Http API

Http API online tutorial

Overview

Http API provides a RESTful-like interactive interface, and both requests and responses data in JSON format. Compared with Telnet/WebConsole’s output unstructured text data, Http API can provide structured data and support more complex interactive functions, such as a series of diagnostic operations in specific application scenarios.

Access address

The Http API address is: http://ip:port/api, the request parameters must be submitted using POST. Such as POST http://127.0.0.1:8563/api.

Note: The telnet port 3658 has compatibility issues with the Chrome browser. It is recommended to use the http port 8563 to access the http api.

Request data format

{
  "action": "exec",
  "requestId": "req112",
  "sessionId": "94766d3c-8b39-42d3-8596-98aee3ccbefb",
  "consumerId": "955dbd1325334a84972b0f3ac19de4f7_2",
  "command": "version",
  "execTimeout": "10000"
}

Request data format description:

  • action : The requested action/behavior, please refer to “Request Actions” for optional values.

  • requestId : Optional request ID, generated by the client.

  • sessionId : Arthas session ID, one-time command does not need to set the session ID.

  • consumerId : Arthas consumer ID, used for multi-person sharing sessions.

  • command : Arthas command line

  • execTimeout : Timeout for executing commands (ms), default value is 30000.

Note: Different actions use different parameters. Set the parameters according to the specific action.

Request Actions

Currently supported request actions are as follows:

  • exec : The command is executed synchronously, and the command results is returned after the command execution end or interrupted.

  • async_exec : The command is executed asynchronously, and the scheduling result of the command is returned immediately. The command execution result is obtained through pull_results action.

  • interrupt_job : To interrupt the foreground command of the session, similar to the function of Telnet Ctrl + c.

  • pull_results : Get the result of the command executed asynchronously, and execute it repeatedly in http long-polling mode.

  • init_session : Create new session.

  • join_session : Join the session, used to support multiple people sharing the same Arthas session.

  • close_session : Close the session.

Response status

The state attribute in the response indicates the request processing state, and its value is as follows:

  • SCHEDULED: When the command is executed asynchronously, it means that the job has been created, and may not be executed yet or is being executed;

  • SUCCEEDED: The request is processed successfully (completed status);

  • FAILED: Request processing failed (completed status), usually accompanied by a message explaining the reason;

  • REFUSED: The request is rejected (completed status), usually accompanied by a message explaining the reason;

One-time command

Similar to executing batch commands, the one-time commands are executed synchronously. No need to create a session, no need to set the sessionId option.

{
  "action": "exec",
  "command": "<Arthas command line>"
}

For example, get the Arthas version number:

curl -Ss -XPOST http://localhost:8563/api -d '
{
  "action":"exec",
  "command":"version"
}
'

The response is as follows:

{
   "state" : "SUCCEEDED",
   "sessionId" : "ee3bc004-4586-43de-bac0-b69d6db7a869",
   "body" : {
      "results" : [
         {
            "type" : "version",
            "version" : "3.3.7",
            "jobId" : 5
         },
         {
            "jobId" : 5,
            "statusCode" : 0,
            "type" : "status"
         }
      ],
      "timeExpired" : false,
      "command" : "version",
      "jobStatus" : "TERMINATED",
      "jobId" : 5
   }
}

Response data format description:

  • state: Request processing status, refer to the description of “Response Status”.

  • sessionId : Arthas session ID, one-time command to automatically create and destroy temporary sessions.

  • body.jobId: The job ID of the command, all output results of the same job are the same jobId.

  • body.jobStatus: The job status of the command.

  • body.timeExpired: Whether the job execution timed out.

  • body/results: Command execution results.

Command result format description

 [{
    "type" : "version",
    "version" : "3.3.7",
    "jobId" : 5
 },
 {
    "jobId" : 5,
    "statusCode" : 0,
    "type" : "status"
 }]
  • type : The command result type, except for the special ones such as status, the others remain the same as the Arthas command name. Please refer to the section “Special command results”.

  • jobId : The job ID of the command.

  • Other fields are the data of each different command.

Note: You can also use a one-time command to execute continuous output commands such as watch/trace, but you can’t interrupt the command execution, and there may be hang up for a long time. Please refer to the example in the “Make watch command output a map object” section.

Please try to deal with it in the following way:

  • Set a reasonable execTimeout to forcibly interrupt the command execution after the timeout period is reached to avoid a long hang.

