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8da54352e5
* Document internal APIs, app services in WIRING.md * Add application services component to WIRING diagram * Fix typo and clarify what mode internal APIs use HTTP
229 lines
13 KiB
Markdown
229 lines
13 KiB
Markdown
# Wiring
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The diagram is incomplete. The following things aren't shown on the diagram:
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* Device Messages
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* User Profiles
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* Notification Counts
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* Sending federation.
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* Querying federation.
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* Other things that aren't shown on the diagram.
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Diagram:
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W -> Writer
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S -> Server/Store/Service/Something/Stuff
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R -> Reader
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+---+ +---+ +---+
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+----------| W | +----------| S | +--------| R |
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| +---+ | Receipts +---+ | Client +---+
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| Federation |>=========================================>| Server |>=====================>| Sync |
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| Receiver | | | | |
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| | +---+ | | | |
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| | +--------| W | | | | |
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| | | Client +---+ | | | |
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| | | Receipt |>=====>| | | |
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| | | Updater | | | | |
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| | +----------+ | | | |
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| | | | | |
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| | +---+ +---+ | | +---+ | |
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| | +------------| W | +------| S | | | +--------| R | | |
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| | | Federation +---+ | Room +---+ | | | Client +---+ | |
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| | | Backfill |>=====>| Server |>=====>| |>=====>| Push | | |
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| | +--------------+ | | +------------+ | | | |
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| | | | | | | |
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| | | |>==========================>| | | |
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| | | | +----------+ | |
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| | | | +---+ | |
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| | | | +-------------| R | | |
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| | | |>=====>| Application +---+ | |
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| | | | | Services | | |
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| | | | +--------------+ | |
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| | | | +---+ | |
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| | | | +--------| R | | |
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| | | | | Client +---+ | |
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| |>========================>| |>==========================>| Search | | |
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| | | | | | | |
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| | | | +----------+ | |
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| | | |>==========================================>| |
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| | | | | |
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| | +---+ | | +---+ | |
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| | +--------| W | | | +----------| S | | |
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| | | Client +---+ | | | Presence +---+ | |
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| | | API |>=====>| |>=====>| Server |>=====================>| |
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| | | /send | +--------+ | | | |
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| | | | | | | |
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| | | |>======================>| |<=====================<| |
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| | +----------+ | | | |
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| | | | | |
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| | +---+ | | | |
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| | +--------| W | | | | |
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| | | Client +---+ | | | |
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| | | Presence |>=====>| | | |
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| | | Setter | | | | |
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| | +----------+ | | | |
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| | | | | |
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| | | | | |
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| |>=========================================>| | | |
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| | +------------+ | |
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| | | |
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| | +---+ | |
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| | +----------| S | | |
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| | | Typing +---+ | |
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| |>=========================================>| Server |>=====================>| |
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+------------+ | | +----------+
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+---+ | |
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+--------| W | | |
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| Client +---+ | |
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| Typing |>=====>| |
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| Setter | | |
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+----------+ +------------+
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# Component Descriptions
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Many of the components are logical rather than physical. For example it is
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possible that all of the client API writers will end up being glued together
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and always deployed as a single unit.
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Outbound federation requests will probably need to be funnelled through a
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choke-point to implement ratelimiting and backoff correctly.
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## Federation Send
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* Handles `/federation/v1/send/` requests.
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* Fetches missing ``prev_events`` from the remote server if needed.
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* Fetches missing room state from the remote server if needed.
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* Checks signatures on remote events, downloading keys if needed.
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* Queries information needed to process events from the Room Server.
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* Writes room events to logs.
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* Writes presence updates to logs.
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* Writes receipt updates to logs.
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* Writes typing updates to logs.
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* Writes other updates to logs.
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## Client API /send
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* Handles puts to `/client/v1/rooms/` that create room events.
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* Queries information needed to process events from the Room Server.
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* Talks to remote servers if needed for joins and invites.
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* Writes room event pdus.
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* Writes presence updates to logs.
