JobScheduler Universal Agent - REST Web Service

Introduction

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The Universal Agent comes with a REST web service that allows it to be controlled from the command line or an application. The service supports the following operations:

• showing status information
  • by use of a REST URI that is called from an HTTP client.
  • by use of the Agent start script that makes use of a Java class that implements the HTTP client.
• sending commands
  
  • via any client application that sends the command with an HTTP request (JSON).

Web Service Status Information

Start Script Status Information

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The Agent start script provides status information by internal use of web services. The information is returned in JSON format.

If the Agent is not available, an exit status is returned accordingly.

The status information is retrieved using:

./jobscheduler_agent.sh status

URI Status Information

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The Universal Agent provides status information via web services. The information is returned in JSON format.

URI Syntax

All API URIs start with an optional prefix (if set on starting the Agent with the command line option -uri-prefix) followed by the path.

• General status information is provided by:
  • http://host:port/jobscheduler/agent/api
• General status information is also provided by:
  
  • http://host:port/jobscheduler/agent/api/overview
• Information about the Agent tasks running is provided by the web service:
  • http://host:port/jobscheduler/agent/api/task
• Information about the active command is provided by the web service:
  
  • http://host:port/jobscheduler/agent/api/tunnel
• Information about the active command is provided by the web service:
  
  • http://host:port/jobscheduler/agent/api/tunnel (without an end forward slash)
• A list of tunnels is provided by the web service:
  
  • http://host:port/jobscheduler/agent/api/tunnel/ (with an end forward slash)
• A summary of the commands running is provided by the web service:
  
  • http://host:port/jobscheduler/agent/api/command (without an end forward slash)
• A list of the commands running is provided by the web service:
  
  • http://host:port/jobscheduler/agent/api/command/ (with an end forward slash)

Note

These web services are read-only (HTTP verb GET).

The following web services are addressed with the verb POST:

• http://host:port/jobscheduler/agent/api/task/command
• http://host:port/jobscheduler/agent/api/tunnel/id

Examples

Response for URI http://host:port/jobscheduler/agent/api Expand source

totalTaskCount: 0
isTerminating: false
system:
  hostname: docker-agent
  mxBeans:
    operatingSystem:
      processCpuLoad: 9.71859949958501E-7
      availableProcessors: 8
      freePhysicalMemorySize: 1791545344
      systemCpuLoad: 0.00774040220626055
      committedVirtualMemorySize: 4809150464
      totalPhysicalMemorySize: 4897579008
currentTaskCount: 0
java:
  systemProperties:
    java.vendor: Azul Systems, Inc.
    os.arch: amd64
    os.version: 3.10.0-229.7.2.el7.x86_64
    os.name: Linux
    java.version: 1.8.0_25
version: 1.10.0-xx
startedAt: '2015-08-19T15:21:42.423Z'

Response for URI http://host:port/jobscheduler/agent/api/task - Agent tasks running Expand source

tasks:
- id: 4-259101459
  tunnelId: '4'
  controllerAddress: 127.0.0.1:9338
  startedAt: '2015-08-19T13:11:18.239Z'
- id: 2-15899022
  tunnelId: '2'
  controllerAddress: 127.0.0.1:9338
  startedAt: '2015-08-19T13:11:18.239Z'
- id: 3-707059672
  tunnelId: '3'
  controllerAddress: 127.0.0.1:9338
  startedAt: '2015-08-19T13:11:18.239Z'

Web Service Commands

Changes are made to the Agent by using the command service (api/command).

• http://host:port/jobscheduler/agent/api/command

The only command is terminate.

Termination Command

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The JobScheduler Universal Agent is terminated by either:

• use of the start script, e.g.
  
  • ./jobscheduler_agent.sh stop
• calling the Agent web service URL for commands with a JSON command
  
  • http://host:port/jobscheduler/agent/api/command

JSON commands to terminate the Agent are sent by an HTTP POST request and include the operations:

• abort immediately:
  
  • the Agent will kill all running tasks and will terminate immediately
  • the web service client sends:
    • { "$TYPE": "AbortImmediately" }
  • this corresponds to the XML command that is used for a Master:
    • <modify_spooler cmd='abort_immediately'/>
• terminate:
  
  • the Agent will not start new tasks, existing tasks can continue and the Agent will terminate after all tasks have completed
  • optionally a SIGTERM can be sent to the tasks
  • the web service client sends:
    • { "$TYPE": "Terminate", "sigtermProcesses": false }
  • this corresponds to the XML command that is used for a Master:
    • <modify_spooler cmd='terminate'/>
• terminate with timeout:
  • the Agent sends all tasks a SIGTERM command and will wait for the specified timeout.
    Should any task not terminate within the specified timeout then it will be killed with a SIGKILL signal.
  • the web service client sends:
    • { "$TYPE": "Terminate", "sigtermProcesses": false, "sigkillProcessesAfter": 15 }
  • this corresponds to the XML command that is used for a Master:
    • <modify_spooler cmd='terminate' timeout='15'/>

Sample Web Service Client for sending Commands

Sample Script

A sample web service client is provided by the class com.sos.scheduler.engine.agent.client.main.AgentClientMain that can be used with individual scripts, e.g. for a Unix environment like this:

export JAVA_HOME=/Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home
export JAVA_BIN=${JAVA_HOME}/bin/java
export SCHEDULER_AGENT_HOME=/Users/ap/Documents/jobscheduler_agent


# set logging impl (log4j or logback)
export SCHEDULER_AGENT_LOG_BRIDGE=logback


export SCHEDULER_AGENT_CLASSPATH="${SCHEDULER_AGENT_HOME}/lib/log/${SCHEDULER_AGENT_LOG_BRIDGE}/*:${SCHEDULER_AGENT_HOME}/lib/3rd-party/*:${SCHEDULER_AGENT_HOME}/lib/sos/*"


"${JAVA_BIN}" -classpath "${SCHEDULER_AGENT_CLASSPATH}" com.sos.scheduler.engine.agent.client.main.AgentClientMain "$@"

Usage for Status Information

./agent-client.sh http://localhost:4445 /overview

The first argument is the Agent URI, for example http://localhost:4445
The following arguments are web service paths (each starting with a slash) or commands (JSON or YAML).
With no argument, the client checks whether the Agent is alive.
 

Usage for Commands

./agent-client.sh http://localhost:4445 '{$TYPE: Terminate, sigtermProcesses: true}' 
./agent-client.sh http://localhost:4445 '{$TYPE: Terminate, sigtermProcesses: true}' /overview

The command responses are written to stdout. In case of an error, the error message is written to stdout and detailed messages are written to stderr.

References

See also

• How to implement a client for REST web services

Change Management References