Selecting License Server Machines

Chapter 4

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This chapter helps you decide which machines to use as license server machines.

Resources Used by the Server

This section discusses the resources used by the license server system. When you select a server machine, you may need to take into account the system limits on these resources. For small numbers of licenses (under about 100), most of these system limits are not a problem on any workstation.

Sockets

When using TCP/IP ports, each FLEXenabled application connected to a license server system uses one or more sockets. The number of sockets any one FLEXenabled application requires is dependant on FLEXnet Licensing implementation details; consult your vendor for this information. The number of sockets available to the license server system is defined by the per-process system limit for file descriptors. The total number of sockets used by the license server system is slightly larger than the total number needed by the FLEXenabled applications which are served by it.

If the number of sockets required by the license server system on a single machine becomes excessive, then it's probably good to split the license file into more than one file, onto different servers, to lighten the networking traffic (which requires the vendor to agree to issue new licenses). FLEXenabled applications then check out licenses from multiple servers using a license-file list via the LM_LICENSE_FILE environment variable.

CPU Time

For small numbers of clients, the license server systems use very little CPU time. The servers might have only a few seconds of CPU time after many days.

For a large number of clients (who are each exchanging heartbeat messages with the server), or for high checkout/checkin activity levels (hundreds per second), the amount of CPU time consumed by the server may start to become significant, although, even here, CPU usage is normally not high. In this case, you may need to ensure that the server machine you select has enough CPU cycles to spare.

Disk Space

The only output files created by the license server systems are the debug and report log files. The report log files are used to generate accurate usage reports by FLEXnet Manager. If you have a lot of license activity, these log files grow very large. You need to consider where to put these files and how often to rotate and archive them. The license administrator has the option to suppress log file output if disk space is at a premium.

It is recommended that the log files are local files on the server machine(s) to avoid networking dependencies.

See Also

"Setting the Path with an Environment Variable"
"Starting the License Server Manager on UNIX Platforms"
Appendix F, "The Report Log File"
Appendix G, "The Debug Log File"

Memory

The FLEXnet license server system uses little memory. On SunOS, lmgrd uses approximately2 MB and the vendor daemons use approximately 2 MB each, although memory usage increases in the vendor daemon with the size of the license file, size of the options file, and the number of concurrent users.

Network Bandwidth

FLEXnet Licensing sends relatively small amounts of data across the network. Each transaction, such as a checkout or checkin, is typically satisfied with less than 1 KB of data transferred. This means that FLEXnet Licensing can be effectively run over slow networks (such as dial-up SLIP lines) for small numbers of clients.

For a large number of FLEXenabled applications (hundreds), each of which exchange heartbeat messages with the vendor daemon, the network bandwidth used may start to become significant. In this case, run the FLEXenabled application and server on the same local area network, which may require splitting licenses between two files for two servers. Users can use a license-file list in the LM_LICENSE_FILE environment variable to have effective access to both servers.

See Also

"Specifying Location of the License File"

Remote Mounted Disks

Macrovision recommends that you do not use remote mounted disks when you run the license server system. In other words, it is recommended that lmgrd, the vendor daemons, the license file, and the debug and report log files are all on locally mounted disks. If any of these files is on a remote mounted disk, you double the points of failure which could lead to a temporary loss of all of your licenses. When all files are mounted locally, the licenses are available as long as the server machine is up; but when the files are on a different machine, then the loss of either the license server machine or the file server machine causes the licenses to be unavailable.

Redundant License Server Systems

If you wish to use redundant license server systems, select stable machines; in other words, do not pick machines that are frequently rebooted or shut down for one reason or another. Redundant license server machines are any that support a license server system.

FLEXnet Licensing supports two methods of redundancy:

via a license-file list in the LM_LICENSE_FILE environment variable
via a set of three redundant license server systems

With LM_LICENSE_FILE list redundancy, each one of a group of license server systems serves a subset of the total licenses. The end user sets LM_LICENSE_FILE to a list of license files, where each license file refers to one of the license server systems. The application then tries each server in the list, in order, until it succeeds or gets to the end of the list.