  • Use the -n parameter to specify a smaller number of executions.

  • Ensure the methods of the command matched can be successfully hit and the condition-express is written correctly. If the watch/trace does not hit, even if -n 1 is specified, it will hang and wait until the execution timeout.

Session interaction

Users create and manage Arthas sessions, which are suitable for complex interactive processes. The access process is as follows:

  • Create a session

  • Join the session (optional)

  • Pull command results

  • Execute a series of commands

  • Interrupt command execution

  • Close the session

Create session

curl -Ss -XPOST http://localhost:8563/api -d '
{
  "action":"init_session"
}
'

Response result:

{
   "sessionId" : "b09f1353-202c-407b-af24-701b744f971e",
   "consumerId" : "5ae4e5fbab8b4e529ac404f260d4e2d1_1",
   "state" : "SUCCEEDED"
}

The new session ID is: b09f1353-202c-407b-af24-701b744f971e, and consumer ID is: 5ae4e5fbab8b4e529ac404f260d4e2d1_1.

Join session

Specify the session ID to join, and the server will assign a new consumer ID. Multiple consumers can receive the same command results of target session. This interface is used to support multiple people sharing the same session or refreshing the page to retrieve the session history.

curl -Ss -XPOST http://localhost:8563/api -d '
{
  "action":"join_session",
  "sessionId" : "b09f1353-202c-407b-af24-701b744f971e"
}
'

Response result:

{
   "consumerId" : "8f7f6ad7bc2d4cb5aa57a530927a95cc_2",
   "sessionId" : "b09f1353-202c-407b-af24-701b744f971e",
   "state" : "SUCCEEDED"
}

The new consumer ID is 8f7f6ad7bc2d4cb5aa57a530927a95cc_2 .

Pull command results

The action of pulling the command result message is pull_results. Please use the Http long-polling method to periodically pull the result messages. The consumer’s timeout period is 5 minutes. After the timeout, you need to call join_session to allocate a new consumer.

Each consumer is allocated a cache queue separately, and the pull order does not affect the content received by the consumer.

The request parameters require session ID and consumer ID:

curl -Ss -XPOST http://localhost:8563/api -d '
{
  "action":"pull_results",
  "sessionId" : "b09f1353-202c-407b-af24-701b744f971e",
  "consumerId" : "8f7f6ad7bc2d4cb5aa57a530927a95cc_2"
}
'

Use Bash scripts to regularly pull results messages:

while true; do curl -Ss -XPOST http://localhost:8563/api -d '
{
  "action":"pull_results",
  "sessionId" : "2b085b5d-883b-4914-ab35-b2c5c1d5aa2a",
  "consumerId" : "8ecb9cb7c7804d5d92e258b23d5245cc_1"
}
' | json_pp; sleep 2; done

Note: The json_pp tool formats the output content as pretty json.

The response content is as follows:

{
   "body" : {
      "results" : [
         {
            "inputStatus" : "DISABLED",
            "jobId" : 0,
            "type" : "input_status"
         },
         {
            "type" : "message",
            "jobId" : 0,
            "message" : "Welcome to arthas!"
         },
         {
            "tutorials" : "https://arthas.aliyun.com/doc/arthas-tutorials.html",
            "time" : "2020-08-06 15:56:43",
            "type" : "welcome",
            "jobId" : 0,
            "pid" : "7909",
            "wiki" : "https://arthas.aliyun.com/doc",
            "version" : "3.3.7"
         },
         {
            "inputStatus" : "ALLOW_INPUT",
            "type" : "input_status",
            "jobId" : 0
         }
      ]
   },
   "sessionId" : "b09f1353-202c-407b-af24-701b744f971e",
   "consumerId" : "8f7f6ad7bc2d4cb5aa57a530927a95cc_2",
   "state" : "SUCCEEDED"
}

Execute commands asynchronously

curl -Ss -XPOST http://localhost:8563/api -d '''
{
  "action":"async_exec",
  "command":"watch demo.MathGame primeFactors \"{params, returnObj, throwExp}\" ",
  "sessionId" : "2b085b5d-883b-4914-ab35-b2c5c1d5aa2a"
}
'''

Response of async_exec:

{
   "sessionId" : "2b085b5d-883b-4914-ab35-b2c5c1d5aa2a",
   "state" : "SCHEDULED",
   "body" : {
      "jobStatus" : "READY",
      "jobId" : 3,
      "command" : "watch demo.MathGame primeFactors \"{params, returnObj, throwExp}\" "
   }
}
  • state : The status of SCHEDULED means that the command has been parsed and generated the job, but the execution has not started.

