Step 2 - Installing Thanos sidecar

Let's take the setup from the previous step and seamlessly install Thanos to add Global View with HA handling feature.

Thanos Components

Thanos is a single Go binary capable to run in different modes. Each mode represents a different component and can be invoked in a single command.

Let's take a look at all the Thanos commands:

docker run --rm quay.io/thanos/thanos:v0.9.0-rc.0 --help

You should see multiple commands that solves different purposes.

In this step we will focus on thanos sidecar:

  sidecar [<flags>]
    sidecar for Prometheus server

Sidecar

Sidecar as the name suggests should be deployed together with Prometheus. Sidecar has multiple features:

• It exposes Prometheus metrics as a common Thanos StoreAPI. StoreAPI is a generic gRPC API allowing Thanos components to fetch metrics from various systems and backends.
• It is essentially in further long term storage options described in next courses.
• It is capable to watch for configuration and Prometheus rules (alerting or recording) and notify Prometheus for dynamic reloads:
  • optionally substitute with environment variables
  • optionally decompress if gzipp-ed

You can read more about sidecar here

Installation

To allow Thanos to efficiently query Prometheus data, let's install sidecar to each Prometheus instances we deployed in the previous step as shown below:

For this setup the only configuration required for sidecar is the Prometheus API URL and access to the configuration file. Former will allow us to access Prometheus metrics, the latter will allow sidecar to reload Prometheus configuration in runtime.

Click snippets to add sidecars to each Prometheus instance.

Adding sidecar to "EU1" Prometheus

docker run -d --net=host --rm \
    -v $(pwd)/prometheus0_eu1.yml:/etc/prometheus/prometheus.yml \
    --name prometheus-0-sidecar-eu1 \
    -u root \
    quay.io/thanos/thanos:v0.9.0-rc.0 \
    sidecar \
    --http-address 0.0.0.0:19090 \
    --grpc-address 0.0.0.0:19190 \
    --reloader.config-file /etc/prometheus/prometheus.yml \
    --prometheus.url http://127.0.0.1:9090 && echo "Started sidecar for Prometheus 0 EU1"

Adding sidecars to each replica of Prometheus in "US1"

docker run -d --net=host --rm \
    -v $(pwd)/prometheus0_us1.yml:/etc/prometheus/prometheus.yml \
    --name prometheus-0-sidecar-us1 \
    -u root \
    quay.io/thanos/thanos:v0.9.0-rc.0 \
    sidecar \
    --http-address 0.0.0.0:19091 \
    --grpc-address 0.0.0.0:19191 \
    --reloader.config-file /etc/prometheus/prometheus.yml \
    --prometheus.url http://127.0.0.1:9091 && echo "Started sidecar for Prometheus 0 US1"

docker run -d --net=host --rm \
    -v $(pwd)/prometheus1_us1.yml:/etc/prometheus/prometheus.yml \
    --name prometheus-1-sidecar-us1 \
    -u root \
    quay.io/thanos/thanos:v0.9.0-rc.0 \
    sidecar \
    --http-address 0.0.0.0:19092 \
    --grpc-address 0.0.0.0:19192 \
    --reloader.config-file /etc/prometheus/prometheus.yml \
    --prometheus.url http://127.0.0.1:9092 && echo "Started sidecar for Prometheus 1 US1"

Verification

Now, to check if sidecars are running well, let's modify Prometheus scrape configuration to include our added sidecars.

As always click Copy To Editor for each config to propagate the configs to each file.

Note that only thanks to the sidecar, all those changes will be immediately reloaded and updated in Prometheus!

global:
  scrape_interval: 15s
  evaluation_interval: 15s
  external_labels:
    cluster: eu1
    replica: 0

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['127.0.0.1:9090']
  - job_name: 'sidecar'
    static_configs:
      - targets: ['127.0.0.1:19090']

global:
  scrape_interval: 15s
  evaluation_interval: 15s
  external_labels:
    cluster: us1
    replica: 0

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['127.0.0.1:9091','127.0.0.1:9092']
  - job_name: 'sidecar'
    static_configs:
      - targets: ['127.0.0.1:19091','127.0.0.1:19092']

global:
  scrape_interval: 15s
  evaluation_interval: 15s
  external_labels:
    cluster: us1
    replica: 1

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['127.0.0.1:9091','127.0.0.1:9092']
  - job_name: 'sidecar'
    static_configs:
      - targets: ['127.0.0.1:19091','127.0.0.1:19092']

Now you should see new, updated configuration on each Prometheus. For example here in Prometheus 0 EU1 /config. In the same time up should show job=sidecar metrics.

Since now Prometheus has access to sidecar metrics we can query for thanos_sidecar_prometheus_up to check if sidecar has access to Prometheus.

