Internal collection of information

Internal collection of information
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The info-provider takes as much information as possible from dCache. To achieve this, it needs the internal information-collecting service, info, to be running and a means to collect that information: httpd. Make sure that both the httpd and info services are running within your dCache instance. By default, the info service is started on the admin-node; but it is possible to configure dCache so it runs on a different node. You should run only one info service per dCache instance.

The traditional (pre-1.9.7) allocation of services to domains has the info cell running in the infoDomain domain. A dCache system that has been migrated from this old configuration will have the following fragment in the node’s layout file:

[infoDomain]
[infoDomain/info]

It is also possible to run the info service inside a domain that runs other services. The following example show the information domain that hosts the admin, httpd, topo and info services.

[information]
[information/admin]
[information/httpd]
[information/topo]
[information/info]

For more information on configuring dCache layout files, see the section called “Defining domains and services”.

Use the dcache services command to see if a particular node is configured to run the info service. The following shows the output if the node has an information domain that is configured to run the info cell.

[root] # /opt/d-cache/bin/dcache services | grep info
information info        info               /var/log/dCache/information.log

If a node has no domain configured to host the info service then the above dcache services command will give no output:

[root] # /opt/d-cache/bin/dcache services | grep info

If no running domain within any node of your dCache instance is running the info service then you must add the service to a domain and restart that domain.

Example:

In this example, the info service is added to the example domain. Note that the specific choice of domain (example) is just to give a concrete example; the same process may be applied to a different domain.

The layouts file for this node includes the following definition for the example domain:

[example]
[example/admin]
[example/httpd]
[example/topo]

By adding the extra line [example/info] to the layouts file, in future, the example domain will host the info service.

[example]
[example/admin]
[example/httpd]
[example/topo]
[example/info]

To actually start the info cell, the example domain must be restarted.

[root] # /opt/d-cache/bin/dcache restart example
Stopping example (pid=30471) 0 done
Starting example done

With the example domain restarted, the info service is now running.

You can also verify both the httpd and info services are running using the wget command. The specific command assumes that you are logged into the node that has the httpd service (by default, the admin node). You may run the command on any node by replacing localhost with the hostname of the node running the httpd service.

The following example shows the output from the wget when the info service is running correctly:

[root] # wget -O/dev/null http://localhost:2288/info
--17:57:38--  http://localhost:2288/info
Resolving localhost... 127.0.0.1
Connecting to localhost|127.0.0.1|:2288... connected.
HTTP request sent, awaiting response... 200 Document follows
Length: 372962 (364K) [application/xml]
Saving to: `/dev/null'

100%[===========================================================================
===>] 372,962     --.-K/s   in 0.001s

17:57:38 (346 MB/s) - `/dev/null' saved [372962/372962]

If the httpd service isn’t running then the command will generate the following output:

[root] # wget -O/dev/null http://localhost:2288/info
  --10:05:35--  http://localhost:2288/info
             => `/dev/null'
  Resolving localhost... 127.0.0.1
  Connecting to localhost|127.0.0.1|:2288... failed: Connection refused.

To fix the problem, ensure that the httpd service is running within your dCache instance. This is the service that provides the web server monitoring within dCache. To enable the service, follow the same procedure for enabling the info cell, but add the httpd service within one of the domains in dCache.

If running the wget command gives an error message with Unable to contact the info cell. Please ensure the info cell is running:

[root] # wget -O/dev/null http://localhost:2288/info
  --10:03:13--  http://localhost:2288/info
             => `/dev/null'
  Resolving localhost... 127.0.0.1
  Connecting to localhost|127.0.0.1|:2288... connected.
  HTTP request sent, awaiting response... 503 Unable to contact the info cell.  Pl
ease ensure the info cell is running.
  10:03:13 ERROR 503: Unable to contact the info cell.  Please ensure the info cel
l is running..

This means that the info service is not running. Follow the instructions for starting the info service given above.