14 KiB

Raw Blame History

Download handlers

Download handlers are Scrapy :ref:`components <topics-components>` used to download :ref:`requests <topics-request-response>` and produce responses from them.

System Message: ERROR/3 (<stdin>, line 7); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 7); backlink

Unknown interpreted text role "ref".

Using download handlers

The :setting:`DOWNLOAD_HANDLERS_BASE` and :setting:`DOWNLOAD_HANDLERS` settings tell Scrapy which handler is responsible for a given URL scheme. Their values are merged into a mapping from scheme names to handler classes. When Scrapy initializes it creates instances of all configured download handlers (except for :ref:`lazy ones <lazy-download-handlers>`) and stores them in a similar mapping. When Scrapy needs to download a request it extracts the scheme from its URL, finds the handler for this scheme, passes the request to it and gets a response from it. If there is no handler for the scheme, the request is not downloaded and a :exc:`~scrapy.exceptions.NotSupported` exception is raised.

System Message: ERROR/3 (<stdin>, line 14); backlink

Unknown interpreted text role "setting".

System Message: ERROR/3 (<stdin>, line 14); backlink

Unknown interpreted text role "setting".

System Message: ERROR/3 (<stdin>, line 14); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 14); backlink

Unknown interpreted text role "exc".

The :setting:`DOWNLOAD_HANDLERS_BASE` setting contains the default mapping of handlers. You can use the :setting:`DOWNLOAD_HANDLERS` setting to add handlers for additional schemes and to replace or disable default ones:

System Message: ERROR/3 (<stdin>, line 24); backlink

Unknown interpreted text role "setting".

System Message: ERROR/3 (<stdin>, line 24); backlink

Unknown interpreted text role "setting".

System Message: WARNING/2 (<stdin>, line 28)

Cannot analyze code. Pygments package not found.

.. code-block:: python

    DOWNLOAD_HANDLERS = {
        # disable support for ftp:// requests
        "ftp": None,
        # replace the default one for http://
        "http": "my.download_handlers.HttpHandler",
        # http:// and https:// are different schemes,
        # even though they may use the same handler
        "https": "my.download_handlers.HttpHandler",
        # support for any custom scheme can be added
        "sftp": "my.download_handlers.SftpHandler",
    }

Replacing HTTP(S) download handlers

While Scrapy provides a default handler for http and https schemes, users may want to use a different handler, provided by Scrapy or by some 3rd-party package. There are several considerations to keep in mind related to this.

First of all, as http and https are separate schemes, they need separate entries in the :setting:`DOWNLOAD_HANDLERS` setting, even though it's likely that the same handler class will be used for both schemes.

System Message: ERROR/3 (<stdin>, line 50); backlink

Unknown interpreted text role "setting".

Additionally, some of the Scrapy settings, like :setting:`DOWNLOAD_MAXSIZE`, are honored by the default HTTP(S) handler but not necessarily by alternative ones. The same may apply to other Scrapy features, e.g. the :signal:`bytes_received` and :signal:`headers_received` signals.

System Message: ERROR/3 (<stdin>, line 54); backlink

Unknown interpreted text role "setting".

System Message: ERROR/3 (<stdin>, line 54); backlink

Unknown interpreted text role "signal".

System Message: ERROR/3 (<stdin>, line 54); backlink

Unknown interpreted text role "signal".

Lazy instantiation of download handlers

A download handler can be marked as "lazy" by setting its lazy class attribute to True. Such handlers are only instantiated when they need to download their first request. This may be useful when the instantiation is slow or requires dependencies that are not always available, and the handler is not needed on every spider run. For example, :class:`the built-in S3 handler <.S3DownloadHandler>` is lazy.

System Message: ERROR/3 (<stdin>, line 64); backlink

Unknown interpreted text role "class".

Writing your own download handler

A download handler is a :ref:`component <topics-components>` that defines the following API:

System Message: ERROR/3 (<stdin>, line 74); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 79)

Unknown directive type "attribute".

