https://docs.google.com/presentation/d/1nfosNvuHAihk2Pe-U9RA6vEA89vnBre9h60GwYlJ_44/edit?usp=sharing

• Prometheus
• What is Prometheus
• Samples vs Metrics vs Cardinality
• PromQL Querying
• Querying Examples
• Metric Types
• Prometheus and Grafana
• What is High Cardinality
• Prometheus: Best Practices and Beastly Pitfalls
• Robust Perception Blog
• Sending Slack/PD/Email notifications with Alertmanager

• Docker setup
• If you don't have Docker setup, try

docker run -d -p 9090:9090 prom/prometheus

• Visit http://localhost:9090
• See all the metrics scraped by Prometheus about itself.

• Play around each of the pages and tabs in Prometheus.
• Go through Prometheus configuration.
• Go through Targets.

• Run a query to understand if Prometheus is up and running.
• Run a query to know how many samples are ingested by Prometheus. Hint: tsdb_head_samples_ap...

global:
  scrape_interval: 15s

scrape_configs:
  # Scrape Prometheus itself
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  # Scrape the service running on localhost:8080
  - job_name: 'api-service'
    static_configs:
      - targets: ['locaohost:8080'] # For gitpod, this has to be gitpod host along with `scheme: https`

docker run -d \
  -p 9090:9090 \
  -v $(pwd)/prometheus.yml:/etc/prometheus/prometheus.yml \
  prom/prometheus --web.enable-lifecycle --config.file=/etc/prometheus/prometheus.yml

docker run -d -p 8080:8080 pierrevincent/prom-http-simulator:0.1

• See all metrics exposed by the HTTP service.
• Verify that Prometheus can scrape metrics from HTTP service.

• See all metrics and corresponding labels the HTTP service emits.
• up{job="api-service"}
• Let's look at the number of requests that this service has received since it started up.
• All requests with status 200 and endpoint /login.
• First taste of aggregation, do a sum of all requests with status 200 and endpoint /login.
• How do we get data for a range instead of a single timestamp? Range vector vs. instant vector.
• Rate of change in the number of requests.
• Bytes allocated by Go for memstats. go_memstats_alloc_bytes
• What's the overall request rate (with a 1 minute rolling window)
• How many requests per minute are errors?
• What's the error rate (in %) of requests to the /users endpoint?
• Top-requested endpoints by status code

# alert-rules.yml
    groups:
    - name: http_health
      rules:
      - alert: HttpSimulatorNotRunning
        expr: absent(up{job="api-service"}) == 1
        for: 1m
        labels:
          severity: major

# prometheus.yml
scrape_configs:
  # Scrape Prometheus itself
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  # Scrape the service running on localhost:8080
  - job_name: 'api-service'
    static_configs:
      - targets: ['localhost:8080']
    scheme: https

rule_files:
 - "/etc/prometheus/alert-rules.yml"

docker run -d   -p 9090:9090   -v $(pwd)/prometheus.yml:/etc/prometheus/prometheus.yml   -v $(pwd)/alert-rules.yml:/etc/prometheus/alert-rules.yml prom/prometheus --web.enable-lifecycle --config.file=/etc/prometheus/prometheus.yml

groups:
    - name: http_health
      rules:
      - alert: HttpSimulatorNotRunning
        expr: absent(up{job="api-service"}) == 1
        for: 1m
        labels:
          severity: major
      - alert: ErrorRateHigh
        expr: sum(rate(http_requests_total{job="api-service", status="500"}[5m])) / sum(rate(http_requests_total{job="api-service"}[5m])) > 0.001
        for: 1m
        labels:
          severity: major
        annotations:
          summary: Alert if the error rate is high
          description: Calculate the error rate for this service and error out if high

Reload the Prometheus configuration with the following command:

curl -X POST :9090/-/reload

• Setup alert-rules
• Verify alert rules are getting evaluated.
• Add one more alert rule and reload config.
• See alert rules turning green and red.

docker run -d -p 3000:3000 grafana/grafana-oss

• First visit to Grafana.
• Adding a data source.
• Create a dashboard.
• Add all previous queries as panels.
• Graph of latency distribution
• Cumulative % graph of endpoint request rate
• Memory usage over time
• CPU usage over time
• Graph % of requests fulfilling the SLO of 400ms for /login endpoint

• Sign up on https://app.last9.io/product/levitate