Package: gocept.lms
The Link Monitoring Server (LMS) is a coherent set of components to regularly
check whether given URLs are reachable. It currently supports HTTP, HTTPS and
FTP URLs.Historygocept.lms is the third version of LMS (hence the major version number of
3.x).The first version was directly integrated into CMFLinkChecker and ran as a
thread.  This was not very stable.The second version used the Twisted framework and a MySQL database. 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 wherever possible. This is stable.ComponentsThe LMS consists of small components that only communicate via storing data in
the ZODB.XML-RPC serverThe XML-RPC server provides the API to talk to the LMS from
applications/clients that want to have their URLs checked. It provides
operations to register and unregister clients and URLs.A management system can register clients. A client can register URLs it wants
to be checked.SchedulerThe scheduler looks over the age of the data from URLs that where added by the
clients. It decides when a URL needs to be checked and inserts it into the
check queue accordingly.CheckerThe checker pulls URLs from the check queue and performs the actual check. It
has measures in place that limit the number of checks performed in parallel
and to avoid pounding too hard on external systems. (Per default it checks up
to 20 URLs at the same time and assures that URLs that belong to the same host
are checked at most once per second).NotifierThe notifier keeps the registered clients updated about the state information
for the URLs they subscribed to. Clients are notified via XML-RPC.Synchroniser/SyncerThe syncer is responsible for keeping the URL databases of the LMS and its
clients synchronized. It does this by regularly getting a full snapshot of the
clients’ databases and provides them with the current status information for
all URLs they are interested in.InstallationThe installation works using a buildout. An example can be found at our SVN:% svn co https://code.gocept.com/svn/gocept/gocept.lms/deployment/profilesThe buildout currently defines two profiles:prod.cfgfor a production setuptest.cfgfor a test setupThe 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:8080To select the test profile create abuildout.cfgwhich includes it:[buildout]
extends = profiles/test.cfgNext, bootstrap the buildout with Python 2.5:% python2.5 bootstrap.pyThis creates the actual buildout script asbin/buildout:% bin/buildoutRunning the buildout created a set of scripts, corresponding to the various
components.  The test profile uses a deployment sandbox, so all the scripts
are contained inparts/deployment/etc/init.d:% ls parts/deployment/etc/init.d/
lms-checker
lms-notifier
lms-scheduler
lms-syncer
lms-web
lms-zeoTo 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 startPoint your browser tohttp://localhost:8080. This opens the grok admin UI.
Create an LMS with the idtest. 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 startThe next step is to register a client. The LMS welcome page has a link to a
very rudimentary form. There you have to enter the following data:Client IdThis is an identifier for the client. It is used in combination with the
password to authenticate XML-RPC requests.PasswordThe password to authenticate the client.Contact nameEmails sent by the LMS will contain the name to address the recipient.Contact email addressEmails sent by the LMS regarding this client will be sent to this address.Callback URLThe callback URL is the XML-RPC point where the callback methods are
invoked. For a gocept.linkchecker installation this would behttp://example.com/portal_linkchecker/database/.After registering the client, you can configuregocept.linkchecker(or any other
client) to talk to the LMS.Changes3.0a6 (2011-02-14)Update reference to SVN.Fix bug while accepting multiple URLs: don’t break if a single URL isn’t
addable (ConstraintNotSatisfied).Correctly handle InvalidURL exceptions from urllib.3.0a5 (2011-02-13)Actually mark URLs that do not have handlers available as ‘uncheckable’.Process at most 1000 items from the queue at once to decrease latency in the
checker.3.0a4 (2011-01-25)Make registration and sync of URLs resilient towards malformed URLs. We now
require URLs to be ASCII only. Please make your client encode the URL before
sending it to us.Increased debug output for client notificationa lot. We show all URLs
that the client gets notified about now.Mark URLs that do not have handlers associated or are forbidden by the
policy as checked so they will only reappar after the same period a
successful check would.3.0a3 (2011-01-18)Provide a minimal UI for inspecting the URL database and allow purging
selected URLs from the database.Fix problem in conflict resolution: if an object relied on the default
of a class then the state dict doesn’t contain that value.Improved error handling for URLs which have an empty string (or bad statust
line) as response.Remove dependency on twisted.Provide a separate state (recommended color: blue) for URLs that the LMS can
not or refuses to check.Don’t classify mailto links (optimization).3.0a2 (2009-05-21)Updated documentation a bit.Declared namespace package.Updated used egg versions.Added missing dependency to pytz.3.0a1 (2009-04-14)first public release.