udata-hydra is an async metadata crawler for data.gouv.fr.
URLs are crawled via aiohttp, catalog and crawled metadata are stored in a PostgreSQL database.
Since it's called hydra, it also has mythical powers embedded:
- analyse remote resource metadata over time to detect changes in the smartest way possible
- if the remote resource is a CSV, convert it to a PostgreSQL table, ready for APIfication
- send crawl and analysis info to a udata instance
The architecture for the full workflow is the following:
The hydra crawler is one of the components of the architecture. It will check if resource is available, analyse the type of file if the resource has been modified, and analyse the CSV content. It will also convert CSV resources to database tables and send the data to a udata instance.
This project uses libmagic, which needs to be installed on your system, eg:
brew install libmagic on MacOS, or sudo apt-get install libmagic-dev on linux.
Install udata-hydra dependencies and cli.
poetry install
poetry run udata-hydra migrate
poetry run udata-hydra load-catalog
poetry run udata-hydra-crawl
It will crawl (forever) the catalog according to config set in udata_hydra/config.toml, with a default config in udata_hydra/config_default.toml.
BATCH_SIZE URLs are queued at each loop run.
The crawler will start with URLs never checked and then proceed with URLs crawled before SINCE interval. It will then wait until something changes (catalog or time).
There's a by-domain backoff mecanism. The crawler will wait when, for a given domain in a given batch, BACKOFF_NB_REQ is exceeded in a period of BACKOFF_PERIOD seconds. It will retry until the backoff is lifted.
If an URL matches one of the EXCLUDED_PATTERNS, it will never be checked.
A job queuing system is used to process long-running tasks. Launch the worker with the following command:
poetry run rq worker -c udata_hydra.worker
Monitor worker status:
poetry run rq info -c udata_hydra.worker --interval 1
Converted CSV tables will be stored in the database specified via config.DATABASE_URL_CSV. For tests it's same database as for the catalog. Locally, docker compose will launch two distinct database containers.
To run the tests, you need to launch the database, the test database, and the Redis broker with docker compose -f docker-compose.yml -f docker-compose.test.yml -f docker-compose.broker.yml up -d.
Then you can run the tests with poetry run pytest.
To run a specific test file, you can pass the path to the file to pytest, like this: poetry run pytest tests/test_app.py.
To run a specific test function, you can pass the path to the file and the name of the function to pytest, like this: poetry run pytest tests/test_app.py::test_get_latest_check.
If you would like to see print statements as they are executed, you can pass the -s flag to pytest (poetry run pytest -s). However, note that this can sometimes be difficult to parse.
Pytest automatically uses the coverage package to generate a coverage report, which is displayed at the end of the test run in the terminal.
The coverage is configured in the pypoject.toml file, in the [tool.pytest.ini_options] section.
You can also override the coverage report configuration when running the tests by passing some flags like --cov-report to pytest. See the pytest-cov documentation for more information.
The API will need a Bearer token for each request on protected endpoints (any endpoint that isn't a GET).
The token is configured in the config.toml file as API_KEY, and has a default value set in the udata_hydra/config_default.toml file.
If you're using hydra as an external service to receive resource events from udata, then udata needs to also configure this
API key in its udata.cfg file:
# Wether udata should publish the resource events
PUBLISH_ON_RESOURCE_EVENTS = True
# Where to publish the events
RESOURCES_ANALYSER_URI = "http://localhost:8000"
# The API key that hydra needs
RESOURCES_ANALYSER_API_KEY = "api_key_to_change"
poetry install
poetry run adev runserver udata_hydra/app.pyThe API serves the following endpoints:
Related to checks:
GETon/api/checks/latest/?url={url}&resource_id={resource_id}to get the latest check for a given URL and/orresource_idGETon/api/checks/all/?url={url}&resource_id={resource_id}to get all checks for a given URL and/orresource_id
Related to resources:
GETon/api/resources/?resource_id={resource_id}to get a resource in the DB "catalog" table from itsresource_idPOSTon/api/resources/to receive a resource creation event from a source. It will create a new resource in the DB "catalog" table and mark it as priority for next crawlingPUTon/api/resources/to update a resource in the DB "catalog" tableDELETEon/api/resources/to delete a resource in the DB "catalog" table
⚠️ Warning: the following routes are deprecated and need be removed in the future:
POSTon/api/resource/created-> usePOSTon/api/resources/insteadPOSTon/api/resource/updated-> usePUTon/api/resources/insteadPOSTon/api/resource/deleted-> useDELETE on/api/resources/instead
Related to some status and health check:
GETon/api/status/crawler/to get the crawling statusGETon/api/status/worker/to get the worker statusGETon/api/stats/to get the crawling stats
More details about some enpoints are provided below with examples, but not for all of them:
Works with ?url={url} and ?resource_id={resource_id}.
