Darkserver

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Darkserver is a service written to help people finding details of build-id(s). People will be able query the service based on build-id(s) or rpm package names. The service will provide output in JSON format as it will be easier for other tools to parse the output.

The whole idea is based on a feature of BUILD-ID which was completed in Fedora 8 time, you can read about it here.

Source Code

Source code is under github and can be found here.

Why we need the service?

To enable developer tools to identify exact package builds from which process images (e.g. core dumps) come. This can enable their analysis, debugging profiling, by finding out where the rpm / elf / dwarf files may be found, so they can download them. (This is even better than abrt-action-install-debuginfo-to-abrt-cache because that apparently cannot query files no longer indexed by repodata.)

darkclient may look like the same what can be done with repoquery: 

$ repoquery -q --enablerepo='*-debuginfo' -f /usr/lib/debug/.build-id/0d/aa18d6291a5d0d174556c8c46f1345eba61a65
bash-debuginfo-0:4.2.10-5.fc16.x86_64

Just with repoquery one has only available:

One does not have available:

This is a real problem making bugreports investigations difficult or even lost in some cases:

It is more common but I have spent more time searching for it.

Also the repoquery -qf way is too slow as it has to download *-filelists.sqlite.bz2 files for all the repositories first.

Requests for this feature of build-id to NVRA queries implemented some other ways have been declined before:

Real world example when repoquery cannot be used

A common problem with longterm running servers is how to analyze their crashes.

Now you have a core file which you want to backtrace/analyze. How do you find symbols for server-1.1-6.fc16.x86_64? Repository fedora contains server-1.1-5.fc16.x86_64 and repository updates contains server-1.1-7.fc16.x86_64.. The system where it crashed has files already with server-1.1-7.fc16.x86_64.

server-1.1-6.fc16.x86_64 is usually still present at the Koji server where it can be downloaded but there is no way how to find out it which file to download from Koji.

Another problem would be if the automatic Koji builds deletion gets in the way. But I cannot say if it can be a problem, we can find it out only after we can find which build at Koji it is. ABRT Retrace Server currently stores copies of all the released builds from the past to workaround both the Koji autodeletion and missing build-id databases.

rpm builds storage

Darkclient currently provides URLs to the Koji server. This may overload its download bandwidth when Darkclient gets in common Tools (GDB etc.) use. This is what the YUM mirrors infrastructure exists there for.

Populating the database

The database needs to contain very every build that may be in use, to be useful at all. There are multiple possible sources of this info. Populating the database should be based on a push (not pull) technology, with some hook at Koji/Bodhi executed after a new build.

Architecture of the project

View this image.

Requirements

The web service does not need any authentication. It will require read only access to the database, the users will only require to query the service.

The information on the database will be filled up by darkserver-import command, which will only execute through bodhi on every update pushed through.


Setting up the Darkserver

Install the darkserver rpms. Edit the configuration file at /etc/darkserver/darkserverweb.conf as 

[darkserverweb]
host=MySQL host name
user=MySQL user 
password=password
database=database name
port=3306

Now for the first time, one has to do Django syncdb, To do so give the following command: 

root@localhost$ python /usr/lib/python2.6/site-packages/darkserverweb/manage.py syncdb

Start the apache server after this.

SELinux Configuration

If running in Enforcing mode, you will need to allow apache to connect to the postgreSQL server. Even if you are not running currently running in Enforcing mode it is still recommended to run the following command to ensure that there are no future issues with SELinux if Enforcing mode is later enabled. 

root@localhost$ setsebool -P httpd_can_network_connect_db 1

Setting up the Koji plugin

In the koji-hub, install the darkserver-kojiplugin package. Then fill up the configuration file under /etc/koji-hub/plugins/darkserver.conf 

[darkserver]
host=MySQL host name
user=MySQL user
password=password
database=database name
port=3306

Then enable the plugin for the koji-hub. Restart the apache.

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