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
#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
-Xmx16g -Xms16g
Besides, if monitoring functions in WCS web interface are not used, the work with memory may be optimized by switching off the interaction between WCS core and WCS manager with the setting in flashphoner.properties file
disable_manager_rmi=true
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.
By default, a maximum number of simultaneous REST connections is set to 200 with the following parameter in flashphoner.properties file
rest_max_connections=200
To escape thred poolexhausting and deadlocks this value should be reduced, for example
rest_max_connections=20
If REST hooks are not used, REST client can be disabled with the following parameter
disable_rest_requests=true
Excessive logging supression
When REST hooks are used, REST client operations, EchoApp default backend operations and REST API server operations are written to WCS core logs. That leads to large number of entries in the log file and, therefore, inceases the server load. The excessive logging may be decreased if necessary using the following parameters in log4j.properties file:
log4j.logger.RestClient=WARN log4j.logger.EchoApp=WARN log4j.logger.RestApiRouter=WARN
UDP tuning
Streaming mediadata are transferred with UDP packets. Those packets can be dropped, for example if server does not have enough time to parse packet queue, that leads to picture quality loss and freezes. To escape this it is necessary to tune UDP sockets buffers with the following settings in flashphoner.properties file
rtp_receive_buffer_size=131072 rtp_send_buffer_size =131072
and to tune system queues with command
ip link set txqueuelen 2000 dev eth0
To diagnose UDP problem, it is necessary to track UDP packets dropping with command
dropwatch -l kas >start
Channel load optimization
Users' playback picture quality depends on bitrate: the higher the bitrate, the higher the quality. However, the higher the bitrate, the higher data transfer channel load and, if the bandwidth between the server and clients is limited, there is a possibility that the channel will be fully loaded. This leads the bitrate dropping and a sharp decline in quality.
In this regard, it is necessary to limit the bitrate to ensure sufficient picture quality with an acceptable channel load.
Publisher bitrate limiting
To reduce the load to the channel from publisher to server, maximum and minimum bitrate values in kbps may be set in publisher script with JavaScript API
session.createStream({ name: streamName, display: localVideo, constraints: { video: { minBitrate: 500 maxBitrate: 1000 } } ... }).publish();
Server bitrate limiting
Minimum and maximum bitrate values in bps on server may be set with the following parameters in flashphoner.properties file
webrtc_cc_min_bitrate=500000 webrtc_cc_max_bitrate=1000000
To exclude fast bitrate rise bu=y browser, the following parameter should be set
webrtc_cc2_twcc=false
Stream decoding on demand only must be switched on to reduce server load:
streaming_video_decoder_fast_start=false
Changing dynamic ports range in Linux
Dynamic or ephemeral port is a temporary port that is opened when establishing IP-connection from certain range of TCP/IP stack. Many Linux kernel versions use ports range 32768 — 61000 as dymanic ports. Enter the following command to check what range is used on server
sysctl net.ipv4.ip_local_port_range
If this range overlaps with WCS standard ports, it should be changed with the following command
sysctl -w net.ipv4.ip_local_port_range="59999 63000"
Adjusting the maximum number of opened files
In the launch script webcallserver
that is in subfolder bin
in WCS home folder, for example
/usr/local/FlashphonerWebCallServer/bin/webcallserver
in start()
function the maximum number of opened files is set
function start() { ... echo -n $"$PRODUCT: starting" ulimit -n 20000 if [[ "$1" == "standalone" ]]; then ... fi ... }
By default, this value is set to 20000, but it may be increased if necessary, following the limitations of the operating system used.