Quick start distributed mode¶
Here is a guide how to quickly setup Frontera for single-machine, multiple process, local hacking. We’re going to deploy the simpliest possible setup with SQLite and ZeroMQ. Please proceed to Cluster setup guide article for a production setup details for broad crawlers.
Here is what services needs to be installed and configured before running Frontera:
- Python 2.7+ or 3.4+
For Ubuntu, type in command line:
$ pip install frontera[distributed,zeromq,sql]
Get a spider example code¶
First checkout a GitHub Frontera repository:
$ git clone https://github.com/scrapinghub/frontera.git
There is a general spider example in
This is a general spider, it does almost nothing except extracting links from downloaded content. It also contains some settings files, please consult settings reference to get more information.
First, let’s start ZeroMQ broker.
$ python -m frontera.contrib.messagebus.zeromq.broker
You should see a log output of broker with statistics on messages transmitted.
All further commands have to be made from
general-spider root directory.
Second, let’s start DB worker.
$ python -m frontera.worker.db --config frontier.workersettings
You should notice that DB is writing messages to the output. It’s ok if nothing is written in ZeroMQ sockets, because of absence of seed URLs in the system.
There are Spanish (.es zone) internet URLs from DMOZ directory in general spider repository, let’s use them as seeds to bootstrap crawling. Starting the spiders:
$ scrapy crawl general -L INFO -s FRONTERA_SETTINGS=frontier.spider_settings -s SEEDS_SOURCE=seeds_es_smp.txt -s SPIDER_PARTITION_ID=0 $ scrapy crawl general -L INFO -s FRONTERA_SETTINGS=frontier.spider_settings -s SPIDER_PARTITION_ID=1
You should end up with 2 spider processes running. Each should read it’s own Frontera config, and first one is using
SEEDS_SOURCE option to read seeds to bootstrap Frontera cluster.
After some time seeds will pass the streams and will be scheduled for downloading by workers. At this moment crawler
is bootstrapped. Now you can periodically check DB worker output or
metadata table contents to see that there is