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## Client Presence Setter
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* Handles puts to the [client API presence paths](https://matrix.org/docs/spec/client_server/unstable.html#id41).
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* Writes presence updates to logs.
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## Client Typing Setter
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* Handles puts to the [client API typing paths](https://matrix.org/docs/spec/client_server/unstable.html#id32).
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* Writes typing updates to logs.
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## Client Receipt Updater
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* Handles puts to the [client API receipt paths](https://matrix.org/docs/spec/client_server/unstable.html#id36).
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* Writes receipt updates to logs.
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## Federation Backfill
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* Backfills events from other servers
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* Writes the resulting room events to logs.
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* Is a different component from the room server itself cause it'll
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be easier if the room server component isn't making outbound HTTP requests
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to remote servers
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## Room Server
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* Reads new and backfilled room events from the logs written by FS, FB and CRS.
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* Tracks the current state of the room and the state at each event.
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* Probably does auth checks on the incoming events.
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* Handles state resolution as part of working out the current state and the
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state at each event.
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* Writes updates to the current state and new events to logs.
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* Shards by room ID.
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## Receipt Server
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* Reads new updates to receipts from the logs written by the FS and CRU.
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* Somehow learns enough information from the room server to workout how the
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current receipt markers move with each update.
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* Writes the new marker positions to logs
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* Shards by room ID?
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* It may be impossible to implement without folding it into the Room Server
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forever coupling the components together.
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## Typing Server
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* Reads new updates to typing from the logs written by the FS and CTS.
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* Updates the current list of people typing in a room.
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* Writes the current list of people typing in a room to the logs.
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* Shards by room ID?
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## Presence Server
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* Reads the current state of the rooms from the logs to track the intersection
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of room membership between users.
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* Reads updates to presence from the logs written by the FS and the CPS.
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* Reads when clients sync from the logs from the Client Sync.
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* Tracks any timers for users.
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* Writes the changes to presence state to the logs.
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* Shards by user ID somehow?
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## Client Sync
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* Handle /client/v2/sync requests.
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* Reads new events and the current state of the rooms from logs written by the Room Server.
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* Reads new receipts positions from the logs written by the Receipts Server.
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* Reads changes to presence from the logs written by the Presence Server.
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* Reads changes to typing from the logs written by the Typing Server.
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* Writes when a client starts and stops syncing to the logs.
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## Client Search
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* Handle whatever the client API path for event search is?
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* Reads new events and the current state of the rooms from logs writeen by the Room Server.
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* Maintains a full text search index of somekind.
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## Client Push
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* Pushes unread messages to remote push servers.
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* Reads new events and the current state of the rooms from logs writeen by the Room Server.
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* Reads the position of the read marker from the Receipts Server.
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* Makes outbound HTTP hits to the push server for the client device.
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## Application Service
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* Receives events from the Room Server.
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* Filters events and sends them to each registered application service.
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* Runs a separate goroutine for each application service.
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# Internal Component API
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Some dendrite components use internal APIs to communicate information back
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and forth between each other. There are two implementations of each API, one
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that uses HTTP requests and one that does not. The HTTP implementation is
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used in multi-process mode, so processes on separate computers may still
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communicate, whereas in single-process or Monolith mode, the direct
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implementation is used. HTTP is preferred here to kafka streams as it allows
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for request responses.
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Running `dendrite-monolith-server` will set up direct connections between
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components, whereas running each individual component (which are only run in
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multi-process mode) will set up HTTP-based connections.
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The functions that make HTTP requests to internal APIs of a component are
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located in `/<component name>/api/<name>.go`, named according to what
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functionality they cover. Each of these requests are handled in `/<component
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name>/<name>/<name>.go`.
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As an example, the `appservices` component allows other Dendrite components
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to query external application services via its internal API. A component
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would call the desired function in `/appservices/api/query.go`. In
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multi-process mode, this would send an internal HTTP request, which would
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be handled by a function in `/appservices/query/query.go`. In single-process
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mode, no internal HTTP request occurs, instead functions are simply called
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directly, thus requiring no changes on the calling component's end.
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