Add hosts dynamically

By default, all configuration changes made to LSF are static. To add or remove hosts within the cluster, you must manually change the configuration and restart all master candidates.

Dynamic host configuration allows you to add and remove hosts without manual reconfiguration. To enable dynamic host configuration, all of the parameters that are described in the following table must be defined.

Parameter	Defined in …	Description
LSF_MASTER_LIST	lsf.conf	Defines a list of master host candidates. These hosts receive information when a dynamic host is added to or removed from the cluster. Do not add dynamic hosts to this list, because dynamic hosts cannot be master hosts.
LSF_DYNAMIC_HOST_WAIT_TIME	lsf.conf	Defines the length of time a dynamic host waits before sending a request to the master LIM to add the host to the cluster.
LSF_HOST_ADDR_RANGE	lsf.cluster.`cluster_name`	Identifies the range of IP addresses for hosts that can dynamically join or leave the cluster.

Important:

If you choose to enable dynamic hosts when you install LSF, the installer adds the parameter LSF_HOST_ADDR_RANGE to lsf.cluster.cluster_name using a default value that allows any host to join the cluster. To enable security, configure LSF_HOST_ADDR_RANGE in lsf.cluster.cluster_name after installation to restrict the hosts that can join your cluster.

How dynamic host configuration works

Master LIM

The master LIM runs on the master host for the cluster. The master LIM receives requests to add hosts, and tells the master host candidates defined by the parameter LSF_MASTER_LIST to update their configuration information when a host is dynamically added or removed.

Upon startup, both static and dynamic hosts wait to receive an acknowledgement from the master LIM. This acknowledgement indicates that the master LIM has added the host to the cluster. Static hosts normally receive an acknowledgement because the master LIM has access to static host information in the LSF configuration files. Dynamic hosts do not receive an acknowledgement, however, until they announce themselves to the master LIM. The parameter LSF_DYNAMIC_HOST_WAIT_TIME in lsf.conf determines how long a dynamic host waits before sending a request to the master LIM to add the host to the cluster.

Master candidate LIMs

The parameter LSF_MASTER_LIST defines the list of master host candidates. These hosts receive updated host information from the master LIM so that any master host candidate can take over as master host for the cluster.

Important:

Master candidate hosts should share LSF configuration and binaries.

Dynamic hosts cannot be master host candidates. By defining the parameter LSF_MASTER_LIST, you ensure that LSF limits the list of master host candidates to specific, static hosts.

mbatchd

mbatchd gets host information from the master LIM; when it detects the addition or removal of a dynamic host within the cluster, mbatchd automatically reconfigures itself.

Tip:

After adding a host dynamically, you might have to wait for mbatchd to detect the host and reconfigure. Depending on system load, mbatchd might wait up to a maximum of 10 minutes before reconfiguring.

lsadmin command

Use the command lsadmin limstartup to start the LIM on a newly added dynamic host.

Allow only certain hosts to join the cluster

By default, any host can be dynamically added to the cluster. To enable security, define LSF_HOST_ADDR_RANGE in lsf.cluster.cluster_name to identify a range of IP addresses for hosts that are allowed to dynamically join the cluster as LSF hosts. IP addresses can have either a dotted quad notation (IPv4) or IP Next Generation (IPv6) format. You can use IPv6 addresses if you define the parameter LSF_ENABLE_SUPPORT_IPV6 in lsf.conf; you do not have to map IPv4 addresses to an IPv6 format.