.. attribute:: lazy
    :type: bool

    If ``False``, the handler will be instantiated when Scrapy is
    initialized.

    If ``True``, the handler will only be instantiated when the first
    request handled by it needs to be downloaded.

System Message: ERROR/3 (<stdin>, line 88)

Unknown directive type "method".

.. method:: download_request(request: Request) -> Response:
    :async:

    Download the given request and return a response.

System Message: ERROR/3 (<stdin>, line 93)

Unknown directive type "method".

.. method:: close() -> None
    :async:

    Clean up any resources used by the handler.

An optional base class for custom handlers is provided:

System Message: ERROR/3 (<stdin>, line 100)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.base.BaseDownloadHandler
    :members:
    :undoc-members:
    :member-order: bysource

Exceptions raised by download handlers

System Message: ERROR/3 (<stdin>, line 110)

Unknown directive type "versionadded".

.. versionadded:: 2.15.0

The built-in download handlers raise Scrapy-specific exceptions instead of implementation-specific ones, so that code that handles these exceptions can be written in a generic way. We recommend custom download handlers to also use these exceptions.

System Message: ERROR/3 (<stdin>, line 117)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.CannotResolveHostError

System Message: ERROR/3 (<stdin>, line 119)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.DownloadCancelledError

System Message: ERROR/3 (<stdin>, line 121)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.DownloadConnectionRefusedError

System Message: ERROR/3 (<stdin>, line 123)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.DownloadFailedError

System Message: ERROR/3 (<stdin>, line 125)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.DownloadTimeoutError

System Message: ERROR/3 (<stdin>, line 127)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.ResponseDataLossError

System Message: ERROR/3 (<stdin>, line 129)

Unknown directive type "autoexception".

.. autoexception:: scrapy.exceptions.UnsupportedURLSchemeError

Built-in HTTP download handlers reference

Scrapy ships several handlers for HTTP and HTTPS requests. While all of them support basic features, they may differ in support of specific Scrapy features and settings and HTTP protocol features. See the documentation of specific handlers and specific settings for more information. Additionally, as the underlying HTTP client implementations differ between handlers, the behavior of specific websites may be different when doing the same Scrapy requests but using different handlers.

Here is a comparison of some features of the built-in HTTP handlers, see the individual handler docs for more differences:

Feature	H2DownloadHandler	HTTP11DownloadHandler	HttpxDownloadHandler
Requires asyncio	No	No	Yes
Requires a reactor	Yes	Yes	No
HTTP/1.1	No	Yes	Yes
HTTP/2	Yes	No	Yes
TLS implementation	`cryptography`	`cryptography`	Stdlib `ssl`
HTTP proxies	No	Yes	Yes
SOCKS proxies	No	No	Yes

You can find additional HTTP download handlers in the scrapy-download-handlers-incubator package. This package is made by the Scrapy developers and contains experimental handlers that may be included in some later Scrapy version but can already be used. Please refer to the documentation of this package for more information.

H2DownloadHandler

System Message: ERROR/3 (<stdin>, line 172)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.http2.H2DownloadHandler

Supported scheme: https.

:ref:`Lazy <lazy-download-handlers>`: yes.

:ref:`Requires asyncio support <using-asyncio>`: no.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: yes.

System Message: ERROR/3 (<stdin>, line 175); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 176); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 177); backlink

Unknown interpreted text role "ref".

This handler supports https://host/path URLs and uses the HTTP/2 protocol for them.

It's implemented using :mod:`twisted.web.client` and the h2 library.

System Message: ERROR/3 (<stdin>, line 182); backlink

Unknown interpreted text role "mod".

For this handler to work you need to install the Twisted[http2] extra dependency.

If you want to use this handler you need to replace the default one for the https scheme:

System Message: WARNING/2 (<stdin>, line 190)

Cannot analyze code. Pygments package not found.

.. code-block:: python

    DOWNLOAD_HANDLERS = {
        "https": "scrapy.core.downloader.handlers.http2.H2DownloadHandler",
    }

Features and limitations

Warning

This handler is experimental, and not yet recommended for production environments. Future Scrapy versions may introduce related changes without a deprecation period or warning.

