udata-hydra 2.0.0.dev2384

Async crawler and parsing service for data.gouv.fr

udata-hydra 🦀

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

Architecture schema

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, analyze the type of file if the resource has been modified, and analyze the CSV content. It will also convert CSV resources to database tables and send the data to a udata instance.

CLI

Create database structure

Install udata-hydra dependencies and cli. poetry install

poetry run udata-hydra migrate

Load (UPSERT) latest catalog version from data.gouv.fr

poetry run udata-hydra load-catalog

Crawler

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.

Worker

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

CSV conversion to database

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.

Tests

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 up -f docker-compose.broker.yml up -d.

Then you can run the tests with poetry run pytest.

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.

Tests coverage

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.

API

Run

poetry install
poetry run adev runserver udata_hydra/app.py

Routes/endpoints

The API serves the following endpoints:

Related to checks:

• GET on /api/checks/latest/ to get the latest check for a given URL or resource
• GET on /api/checks/all/ to get all checks for a given URL or resource

Related to resources:

• POST on /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 crawling
• PUT on /api/resources/ to update a resource in the DB "catalog" table
• DELETE on /api/resources/ to delete a resource in the DB "catalog" table

:warning: Warning: the following routes are deprecated and need be removed in the future:

• POST on /api/resource/created -> use POST on /api/resources/ instead
• POST on /api/resource/updated -> use PUT on /api/resources/ instead
• POST on /api/resource/deleted -> use DELETE on /api/resources/ instead

Related to some status and health check:

• GET on /api/status/crawler/ to get the crawling status
• GET on /api/status/worker/ to get the worker status
• GET on /api/stats/ to get the crawling stats

More details about some enpoints are provided below with examples, but not for all of them:

Get latest check

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"
   }
}

Get all checks for an URL or resource

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
   }
]

Get crawling status

$ 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
}

Get worker status

$ curl -s "http://localhost:8000/api/status/worker/" | json_pp
{
   "queued" : {
      "default" : 0,
      "high" : 825,
      "low" : 655
   }
}

Get crawling stats

$ 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
      }
   ]
}

Using Webhook integration

** 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 analyzed 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",
}

Development

docker-compose

Multiple docker-compose files are provided:

• a minimal docker-compose.yml with two PostgreSQL containers (one for catalog and metadata, the other for converted CSV to database)
• docker-compose.broker.yml adds a Redis broker
• docker-compose.test.yml launches 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

Logging & Debugging

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 .

Writing a migration

1. Add a file named migrations/{YYYYMMDD}_{description}.sql and write the SQL you need to perform migration.
2. udata-hydra migrate will migrate the database as needeed.

Deployment

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_SETTINGS env var to point to your custom config.toml
• use HYDRA_APP_SOCKET_PATH to configure where aiohttp should listen to a reverse proxy connection (eg nginx) and use udata-hydra-app to launch the app server

Contributing

Before contributing to the repository and making any PR, it is necessary to initialize the pre-commit hooks:

pre-commit install

Once 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 --select I .
ruff format .