Event interface

Available Protocols

The Supvisors Event Interface can be created either using a ZeroMQ socket or using websockets.

All messages consist in a header and a body.

Attention

The websockets implementation requires a Python version 3.7 or later.

Message header

This header is a unicode string that identifies the type of the event and that is defined as follows in the supvisors.ttypes module:

class EventHeaders(Enum):
    """ Strings used as headers in messages between EventPublisher and Supvisors' Client. """
    SUPVISORS = 'supvisors'
    INSTANCE = 'instance'
    APPLICATION = 'application'
    PROCESS_EVENT = 'event'
    PROCESS_STATUS = 'process'
    HOST_STATISTICS = 'hstats'
    PROCESS_STATISTICS = 'pstats'

The header value is used to set the event subscriptions.

Message data

The second part of the message is a dictionary serialized in JSON. Of course, the contents depends on the message type.

Supvisors status

Key	Type	Value
‘fsm_statecode’	`int`	The state of Supvisors, in [0;6].
‘fsm_statename’	`str`	The string state of Supvisors, among { `'INITIALIZATION'`, `'DISTRIBUTION'`, `'OPERATION'`, `'CONCILIATION'`, `'RESTARTING'`, `'SHUTTING_DOWN'`, `'FINAL'` }.
‘discovery_mode’	`bool`	True if the Supvisors discovery mode is activated.
‘starting_jobs’	`list(str)`	The list of Supvisors instances having starting jobs in progress.
‘stopping_jobs’	`list(str)`	The list of Supvisors instances having stopping jobs in progress.

Supvisors instance status

Key	Type	Value
‘identifier’	`str`	The deduced name of the Supvisors instance.
‘node_name’	`str`	The name of the node where the Supvisors instance is running.
‘port’	`int`	The HTTP port of the Supvisors instance.
‘statecode’	`int`	The Supvisors instance state, in [0;6].
‘statename’	`str`	The Supvisors instance state as string, among { `'UNKNOWN'`, `'CHECKING'`, ‘CHECKED’`, `'RUNNING'`, `'SILENT'`, `'FAILED'`, `'ISOLATED'` }.
‘discovery_mode’	`bool`	True if the discovery mode is activated in the Supvisors instance.
‘remote_sequence_counter’	`int`	The remote TICK counter, i.e. the number of TICK events received since the remote Supvisors instance is running.
‘remote_mtime’	`float`	The monotonic time received in the last heartbeat sent by the remote Supvisors instance, in seconds since the remote host started.
‘remote_time’	`float`	The POSIX time received in the last heartbeat sent by the remote Supvisors instance, in seconds and in the remote reference time.
‘local_sequence_counter’	`int`	The local TICK counter when the latest TICK was received from the remote Supvisors instance.
‘local_mtime’	`float`	The monotonic time when the latest TICK was received from the remote Supvisors instance, in seconds since the local host started.
‘local_time’	`float`	The POSIX time when the latest TICK was received from the remote Supvisors instance, in seconds and in the local reference time.
‘loading’	`int`	The sum of the expected loading of the processes running on the node, in [0;100]%.
‘process_failure’	`bool`	True if one of the local processes has crashed or has exited unexpectedly.

Application status

Key	Type	Value
‘application_name’	`str`	The Application name.
‘statecode’	`int`	The Application state, in [0;3].
‘statename’	`str`	The Application state as string, among { `'STOPPED'`, `'STARTING'`, `'RUNNING'`, `'STOPPING'` }.
‘major_failure’	`bool`	True if the application is running and at least one required process is not started.
‘minor_failure’	`bool`	True if the application is running and at least one optional (not required) process is not started.

Process status

Key	Type	Value
‘application_name’	`str`	The Application name.
‘process_name’	`str`	The Process name.
‘statecode’	`int`	The Process state, in {0, 10, 20, 30, 40, 100, 200, 1000}. A special value -1 means that the process has been deleted as a consequence of an XML-RPC `update_numprocs`.
‘statename’	`str`	The Process state as string, among { `'STOPPED'`, `'STARTING'`, `'RUNNING'`, `'BACKOFF'`, `'STOPPING'`, `'EXITED'`, `'FATAL'`, `'UNKNOWN'` }. A special value `DELETED` means that the process has been deleted as a consequence of an XML-RPC `update_numprocs`.
‘expected_exit’	`bool`	True if the exit status is expected (only when state is `'EXITED'`).
‘last_event_time’	`float`	The date of the last process event received for this process, regardless of the originating Supvisors instance.
‘identifiers’	`list(str)`	The deduced names of the Supvisors instances where the process is running.
‘extra_args’	`str`	The additional arguments passed to the command line of the process.

