Frontier objects

Frontier uses 2 object types: Request and Response. They are used to represent crawling HTTP requests and responses respectively.

These classes are used by most Frontier API methods either as a parameter or as a return value depending on the method used.

Frontier also uses these objects to internally communicate between different components (middlewares and backend).

Request objects

Response objects

Fields domain and fingerprint are added by built-in middlewares

Identifying unique objects

As frontier objects are shared between the crawler and the frontier, some mechanism to uniquely identify objects is needed. This method may vary depending on the frontier logic (in most cases due to the backend used).

By default, Crawl Frontier activates the fingerprint middleware to generate a unique fingerprint calculated from the Request.url and Response.url fields, which is added to the Request.meta and Response.meta fields respectively. You can use this middleware or implement your own method to manage frontier objects identification.

An example of a generated fingerprint for a Request object:

>>> request.url

>>> request.meta['fingerprint']

Adding additional data to objects

In most cases frontier objects can be used to represent the information needed to manage the frontier logic/policy.

Also, additional data can be stored by components using the Request.meta and Response.meta fields.

For instance the frontier domain middleware adds a domain info field for every Request.meta and Response.meta if is activated:

>>> request.url

>>> request.meta['domain']
    "name": "",
    "netloc": "",
    "scheme": "http",
    "sld": "scrapinghub",
    "subdomain": "www",
    "tld": "com"