udata-hydra 2.0.0.dev1721

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.

API

Run

poetry install
poetry run adev runserver udata_hydra/app.py

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