[james-project] 09/10: JAMES-3769 Propose an ADR

[bt...@apache.org]

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commit 25ddd15de079ce709c70337f99087a61c679f16e
Author: Benoit Tellier <bt...@linagora.com>
AuthorDate: Mon May 16 15:09:03 2022 +0700

    JAMES-3769 Propose an ADR
---
 src/adr/0054-elasticsearch-search-overrides.md | 76 ++++++++++++++++++++++++++
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+# 54. ElasticSearch search overrides
+
+Date: 2022-05-16
+
+## Status
+
+Accepted (lazy consensus).
+
+Implemented.
+
+## Context
+
+IMAP SEARCH requests can of course be used for user searches. But many applications (eg Samsung email client) also uses
+IMAP SEARCH for resynchronization.
+
+The use of ElasticSearch in the context of resynchronization is a problem as:
+
+ - Resynchronization incurs many requests that ElasticSearch is not made to cope with.
+ - This has a performance impact, and some 60+ seconds can be spotted.
+ - ElasticSearch indexing is asynchronous which is not ideal for resynchronization
+ - An ElasticSearch downtime would imply a full downtime for these clients.
+ 
+Those resynchronization queries would better be served by the metadata database
+
+## Decision
+
+Define an API, `SearchOverride` that can be called on matching search queries and thus offload ElasticSearch.
+
+Provide an extension mechanism for search overrides, where potentially custom implementations can be loaded from the
+configuration.
+
+Provide well targeted `SearchOverride`, implemented on top of `Cassandra` database.
+
+## Consequences
+
+We expect to :
+
+ - Observe less IMAP SEARCH slow requests
+ - ElasticSearch downtime should not impact IMAP clients using IMAP SEARCH like IMAP Samsung application
+ - Thus also be able to support a higher IMAP workload as Cassandra is more suited to resynchronisation requests
+
+## Sample IMAP requests
+
+
+```
+SearchOperation{key=SearchKey{type=TYPE_UID, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=[IdRange : TYPE: FROM UID: MessageUid{uid=1}:MessageUid{uid=9223372036854775807}], sequences=null, keys=Optional.empty}, options=[]}
+```
+
+```
+SearchOperation{key=SearchKey{type=TYPE_AND, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional[[
+    SearchKey{type=TYPE_SEQUENCE_SET, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=[IdRange ( 1->9223372036854775807 )], keys=Optional.empty}, 
+    SearchKey{type=TYPE_DELETED, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional.empty}]]},
+    options=[COUNT]}
+```
+
+```
+SearchOperation{key=SearchKey{type=TYPE_AND, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional[[
+    SearchKey{type=TYPE_UID, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=[IdRange : TYPE: FROM UID: MessageUid{uid=1}:MessageUid{uid=9223372036854775807}], sequences=null, keys=Optional.empty}, 
+    SearchKey{type=TYPE_UNSEEN, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional.empty}]]}, options=[COUNT]}
+```
+
+```
+SearchOperation{key=SearchKey{type=TYPE_AND, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional[[
+    SearchKey{type=TYPE_SEQUENCE_SET, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=[IdRange ( 1->9223372036854775807 )], keys=Optional.empty}, 
+     SearchKey{type=TYPE_NOT, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional[[
+        SearchKey{type=TYPE_DELETED, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional.empty}]]}]]}, options=[ALL]}
+```
+
+```
+SearchOperation{key=SearchKey{type=TYPE_ALL, date=null, size=0, value=null, seconds=-1, modSeq=-1, uids=null, sequences=null, keys=Optional.empty}, options=[]}
+```
+
+
+## References
+
+- [JIRA](https://issues.apache.org/jira/browse/JAMES-3769)
\ No newline at end of file


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