Troubleshoot Common Problems
This section offers advice on solving problems you might encounter with MATLAB® Parallel Server™ software.
When starting a MATLAB worker, a licensing problem might result in the message
License checkout failed. No such FEATURE exists. License Manager Error -5
There are many reasons why you might receive this error:
This message usually indicates that you are trying to use a product for which you are not licensed. Look at your
license.datfile located within your MATLAB installation to see if you are licensed to use this product.
If you are licensed for this product, this error may be the result of having extra carriage returns or tabs in your license file. To avoid this, ensure that each line begins with either
After fixing your
license.datfile, restart the network license manager and MATLAB should work properly.
This error may also be the result of an incorrect system date. If your system date is before the date that your license was made, you will get this error.
If you receive this error when starting a worker with MATLAB Parallel Server software:
You may be calling the
startworkercommand from an installation that does not have access to a worker license. For example, starting a worker from a client installation of the Parallel Computing Toolbox™ product causes the following error:
The mjs service on the host hostname returned the following error: Problem starting the MATLAB worker. The cause of this problem is: ============================================================== Most likely, the MATLAB worker failed to start due to a licensing problem, or MATLAB crashed during startup. Check the worker log file /tmp/mjs_user/node_node_worker_05-11-01_16-52-03_953.log for more detailed information. The mjs log file /tmp/mjs_user/mjs-service.log may also contain some additional information. ===============================================================
In the worker log files, you see the following information:
License checkout failed. License Manager Error -15 MATLAB is unable to connect to the license server. Check that the license manager has been started, and that the MATLAB client machine can communicate with the license server. Troubleshoot this issue by visiting: https://www.mathworks.com/support/lme/R2009a/15 Diagnostic Information: Feature: MATLAB_Distrib_Comp_Engine License path: /apps/matlab/etc/license.dat FLEXnet Licensing error: -15,570. System Error: 115
If you installed only the Parallel Computing Toolbox product, and you are attempting to run a worker on the same machine, you will receive this error because the MATLAB Parallel Server product is not installed, and therefore the worker cannot obtain a license.
Memory Errors on UNIX Operating Systems
If the number of processes created by the server services on a machine running a UNIX® operating system (Linux® or Macintosh) exceeds the operating system limits, the services fail and generate an out-of-memory error. It is recommended that you adjust your system limits. For more information, see Recommended System Limits for Macintosh and Linux (Parallel Computing Toolbox).
Run Server Processes on Windows Network Installation
Many networks are configured not to allow
LocalSystem to have access to
UNC or mapped network shares. In this case, run the mjs process under a different user with
rights to log on as a service. See Set the User.
With Job Manager
mjs_def file specifies and describes the ports required by the job
manager and all workers. See the following file in the MATLAB installation used for each cluster process:
(on UNIX operating systems)
(on Windows® operating systems)
Communicating Jobs. On worker machines running a UNIX operating system, the number of ports required by MPICH for the running of
communicating jobs ranges from
BASE_PORT + 1000 to
With Third-Party Scheduler
Before the worker processes start, you can control the range of ports used by the workers
for communicating jobs by defining the environment variable
with the value
pctconfig (Parallel Computing Toolbox) function, you specify the ports used by
the client. If the default ports cannot be used, this function allows you to configure ports
separately for communication with the job scheduler and communication with a parallel
Ephemeral TCP Ports with Job Manager
If you use the job manager on a cluster of nodes running Windows operating systems, you must make sure that a large number of ephemeral TCP ports are available on the job manager machine. By default, the maximum valid ephemeral TCP port number on a Windows operating system is 5000, but transfers of large data sets might fail if this setting is not increased. In particular, if your cluster has 32 or more workers, you should increase the maximum valid ephemeral TCP port number using the following procedure:
Start the Registry Editor.
Locate the following subkey in the registry, and click Parameters:
On the Registry Editor window, select Edit > New > DWORD Value.
In the list of entries on the right, change the new value name to
MaxUserPortand press Enter.
Right-click on the
MaxUserPortentry name and select Modify.
In the Edit DWORD Value dialog, enter
65534in the Value data field. Select
Decimalfor the Base value. Click OK.
This parameter controls the maximum port number that is used when a program requests any available user port from the system. Typically, ephemeral (short-lived) ports are allocated between the values of 1024 and 5000 inclusive. This action allows allocation for port numbers up to 65534.
Quit the Registry Editor.
Reboot your machine.
Host Communications Problems
If a worker is not able to make a connection with its MATLAB Job Scheduler, or if a client session cannot validate a profile that uses that scheduler, this might indicate communications problems between nodes.
With Command-Line Interface
First, be sure that the machines in question agree on their IP resolutions. The IP
address for a particular host should be the same for itself as it is from the perspective of
another host. For example, if a process on
hostB cannot connect to one on
hostA, find out the
hostA IP address for itself, then
see what the IP address for
hostA is from
should be the same.
If the machines can identify each other, the
nodestatus command can be useful for diagnosing problems between their processes.
