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dali (named after the great painter Salvador Dali) is a service which performs image transformations. It is used byOLX to process and serve images for users in around 40 countries.The application supports:
- Retrieving source images from an HTTP URL
- Encoding images to PNG, JPEG, WEBP or HEIC
- Resizing an image
- Rotating an image
- Apply a watermark image to an image
All configuration should be provided through either a json config file or environment variables. The application will search first by a file namedconfig/default.json, then if the environment variableRUN_MODE is set it will search forconfig/RUN_MODE, override the values and lastly it will override with environment variables.
| Name | Type | Description | Required | Possible Values | Notes |
|---|---|---|---|---|---|
log_level | Enum(trace, debug, info, warn, error) | Logging level for the application | N |
| Default value isinfo. |
app_port | integer | Port which the web server listens to for requests | Y | - | |
health_port | integer | Port which the web server listens to for the health requests | Y | - | |
vips_threads | integer | Max number of threads for image processing that will be used | N | - | if not specified it will takenum_of_cpus/2 with a minimum of 1 |
reqwest_timeout_millis | integer | Only applicable when running Dali with thereqwest feature which implies that the images that have to be processed are stored behind an http server and will be download with a Reqwest client. Enables a request timeout for the Reqwest client. The timeout is applied from when the request starts connecting until the response body has finished. | N (only inreqwest mode) | - | if not specified, the default is2000 milliseconds |
reqwest_connection_timeout_millis | integer | Only applicable when running Dali with thereqwest feature which implies that the images that have to be processed are stored behind an http server and will be downloaded with a Reqwest http client. Set a timeout for only the connect phase of a Client. | N (only inreqwest mode) | - | if not specified, the default is2000 milliseconds |
reqwest_pool_max_idle_per_host | integer | Only applicable when running Dali with thereqwest feature which implies that the images that have to be processed are stored behind an http server and will be downloaded with a Reqwest http client. Sets the maximum idle connection per host allowed in the pool. | N (only inreqwest mode) | - | if not specified, the default is10 connections |
reqwest_pool_idle_timeout_millis | integer | Only applicable when running Dali with thereqwest feature which implies that the images that have to be processed are stored behind an http server and will be downloaded with a Reqwest http client. Set an optional timeout for idle sockets being kept-alive. | N (only inreqwest mode) | - | if not specified, the default is60000 milliseconds |
s3_region | String | Only applicable when running Dali with thes3 feature which implies that the images that have to be processed are stored in an S3 bucket. The region where the bucket resides. | Y (only in S3 mode) | - | if not provided, Dali panics while trying to instantiate the S3 client |
s3_key | String | Only applicable when running Dali with thes3 feature which implies that the images that have to be processed are stored in an S3 bucket. The key of an AWS IAM user configured for programatic access to download the images from S3. | N (only in S3 mode) | - | if not provided together with thes3_secret, the S3 client tries to instantiate the S3 client based on the enviroment variables |
s3_secret | String | Only applicable when running Dali with thes3 feature which implies that the images that have to be processed are stored in an S3 bucket. The secret of an AWS IAM user configured for programatic access to download the images from S3. | N (only in S3 mode) | - | if not provided together with thes3_key, the S3 client tries to instantiate the S3 client based on the enviroment variables |
s3_endpoint | String | Only applicable when running Dali with thes3 feature which implies that the images that have to be processed are stored in an S3 bucket. This configuration property is only needed for the local dev environment where MinIO is used to emulate S3. | N (only in S3 mode) | - | it's only needed when wanting to use MinIO for the local development environment. has to be ommited when using Dali in production with the real S3 |
s3_bucket | String | Only applicable when running Dali with thes3 feature which implies that the images that have to be processed are stored in an S3 bucket. The name of the S3 bucket from where Dali will download the images that need processing. | Y (only in S3 mode) | - | if not provided Dali panics while trying to instantiate the S3 client |
max_file_size | integer | Maximum allowed size for the file to be processed. If the file size exceeds this limit, the download will be aborted. | N | - | if not provided, Dali will not check the file size |
The application will compute the number of threads by the following formula:pod_number_of_cpus * cpu_usage_percentage / 100. This number will be divided by 2 and half will be assigned to the HTTP connection listener and half will be assigned tolibvips (the image library). An extra worker will be created to listen to thehealth endpoint (this was done to be sure the application won't block thehealth endpoint even when overloaded).