HTTP proxies	No (not implemented)
SOCKS proxies	No (not supported by the library)
HTTP/2	Yes
`response.certificate`	:class:`twisted.internet.ssl.Certificate` object System Message: ERROR/3 (`<stdin>`, line 210); backlink Unknown interpreted text role "class".
Per-request `bindaddress`	Yes
TLS implementation	`pyOpenSSL`/`cryptography`

Other limitations:

No support for HTTP/1.1.
IPv6 support requires setting :setting:`TWISTED_DNS_RESOLVER` to scrapy.resolver.CachingHostnameResolver.

System Message: ERROR/3 (<stdin>, line 218); backlink

Unknown interpreted text role "setting".
No support for the :signal:`bytes_received` and :signal:`headers_received` signals.

System Message: ERROR/3 (<stdin>, line 221); backlink

Unknown interpreted text role "signal".

System Message: ERROR/3 (<stdin>, line 221); backlink

Unknown interpreted text role "signal".

Known limitations of the HTTP/2 support:

No support for HTTP/2 Cleartext (h2c), since no major browser supports HTTP/2 unencrypted (refer http2 faq).
No setting to specify a maximum frame size larger than the default value, 16384. Connections to servers that send a larger frame will fail.
No support for server pushes, which are ignored.

HTTP11DownloadHandler

System Message: ERROR/3 (<stdin>, line 241)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.http11.HTTP11DownloadHandler

Supported schemes: http, https.

:ref:`Lazy <lazy-download-handlers>`: no.

:ref:`Requires asyncio support <using-asyncio>`: no.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: yes.

System Message: ERROR/3 (<stdin>, line 244); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 245); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 246); backlink

Unknown interpreted text role "ref".

This handler supports http://host/path and https://host/path URLs and uses the HTTP/1.1 protocol for them.

It's implemented using :mod:`twisted.web.client`.

System Message: ERROR/3 (<stdin>, line 251); backlink

Unknown interpreted text role "mod".

Features and limitations

HTTP proxies	Yes
SOCKS proxies	No (not supported by the library)
HTTP/2	No (implemented as a separate handler)
`response.certificate`	:class:`twisted.internet.ssl.Certificate` object System Message: ERROR/3 (`<stdin>`, line 261); backlink Unknown interpreted text role "class".
Per-request `bindaddress`	Yes
TLS implementation	`pyOpenSSL`/`cryptography`

Other limitations:

IPv6 support requires setting :setting:`TWISTED_DNS_RESOLVER` to scrapy.resolver.CachingHostnameResolver.

System Message: ERROR/3 (<stdin>, line 267); backlink

Unknown interpreted text role "setting".
HTTPS proxies to HTTPS destinations are not supported.

HttpxDownloadHandler

System Message: ERROR/3 (<stdin>, line 275)

Unknown directive type "versionadded".

.. versionadded:: 2.15.0

System Message: ERROR/3 (<stdin>, line 277)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers._httpx.HttpxDownloadHandler

Supported schemes: http, https.

:ref:`Lazy <lazy-download-handlers>`: no.

:ref:`Requires asyncio support <using-asyncio>`: yes.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: no.

System Message: ERROR/3 (<stdin>, line 280); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 281); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 282); backlink

Unknown interpreted text role "ref".

This handler supports http://host/path and https://host/path URLs and uses the HTTP/1.1 or HTTP/2 protocol for them.

It's implemented using the httpx library and needs it to be installed.

If you want to use this handler you need to replace the default ones for the http and https schemes:

System Message: WARNING/2 (<stdin>, line 292)

Cannot analyze code. Pygments package not found.

.. code-block:: python

    DOWNLOAD_HANDLERS = {
        "http": "scrapy.core.downloader.handlers._httpx.HttpxDownloadHandler",
        "https": "scrapy.core.downloader.handlers._httpx.HttpxDownloadHandler",
    }

Features and limitations

Warning

This handler is experimental, and not yet recommended for production environments. Future Scrapy versions may introduce related changes without a deprecation period or warning or even remove it altogether.

