Increase the Guzzle HTTP Client request timeout in Drupal 8

During some migration operations on a Drupal 8 site, I needed to make an HTTP request that took > 30 seconds to return all the data... and when I ran the migration, I'd end up with exceptions like:

Migration failed with source plugin exception: Error message: cURL error 28: Operation timed out after 29992 milliseconds with 2031262 out of 2262702 bytes received (see

The solution, it turns out, is pretty simple! Drupal's \Drupal\Core\Http\ClientFactory is the default way that plugins like Migrate's HTTP fetching plugin get a Guzzle client to make HTTP requests (though you could swap things out if you want via services.yml), and in the code for that factory, there's a line after the defaults (where the 'timeout' => 30 is defined) like:

= NestedArray::mergeDeep($default_config, Settings::get('http_client_config', []), $config);

Seeing that, I know at a glance that Drupal is pulling any http_client_config configuration overrides from settings.php and applying them to the Guzzle Clients that this factory creates. Therefore, I can add the following to my site's settings.php to set the default timeout to 60 seconds instead of the default 30:

 * HTTP Client config.
$settings['http_client_config']['timeout'] = 60;

Pretty simple! You can override any of the other settings this way too, like the proxy settings (there's an example in the default settings.php file), headers, and whether to verify certificates for https requests.