  • body.jobId : The job id of command execution, filter the command results output in pull_results according to this job ID.

  • body.jobStatus : The job status READY means that execution has not started.

The shell output of the script that continuously pulls the result message:

{
   "body" : {
      "results" : [
         {
            "type" : "command",
            "jobId" : 3,
            "state" : "SCHEDULED",
            "command" : "watch demo.MathGame primeFactors \"{params, returnObj, throwExp}\" "
         },
         {
            "inputStatus" : "ALLOW_INTERRUPT",
            "jobId" : 0,
            "type" : "input_status"
         },
         {
            "success" : true,
            "jobId" : 3,
            "effect" : {
               "listenerId" : 3,
               "cost" : 24,
               "classCount" : 1,
               "methodCount" : 1
            },
            "type" : "enhancer"
         },
         {
            "sizeLimit" : 10485760,
            "expand" : 1,
            "jobId" : 3,
            "type" : "watch",
            "cost" : 0.071499,
            "ts" : 1596703453237,
            "value" : [
               [
                  -170365
               ],
               null,
               {
                  "stackTrace" : [
                     {
                        "className" : "demo.MathGame",
                        "classLoaderName" : "app",
                        "methodName" : "primeFactors",
                        "nativeMethod" : false,
                        "lineNumber" : 46,
                        "fileName" : "MathGame.java"
                     },
                     ...
                  ],
                  "localizedMessage" : "number is: -170365, need >= 2",
                  "@type" : "java.lang.IllegalArgumentException",
                  "message" : "number is: -170365, need >= 2"
               }
            ]
         },
         {
            "type" : "watch",
            "cost" : 0.033375,
            "jobId" : 3,
            "ts" : 1596703454241,
            "value" : [
               [
                  1
               ],
               [
                  2,
                  2,
                  2,
                  2,
                  13,
                  491
               ],
               null
            ],
            "sizeLimit" : 10485760,
            "expand" : 1
         }
      ]
   },
   "consumerId" : "8ecb9cb7c7804d5d92e258b23d5245cc_1",
   "sessionId" : "2b085b5d-883b-4914-ab35-b2c5c1d5aa2a",
   "state" : "SUCCEEDED"
}

The value of the watch command result is the value of watch-experss, and the above command is {params, returnObj, throwExp}, so the value of the watch result is an array of length 3, and each element corresponds to the expression in the corresponding order.

Please refer to the section “Make watch command output a map object”.

Interrupt command execution

Interrupt the running foreground job of the session:

curl -Ss -XPOST http://localhost:8563/api -d '''
{
  "action":"interrupt_job",
  "sessionId" : "2b085b5d-883b-4914-ab35-b2c5c1d5aa2a"
}
'''
{
   "state" : "SUCCEEDED",
   "body" : {
      "jobStatus" : "TERMINATED",
      "jobId" : 3
   }
}

Close session

Specify the session ID to close the session.

curl -Ss -XPOST http://localhost:8563/api -d '''
{
  "action":"close_session",
  "sessionId" : "2b085b5d-883b-4914-ab35-b2c5c1d5aa2a"
}
'''
{
   "state" : "SUCCEEDED"
}

Authentication

Web UI

arthas web ui

A Web UI based on Http API, visit url : http://127.0.0.1:8563/ui .

Completed functions:

  • Create a session

  • Copy and open the url to join the session, share the session with multiple people

  • Continuously pull session command result messages

  • Refresh the web page or join the session to pull command messages history

  • Control input or interrupt command status

Pending function:

  • Improve the readability of command result messages

  • Support automatic completion of input commands and command templates

  • Provide command help

  • Support personal profile settings

Special command results

status

{
    "jobId" : 5,
    "statusCode" : 0,
    "type" : "status"
}

type is status to indicate the command execution status:

After each command is executed, there is a unique status result. If the statusCode is 0, it means the execution is successful, and the statusCode is a non-zero value that means the execution failed, similar to the process exit code.

When the command execution fails, an error message is generally provided, such as:

{
  "jobId":3,
  "message":"The argument 'class-pattern' is required",
  "statusCode":-10,
  "type":"status"
}

input_status

 {
    "inputStatus" : "ALLOW_INPUT",
    "type" : "input_status",
    "jobId" : 0
 }

type is input_status to indicate input status:

It is used to control user input during UI interaction, and a change message will be sent before and after each command is executed.

