sonic-buildimage/files/image_config/monit/container_checker

#!/usr/bin/env python3

"""
container_checker

This script is intended to be run by Monit. It will write an alerting message into
syslog if it found containers which were expected to run but were not running. At
the same time, if some containers were unexpected to run, it also writes an alerting
syslog message. Note that if print(...) statement in this script was executed, the
string in it will be appended to Monit syslog messages.

The following is an example in Monit configuration file to show how Monit will run
this script:

check program container_checker with path "/usr/bin/container_checker"
    if status != 0 for 5 times within 5 cycles then alert repeat every 1 cycles
"""

import docker
import sys

import swsssdk
from sonic_py_common import multi_asic
from swsscommon import swsscommon


def get_expected_running_containers():
    """
    @summary: This function will get the expected running & always-enabled containers by following the rule:
              The 'state' field of container in 'FEATURE' table should not be 'disabled' or 'always_disabled'.
              If the device has Multi-ASIC, this function will get container list by determining the
              value of field 'has_global_scope', the number of ASICs and the value of field
              'has_per_asic_scope'.
              If the device has single ASIC, the container name was put into the list.
    @return:  A set which contains the expected running containers and a set that has 
              containers marked as "always_enabled".
    """
    config_db = swsssdk.ConfigDBConnector()
    config_db.connect()
    feature_table = config_db.get_table("FEATURE")

    expected_running_containers = set()
    always_running_containers = set()

    for container_name in feature_table.keys():
        if feature_table[container_name]["state"] not in ["disabled", "always_disabled"]:
            if multi_asic.is_multi_asic():
                if feature_table[container_name]["has_global_scope"] == "True":
                    expected_running_containers.add(container_name)
                if feature_table[container_name]["has_per_asic_scope"] == "True":
                    num_asics = multi_asic.get_num_asics()
                    for asic_id in range(num_asics):
                        expected_running_containers.add(container_name + str(asic_id))
            elif feature_table[container_name]["state"] == 'always_enabled':
                always_running_containers.add(container_name)
            else:
                expected_running_containers.add(container_name)

    return expected_running_containers, always_running_containers


def get_current_running_from_DB(always_running_containers):
    """
    @summary: This function will get the current running container list
              from FEATURE table @ STATE_DB, if this table is available.
    @return:  a tuple
              First: Return value indicating if info can be obtained from
              DB or not.
              Second: A set which contains the current running containers,
              if this info is available in DB.
    """
    running_containers = set()

    state_db = swsscommon.DBConnector("STATE_DB", 0)
    tbl = swsscommon.Table(state_db, "FEATURE")
    if not tbl.getKeys():
        return False, None

    for name in tbl.getKeys():
        data = dict(tbl.get(name)[1])
        if data.get('container_id'):
            running_containers.add(name)

    DOCKER_CLIENT = docker.DockerClient(base_url='unix://var/run/docker.sock')
    RUNNING = 'running'
    for name in always_running_containers:
        try:
            container = DOCKER_CLIENT.containers.get(name)
            container_state = container.attrs.get('State', {})
            if container_state.get('Status', "") == RUNNING:
                running_containers.add(name)
        except (docker.errors.NotFound, docker.errors.APIError) as err:
            print("Failed to get container '{}'. Error: '{}'".format(name, err))
            pass

    return True, running_containers


def get_current_running_from_dockers():
    """
    @summary: This function will get all running containers from
              the list of docker containers in running state.
    @return:  A set which contains containers that are
              in running state.
    """
    DOCKER_CLIENT = docker.DockerClient(base_url='unix://var/run/docker.sock')
    running_containers = set()
    ctrs = DOCKER_CLIENT.containers
    try:
        lst = ctrs.list(filters={"status": "running"})
        for ctr in lst:
            running_containers.add(ctr.name)
    except docker.errors.APIError as err:
        print("Failed to retrieve the running container list. Error: '{}'".format(err))
        pass
    return running_containers


def get_current_running_containers(always_running_containers):
    """
    @summary: This function will get the list of currently running containers.
              If available in STATE-DB, get from DB else from list of dockers.
              
    @return:  A set of currently running containers.
    """

    ret, current_running_containers = get_current_running_from_DB(always_running_containers)
    if not ret:
        current_running_containers = get_current_running_from_dockers()
    return current_running_containers


def main():
    """
    @summary: This function will compare the difference between the current running containers
              and the containers which were expected to run. If containers which were exepcted
              to run were not running, then an alerting message will be written into syslog.
    """
    expected_running_containers, always_running_containers = get_expected_running_containers()
    current_running_containers = get_current_running_containers(always_running_containers)

    expected_running_containers |= always_running_containers
    not_running_containers = expected_running_containers.difference(current_running_containers)
    if not_running_containers:
        print("Expected containers not running: " + ", ".join(not_running_containers))
        sys.exit(3)

    unexpected_running_containers = current_running_containers.difference(expected_running_containers)
    if unexpected_running_containers:
        print("Unexpected running containers: " + ", ".join(unexpected_running_containers))
        sys.exit(4)


if __name__ == "__main__":
    main()
    sys.exit(0)