definitions, which defines re-usable objects used in requests and responsespaths, which defines the API endpoints (and some inline objects which don't need to be reusable)
To make an edit, first look for the endpoint you want to edit under paths, then make the required edits. Endpoints may reference reusable objects with $ref, which can be found in the definitions section.
There is hopefully enough example material in the file for you to copy a similar pattern from elsewhere in the file (e.g. adding new fields or endpoints), but for the full reference, see the Swagger specification.
swagger.yaml is validated by hack/validate/swagger to ensure it is a valid Swagger definition. This is useful when making edits to ensure you are doing the right thing.
Viewing the API documentation
When you make edits to swagger.yaml, you may want to check the generated API documentation to ensure it renders correctly.
Run make swagger-docs and a preview will be running at http://localhost. Some of the styling may be incorrect, but you'll be able to ensure that it is generating the correct documentation.
The production documentation is generated by vendoring swagger.yaml into docker/docker.github.io.