...
Server default settings are mostly universal and need to be tuned to certain client case.
Server load and memory consumption optimization
Garbage collector tuning
Garbage collector (GC) is an important part of Java VM. When GC is running, it dramatically increases the server load and may stop another tasks execution, therefore it is recommended to minimize GC launch with the following settings in wcs-core.properties file
Code Block | ||||
---|---|---|---|---|
| ||||
#Disable heuristic rules
-XX:+UseCMSInitiatingOccupancyOnly
#Reduce Old Gen threshold
-XX:CMSInitiatingOccupancyFraction=70
# Use System.gc() concurrently in CMS
-XX:+ExplicitGCInvokesConcurrent
# Disable System.gc() for RMI, for 10000 hours
-Dsun.rmi.dgc.client.gcInterval=36000000000
-Dsun.rmi.dgc.server.gcInterval=36000000000 |
Heap memory tuning
Many objects with data are created and destroyed in memory while streaming. Therefore it is recommended to allocate at least 1/2 of server physical memory for Java memory heap. For example, if server RAM is 32 Gb, then it is recommended to allocate 16 Gb with the following settings in wcs-core.properties file
Code Block | ||||
---|---|---|---|---|
| ||||
-Xmx16g
-Xms16g |
REST client tuning
When REST hooks are used, on every WCS server action (establishing client connection, publishing and playing a stream, making a SIP call etc) HTTP REST connection to backend server is established. With a large number of simultaneously publishing clients or subscribers, with the default WCS settings it is possible to exhaust the WCS REST client thread pool, that is lead to deadlocks. Then, server stops to publish and play streams.
...
Adjusting the maximum number of opened files
Legacy settings (before build 5.2.762)
In the launch script webcallserver
that is in subfolder bin
in WCS home folder, for example
...
By default, this value is set to 20000, but it may be increased if necessary, following the limitations of the operating system used.
Using environment variable (since build 5.2.762)
Since build 5.2.762, maximum opened files limit can be set using the following environment variable
Code Block | ||
---|---|---|
| ||
WCS_FD_LIMIT=20000 |
in setenv.sh file. When updating WCS from previous builds, this variable should be added to setenv.sh manually, for example
Code Block | ||
---|---|---|
| ||
export WCS_FD_LIMIT=100000 |
Unlike the webcallserver startup script, the setenv.sh file is not overwritten on subsequent updates, therefore it is not necessary to restore this setting after every update.
Using service parameter while launching from non-root user (since build 5.2.801)
Since build 5.2.801, WCS is launching from 'flashphoner' user for better security. In this case, maximum opened files limit can be set using service parameters
Code Block | ||||
---|---|---|---|---|
| ||||
sudo nano /etc/systemd/system/webcallserver.service |
Maximum opened files limit is set with LimitNOFILE
parameter, for example
Code Block | ||
---|---|---|
| ||
[Service]
User=flashphoner
Group=flashphoner
LimitNOFILE=100000
... |
Traffic encryption in a separate thread for each client session
By default, one CPU thread encrypts medai traffic for all the client sessions. This leads to one CPU core overload by such thread, espacyally on low-power servers, for big subscribers amount. Then, server can not send mediapackets to all subscribers, and streams viewed are degrading, FPS lowering and freezing.
To distribute the load evenly across the CPU cores, it is necessary to enable traffic encryption in a separate thread for each client session with the following parameters
Code Block | ||
---|---|---|
| ||
rtp_paced_sender=true
rtp_paced_sender_initial_rate=200000
rtp_paced_sender_increase_interval=50
rtp_paced_sender_k_up=0.9 |
and restart WCS.
Stream distribution optimization
A stream playback quality may drop when a number of subscribers are viewing it simutlaneouly (from 100 and more): low FPS, freezes. However, server capacity and channel bandwidth may be enough. In this case it is recommended to enable multithreaded stream distribution to subscribers using the following parameter
Code Block | ||
---|---|---|
| ||
streaming_distributor_subgroup_enabled=true |
In this case, audio and video client sessions are distributed by groups.
Maximum number of video sessions per group can be set with the following parameter
Code Block | ||
---|---|---|
| ||
streaming_distributor_subgroup_size=50 |
Maximum number of audio sessions per group can be set with the following parameter
Code Block | ||
---|---|---|
| ||
streaming_distributor_audio_subgroup_size=500 |
Frame queue size per group and maximum frame waiting time (in milliseconds) are set by the following parameters
Code Block | ||
---|---|---|
| ||
streaming_distributor_subgroup_queue_size=300
streaming_distributor_subgroup_queue_max_waiting_time=5000 |
for video and
Code Block | ||
---|---|---|
| ||
streaming_distributor_audio_subgroup_queue_size=300
streaming_distributor_audio_subgroup_queue_max_waiting_time=5000 |
for audio sessions respectively.