- Libvips
- A HTTP server for images
- Docker
- Rust (1.74.0)
This application relies on C libvips library. That means it has to be previously installed into the system before compiling and/or running.
For installation follow thisinstructions. (Required minimum version 8.10.1)
Usingrustup is the recommended way to installrust. It is a tool that manages and updates rust versions (likenvm for node for example). To install it, simply runcurl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh. Then runrustup install 1.74.0.
To build and run the application, run the following command:
cargo run
Note: if you're building the application on alinux musl system, you'll need to set this env variable:RUSTFLAGS='-C target-feature=-crt-static'if it fails to compile because of the linker, try to add the result ofpkg-config --libs vips toRUSTFLAGS= env variable`
dev-env.startlocally starts a MinIO server inside a docker container. This server acts as both an HTTP server and an S3 emulator. This is achieved by having two buckets that both contain the sametest-image.jpegfile:
dali-publicwhich is publicly avaialble hence the image can be fetched over http using the following url:http://localhost:2969/dali-public/test-image.jpegdali-privatewhich can only be accesed by the dummy credentials present within thedefault.jsonconfig file.
dev-env.stopstops the MinIO server that runs locally.
There are 3 kinds of tests: unit, integration and benchmark tests.
At the moment, the only logic the application has is regarding resizing and watermark positioning. There are some unit tests around these use cases in the packageimage_processor. All other functions are deeply tied to thelibvips library which complicates testing since it is not easily mockable.To run them, simply execute:cargo test --bin dali. The parameter--bin is needed because otherwise it would run also integration tests.
This tests run over a running application.To run the tests, the script will start the containers throughdocker-compose, copy some sample files to thehttp container and run the tests over the application, checking the array of bytes from the responses against expected result images stored in thetests/resources/results directory. To run the whole flow, simply run:make test.
This is an experimental feature from rust, so in order to use, the nightly rust toolchain has to be enabled. To do that run:
rustup toolchain install nightlyrustup default nightlyTo rollback to stable, runrustup default stable.
To run the benchmark, simply callcargo bench (application must be running at localhost on port 8080).
It outputs the average time per iteration and the deviation between max and min. Example output from a 4 core 2.3GHz MacBook (application running inside docker limited to 4 cores and with 4 workers):
test bench_highhes ... bench: 71,112,344 ns/iter (+/- 7,798,699)
The application supports the following endpoints.
Signifies the application is healthy by returning a HTTP Status OK - 200 return code.
Prometheus formatted metrics. Currently exposes request count and duration per endpoint
Fetches and processes an image file. The only mandatory parameter is theimage_address.
| Parameter | Description |
|---|---|
image_address | The address for the Image. Should be a HTTP, HTTPS or HTTP valid URI. |
format | desired image format. Possible values areJpeg,Png,Heic andWebp. Defaults to Jpeg |
quality | desired quality for the image. For Jpeg, it goes from 0 to 100 (defaults to 75) |
size[width] | desired width for the image. Images won't get upscaled or have their aspect ratio changed by variations on parameters for width and height. |
size[height] | desired height for the image. Images won't get upscaled or have their aspect ratio changed by variations on parameters for width and height. |
rotation | optional rotation of the image. Possible values areR90,R180 andR270 |
Watermarks is an array parameter and therefore, must be indexed when informed (0 indexed).
| Parameter | Description |
|---|---|
watermarks[0][image_address] | watermark file. File has to be smaller than original file. Should be a HTTP, HTTPS or HTTP valid URI. |
watermarks[0][alpha] | opacity from the watermark over the original image. it is a floating point number from 0 to 1. |
watermarks[0][position][x][origin] | identifier to position the watermark based on a point or centered (X axis). Possible values: Left (default), Right, Center. |
watermarks[0][position][y][origin] | identifier to position the watermark based on a point or centered (Y axis). Possible values: Top (default), Bottom, Center. |
watermarks[0][position][x][pos] | position of the watermark in the X axis. Value in pixels. |
watermarks[0][position][y][pos] | position of the watermark in the Y axis. Value in pixels. |
watermarks[0][size] | optional size of the watermark. It should be a value between 1 and 100 representing a percentage from the original image. |
(c) Copyright 2019-2024OLX. Released underApache 2 License
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An image processor service