gocept Link Monitoring Server
The Link Monitoring Server (lms) is a coherent set of components to regularly check that URLs area reachable. It currently supports http, https and ftp URLs.
gocept.lms is the third version of lms (hence the initial version of 3.x).
The first version was directly integrated into CMFLinkChecker and ran as a thread. This was not very stable.
The second version was using the Twisted framework and used a MySQL as a backend. This was not very stable either.
The third version now is written in Zope 3 / Grok, uses the ZODB as data storage and separates concerns where ever possible. This is stable.
The lms consists of little blocks which only communicate via storing data in the ZODB.
The XML-RPC server is the API to talk to the lms. It provides functions to register and deregister clients and urls. A management system can register clients. A client can register URLs it wants to be checked by the lms.
The scheduler looks over the URLs that where added by the clients. It decides which URLs have to be checked and puts them into the check queue.
The checker pulls URLs from the check queue and checks them. It checks up to 20 URLs at the same time, but only once per second per host to avoid overload.
The notifier keeps the registered clients updated about the state information for the URLs they subscribed to. Clients are notified via XML-RPC.
Synchroniser / Syncer
The syncer is responsible to keep the URL databases of the lms and the clients synchronized. It does this daily by getting a full snapshot of the clients’ databases and provides them with the current status information for all URLs they are interested in.
The installation works with a buildout. An example can be found at our SVN:
% svn co http://svn.gocept.com/repos/gocept/gocept.lms/deployment/profiles
The buildout currently defines two profiles:
prod.cfg for a production setup
test.cfg for a test setup
The profiles are not really different right now, though. They’re there to illustrate the possibilities. The test profile looks like this:
[buildout] extends = base.cfg [app] admin-password = admin appname = test mail-server-host = localhost [zeo] address = localhost:8100 [lms] address = localhost:8080
To select the test profile create a buildout.cfg which includes it:
[buildout] extends = profiles/test.cfg
Next, bootstrap the buildout with python 2.5:
% python2.5 bootstrap.py
This creates the actual buildout script as bin/buildout:
After the buildout was run there are scripts created to start the various parts. The test profile uses a deployment sandbox, so all the scripts are contained in parts/deployment/etc/init.d:
% ls parts/deployment/etc/init.d/ lms-checker lms-notifier lms-scheduler lms-syncer lms-web lms-zeo
To get started, first start the ZEO and the lms web interface:
% parts/deployment/etc/init.d/lms-zeo start % parts/deployment/etc/init.d/lms-web start
Point your browser to http://localhost:8080. this opens the grok admin UI. Create a lms with the id test. Once created the lms will display “Congratulations”.
Start the other services now:
% parts/deployment/etc/init.d/lms-checker start % parts/deployment/etc/init.d/lms-notifier start % parts/deployment/etc/init.d/lms-scheduler start % parts/deployment/etc/init.d/lms-syncer start
The next step is to register a client. The lms welcome page has a link to a very rudimentary form. There you have to enter:
- Client Id
This is an identificator for the client. It is used to authenticate.
The password to authenticate the client.
- Contact name
Emails sent by the lms will contain the name to address the recipient.
- Contact email address
Emails sent by the lms regarding this client will be sent to this address.
- Callback URL
The callback url is the XML-RPC point where the callback methods are called. For a gocept.linkchecker installation this would be http://example.com/portal_linkchecker/database/.
After registring the client you can configure gocept.linkchecker (or any other client) to talk to the lms.
first public release.
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