Troubleshooting Snowplow

Monitoring

This page covers dashboards and alerts coming from a number of internal tools.

For a brief video overview of the tools used to monitor Snowplow usage, please check out this internal video (you must be logged into GitLab Unfiltered to view).

Good events drop

Symptoms

You will be alarmed via a Sisense alert that is sent to #g_product_intelligence Slack channel

Locating the problem

First you need to identify at which stage in Snowplow the data pipeline the drop is occurring. Start at Snowplow dashboard on CloudWatch, if you do not have access to CloudWatch you need to create an access request issue first. While on CloudWatch dashboard set time range to last 4 weeks, to get better picture of system characteristics over time. Than visit following charts:

  1. ELB New Flow Count and Collector Auto Scaling Group Network In/Out - they show in order: number of connections to collectors via load balancers and data volume (in bytes) processed by collectors. If there is drop visible there, it means less events were fired from the GitLab application. Proceed to application layer guide for more details
  2. Firehose Records to S3 - it shows how many event records were saved to S3 bucket, if there was drop on this chart but not on the charts from 1. it means that problem is located at AWS infrastructure layer, please refer to AWS layer guide
  3. If drop wasn’t visible on any of previous charts it means that problem is at data warehouse layer, please refer to data warehouse layer guide

Troubleshooting GitLab application layer

Drop occurring at application layer can be symptom of some issue, but it might be also a result of normal application lifecycle, intended changes done to product intelligence or experiments tracking or even a result of a public holiday in some regions of the world with a larger user-base. To verify if there is an underlying problem to solve, you can check following things:

  1. Check about.gitlab.com website traffic on Google Analytics to verify if some public holiday might impact overall use of GitLab system
    1. You may require to open an access request for Google Analytics access first, for example: access request internal issue
  2. Plot select date(dvce_created_tstamp) , event , count(*) from legacy.snowplow_unnested_events_90 where dvce_created_tstamp > '2021-06-15' and dvce_created_tstamp < '2021-07-10' group by 1 , 2 order by 1 , 2 in SiSense to see what type of events was responsible for drop
  3. Plot select date(dvce_created_tstamp) ,se_category , count(*) from legacy.snowplow_unnested_events_90 where dvce_created_tstamp > '2021-06-15' and dvce_created_tstamp < '2021-07-31' and event = 'struct' group by 1 , 2 order by 1, 2 what events recorded the biggest drops in suspected category
  4. Check if there was any MR merged that might cause reduction in reported events, pay an attention to ~"product intelligence" and ~"growth experiment" labeled MRs
  5. Check (via Grafana explore tab ) following Prometheus counters gitlab_snowplow_events_total, gitlab_snowplow_failed_events_total and gitlab_snowplow_successful_events_total to see how many events were fired correctly from GitLab.com. Example query to use sum(rate(gitlab_snowplow_successful_events_total{env="gprd"}[5m])) / sum(rate(gitlab_snowplow_events_total{env="gprd"}[5m])) would chart rate at which number of good events rose in comparison to events sent in total. If number drops from 1 it means that problem might be in communication between GitLab and AWS collectors fleet.
  6. Check logs in Kibana and filter with { "query": { "match_phrase": { "json.message": "failed to be reported to collector at" } } } if there are some failed events logged

For results about an investigation conducted into an unexpected drop in snowplow events volume, see this issue.

Troubleshooting AWS layer

Already conducted investigations:

Troubleshooting data warehouse layer

Reach out to Data team to ask about current state of data warehouse. On their handbook page there is a section with contact details

Delay in Snowplow Enrichers

If there is an alert for Snowplow Raw Good Stream Backing Up, we receive an email notification. This sometimes happens because Snowplow Enrichers don’t scale well enough for the amount of Snowplow events.

If the delay goes over 48 hours, we lose data.

Contact SRE on-call

Send a message in the #infrastructure_lounge Slack channel using the following template: 

Hello team!

We received an alert for [Snowplow Raw Good Stream Backing Up](https://us-east-1.console.aws.amazon.com/cloudwatch/home?region=us-east-1#alarmsV2:alarm/SnowPlow+Raw+Good+Stream+Backing+Up?).

Enrichers are not scalling well for the amount of events we receive.

See the [dashboard](https://us-east-1.console.aws.amazon.com/cloudwatch/home?region=us-east-1#dashboards:name=SnowPlow).

Could we get assistance to fix the delay?

Thank you!