HTTP proxies	Yes
SOCKS proxies	Yes (SOCKS5; requires `httpx[socks]`)
HTTP/2	Yes (requires `httpx[http2]`)
`response.certificate`	DER bytes
Per-request `bindaddress`	No (not supported by the library)
TLS implementation	Standard library `ssl`

Other limitations:

The handler creates a separate connection pool for each proxy URL (due to limitations of httpx) which may lead to higher resource usage when using proxy rotation.

System Message: ERROR/3 (<stdin>, line 323)

Unknown directive type "setting".

.. setting:: HTTPX_HTTP2_ENABLED

HTTPX_HTTP2_ENABLED

Default: False

Whether to enable HTTP/2 support in this handler. The httpx[http2] extra needs to be installed if you want to enable this setting.

System Message: ERROR/3 (<stdin>, line 333)

Unknown directive type "versionadded".

.. versionadded:: VERSION

Built-in non-HTTP download handlers reference

DataURIDownloadHandler

System Message: ERROR/3 (<stdin>, line 341)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.datauri.DataURIDownloadHandler

Supported scheme: data.

:ref:`Lazy <lazy-download-handlers>`: no.

:ref:`Requires asyncio support <using-asyncio>`: no.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: no.

System Message: ERROR/3 (<stdin>, line 344); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 345); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 346); backlink

Unknown interpreted text role "ref".

This handler supports RFC 2397 data:content/type;base64, data URIs.

FileDownloadHandler

System Message: ERROR/3 (<stdin>, line 353)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.file.FileDownloadHandler

Supported scheme: file.

:ref:`Lazy <lazy-download-handlers>`: no.

:ref:`Requires asyncio support <using-asyncio>`: no.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: no.

System Message: ERROR/3 (<stdin>, line 356); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 357); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 358); backlink

Unknown interpreted text role "ref".

This handler supports file:///path local file URIs. It doesn't support remote files.

FTPDownloadHandler

System Message: ERROR/3 (<stdin>, line 366)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.ftp.FTPDownloadHandler

Supported scheme: ftp.

:ref:`Lazy <lazy-download-handlers>`: no.

:ref:`Requires asyncio support <using-asyncio>`: no.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: yes.

System Message: ERROR/3 (<stdin>, line 369); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 370); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 371); backlink

Unknown interpreted text role "ref".

This handler supports ftp://host/path FTP URIs.

It's implemented using :mod:`twisted.protocols.ftp`.

System Message: ERROR/3 (<stdin>, line 375); backlink

Unknown interpreted text role "mod".

S3DownloadHandler

System Message: ERROR/3 (<stdin>, line 380)

Unknown directive type "autoclass".

.. autoclass:: scrapy.core.downloader.handlers.s3.S3DownloadHandler

Supported scheme: s3.

:ref:`Lazy <lazy-download-handlers>`: yes.

:ref:`Requires asyncio support <using-asyncio>`: no.

:ref:`Requires a Twisted reactor <asyncio-without-reactor>`: no.

System Message: ERROR/3 (<stdin>, line 383); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 384); backlink

Unknown interpreted text role "ref".

System Message: ERROR/3 (<stdin>, line 385); backlink

Unknown interpreted text role "ref".

This handler supports s3://bucket/path S3 URIs.

It's implemented using the botocore library and needs it to be installed.

</html>

14 KiB Raw Blame History

Download handlers

Using download handlers

Replacing HTTP(S) download handlers

Lazy instantiation of download handlers

Writing your own download handler

Exceptions raised by download handlers

Built-in HTTP download handlers reference

H2DownloadHandler

Features and limitations

HTTP11DownloadHandler

Features and limitations

HttpxDownloadHandler

Features and limitations

HTTPX_HTTP2_ENABLED

Built-in non-HTTP download handlers reference

DataURIDownloadHandler

FileDownloadHandler

FTPDownloadHandler

S3DownloadHandler

14 KiB

Raw Blame History