Distributed caching for the Apollo Router

If you have multiple Apollo Router instances, those instances can share a Redis-backed cache for their query plans and automatic persisted queries (APQ). This means that if any of your router instances caches a particular value, all of your instances can look up that value to significantly improve responsiveness.

To use this feature:

• You must have a Redis cluster (or single instance) that your router instances can communicate with.
• You must have a GraphOS Enterprise plan and connect your router to GraphOS.

How it works

Whenever a router instance requires a query plan or APQ query string to resolve a client operation:

1. The router instance checks its own in-memory cache for the required value and uses it if found.
2. If not found, the router instance then checks the distributed Redis cache for the required value and uses it if found. It also then replicates the found value in its own in-memory cache.
3. If not found, the router instance generates the required query plan or requests the full operation string from the client for APQ.
4. The router instance stores the obtained value in both the distributed cache and its in-memory cache.

Redis URL configuration

The distributed caching configuration must contain one or more URLs using different schemes depending on the expected deployment:

• redis - TCP connected to a centralized server.
• rediss - TLS connected to a centralized server.
• redis-cluster - TCP connected to a cluster.
• rediss-cluster - TLS connected to a cluster.
• redis-sentinel - TCP connected to a centralized server behind a sentinel layer.
• rediss-sentinel - TLS connected to a centralized server behind a sentinel layer.

The URLs must have the following format:

One node

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redis|rediss :// [[username:]password@] host [:port][/database]

Example: redis://localhost:6379

Clustered

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redis|rediss[-cluster] :// [[username:]password@] host [:port][?[node=host1:port1][&node=host2:port2][&node=hostN:portN]]

or, if configured with multiple URLs:

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[
2
  "redis|rediss[-cluster] :// [[username:]password@] host [:port]",
3
  "redis|rediss[-cluster] :// [[username:]password@] host1 [:port1]",
4
  "redis|rediss[-cluster] :// [[username:]password@] host2 [:port2]"
5
]

Sentinel

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redis|rediss[-sentinel] :// [[username1:]password1@] host [:port][/database][?[node=host1:port1][&node=host2:port2][&node=hostN:portN]
2
                            [&sentinelServiceName=myservice][&sentinelUsername=username2][&sentinelPassword=password2]]

or, if configured with multiple URLs:

1
[
2
  "redis|rediss[-sentinel] :// [[username:]password@] host [:port][/database][?[&sentinelServiceName=myservice][&sentinelUsername=username2][&sentinelPassword=password2]]",
3
  "redis|rediss[-sentinel] :// [[username1:]password1@] host [:port][/database][?[&sentinelServiceName=myservice][&sentinelUsername=username2][&sentinelPassword=password2]]"
4
]

Distributed query plan caching

To enable distributed caching of query plans, add the following to your router's YAML config file:

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supergraph:
2
  query_planning:
3
    experimental_cache:
4
      redis: 
5
        urls: ["redis://..."] 
6
        timeout: 5ms # Optional, by default: 2ms

The value of urls is a list of URLs for all Redis instances in your cluster.

Distributed APQ caching

To enable distributed caching of automatic persisted queries (APQ), add the following to your router's YAML config file:

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apq:
2
  router:
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    cache:
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      redis: 
5
        urls: ["redis://..."] 
6
        timeout: 5ms # Optional, by default: 2ms

The value of urls is a list of URLs for all Redis instances in your cluster.