Next

Great! Now you should have setup deployed as in the presented image:

In the next step, we will add a final component allowing us to fetch Prometheus metrics from a single endpoint.

Step 3 - Adding Thanos Querier

Thanks to the previous step we have three running Prometheus instances with a sidecar each. In this step we will install Thanos Querier which will use sidecars and allow querying all metrics from the single place as presented below:

But before that, let's take a closer look at what the Querier component does:

Querier

The Querier component (also called "Query") is essentially a vanilla PromQL Prometheus engine that fetches the data from any service that implements Thanos StoreAPI. This means that Querier exposes the Prometheus HTTP v1 API to query the data in a common PromQL language. This allows compatibility with Grafana or other consumers of Prometheus' API.

Additionally, Querier is capable of deduplicating StoreAPIs that are in the same HA group. We will see how it looks in practice later on.

You can read more about Thanos Querier here

Deploying Thanos Querier

Let' now start the Query component. As you remember Thanos sidecar exposes StoreAPI so we will make sure we point the Querier to the gRPC endpoints of all our three sidecars:

Click below snippet to start the Querier.

docker run -d --net=host --rm \
    --name querier \
    quay.io/thanos/thanos:v0.9.0-rc.0 \
    query \
    --http-address 0.0.0.0:29090 \
    --query.replica-label replica \
    --store 127.0.0.1:19190 \
    --store 127.0.0.1:19191 \
    --store 127.0.0.1:19192 && echo "Started Thanos Querier"

Setup verification

Thanos Querier exposes very similar UI to the Prometheus, but on top of many `StoreAPIs you wish to connect to.

To check if the Querier works as intended let's look on Querier UI Store page.

This should list all our three sidecars, including their external labels.

Global view - Not challenging anymore?

Now, let's get back to our challenge from step 1, so finding the answer to How many series (metrics) we collect overall on all Prometheus instances we have?

With the querier this is now super simple.

It's just enough to query Querier for sum(prometheus_tsdb_head_series)

You should see the single value representing the number of series scraped in both clusters in the current mode.

If we will query prometheus_tsdb_head_series we will see that we have complete info about all three Prometheus instances:

prometheus_tsdb_head_series{cluster="eu1",instance="127.0.0.1:9090",job="prometheus"}
prometheus_tsdb_head_series{cluster="us1",instance="127.0.0.1:9091",job="prometheus"}
prometheus_tsdb_head_series{cluster="us1",instance="127.0.0.1:9092",job="prometheus"}

Handling of Highly Availabile Prometheus

Now, as you remember we configured Prometheus 0 US1 and Prometheus 1 US1 to scrape the same things. We also connect Querier to both, so how Querier knows what is an HA group?

Try to query the same query as before: sum(prometheus_tsdb_head_series)

Now turn off deduplication (deduplication button on Querier UI) and hit Execute again. Now you should see 5 results:

prometheus_tsdb_head_series{cluster="eu1",instance="127.0.0.1:9090",job="prometheus",replica="0"}
prometheus_tsdb_head_series{cluster="us1",instance="127.0.0.1:9091",job="prometheus",replica="0"}
prometheus_tsdb_head_series{cluster="us1",instance="127.0.0.1:9091",job="prometheus",replica="1"}
prometheus_tsdb_head_series{cluster="us1",instance="127.0.0.1:9092",job="prometheus",replica="0"}
prometheus_tsdb_head_series{cluster="us1",instance="127.0.0.1:9092",job="prometheus",replica="1"}

So how Thanos Querier knows how to deduplicate correctly?

If we would look again into Querier configuration we can see that we also set query.replica-label flag. This is exactly the label Querier will try to deduplicate by for HA groups. This means that any metric with exactly the same labels except replica label will be assumed as the metric from the same HA group, and deduplicated accordingly.

If we would open prometheus1_us1.yml config file in the editor or if you go to Prometheus 1 US1 /config. you should see our external labels in external_labels YAML option:

  external_labels:
    cluster: us1
    replica: 1

Now if we compare to prometheus0_us1.yaml:

  external_labels:
    cluster: us1
    replica: 0

We can see that since those two replicas scrape the same targets, any metric will be produced twice. Once by replica=1, cluster=us1 Prometheus and once by replica=0, cluster=us1 Prometheus. If we configure Querier to deduplicate by replica we can transparently handle this High Available pair of Prometheus instances to the user.

Production deployment

Normally Querier runs in some central global location (e.g next to Grafana) with remote access to all Prometheus-es (e.g via ingress, proxies vpn or peering)

You can also stack (federate) Queriers on top of other Queries, as Query expose StoreAPI as well!

More information about those advanced topics can be found in the next courses that will be added soon.

Next

Awesome! Feel free to play around with the following setup:

Once done hit Continue for summary.