Cache ZedTokens for resources using NATS #209
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Using full consistency when doing permissions checks is slow. In general, this is addressed by using ZedTokens to indicate minimum bounds on freshness when looking up cached data. Something has to keep track of those tokens, either on the client side or server-side. This commit introduces worker caching of ZedTokens for resources on updates to relationships and updates the query engine to use those tokens when performing permissions checks. When a worker updates a relationship, it persists the ZedToken for all resources directly affected by that update to a NATS KV bucket. NATS KV writes are immediately consistent, so the new ZedToken for that resource is available to all consumers, including permissions-api API frontends. When the query engine performs a permissions check, it checks to see if a ZedToken is available for the resource. If a ZedToken was found, that ZedToken is used along with the at_least_as_fresh SpiceDB API consistency strategy. If not, or if there was an error accessing NATS, the query engine falls back to the minimize_latency API consistency strategy. If the NATS KV bucket is configured with a TTL at least as high as the quantization interval for SpiceDB, this ensures that by the time the ZedToken is evicted from the cache, all SpiceDB frontends will be updated with data at least as fresh as the last relationship update for a resource. Clients that wish to force an update for a resource (e.g., making role changes immediately available to tenant users) can thus issue a relationship update to permissions-api and get the latest data for that resource. This commit assumes that the KV bucket used already exists; permissions-api will not attempt to create it. This is because the intention is that the KV bucket has a TTL set to something close to the SpiceDB quantization interval, which permissions-api is not necessarily aware of. Signed-off-by: John Schaeffer <[email protected]>
This commit adds the necessary configs to the Helm chart to support populating a ZedToken cache for permissions-api. Signed-off-by: John Schaeffer <[email protected]>
fishnix
previously approved these changes
Jan 16, 2024
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| // If an error happened when creating or updating the token, record it. | ||
| if err != nil { |
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ill be interested to see how often we hit this condition - i expect not a lot since its for an individual relationship
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Probably not often, but I can think of a few cases:
- NATS is unavailable
- Something created a bucket entry before this function did
- Something updated a bucket entry
| // updateRelationshipZedTokens updates the NATS KV bucket for ZedTokens, setting the given ZedToken | ||
| // as the latest point in time snapshot for every resource in the given list of relationships. | ||
| func (e *engine) updateRelationshipZedTokens(ctx context.Context, rels []types.Relationship, zedToken string) { | ||
| resourceIDMap := map[string]struct{}{} |
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why this over just a slice here since you're just looping over the keys anyways?
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Relationships don't necessarily need to refer to unique resources (i.e., multiple relationships could be persisted that affect the same tenant). This just ensures that we aren't sending redundant ZedToken updates.
This commit adds NATS creds to the server deployment in the Helm chart. Signed-off-by: John Schaeffer <[email protected]>
mikemrm
previously approved these changes
Jan 16, 2024
This commit adds tests for determineConsistency. Signed-off-by: John Schaeffer <[email protected]>
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mikemrm
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fishnix
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Using full consistency when doing permissions checks is slow. In general, this is addressed by using ZedTokens to indicate minimum bounds on freshness when looking up cached data. Something has to keep track of those tokens, either on the client side or server-side.
This PR introduces worker caching of ZedTokens for resources on updates to relationships and updates the query engine to use those tokens when performing permissions checks. When a worker updates a relationship, it persists the ZedToken for all resources directly affected by that update to a NATS KV bucket. NATS KV writes are immediately consistent, so the new ZedToken for that resource is available to all consumers, including permissions-api API frontends. When the query engine performs a permissions check, it checks to see if a ZedToken is available for the resource.
If a ZedToken was found, that ZedToken is used along with the
at_least_as_freshSpiceDB API consistency strategy. If not, or if there was an error accessing NATS, the query engine falls back to theminimize_latencyAPI consistency strategy. If the NATS KV bucket is configured with a TTL at least as high as the quantization interval for SpiceDB, this ensures that by the time the ZedToken is evicted from the cache, all SpiceDB frontends will be updated with data at least as fresh as the last relationship update for a resource. Clients that wish to force an update for a resource (e.g., making role changes immediately available to tenant users) can thus issue a relationship update to permissions-api and get the latest data for that resource.This PR assumes that the KV bucket used already exists; permissions-api will not attempt to create it. This is because the intention is that the KV bucket has a TTL set to something close to the SpiceDB quantization interval, which permissions-api is not necessarily aware of.