filegen-server

README

filegen-server

The filegen-server daemon serves computed files for the Dominator system.

The dominator queries zero or more filegen-server instances when it needs to distribute computed files. This filegen-server is a reference implementation and serves some simple computed files. For more custom types of computed files, see the documentation for the lib/filegen package. This reference implementation may be used as a template for writing your own file generator.

Status page

The filegen-server provides a web interface on port 6972 which provides a status page, links to built-in dashboards and access to performance metrics and logs. If filegen-server is running on host myhost then the URL of the main status page is http://myhost:6972/. An RPC over HTTP interface is also provided over the same port.

Startup

Filegen-Server is started at boot time, usually by one of the provided init scripts. The filegen-server process is baby-sat by the init script; if the process dies the init script will re-start it. It may be stopped with the command:

service filegen-server stop

which also kills the baby-sitting init script. It may be started with the comand:

service filegen-server start

There are many command-line flags which may change the behaviour of filegen-server but many have defaults which should be adequate for most deployments. Built-in help is available with the command:

filegen-server -h

Key configuration parameters

The init script reads configuration parameters from the /etc/default/filegen-server file. The following is the minimum likely set of parameters that will need to be configured.

The CONFIG_FILE variable specifies the name of the file from which to read the configuration.

The USERNAME variable specifies the username that filegen-server should run as. Since filegen-server does not need root privileges, the init script runs filegen-server as this user.

Security

RPC access is restricted using TLS client authentication. Filegen-Server expects a root certificate in the file /etc/ssl/CA.pem which it trusts to sign certificates which grant access. It also requires a certificate and key which clients will use to validate the server. These should be in the files /etc/ssl/filegen-server/cert.pem and /etc/ssl/filegen-server/key.pem, respectively.

Configuration file

The configuration file contains zero or more lines of the form: keyword pathname [args...]. The keyword specifies an algorithm to use to generate data for the specified pathname. The following keywords are supported:

• DynamicTemplateFile pathname filename: the contents of filename are used as a template to generate the file data. If the file contains sections of the form {{.MyVar}} then the value of the MyVar variable from the MDB for the host are used to replace the section. If filename changes (replaced with a different inode), then the data are regenerated and distributed to all clients

• File pathname filename: the contents of filename are used to provide the file data. If filename changes (replaced with a different inode), then the data are regenerated and distributed to all clients

• MDB pathname: the file data are the JSON encoding the MDB data for the host

• StaticTemplateFile pathname filename: the contents of filename are used as a template to generate the file data. If the file contains sections of the form {{.MyVar}} then the value of the MyVar variable from the MDB for the host are used to replace the section