$ curl -s "http://localhost:8000/api/checks/latest/?url=http://opendata-sig.saintdenis.re/datasets/661e19974bcc48849bbff7c9637c5c28_1.csv" | json_pp
{
"status" : 200,
"catalog_id" : 64148,
"deleted" : false,
"error" : null,
"created_at" : "2021-02-06T12:19:08.203055",
"response_time" : 0.830198049545288,
"url" : "http://opendata-sig.saintdenis.re/datasets/661e19974bcc48849bbff7c9637c5c28_1.csv",
"domain" : "opendata-sig.saintdenis.re",
"timeout" : false,
"id" : 114750,
"dataset_id" : "5c34944606e3e73d4a551889",
"resource_id" : "b3678c59-5b35-43ad-9379-fce29e5b56fe",
"headers" : {
"content-disposition" : "attachment; filename=\"xn--Dlimitation_des_cantons-bcc.csv\"",
"server" : "openresty",
"x-amz-meta-cachetime" : "191",
"last-modified" : "Wed, 29 Apr 2020 02:19:04 GMT",
"content-encoding" : "gzip",
"content-type" : "text/csv",
"cache-control" : "must-revalidate",
"etag" : "\"20415964703d9ccc4815d7126aa3a6d8\"",
"content-length" : "207",
"date" : "Sat, 06 Feb 2021 12:19:08 GMT",
"x-amz-meta-contentlastmodified" : "2018-11-19T09:38:28.490Z",
"connection" : "keep-alive",
"vary" : "Accept-Encoding"
}
}Works with ?url={url} and ?resource_id={resource_id}.
$ curl -s "http://localhost:8000/api/checks/all/?url=http://www.drees.sante.gouv.fr/IMG/xls/er864.xls" | json_pp
[
{
"domain" : "www.drees.sante.gouv.fr",
"dataset_id" : "53d6eadba3a72954d9dd62f5",
"timeout" : false,
"deleted" : false,
"response_time" : null,
"error" : "Cannot connect to host www.drees.sante.gouv.fr:443 ssl:True [SSLCertVerificationError: (1, \"[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: Hostname mismatch, certificate is not valid for 'www.drees.sante.gouv.fr'. (_ssl.c:1122)\")]",
"catalog_id" : 232112,
"url" : "http://www.drees.sante.gouv.fr/IMG/xls/er864.xls",
"headers" : {},
"id" : 165107,
"created_at" : "2021-02-06T14:32:47.675854",
"resource_id" : "93dfd449-9d26-4bb0-a6a9-ee49b1b8a4d7",
"status" : null
},
{
"timeout" : false,
"deleted" : false,
"response_time" : null,
"error" : "Cannot connect to host www.drees.sante.gouv.fr:443 ssl:True [SSLCertVerificationError: (1, \"[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: Hostname mismatch, certificate is not valid for 'www.drees.sante.gouv.fr'. (_ssl.c:1122)\")]",
"domain" : "www.drees.sante.gouv.fr",
"dataset_id" : "53d6eadba3a72954d9dd62f5",
"created_at" : "2020-12-24T17:06:58.158125",
"resource_id" : "93dfd449-9d26-4bb0-a6a9-ee49b1b8a4d7",
"status" : null,
"catalog_id" : 232112,
"url" : "http://www.drees.sante.gouv.fr/IMG/xls/er864.xls",
"headers" : {},
"id" : 65092
}
]$ curl -s "http://localhost:8000/api/status/crawler/" | json_pp
{
"fresh_checks_percentage" : 0.4,
"pending_checks" : 142153,
"total" : 142687,
"fresh_checks" : 534,
"checks_percentage" : 0.4
}$ curl -s "http://localhost:8000/api/status/worker/" | json_pp
{
"queued" : {
"default" : 0,
"high" : 825,
"low" : 655
}
}$ curl -s "http://localhost:8000/api/stats/" | json_pp
{
"status" : [
{
"count" : 525,
"percentage" : 98.3,
"label" : "ok"
},
{
"label" : "error",
"percentage" : 1.3,
