.. _sd2_epmon_overview:

============================
Endpoint Monitoring overview
============================


EpMon is a standalone Python based process targeting every OTC service. It
looks up the services from the service catalog and sends GET requests to
the configured endpoints.

While performing extensive tests like provisioning a server provides a great
coverage and deep insights, it is a rather expensive and complex activity.
It can only be performed every so often and leaves certain gaps on the
timescale of monitoring. To cover this gap, the EpMon plugin sends
GET-requests to a list of URLs endpoints discovered from the OTC service
catalog and augmented by simple paths like ``/server``. Such requests
are cheap and can be sent in a loop, i.e. every five seconds.
The latency and the HTTP status code of those calls are captured,
stored in a time series database, and further processed by the Metric
Processor.

Currently EpMon configuration is located in the project ``stackmon-config``:

  https://github.com/opentelekomcloud-infra/stackmon-config/blob/main/epmon/config.yaml

It defines the query HTTP targets (urls) for every single OTC service.

An entry in the OTC service catalog is a prerequisite to enable service
to be queried by EpMon:

  https://git.tsi-dev.otc-service.com/ecosystem/service_catalog

If there are multiple entries in service catalog, such service entries
can be marked for skip in case they are obsolete. EpMon ``config.yaml``
only defines the service queries but doesn't say how and when to use them.
For actual use across different monitoring sources and targets the
configuration matrix is defined in:

  https://github.com/opentelekomcloud-infra/stackmon-config/blob/main/config.yaml

The following example configures the autoscaling service (``as``) in
EpMon and adds four paths to the service endpoint (three URL path
for the Swisscloud):

.. code:: yaml

  as:
    service_type: as
    sdk_proxy: auto_scaling
    urls:
      - /
      - /scaling_group
      - /scaling_configuration
      - /scaling_policy
  as_swiss:
    service_type: as
    sdk_proxy: auto_scaling
    urls:
      - /
      - /scaling_group
      - /scaling_configuration
  as_skip_v1:
    service_type: asv1
    urls: []

There are three separate items defined for the autoscaling service: 

- The ``as`` entry is the default. It is used for the public OTC regions.
- The ``as_swiss`` entry defines the specific settings for the Swisscloud.
- The ``as_skip_v1`` entry is entry to be skipped from EpMon.

By default all entries in service catalog are triggered for EpMon.

The mandatory parameter for all entries is ``service_type``. This has to
match the ``service_type`` entry in the OTC service catalog.

Another important parameter is ``sdk_proxy``. This attribute identifies
which otcextension module should be used for the execution of HTTP GET-queries.

The most important parameter is ``urls``. It defines a list of URLs which
EpMon triggers for this service. As ``service_type`` is known then not
full url is required to be defined but only required is its path which
appears after the predefined url from the OTC service catalog.

If some specific service (or some specific service version) is should be
skipped from endpoint monitoring, the value of the ``urls`` key has to
be set to the empty list in the EpMon configuration file. This ensures that
even default queries from service catalog are overwritten by the empty
list in this configuration. In this example, the service type asv1 (entry from
the OTC service catalog) is not being triggered by EpMon at all as it
contains an empty ``urls`` list.

Collected response codes and response times are sent to the Graphite time
series database for further processing by the Metrics Processor.