Hint

The expected_exit information of this event provides an answer to the following Supervisor request:

#1150 - Why do event listeners not report the process exit status when stopped/crashed?

Process event

Key	Type	Value
‘group’	`str`	The Application name.
‘name’	`str`	The Process name.
‘state’	`int`	The Process state, in {0, 10, 20, 30, 40, 100, 200, 1000}. A special value -1 means that the process has been deleted as a consequence of an XML-RPC `update_numprocs`.
‘expected’	`bool`	True if the exit status is expected (only when state is 100 - `EXITED`).
‘now’	`float`	The monotonic time of the event in the reference time of the host.
‘pid’	`int`	The UNIX process ID (only when state is 20 - `RUNNING` or 40 - `STOPPING`).
‘identifier’	`str`	The deduced name of the Supvisors instance that sent the initial event.
‘extra_args’	`str`	The additional arguments passed to the command line of the process.
‘disabled’	`bool`	True if the process is disabled on the Supvisors instance.

Host statistics

Key	Type	Value
‘identifier’	`str`	The deduced name of the Supvisors instance.
‘target_period’	`float`	The configured integration period.
‘period’	`list(float)`	The start and end uptimes of the integration period, as a list of 2 values.
‘cpu’	`list(float)`	The CPU (IRIX mode) on the node. The first element of the list is the average CPU. The following elements correspond to the CPU on every processor core.
‘mem’	`float`	The memory occupation on the node.
‘io’	`dict(str,list(float)`	The Process namespec.

Process statistics

Key	Type	Value
‘namespec’	`str`	The Process namespec.
‘identifier’	`str`	The deduced name of the Supvisors instance.
‘target_period’	`float`	The configured integration period.
‘period’	`list(float)`	The start and end uptimes of the integration period, as a list of 2 values.
‘cpu’	`float`	The CPU (IRIX mode) of the process on the node.
‘mem’	`float`	The memory occupation of the process on the node.

ZeroMQ Implementation

The ZeroMQ implementation relies on a PUB-SUB pattern provided by PyZMQ (Python binding of ZeroMQ).

When the event_link option is set to ZMQ, Supvisors binds a PUBLISH PyZMQ socket on all interfaces using the event_port option defined in the rpcinterface extension point of the Supervisor configuration file.

Supvisors publishes the events in multi-parts messages. The first part is the message header, as a unicode string. The body follows, encoded in JSON.

To receive the Supvisors events, the client application must connect a SUBSCRIBE PyZMQ socket to the address defined by the node name and the port number where the Supvisors PUBLISH PyZMQ socket is bound.

PyZMQ makes it possible to filter the messages received on the client side by subscribing to a part of them. To receive all messages, just subscribe using an empty string.

For example, the following Python instructions configure the PyZMQ socket so as to receive only the Supvisors Status and Process Status events:

socket.setsockopt(zmq.SUBSCRIBE, EventHeaders.SUPVISORS.value.encode('utf-8'))
socket.setsockopt(zmq.SUBSCRIBE, EventHeaders.PROCESS_STATUS.value.encode('utf-8'))

Python Client

Supvisors provides a Python implementation of the ZeroMQ client subscriber. The SupvisorsZmqEventInterface is designed to receive the Supvisors events from a Supvisors instance. It requires PyZMQ to be installed.

class supvisors.client.zmqsubscriber.SupvisorsZmqEventInterface(zmq_context: Context, node_name: str, event_port: int, logger: Logger)

The SupvisorsZmqEventInterface connects to Supvisors and receives the events published using the PyZMQ interface.

The SupvisorsEventInterface requires:

an asynchronous PyZMQ context,
the node name where the Supvisors instance is running and publishing its events,
the event port number used by the Supvisors instance to publish its events,
a logger.

This event port number MUST correspond to the event_port value set in the [supvisors] section of the Supervisor configuration file.

The default behaviour is to print the messages received. For any other behaviour, just specialize the methods on_xxx_status.

WARN: Notifications are received in the context of the client thread.

Example:

import zmq.asyncio from supvisors.client.zmqsubscriber import SupvisorsZmqEventInterface

intf = SupvisorsZmqEventInterface(zmq.asyncio.Context.instance(), ‘localhost’, 9003, logger) intf.subscribe_all() intf.start() # … receive notifications … intf.stop()

on_supvisors_status(data)

Receive and log the contents of the Supvisors Status message.

Parameters:: data – the latest Supvisors status
Returns:: None

on_instance_status(data)

Receive and log the contents of the Supvisors Instance Status message.

