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== Overview ==
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This document serves as a technical proposal for a new search API - V3 ([[Open Food Facts Search API Version 2|see V2 here]]).
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'''IMPORTANT:''' our goal have shifted a bit on this project. See [https://docs.google.com/document/d/1mibE8nACcmen6paSrqT9JQk5VbuvlFUXI1S93yHCK2I/edit Search-a-licious roadmap architecture notes]
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=== Goals ===
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Create new search APIs to facilitate:
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* Autocomplete (currently unsupported)
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* Facet search (replacing our current search API)
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* Migrating internal services (such as the search bar) to this API. However, performing this migration is not in scope.
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=== Non Goals ===
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* Improving the current API
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* Modifying the current search UX
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== Elasticsearch ==
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Elasticsearch has been chosen for several reasons:
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* Advanced search functionality (easy to support features such as autocomplete)
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* Mature ecosystem
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* Easy to host, completely free version suits our needs
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=== Configuration ===
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We will use Elasticsearch 8.3.3 (latest), deployed via Docker. We will use a replication factor of one (ie, two copies of the data in total), with shards split across two nodes.
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From testing on a M1 Macbook Pro, we see:
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* Memory: ~1GB per node
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* CPU: Low single digits
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* Disk usage: ~6GB after indexing, reduces to ~4GB over time
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* Latency: Autocomplete queries take ~0.1s on average
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* Import time (full index from CSV): ~15 mins
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Given the relatively low resource usage, we could likely use more nodes. For now, it is suggested to monitor resource usage, and add nodes (and increase the replication factor) if needed.
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X-Pack security will be turned off, as we do not need to encrypt any communication to Elasticsearch or between the nodes. This simplifies the setup and install of elasticvue (below). If this index was used for more sensitive data in the future, this decision should be revisited. 
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=== Monitoring ===
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We will use [https://elasticvue.com/ elasticvue] to see information such as resource usage, sharding, and perform debugging. Query stats (to monitor ongoing use) can be seen at elasticvue --> indices --> settings/cog --> Show stats.
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=== Data ===
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The core datatype will be the ''Product''. This data will be stored sparsely (ie, fields that are not set will not be stored in the index) to reduce space.
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To enable API cases such as partial text search, a rich autocomplete, and the possibility of eventually serving as a unified read layer, [https://static.openfoodfacts.org/data/data-fields.txt all fields] will be added to the index. Only product names, brands and categories will be indexed for autocomplete queries.
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An argument could be made for storing fewer fields, and reducing disk usage. However, as illustrated above, disk usage is quite reasonable.
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== Search Service ==
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The Search Service will be written in Python, using [https://fastapi.tiangolo.com/ FastAPI]. It will leverage [https://elasticsearch-dsl.readthedocs.io/en/latest/ Elasticsearch DSL] to aid in data modeling and query writing.
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=== Importing Data ===
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A Redis container will be created, which will serve as a queue/buffer for writing data. Using this approach is preferable to a webhook as search service instability will not affect the main server, and we can better handle write spikes/DOS attacks.
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Data will be added to the queue when the [https://github.com/openfoodfacts/openfoodfacts-server/blob/af59dc1155a096328e9dc4710985a12a8be878c3/lib/ProductOpener/Products.pm#L968 ''store_product'' method] is called on the main service. This data will contain the full product definition and a field will indicate if this is an upsert or a delete.
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The Search Service will consume from this queue via the [https://redis-py.readthedocs.io/en/stable/ Redis Python API], indexing (or deleting) each product as it receives messages.