Use the function to determine what MATLAB
Parallel Server processes are running on the local host, and which are accessible from remote
hosts. If a worker on
hostA cannot register with its job manager on
nodestatus on both hosts to see what each can
nodestatus -remotehost hostB
hostA, run exactly the same command:
nodestatus -remotehost hostB
The results should be the same, showing the same listing of job managers and workers.
If the output indicates problems, run the command again with a higher information level to receive more detailed information:
nodestatus -remotehost hostB -infolevel 3
With Admin Center GUI
You can diagnose some communications problems using Admin Center.
If you cannot successfully add hosts to the listing by specifying host name, you can use their IP addresses instead (see Add Hosts). If you suspect any communications problems, in the Admin Center GUI click Test Connectivity (see Test Connectivity). This testing verifies that the nodes can identify each other and allow their processes to communicate with each other.
Verify Network Communications for Cluster Discovery
If you want to use the discover cluster capabilities in Parallel Computing Toolbox, your network must be configured with at least one of the following:
DNS SRV Record
When you use DNS for cluster discovery you require a DNS SRV record for each domain. You can have multiple DNS SRV records for multiple MATLAB Job Schedulers. Use the following general form for each DNS SRV record.
_mdcs._tcp.<domain> <TTL> IN SRV <priority> <weight> <port> <hostname>.
Construct a DNS SRV record for a MATLAB Job Scheduler server using the following parts.
<domain>is the domain name (like
university.edu) that the client machine searches.
<TTL>indicates how long (in seconds) the DNS record can be cached.
IN SRVis required as shown, indicating that this is a service record.
<weight>indicate priority and weight values. If you create multiple DNS SRV records, you can specify their priority with these fields. A value of
0is recommended for each. The lower
<priority>is, the higher priority the host has. When two records have the same
<priority>, the record with the highest
<weight>is used first. Use the
<weight>value to specify server preference.
<port>is the port on which you connect to the MATLAB Job Scheduler server. The default port is
27350. If you change port for the MATLAB Job Scheduler server, change
<hostname>is the fully qualified domain name for the host serving the MATLAB Job Scheduler. The machine
mjs-1on the domain
company.comhas a fully qualified domain name
A valid DNS SRV record for the
company.com network running a
MATLAB Job Scheduler on machine
mjs-1 might look like this:
_mdcs._tcp.company.com 3600 IN SRV 0 0 27350 mjs-1.company.com.
If multiple domains are required to locate the cluster, use a DNS SRV record for each domain. If the network accessed by users via VPN has different DNS SRV records to your internal network, ensure that a DNS SRV record exists for each domain.
Use the standard procedure for your DNS system to create appropriate DNS SRV records. You
can use standard utilities such as the
nslookup command to verify that your
network is configured with the necessary DNS SRV records. To examine MATLAB Job Scheduler DNS SRV records for the
company.com domain, use
the following command.
nslookup -type=SRV _mdcs._tcp.company.com
To use multicast, it is required on the head node running the MATLAB Job Scheduler and on the client system.
Multicast, unlike TCP/IP or UDP, is a subscription-based protocol where a number of machines on a network indicate to the network their interest in particular packets originating somewhere on that network. By contrast, both UDP and TCP packets are always bound for a single machine, usually indicated by its IP address.
The main tools for investigating this type of packet are:
tcpdumpfor UNIX operating systems
etherealfor Microsoft® Windows operating systems
A Java® class included with the parallel computing products.
The Java class is called
com.mathworks.toolbox.distcomp.mjs.test.MulticastTester. Both its static
main method and its constructor take two input arguments: the multicast group to join and the
port number to use.
This Java class has a number of simple methods to attempt to join a specified multicast group. Once the class has successfully joined the group, it has methods to send messages to the group, listen for messages from the group, and display what it receives. You can use this class both from a command-line call to Java software and inside MATLAB.
From a shell prompt (assuming that
java is on your path), type
java -cp distcomp.jar com.mathworks.toolbox.distcomp.mjs.test.MulticastTester
You should see an output something like this:
0 : host1name : 0 1 : host2name : 0
The following example shows how to use the Java class inside MATLAB.
Start MATLAB on two machines (e.g.,
host2name) for which you want to test multicast. In each MATLAB session,
enter the following commands:
m = com.mathworks.toolbox.distcomp.mjs.test.MulticastTester('18.104.22.168', 9999); m.startSendingThread; m.startListeningThread;
These instructions cause each MATLAB session to issue a stream of multicast test packets, and to listen for test packets. If multicast is working between the machines, you see a stream of lines like the following:
0 : host1name : 0 1 : host2name : 0 2 : host2name : 1 3 : host2name : 2
The number on the left in each character vector is the line number for the received packet. The text in the center is the host from which the packet is received. The number on the right is the packet number sent by the sending host. It is normal for a host to report a test packet from itself.
If either machine does not receive a stream of test packets, or if the remote host is not included in either stream, then multicast communication is not operating properly.
To terminate the test stream, execute the following in both MATLAB sessions: