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Components

This section explains what the responsibilities of every 3scale component are and what is the impact when each of them is not available.

3scale pods by Type
Table of Contents

apicast-production

Responsibilities

  • 3scale API Gateway

  • APIcast enforces traffic policies, either returning an error or proxying the API call to the customer’s API backend

  • APIcast fetches its operating configuration from system-app component when the gateway starts

  • Each incoming/managed API call produces a sync/auth request from the API Gateway to backend-listener

  • Reduces latency by introducing the API Gateway in the traffic flow

Impact when down

  • Clients will not be able to reach the provider’s API using that APIcast instance

apicast-staging

Responsibilities

  • Same as apicast-production, but affecting staging traffic

Impact when down

  • Same as apicast-production, but affecting staging traffic

backend-listener

Responsibilities

  • This is the most critical component, responsible for authorizing and rate-limiting requests

Impact when down

  • APIcast will not be able to tell whether a request should be authorized or not and simply denies everything

  • APIs configured using 3scale are down

  • This service distuption can be mitigated by using the APIcast auth caching policy. There are some trade-offs when using this policy (service availability upon possible outages vs. service available but possibly using outdated configuration), so make sure you understand the implications before using it

backend-worker

Responsibilities

  • Process the background jobs created by backend-listener

  • Runs enqueued jobs, mainly related to traffic reporting

Impact when down

  • Reported metrics can’t be made effective, so the rate-limiting functionality loses accuracy because those pending reports are not taken into account

  • Statistics will not be up to date and the alerts and errors shown in the admin portal will not be triggered

  • Because accounting will not work, authorizations will not be correct

  • Jobs will not be processed and will start accumulating in backend-redis, which could lead to database out of memory related problems

backend-cron

Responsibilities

  • This is a simple task that acts as a cron like scheduler to retry failed jobs

  • When a backend-worker job fails, it is pushed to a "failed jobs" queue so that it can be retried later. Jobs can fail, for example, when there’s a Redis timeout

  • It is also responsible for deleting the stats of services that have been removed. This is run every 24h

Impact when down

  • Failed jobs will not be rescheduled

  • If it crashes in the middle of the delete process, it will just continue the next time it runs

  • If the 3scale installation is working correctly, the failed jobs queue will be empty at almost all times, so backend-cron being down is not critical

backend-redis

Responsibilities

  • It is the database used by backend-listener and backend-worker

  • It is used both for data persistence (metrics…​) and to store job queues

Impact when down

  • backend-listener and backend-worker cannot function without access to the storage, so both components can be considered as down. Refer to the sections on backend-listener and backend-worker to review impact when these components are down

system-app

Responsibilities

  • Developer and Admin Portal UI/API

  • 3scale APIs (Accounts, Analytics)

Impact when down

  • Developer and Admin Portal UI/API will not be available

  • 3scale APIs (Accounts, Analytics) will not be available

  • apicast will not be able to retrieve the gateway configuration, so new apicast deployments will not work

  • Already running apicast Pods will continue serving traffic using the latest retrieved configuration (cached)

system-sidekiq

Responsibilities

  • It is the job manager used by system-app to process jobs in the background asynchronously

Impact when down

  • Emails are not sent

  • Communication with backend-listener breaks: changes in Admin Portal will not propagate to Backend

  • Backend alerts will not be triggered

  • Webhooks will not be triggered

  • Zync will not receive any updates

  • Background jobs will not be processed and will start accumulating in system-redis, which could lead to database out of memory related problems

system-mysql or system-postgresql

Responsibilities

  • It is the main relational database used by system-app

Impact when down

  • Both system-app and system-sidekiq components can be considered down if access to the relational database is lost. Refer to the sections on system-app and system-sidekiq to review impact when these components are down

system-redis

Responsibilities

  • It is the database used by system-app to enqueue the jobs consumed by system-sidekiq

Impact when down

  • system-app and system-sidekiq cannot function without access to the storage, so both components can be considered as down. Refer to the sections on system-app and system-sidekiq to review impact when these components are down

system-memcache

Responsibilities

  • system-memcached is an ephemeral cache of values used to speed-up the performance of the system-app web application

Impact when down

  • system-app will run slightly slower (UI page loading times will be worse) while the cache is not accessible. Cache will be rebuilt once the memcached instance is back online

system-sphinx

Responsibilities

  • Full-text search for system-app

Impact when down

  • The search functionality on the system-app Admin/Developer Portal (accounts and proxy rules search bars, templates, forum searches…​) stops working

zync

Responsibilities

  • Receives events from system-sidekiq

  • Enqueue those events as new jobs to be processed in the background by zync-que

  • Those enqueued jobs can be:

    • Creation/Update of OpenShift Routes (Admin/Developer portals of each tenant)

    • Creation/Update of OpenShift Routes (apicast-staging or apicast-production domains of each API)

    • Synchronization of information with configured 3rd party IDPs

Impact when down

  • Synchronization of OpenShift Routes for apicast-staging and apicast-production will not work

  • Synchronization of OpenShift Routes for the Admin Portal and the Developer Portal domains will not work

  • Synchronization with 3rd party IDPs will not work

  • system-sidekiq will retry the failed requests for some time

zync-que

Responsibilities

  • Process the enqueued jobs created by zync

  • Those jobs can be:

    • Creation/Update of OpenShift Routes (Admin/Developer portals of each tenant)

    • Creation/Update of OpenShift Routes (apicast-staging or apicast-production domains of each API)

    • Synchronization of information with configured 3rd party IDPs

Impact when down

  • Synchronization of OpenShift Routes for apicast-staging and apicast-production will not work

  • Synchronization of OpenShift Routes for the Admin Portal and the Developer Portal domains will not work

  • Synchronization with 3rd party IDPs will not work

  • Jobs will not be processed and will start accumulating in zync-database, which could lead to database out of disk space related problems

zync-database

Responsibilities

  • It is the database used by zync

  • It contains job queues and also some data synchronized from system-app

Impact when down

  • zync will not be able to enqueue jobs and zync-que will not be able to consume them, so both components can be considered down when database access is lost. Refer to the sections on zync and zync-que to review impact when these components are down