With three-server redundancy, if any two of the three license server systems are up and running (two out of three license server systems is referred to as a quorum), the system is functional and serves its total complement of licenses.

See Also

"Managing Multiple License Files."

Redundancy via License-File List

This is best explained by example. If ten licenses are desired for both "f1" and "f2," the vendor issues two sets of licenses with a count of 5 for each of "f1" and "f2." The server machines (unlike three-server redundancy) can be physically distant.

The license files look like:

License 1 for "chicago"

SERVER chicago 17007ea8 1700
VENDOR sampled /etc/mydaemon
FEATURE f1 sampled 1.000 01-jan-2005 5 26C7DD9C0186
FEATURE f2 sampled 1.000 01-jan-2005 5 8CE46C57041D

License 2 for "tokyo"

SERVER tokyo 17a07e08 1700
VENDOR sampled /etc/mydaemon
FEATURE f1 sampled 1.000 01-jan-2005 5 16BE40E1D98D
FEATURE f2 sampled 1.000 01-jan-2005 5 6DB6F3E402DF

The user in Chicago could set LM_LICENSE_FILE to:

1700@chicago:1700@tokyo

The user in Tokyo could set LM_LICENSE_FILE to:

1700@tokyo:1700@chicago

Remember to separate the license file names with a colon (" : ") on UNIX and with a semicolon (" ; ") on Windows. The application attempts the first server in the list, and if that fails for any reason, the second server is tried.

Three-Server Redundancy

The machines that comprise a three-server redundant configuration are required to have excellent communications. This form of redundancy requires that the servers exchange heartbeats periodically, and poor communications can cause poor performance. Avoid configuring redundant servers with slow communications or dial-up links.

Three-server redundancy is designed to provide hardware fail-over protection only and does not provide load-balancing. Use LM_LICENSE_FILE list, instead, if load-balancing is desired. This is because with three-server redundancy, only one of the three servers is "master," capable of issuing licenses. Since all clients must contact the "master," all clients must have reliable networking to a single machine. For more details, see "Three-Server Redundant Configurations."

Comparing Three-Server to License-File List

Are there any drawbacks to using the license-file list for redundancy?

Yes. By default, once a FLEXenabled application has successfully checked out a license from a given license server system, all subsequent license requests from the same application must be satisfied from the same server system. In the event that the application makes subsequent license requests and no more licenses are available from that server system, the license request is denied even though licenses may exist on another server. An application can bypass this restriction if it is coded with the use of multiple FLEXnet license jobs. Only your publisher knows if their application is programmed in this manner.

If the application supports license queueing, all licenses are queued only from the first license server system on the list rather than the request moving to another server on the list.

Finally, if one server becomes unavailable, some licenses are unavailable.

When is it recommended to use a license-file list for redundancy rather than three-server redundant servers?

When there's less system administration available to monitor license server systems.
When load-balancing is needed for FLEXenabled applications located far apart, e.g., London and Tokyo, make servers available locally, with remote servers available as backup.
License-file list is more forgiving if you lose quorum.
License-file list is not limited to three servers (any number work).
Clients do not require reliable networking to a single machine with license-file list, so this is recommended where networking itself requires redundancy.

Counted vs. Uncounted Licenses

The license file determines whether a license server system is needed. If all the FEATURE (or INCREMENT) lines have a license count of 0 (unlimited) or "uncounted", then no server is needed. This type of license is called uncounted. Alternatively, if any FEATURE lines have a non-zero license count, then a server is required to count those licenses. If a vendor wants to use FLEXnet Licensing without a server, they must issue uncounted licenses.

The license server system is able to serve uncounted licenses as well. This is done so that:

transactions can be logged into the report log for all license requests, which can then be reported on by FLEXnet Manager
options file constraints can be applied to the licenses

To have uncounted licenses served, include a SERVER line in the license file, and put the USE_SERVER line immediately after the SERVER line. The vendor daemon serves the uncounted licenses, and the USE_SERVER line indicates to applications that requests must go to the license server system for authorization.

	FLEXnet Licensing Version Notes

"uncounted" keyword introduced in v6 FLEXnet Licensing client library.