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Thomas Mueller commented on OAK-8523: ------------------------------------- > Usually it'd not be that many strings - much lower in fact (order of 10^1) - > it can go as high as 10^3 in rare cases What you could do is store it as a MV string property in the normal case, and as a binary if it's larger. But that would make it more complex, so it's probably easier to always store it as a binary. > a persisted reference-cache I don't know what that is so I can't comment. Maybe you can give some examples? > write binary-prop serialization/deserialization is slightly more involved Hm, maybe you want to convert the string array to JSON. Of course it's a few more lines of code, but shouldn't be that complicated. > concrete reasons Yes. Storing large strings or large multi-value properties comes with a high cost if there are many updates, because you have to store them each time. Also, very large nodes are a problem for caches. > Best Practices - Property Value Length Limit > -------------------------------------------- > > Key: OAK-8523 > URL: https://issues.apache.org/jira/browse/OAK-8523 > Project: Jackrabbit Oak > Issue Type: Improvement > Components: core, jcr > Reporter: Thomas Mueller > Priority: Major > > Right now, Oak supports very large properties (e.g. String). But 1 MB (or > larger) properties are problematic in multiple areas like indexing. It is > more important for software-as-a-service, where we need to guarantee SLOs, > but it also helps other cases. So we should: > * (1) Document best practises, e.g. "Property values should be smaller than > 100 KB". > * (2) Introduce "softLimit" and "hardLimit", where softLimit is e.g. 100 KB > and hardLimit is configurable, and (initially) by default Integer.MAX_VALUE. > Setting the hard limits to a lower value by default is problematic, because > it can break existing applications. With default value infinity, customers > can set lower limits e.g. in tests first, and once they are happy, in > production as well. > * (3) Log a warning if a property is larger than "softLimit". To avoid > logging many warnings (if there are many such properties) we then set > softLimit = softLimit * 1.1 (reset to 100 KB in the next repository start). > Logging is needed to know what _exactly_ is broken (path, stack trace of the > actual usage...) > * (4) Add a metric (monitoring) for detected large properties. Just logging > warnings might not be enough. > * (5) Throttling: we could add flow control (pauses; Thread.sleep) after > violations, to improve isolation (to prevent affecting other threads that > don't violate the contract). > * (6) We could expose the violation info in the session, so a framework could > check that data after executing custom code, and add more info (e.g. log). > * (7) If larger than the configurable hardLimit, fail the commit or reject > setProperty (throw an exception). > * (8) At some point, in a new Oak version, change the default value for > hardLimit to some reasonable number, e.g. 1 MB. > The "property length" is just one case. There are multiple candidates: > > * Number of properties for a node > * Number of elements for multi-valued properties > * Total size of a node (including inlined properties) > * Number of direct child nodes for orderable child nodes > * Number of direct child nodes for non-orderable child nodes > * Size of transaction > * Adding observations listeners that listen for all changes (global listeners) > For those cases, new Jira issue should be made. -- This message was sent by Atlassian Jira (v8.3.4#803005)