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A manual import script will also be written, to take the CSV file and [https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-bulk.html bulk import] items. To ensure that data from the manual import script is up to date (ie, no gap from the time of running the script and when data is imported), we need to:
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* Modify the Search Service to perform a set like:
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** ''SET product:<timestamp>:<barcode> <full_product_definition> EX 129600''
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** Explanation: Set a key for each product that expires in 36 hours
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* Modify the import script to:
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** See when the last updated/created timestamp was, store as import_cutoff
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** Fetch all recent writes from redis with a ''SCAN'', matching anything of the form product:*
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** Iterate through timestamps in order that are after import_cutoff
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** Apply those writes
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=== API Overview ===
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These APIs will:
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* Return a maximum of 100 items
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* Require robust unit tests
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* [https://openfoodfacts.github.io/api-documentation/#3SEARCHRequests Require documentation]
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* [https://github.com/openfoodfacts/openfoodfacts-server/tree/111e0afdbac3c20ea34652b0b413be58be6dfae5/conf/nginx Need to be exposed in the Nginx configuration]
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* Be prefixed with ''/v3'' (redirecting at the Nginx layer, but not using the v3 prefix at the Search Service layer)
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The proposed API definition is below. Note that the requests are represented as Python objects as used in FastAPI - in reality, this is a JSON payload:
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<pre>
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class SearchBase(BaseModel):
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    response_fields: Optional[Set[str]]
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class AutocompleteRequest(SearchBase):
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    text: str
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    search_fields: List[str] = constants.AUTOCOMPLETE_FIELDS
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class StringFilter(BaseModel):
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    field: str
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    value: str
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    # One of eq, ne, like
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    operator: str = 'eq'
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class NumericFilter(BaseModel):
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    field: str
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    value: float
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    # One of eq, ne, lt, gt
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    operator: str = 'eq'
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class DateTimeFilter(BaseModel):
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    field: str
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    value: datetime.datetime
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    # One of lt, gt
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    operator: str = 'eq'
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class SearchRequest(SearchBase):
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    # Works as an intersection/AND query
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    string_filters: List[StringFilter]
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    numeric_filters: List[NumericFilter]
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    date_time_filters: List[DateTimeFilter]
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</pre>
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These are then used as follows:
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<pre>
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# Gets the product matching a barcode, included to demonstrate potential usage to replace the main read API, this should not be exposed unless it is decided to send all reads through this service
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GET /barcode/<barcode>
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# Autocomplete request
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POST /autocomplete, body=AutocompleteRequest
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# Fully fledged search
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POST /search, body=SearchRequest
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</pre>
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=== API Discussion ===
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The barcode GET API is included to demonstrate how this service could easily replace our existing read APIs, but is not intended to be used for the moment.
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The remaining APIs have several commonalities:
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* An optional ''response_fields'' parameter is provided, to limit the fields in the response further
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* POST is used, to support a complex request body
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The ''/search'' API is the most complex as it allows a series of filters to support the use cases in the [https://openfoodfacts.github.io/api-documentation/#3SEARCHRequests current API]. These filters will work like an intersection/AND query. Of interest are the:
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* ''like'' operator, which does not need to match to exact fields, but rather will match by use of the [https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-snowball-tokenfilter.html snowball token filter] in Elasticsearch if the field supports it.
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* ''gt'', ''lt'' (greater than, less than) operators are provided.
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* There is no support for an OR operator (which is supported in the [[Open Food Facts Search API Version 2|V2 API]]), however clients can perform this logic themselves if they wish through multiple API calls.
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=== Relationship With Existing APIs ===
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The autocomplete API does not overlap with the other APIs. However, the new proposed ''/search'' API has a lot of conceptual overlap with the current search APIs. It is proposed to encourage users to migrate to this new V3 API (and to use it when writing new code) through guidance in the API docs.
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Furthermore, once the new API has proven its stability, the legacy ''search.pl'' should be able to be switched over (with a translation layer to map between old and new API request and response norms). The v2 API can also be migrated, but will require a solution to supporting the OR operator (potentially dropping support, using another translation layer with multiple requests, or modifying the API).
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This work is considered out of scope for this proposal.
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== Work Plan ==
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* Completed
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** Product document definition
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** Bulk import script
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** API definition
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** API implementation
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** Docker, Elasticvue configuration
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** API tests
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** Redis Integration
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* TODO:
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** Deploy (without any traffic)
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** Redis writer on the Perl side
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** Final testing
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** Document API
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** Ongoing monitoring
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== Future Work ==
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There appears to be a lot of opportunities to utilize this infrastructure further:
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* Incorporate the autocomplete API in to the main search bar
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* Use the new search API to handle searches on the primary website (should result in improved ranking, matching, lower DB load)
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* Robotoff could use the same cluster
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* Current search APIs could be switched over (with a translation layer)
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[[Category:Search]]
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