Parameters:: data – the latest status about a given Supvisors instance
Returns:: None

on_application_status(data)

Receive and log the contents of the Application Status message.

Parameters:: data – the latest status about a given Application
Returns:: None

on_process_status(data)

Receive and log the contents of the Process Status message.

Parameters:: data – the latest status about a given Process
Returns:: None

on_process_event(data)

Receive and log the contents of the Process Event message.

Parameters:: data – the latest event about a given Process
Returns:: None

on_host_statistics(data)

Receive and log the contents of the Host Statistics message.

Parameters:: data – the latest statistics about a given host where Supvisors is running
Returns:: None

on_process_statistics(data)

Receive and log the contents of the Process Statistics message.

Parameters:: data – the latest statistics about a given process running in Supvisors
Returns:: None

import zmq.asyncio
from supvisors.client.clientutils import create_logger
from supvisors.client.zmqsubscriber import SupvisorsZmqEventInterface

# create the subscriber thread
subscriber = SupvisorsZmqEventInterface(zmq.asyncio.Context.instance(), 'localhost', 9003, create_logger())
# subscribe to all messages
subscriber.subscribe_all()
# start the thread
subscriber.start()

JAVA Client

A JAVA implementation of the ZeroMQ client subscriber is made available with each Supvisors release through a JAR file. This file can be downloaded from the Supvisors releases.

The SupvisorsEventSubscriber of the org.supvisors.event package is designed to receive the Supvisors events from the local Supvisors instance. A SupvisorsEventListener with a specialization of the methods onXxxStatus must be attached to the SupvisorsEventSubscriber instance to receive the notifications.

It requires the following additional dependencies:

JeroMQ.

Gson.

The binary JAR of JeroMQ 0.5.2 is available in the JeroMQ MAVEN repository.

The binary JAR of Google Gson 2.8.6 is available in the Gson MAVEN repository.

import org.supvisors.event.*;

// create ZeroMQ context
Context context = ZMQ.context(1);

// create and configure the subscriber
SupvisorsEventSubscriber subscriber = new SupvisorsEventSubscriber(9003, context);
subscriber.subscribeToAll();
subscriber.setListener(new SupvisorsEventListener() {

    @Override
    public void onSupvisorsStatus(final SupvisorsStatus status) {
        System.out.println(status);
    }

    @Override
    public void onInstanceStatus(final SupvisorsInstanceInfo status) {
        System.out.println(status);
    }

    @Override
    public void onApplicationStatus(final SupvisorsApplicationInfo status) {
        System.out.println(status);
    }

    @Override
    public void onProcessStatus(final SupvisorsProcessInfo status) {
        System.out.println(status);
    }

    @Override
    public void onProcessEvent(final SupvisorsProcessEvent event) {
        System.out.println(event);
    }

    @Override
    public void onHostStatistics(final SupvisorsHostStatistics status) {
        System.out.println(status);
    }

    @Override
    public void onProcessStatistics(final SupvisorsProcessStatistics status) {
        System.out.println(status);
    }
});

// start subscriber in thread
Thread t = new Thread(subscriber);
t.start();

websockets Implementation

Attention

The websockets implementation requires a Python version 3.7 or later.

When the event_link option is set to WS, Supvisors creates a websockets server that binds on all interfaces using the event_port option defined in the rpcinterface extension point of the Supervisor configuration file.

Supvisors publishes the event messages as a tuple of header, as a unicode string, and body, encoded in JSON.

To receive the Supvisors events, the client application must create a websockets client that connects to the address defined by the node name and the port number where the Supvisors websockets server has bound.

Filtering the messages is performed by adding headers to the path of the URI. To receive all messages, just add all to the path of the URI.

For example, the following Python instructions configure the websockets client so as to receive only the Supvisors Status and Process Status events:

import websockets

uri = 'ws://localhost:9003/supvisors/process'
async with websockets.connect(uri) as ws:
    ...

Python Client

Supvisors provides a Python implementation of the websockets client. The SupvisorsWsEventInterface is designed to receive the Supvisors events from a Supvisors instance. It requires websockets to be installed.

class supvisors.client.wssubscriber.SupvisorsWsEventInterface(node_name: str, event_port: int, logger: Logger)

The SupvisorsWsEventInterface connects to Supvisors and receives the events published using the Websockets interface.

The SupvisorsWsEventInterface requires:

the node name where the Supvisors instance is running and publishing its events ;
the event port number used by the Supvisors instance to publish its events ;
a logger.

Considering the [supvisors] section of the Supervisor configuration file:

the event_link option MUST be set to WS ;
the event_port value MUST be used when creating an instance of this class.