Transforming VLC into an SA-Aware Application - Telecommunications Software Engineering Lab Concordia University Presenters: Anik Mishra and Ali Kanso
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Transforming VLC into an SA-Aware
Application
Telecommunications Software Engineering Lab
Concordia University
Presenters: Anik Mishra and Ali Kanso
1Overview
• Objective of the Work
• VLC
– Introduction
– Workflow
• Design of a SAF Compliant VLC
– Choosing components
– Levels of Integration
– Sample system configuration
• Evaluation of the Work
2Objective of the Work
• Go through the steps of modifying a regular
application for High Availability and Service
Continuity using SAF standards
• Have a running application for testing and analyzing
configuration and upgrade campaign generation
• Document methodology/lessons learned
• Contrast results achieved with effort required
3Introduction to VLC
• Started as an academic project in 1996 at the École
Centrale Paris
• Intended to consist of a client and server to stream
videos across a campus network
• Server portion later integrated with client
• Now managed by the VideoLAN non-profit
organization
4VLC Workflow
RTSP server
Control module «create»
«create»
VLM Internet
«create»
(as needed) File IO, demux,
RTP send
5Choosing Components
• Multiple criteria for choosing components:
– Unit of failure detection and/or recovery
• One aspect of components is failure detection and recovery
• Components must be able to be started separately
– Unit of service
• At what granularity is the service request?
• VLC: highly threaded design
– Each RTP stream in its own thread
– However, threads are not separable
Therefore
– Two possible configurations
6Choosing Components
• VLC as a Container component:
– Broadcast: streams as a contained component
• Each CSI represents one stream
– VoD: RTSP servers as contained components (?)
• Each RTSP server is its own CSI?
• Each different media stream is its own CSI?
• Container components not supported by OpenSAF at
design time
• VLC as single component
– Unit of failure: only one process
7VLC Component: Arguments
• VLC needs to be configured
– Objective: simplest configuration possible
• One argument:
Non-proxied non-SA aware
VLC SA-aware File
Configuration
specified as a command line argument specified as CSI Attribute
8Levels of Integration Higher availability
& complexity
VLC with
checkpointed
positions
SA Aware
VLC
(no service
continuity)
Non-SA Aware
Non-proxied
VLC
VLC
9Target Configuration
• Two components
IP address VLC
Comp category: Non-proxied non-sa- SA Aware
aware: no state
Dependency: none Depends on IP
address component
10Configuration
Application
SG
Node 1 SU 1 SU 2 Node 2
IP-Comp IP-Comp
VLC-Comp VLC-Comp
SI
IP-CSI
Video-CSI
11Redundancy Model
• Redundancy model should be based on component
capabilities and desired availability
• In our case:
– Non-proxied Non-SaAware: non-preinstantiable
– SaAware: 1_active_or_1_standby
• Chosen redundancy models:
– Non-proxied Non-SaAware : NoRed
– SaAware: 2N
12Evaluation: Non-Preinstantiable SAF
Managed Component
• Client experience after administrative action
– Broadcast: video restarts after client resynchronisation timeout
(~10 seconds for VLC GUI)
– VoD: Client required to re-request video stream
• Benefits:
– Managed by SAF
• Administrative functions (like locking)
• Benefits w/IP component
– Broadcast: None
– VoD: Server immediately available at same IP after
management operation
13Non-Preinstantiable SAF Managed
Component: Implementation
• Problems:
– VLC failures not detected by OpenSAF (no monitoring)
• Passive monitoring needed
• Difficulty: Low
• Effort:
– “3” lifecycle commands
– IMM XML:
• VLC component: ~295 “lines”
• IP components: +110 “lines”
– No changes to VLC needed
14Non-Preinstantiable SAF Managed Component:
VLC CLC CLI
• Instantiate:
– cvlc --daemon --pidfile /var/run/vlc/vlc.pid
• Terminate
– kill "$(< /var/run/vlc/vlc.pid)“
• Cleanup
– kill -9 "$(< /var/run/vlc/vlc.pid)“
– rm /var/run/vlc/vlc.pid
15Non-Preinstantiable SAF Managed Component:
IP CLC CLI
• Instantiate:
– ip addr add $ip dev $dev
– arping -U -c 1 –I $dev $ip
• Terminate/Cleanup
– ip addr del $ip dev $dev
16Evaluation: SA Aware
• Client Experience:
– Same as Non-Preinstantiable
– However, VLC crashes are noticed (and corrected)
without passive monitoring
• Added Benefits:
– Program crashes detected by SAF; extra healthchecks
possible
– Configuration through CSI Arguments
– Faster recovery after failure (executable already pre-
instantiated)
17SA Aware: Implementation
• Difficulty:
– Medium (VLC architecture knowledge needed)
• Changes to VLC needed:
– Additional control module
• Effort:
– Control module: ~400 lines + 30 lines build system
– Only “2” lifecycle commands
– IMM XML: Roughly the same
18SA Aware: Control Module
• Implements VLC’s control module interface
• Also implements AMF’s callback interface
– saAmfCSISetCallback
– saAmfCSIRemoveCallback
– saAmfComponentTerminateCallback
• CSI Set can receive 4 states
– STANDBY
– ACTIVE
– QUIESCED
– QUIESCING
19Evaluation: Checkpointing Broadcast Streams
• Client Experience After Failure:
– Video resumes at roughly the same position
after a brief pause
• Added Benefits:
– Better user experience
• Difficulty:
– High, edits to main VLC code needed
20Checkpointing: Implementation
• Changes to VLC needed:
– Edits to VL Manager:
• Move over current configuration
• Restart streams at a specific offset
– Edits to RTP stream_out to bind specific source
IP/port
• Effort:
– Control module: +~390 LoC
– VLM and RTP changes: ~150 LoC
21VLC modified workflow
Control module
(OpenSAF) Playlist Internet
Video status VLM
Video status
File IO, demux,
RTP send
22Summary
Integration level Effort Added benefit Shortcoming
Non-proxied Non- •Lowest •SAF managed (After a failure)
•No changes to VLC •Redundant server is •User experiences
SaAware VLC available after failure service outage
•User has to request
the video again (VoD)
SaAware VLC •Higher •Crashes automatically •No service continuity
•New VLC control detected by AMF (the video starts over
module •Faster recovery after failure)
SaAware VLC •Highest •Better user
•Additional changes to experience (after a
With control module failure the video −
Checkpointing •Synchronization resumes at roughly the
through checkpoint same position after a
service brief pause)
23• Work done in context of MAGIC
• MAGIC: Modeling and Automatic Generation of Information
and upgrade Campaigns for Service Availability
• A collaboration between Ericsson and Concordia
• Funded by NSERC and Ericsson
24Discussion?
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