[id='monitor-xsite-replication']
= Monitoring the status of cross-site replication

Monitor the site status of your backup locations to detect interruptions in the communication between the sites.
When a remote site status changes to `offline`, {brandname} stops replicating your data to the backup location.
Your data become out of sync and you must fix the inconsistencies before bringing the clusters back online.

Monitoring cross-site events is necessary for early problem detection.
Use one of the following monitoring strategies:

* link:#monitoring-cross-site-rest[Monitoring cross-site replication with the REST API]
* link:#monitoring-cross-site-prometheus[Monitoring cross-site replication with the Prometheus metrics] or any other monitoring system

[[monitoring-cross-site-rest]]
[discrete]
==  Monitoring cross-site replication with the REST API
Monitor the status of cross-site replication for all caches using the REST endpoint.
You can implement a custom script to poll the REST endpoint or use the following example.

.Prerequisites
* Enable cross-site replication.

.Procedure
. Implement a script to poll the REST endpoint.
+
The following example demonstrates how you can use a Python script to poll the site status every five seconds.

[source,python,options="nowrap",subs=attributes+]
----
include::python/monitor_site_status.py[]
----

When a site status changes from `online` to `offline` or vice-versa, the function `on_event` is invoked.

If you want to use this script, you must specify the following variables:

* `USERNAME` and `PASSWORD`: The username and password of {brandname} user with permission to access the REST endpoint.
* `POLL_INTERVAL_SEC`: The number of seconds between polls.
* `SERVERS`: The list of {brandname} Servers at this site.
The script only requires a single valid response but the list is provided to allow fail over.
* `REMOTE_SITES`: The list of remote sites to monitor on these servers.
* `CACHES`: The list of cache names to monitor.

[role="_additional-resources"]
.Additional resources
* link:{rest_docs}#rest_v2_cache_manager_site_status_rest[REST API: Getting status of backup locations]

[[monitoring-cross-site-prometheus]]
[discrete]
== Monitoring cross-site replication with the Prometheus metrics

Prometheus, and other monitoring systems, let you configure alerts to detect when a site status changes to `offline`.

TIP: Monitoring cross-site latency metrics can help you to discover potential issues.

.Prerequisites
* Enable cross-site replication.

.Procedure
. Configure {brandname} metrics.
. Configure alerting rules using the Prometheus metrics format.
* For the site status, use `1` for `online` and `0` for `offline`.
* For the `expr` filed, use the following format: +
`vendor_cache_manager_default_cache_<cache name>_x_site_admin_<site name>_status`.
+
In the following example, Prometheus alerts you when the *NYC* site gets `offline` for cache named `work` or `sessions`.
+
[source,yaml,options="nowrap",subs=attributes+]
----
include::yaml/prometheus_xsite_rules.yml[]
----
+
The following image shows an alert that the *NYC* site is `offline` for cache `work`.
+
image::prometheus_xsite_alert.png[align="center",title="Prometheus Alert"]

[role="_additional-resources"]
.Additional resources
* link:{server_docs}#configuring-metrics_statistics-jmx[Configuring {brandname} metrics]
* link:https://prometheus.io/docs/alerting/latest/overview/[Prometheus Alerting Overview]
* link:https://grafana.com/docs/grafana/latest/alerting/[Grafana Alerting Documentation]
* link:https://docs.openshift.com/container-platform/latest/monitoring/managing-alerts.html#creating-alerting-rules-for-user-defined-projects_managing-alerts[Openshift Managing Alerts]
