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The advantage of multiple processes is that legacy applications that are not thread-aware or
thread-safe can be run more eectively in Sun Java System Web Server. However, because all of
the Sun Java System extensions are built to support a single-process threaded environment, they
might not run in the multi-process mode. The Search plug-ins fail on startup if the server is in
multi-process mode, and if session replication is enabled, the server will fail to start in
multi-process mode.
In the multi-process mode, the server spawns multiple server processes at startup. Each process
contains one or more threads (depending on the conguration) that receive incoming requests.
Since each process is completely independent, each one has its own copies of global variables,
caches, and other resources. Using multiple processes requires more resources from your
system. Also, if you try to install an application that requires shared state, it has to synchronize
that state across multiple processes. NSAPI provides no helper functions for implementing
cross-process synchronization.
When you specify a MaxProcs value greater than 1, the server relies on the operating system to
distribute connections among multiple server processes (see
“MaxProcs (UNIX/Linux)” on
page 45
for information about the MaxProcs directive). However, many modern operating
systems do not distribute connections evenly, particularly when there are a small number of
concurrent connections.
Because Sun Java System Web Server cannot guarantee that load is distributed evenly among
server processes, you might encounter performance problems if you set Maximum Threads to 1
and MaxProcs greater than 1 to accommodate a legacy application that is not thread-safe. The
problem is especially pronounced if the legacy application takes a long time to respond to
requests (for example, if the legacy application contacts a back-end database). In this scenario, it
might be preferable to use the default value for Maximum Threads and serialize access to the
legacy application using thread pools. For more information about creating a thread pool, see
“thread-pool-init” in Sun Java System Web Server 7.0 Update 1 Administrator’s Conguration
File Reference.
If you are not running any NSAPI in your server, you should use the default settings: one
process and many threads. If you are running an application that is not scalable in a threaded
environment, you should use a few processes and many threads, for example, 4 or 8 processes
and 128 or 512 threads per process.
MaxProcs (UNIX/Linux)
To run a UNIX or Linux server in multi-process mode, set the MaxProcs directive to a value
that is greater than 1. Multi-process mode might provide higher scalability on multi-processor
machines and improve the overall server throughput on large systems such as the Sun Fire
TM
T2000 server. If you set the value to less than 1, it is ignored and the default value of 1 is used.
Use the MaxProcs directive to improve overall server throughput for the following types of
applications:
■
NSAPI applications that do not implement ne-grained locking
UnderstandingThreads,Processes,andConnections
Chapter2 • TuningSunJavaSystemWebServer 45