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

• MdbFieldDirectory pathname field directory [interval]: the named field of the MDB data for the host is used as the filename under the specified directory. This file contains the data for the host. For example, the Hostname field would be used to specify a file for every host. If the file does not exist the '*' file is read to load default data. An optional reload interval may be specified

• 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