Possible values ​​of inputStatus:

  • ALLOW_INPUT : Allow users to enter commands, which means that the session has no foreground command being executed and can accept new command.

  • ALLOW_INTERRUPT : Allow the user to interrupt the command execution, indicating that a command is currently being executed, and the user can send interrupt_job to interrupt the execution.

  • DISABLED : In the disabled state, commands cannot be entered or interrupted.

command

 {
    "type" : "command",
    "jobId" : 3,
    "state" : "SCHEDULED",
    "command" : "watch demo.MathGame primeFactors \"{params, returnObj, throwExp}\" "
 }

type is command to indicate the input command data:

It is used for the interactive UI to echo the commands entered by the user. The pulled session command message history will contain messages of type command, which can be processed in order.

enhancer

 {
    "success" : true,
    "jobId" : 3,
    "effect" : {
       "listenerId" : 3,
       "cost" : 24,
       "classCount" : 1,
       "methodCount" : 1
    },
    "type" : "enhancer"
 }

type is enhancer to indicate the result of class enhancement:

Commands such as trace/watch/jad/tt need to enhance the class and will receive this enhancer result. It may happen that the result of enhancer is successful, but there is no hit method. The client can prompt the user according to the result of enhancer.

Cases

Get classpath of Java application

Get system properties of the Java application through Http api and extract the value of java.class.path.

json_data=$(curl -Ss -XPOST http://localhost:8563/api -d '
{
  "action":"exec",
  "command":"sysprop"
}')
  • Extract value with sed:

class_path=$(echo $json_data | tr -d '\n' | sed 's/.*"java.class.path":"\([^"]*\).*/\1/')
echo "classpath: $class_path"
  • Extract value with json_pp/awk:

class_path=$(echo $json_data | tr -d '\n' | json_pp | grep java.class.path | awk -F'"' '{ print $4 }')
echo "classpath: $class_path"

Output:

classpath: demo-arthas-spring-boot.jar

NOTE:

  • echo $json_data | tr -d '\n' : Delete line breaks (the value of line.separator) to avoid affecting the processing of sed/json_pp commands.

  • awk -F'"' '{ print $4 }' : Use double quote as delimiter

Make watch command output a map object

The result value of watch is generated by calculating the watch-express ognl expression. You can change the ognl expression to generate the desired value, please refer to OGNL document.

Maps can also be created using a special syntax.

#{ “foo” : “foo value”, “bar” : “bar value” }

This creates a Map initialized with mappings for “foo” and “bar”.

The following command generates values ​​in map format:

watch *MathGame prime* '#{ "params" : params, "returnObj" : returnObj, "throwExp": throwExp}' -x 2 -n 5

Execute the above command in Telnet shell/WebConsole, the output result:

ts=2020-08-06 16:57:20; [cost=0.241735ms] result=@LinkedHashMap[
    @String[params]:@Object[][
        @Integer[1],
    ],
    @String[returnObj]:@ArrayList[
        @Integer[2],
        @Integer[241],
        @Integer[379],
    ],
    @String[throwExp]:null,
]

Execute the above command with Http api, pay attention to escaping the JSON double quotes:

curl -Ss -XPOST http://localhost:8563/api -d @- << EOF
{
  "action":"exec",
  "execTimeout": 30000,
  "command":"watch *MathGame prime* '#{ \"params\" : params, \"returnObj\" : returnObj, \"throwExp\": throwExp}' -n 3 "
}
EOF

Http api execution result:

{
    "body": {
         ...
        "results": [
            ...
            {
                ...
                "type": "watch",
                "value": {
                    "params": [
                        1
                    ],
                    "returnObj": [
                        2,
                        5,
                        17,
                        23,
                        23
                    ]
                }
            },
            {
                ...
                "type": "watch",
                "value": {
                    "params": [
                        -98278
                    ],
                    "throwExp": {
                        "@type": "java.lang.IllegalArgumentException",
                        "localizedMessage": "number is: -98278, need >= 2",
                        "message": "number is: -98278, need >= 2",
                        "stackTrace": [
                            ...
                        ]
                    }
                }
            },
            ...
}

You can see that the value of the watch result becomes a map object, and the program can read value through a key .