notifier-test-task

This project consist Go test task solution for "Senior Go Backend Developer" position at some international company.

To get full description of the task see docs/TASK_DESCRIPTION.md file.

The layout of the project based on golang-standards/project-layout. Hence, the library is stored at pkg/notifier directory, and the executable is stored in cmd/notify directory.

Solution explanation

• A client is configured with a URL to which notifications are sent. Done using New(url string, params *ClientParams) *Client.
• It implements a function that takes messages and notifies about them. Done using Notify(messages ...string) (int, error) [1]
• This operation should be non-blocking for the caller.
• Allow the caller to handle notification failures in case any requests should fail. Done using OnError(handler func(message []byte, err error)).
• Make sure to handle spikes in notification activity don’t overload the event-handling service or exhaust your file descriptors. [2]
• But be efficient and don’t just send requests serially. [3]

Assumptions

• [1] As soon as there is no information about server in task description I assumed that it's ok do not check HTTP response codes like 200 or others. As a library author I can't get assumptions about how exactly event-handling server will be implemented.

• [2] To prevent exhausting file descriptors I check syscall.Rlimit and set workers limit less than available descriptors. At the same time there is no warranty that caller doesn't have some other files or connections already opened, so it's just sanity check. Also, I check http.Transport limits and adjust workers limit to those limits if it's possible. To prevent overloading of the event-handling service I use internal rateLimiter. At the same time I know nothing about the server. Hence, I provided ClientParams which library user can use to adjust rate limits and workers limits.

• [3] Because http.Client is safe for concurrent calls I decided it will be efficient to handle each message in separate goroutine. At the same time I decided to limit number of workers to avoid exhausting a lot of memory and CPU resources. Caller can get an error from Notify and take care of it, if workers limit is exceeded.

Requirements

You need golangci-lint installed locally to run linters with:

$ make lint

Docs

Docs are available at http://localhost:8888 after you start $ make docs. It will also show you link to the package in the console output to faster navigation.

Build

Just run:

$ make build

It will create notify binary inside the project root which is The Executable application from docs/TASK_DESCRIPTION.md. Also, it will create notify-test-server which is simple http server created for testing purposes.

Test

All tests can be started using:

$ make test

You also can get coverage report using:

$ make coverage