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Experiment: Step by Step Author: Anna Bekkerman [email protected] Setup Node Client Server Target system Data LMM Node LMM Node Client LMM Configuration File Describes an experiment – Nodes – – – – Commands to start/stop involved processes Collected metrics (CPU/memory utilization, etc.) Monitored processes Net control parameters – IP addresses, types (SOCC node/radar node), etc. Delays, drop rates Refresh rates Start LMMs When started, RAPIDS server: – Grabs two ports: – – – – 49162 - to communicate with LMMs 8888 - to communicate with RAPIDS clients FIXME: Server Reads a configuration file Starts LMMs on all nodes through SSH connections Waits for ack signals from all LMMs Starts setting LMMs up according to the configuration file will wait indefinitely for the acks from all LMMs. A time-out mechanism should be introduced. Set LMMs Up Home-made protocol is used to set up LMM parameters Examples of commands sent from the server to LMMs: – – – – – STM STP STE STT SPP set metric set monitored process set start-up command start stop When a parameter is set, LMM sends an ack signal back to the server At the end of each step, server waits for acks from all LMMs Start Monitoring When LMM receives the start command: – If needed, network control application is started • Network control application runs only if iptables are turned on. • iptables select IP packets (as specified in iptables rules) and queue them for processing by the application. • The application introduces delays and/or drops packets according to the settings in the configuration file. Start Monitoring When LMM receives the start command: – – If needed, network control application is started RAPIDS Message Queues (RMQ) are initialized • A mechanism used for communication between RAPIDS and monitored applications. • See more in the “RMQ” section. Start Monitoring When LMM receives the start command: – – – If needed, network control application is started RAPIDS Message Queues (RMQ) are initialized Heartbeat applications are started • Send “I’m alive” signals from radar nodes to SOCC nodes. • If a signal has not been received, RAPIDS reports link failure. FIXME: Timeout mechanism should be added to minimize false alarms. Start Monitoring When LMM receives the start command: – – – – If needed, network control application is started RAPIDS Message Queues (RMQ) are initialized Heartbeat applications are started Processes are started Commands are specified by user in the configuration file Start Monitoring When LMM receives the start command: – – – – If needed, network control application is started RAPIDS Message Queues (RMQ) are initialized Heartbeat applications are started Processes are started – Commands are specified by user in the configuration file “Collection sessions” are started every t seconds According to the refresh rates provided by user in the configuration file Collection Session During each collection session LMM: – – – Collects metrics Reads events accumulated in RMQ Sends the metrics and events to the RAPIDS server More details in the “LMM” section Stop Monitoring When the server is stopped, it sends stop commands to all LMMs Upon receiving the stop signal, LMM: – – Stops launching collection sessions Stops processes – – – Using the commands specified by user in the configuration file Heartbeat applications are stopped RMQ is deleted Network control applications are stopped What Might Go Wrong? When the server is stopped, it sends stop commands to all LMMs Upon receiving the stop signal, LMM: – – If “untrappable” signals (SIGKILL Stops launching collection sessions and SIGSTOP) are used to kill the Stops processes server, the shut-down procedures – – – not be executed! Using thewill commands specified by user in the configuration file Heartbeat applications are stopped RMQ is deleted Network control applications are stopped What Might Go Wrong? • If commands provided by user do not stop all processes, LMM will hang waiting for their termination. When theanserver is stopped, it sends stop with • While LMM is hanging the port used for communication the server remains unreleased, which means that the new commands to all LMMs experiment cannot be started until LMMs are stopped and all Uponnecessary receiving the stop have signal, LMM: clean-up procedures been completed. – – Stops launching collection sessions Stops processes – – – Using the commands specified by user in the configuration file Heartbeat applications are stopped RMQ is deleted Network control applications are stopped What Might Go Wrong? When the server is stopped, it sends stop commands toFIXME: all LMMs • These applications do not always react Upon receiving the stop signal, LMM: to the termination signal properly. – – Stops launching collection sessions • Symptom: sometimes a number of zombie processes appear Stops processes – – – Using the commands specified by user in the configuration file Heartbeat applications are stopped RMQ is deleted Network control applications are stopped