"count" : 7
},
{
"label" : "timeout",
"percentage" : 0.4,
"count" : 2
}
],
"status_codes" : [
{
"code" : 200,
"count" : 413,
"percentage" : 78.7
},
{
"code" : 501,
"percentage" : 12.4,
"count" : 65
},
{
"percentage" : 6.1,
"count" : 32,
"code" : 404
},
{
"code" : 500,
"percentage" : 2.7,
"count" : 14
},
{
"code" : 502,
"count" : 1,
"percentage" : 0.2
}
]
}** Set the config values**
Create a config.toml where your service and commands are launched, or specify a path to a TOML file via the HYDRA_SETTINGS environment variable. config.toml or equivalent will override values from udata_hydra/config_default.toml, lookup there for values that can/need to be defined.
UDATA_URI = "https://dev.local:7000/api/2"
UDATA_URI_API_KEY = "example.api.key"
SENTRY_DSN = "https://{my-sentry-dsn}"The webhook integration sends HTTP messages to udata when resources are analysed or checked to fill resources extras.
Regarding analysis, there is a phase called "change detection". It will try to guess if a resource has been modified based on different criterions:
- harvest modified date in catalog
- content-length and last-modified headers
- checksum comparison over time
The payload should look something like:
{
"analysis:content-length": 91661,
"analysis:mime-type": "application/zip",
"analysis:checksum": "bef1de04601dedaf2d127418759b16915ba083be",
"analysis:last-modified-at": "2022-11-27T23:00:54.762000",
"analysis:last-modified-detection": "harvest-resource-metadata",
}Multiple docker-compose files are provided:
- a minimal
docker-compose.ymlwith two PostgreSQL containers (one for catalog and metadata, the other for converted CSV to database) docker-compose.broker.ymladds a Redis brokerdocker-compose.test.ymllaunches a test DB, needed to run tests
NB: you can launch compose from multiple files like this: docker compose -f docker-compose.yml -f docker-compose.test.yml up
The log level can be adjusted using the environment variable LOG_LEVEL.
For example, to set the log level to DEBUG when initializing the database, use LOG_LEVEL="DEBUG" udata-hydra init_db .
- Add a file named
migrations/{YYYYMMDD}_{description}.sqland write the SQL you need to perform migration. udata-hydra migratewill migrate the database as needeed.
3 services need to be deployed for the full stack to run:
- worker
- api / app
- crawler
Refer to each section to learn how to launch them. The only differences from dev to prod are:
- use
HYDRA_SETTINGSenv var to point to your customconfig.toml - use
HYDRA_APP_SOCKET_PATHto configure where aiohttp should listen to a reverse proxy connection (eg nginx) and useudata-hydra-appto launch the app server
Before contributing to the repository and making any PR, it is necessary to initialize the pre-commit hooks:
pre-commit installOnce this is done, code formatting and linting, as well as import sorting, will be automatically checked before each commit.
If you cannot use pre-commit, it is necessary to format, lint, and sort imports with Ruff before committing:
ruff check --fix .
ruff format .