Service discovery has a vital place in Thanos components that allows them to perform some logic against given set of APIs. Currently there are 2 places like this:
Thanos Query
needs to know about StoreAPI servers in order to query metrics from them.Thanos Rule
needs to know about QueryAPI
servers in order to evaluate recording and alerting rules.Currently there are several ways to configure this and they are described below.
The simplest way to tell a component about a peer is to use a static flag.
The repeatable flag --store=<store>
can be used to specify a StoreAPI
that Thanos Query
should use.
The repeatable flag --query=<query>
can be used to specify a QueryAPI
that Thanos Rule
should use.
File Service Discovery is another mechanism for configuring components. With File SD, a list of files can be watched for updates, and the new configuration will be dynamically loaded when a change occurs. The list of files to watch is passed to a component via a flag shown in the component specific sections below.
The format of the configuration file is the same as the one used in Prometheus’ File SD. Both YAML and JSON files can be used. The format of the files is this:
[
{
"targets": ["localhost:9090", "example.org:443"]
}
]
- targets: ['localhost:9090', 'example.org:443']
As a fallback, the file contents are periodically re-read at an interval that can be set using a flag specific for the component and shown below. The default value for all File SD re-read intervals is 5 minutes.
The repeatable flag --store.sd-files=<path>
can be used to specify the path to files that contain addresses of StoreAPI
servers. The <path>
can be a glob pattern so you can specify several files using a single flag.
The flag --store.sd-interval=<5m>
can be used to change the fallback re-read interval from the default 5 minutes.
The repeatable flag --query.sd-files=<path>
can be used to specify the path to files that contain addresses of QueryAPI
servers. Again, the <path>
can be a glob pattern.
The flag --query.sd-interval=<5m>
can be used to change the fallback re-read interval.
DNS Service Discovery is another mechanism for finding components that can be used in conjunction with Static Flags or File SD. With DNS SD, a domain name can be specified and it will be periodically queried to discover a list of IPs.
To use DNS SD, just add one of the following prefixes to the domain name in your configuration:
dns+
- the domain name after this prefix will be looked up as an A/AAAA query. A port is required for this query type. An example using this lookup with a static flag:--store=dns+stores.thanos.mycompany.org:9090
dnssrv+
- the domain name after this prefix will be looked up as a SRV query. You do not need to specify a port as the one from the query results will be used. An example:--store=dnssrv+_thanosstores._tcp.mycompany.org
The default interval between DNS lookups is 30s. You can change it using the store.sd-dns-interval
flag for StoreAPI
configuration in Thanos Query
, or query.sd-dns-interval
for QueryAPI
configuration in Thanos Rule
.
Currently, there are no plans of adding other Service Discovery mechanisms like Consul SD, kube SD, etc. However, we welcome people implementing their preferred Service Discovery by writing the results to File SD which will propagate them to the different Thanos components.