Responding to Callbacks
Callbacks are points in the solving of a job of type SOLVER where a user provided function is evaluated. The Compute Interface supports a number of solver callbacks and these can be individually enabled in the job submission request. For more information, see
Supported Callbacks.
When a callback point is reached in the solving process, the solving is suspended and the client receives the following message of type
APP_MESSAGE:
{
"computeJobId": "my-job"
"messageType": "APP_MESSAGE"
"messagePayload": {
"appMessageId": "uuid"
"appMessageType": "BARLOG"
"appMessageFile": "url to download from (INTSOL only)"
"appMessage": {
"problemName": "problem-name"
"attributes" : {
"att1Name" : {
"key" 1234,
"name": "att1Name"
"value": "value"
}
}
}
}
}
Each callback message includes the list of all solver attributes with their current values. The INTSOL callback includes a URL to request the current solution for the appMessageFile property.
A callback must be acknowledged. If the server does not receive an acknowledgment within 60 seconds then the job is terminated and marked as failed. This setting is configurable, for more see the following section, Editing the Callback Acknowledgment Timeout.
To acknowledge a callback and continue, send the message below. The response must include the appMessageId value of the message it is responding to. The response can also set solver controls to new values.{
"computeJobId": "my-job"
"messageType": APP_MESSAGE_RESPONSE
"messagePayload": {
"appMessageId": "id_of_the_received_message",
"appMessage": {
"interruptSolve": false,
"controls": {
"key": "newvalue"
}
}
}
}
To acknowledge a callback and end the solve, send the message below.
{
"computeJobId": "my-job"
"messageType": "APP_MESSAGE_RESPONSE",
"messagePayload": {
"appMessageId": "id_of_the_received_message",
"appMessage": {
"interruptSolve": true
}
}
}