A common error is to connect to the remote server successfully but raise a
`http_client.RemoteDisconnected` exception when trying to begin
downloading. Its caused by call `prox_rec_res.begin(...)` which calls
`http_client._read_status()`. In that case, we also add the target
`hostname:port` to the `bad_hostnames_ports` cache.
Modify 2 unit tests to clear the `bad_hostnames_ports` cache because
localhost is added from previous tests and this breaks them.
Do not add entries to bad_hostnames_ports during connection running if
an exception occurs. Do it only on connection init because for some
unclear reason unit tests fail in that case.
If connection to a hostname:port fails, add it to a `TTLCache` with
60 sec expiration time. Subsequent requests to the same hostname:port
return really quickly as we check the cache and avoid trying a new
network connection.
The short expiration time guarantees that if a host becomes OK again,
we'll be able to connect to it quickly.
Adding `cachetools` dependency was necessary as there isn't any other
way to have an expiring in-memory cache using stdlib. The library
doesn't have any other dependencies, it has good test coverage and seems
maintained. It also supports Python 3.7.
In addition to checking for scheme='http', we should also check that
netloc has a value. There are many meaningless URLs that pass the
current check. For instance:
```
In [5]: urlparse("http://")
Out[5]: ParseResult(scheme='http', netloc='', path='', params='',
query='', fragment='')
In [6]: urlparse("http:///")
Out[6]: ParseResult(scheme='http', netloc='', path='/', params='',
query='', fragment='')
```
netloc should always have a value.
In python2/3, urllib parse caches in memory URL parsing results to
avoid repeating the process for the same URL. The problem is that the
default in memory cache size is just 20.
https://github.com/python/cpython/blob/3.7/Lib/urllib/parse.py#L80
Since we do a lot of URL parsing, it makes sense to increase cache size.
`http.client` has an arbitrary limit of MAXHEADERS=100. If a target URL
has more it raises an HTTPException and the request fails. (The target
pages are perfectly fine besides having more than 100 headers).
https://github.com/python/cpython/blob/3.7/Lib/http/client.py#L113
We increase this limit to 7000. We currently use this in production WBM.
We bumped into the same issue trying to replay pages with too many
HTTP headers. We increased the limit progressively from 100 to 500, 1000
etc and we found that 7000 is a good place to stop.
* master:
account for surt fix in urlcanon 0.3.0
every change is a point release now
Upgrade PyYAML to >=5.1
Use YAML instead of JSON
Add option to load logging conf from JSON file
New option `--logging-conf-file` to load `logging` conf from a JSON
file.
Prefer JSON over the `configparser` format supported by
`logging.config.fileConfig` because JSON format is much better (nesting
is supported) and its easier to detect errors.
