diff --git a/docs/collaboration-v1-plan.md b/docs/collaboration-v1-plan.md new file mode 100644 index 0000000000..1064d9d3bc --- /dev/null +++ b/docs/collaboration-v1-plan.md @@ -0,0 +1,114 @@ +# Collaboration V1 + + +## Sharing UI + +* For each worktree that I edit in Zed, there is a *Share* button that I can click to turn *sharing* + on or off for that worktree. +* For each worktree that I share, Zed shows me a URL that I can give to others to let them + collaboratively edit that worktree. +* __Question__ - Does the sharing on/off state of each worktree persist across application restart? + When I close Zed while sharing a worktree, should I resume sharing when I reopen Zed? + Pros: + * This would remove friction from teams collaborating continuously. + Cons: + * I might have added something secret to the worktree since I last opened Zed. Could we detect + changes that have occured outside of Zed, and avoid auto-sharing on startup when that has + happened? + +## Sharing Semantics + +* While sharing, the entire state of my worktree is replicated and stored forever on the Zed server. + Other collaborators can freely read the last state of my worktree, even after I've quit Zed. +* __Potential Scope Cut__ - For now, we won't store the history locally, as this isn't needed for + collaboration. Later, we may explore keeping a partial history locally as well, to support using + the history while offline. A local history would allow: + * Undo after re-opening a buffer. + * Avoiding redundant uploads when re-opening a buffer while sharing. + +* When I begin sharing: + * Immediately, I upload a list of all the paths in my worktree, along a digest of each path + * The server responds with a list of paths that needs + * First, I upload the contents of all of my open buffers. + * At this point, sharing has begun. I am shown a URL. + * Asynchronously, I upload the contents of all other files in my worktree that the server needs. +* While I'm sharing: + * Buffer operations are streamed to the Zed server, and to any peers that I'm collaborating with. + * When FS changes are detected to files that I *don't* have open: + * I again upload to the server a list of the paths that changed and their new digests. + * The server responds with a list of paths that it needs + * Asynchronously, I upload the new contents of these paths. + * If a peer requests to open one of my files that I haven't yet asynchronously uploaded, then + the server tells me to upload the contents of that file immediately. +* When I stop sharing: + * I immediately stop uploading anything to the Zed server. + +* __Question__ - If, while sharing, I undo an operation that I performed while *not* sharing, what + information do I need to send to the server? + * Can we transmit the operation as a new `Edit`, instead of as an `Undo`, so that the server can see + the details of the operation? Will this be guaranteed to converge, since there can't have been any + operations concurrent with the undone operation? + +### Further Improvements + +* When we add a local persisten history of our worktree, we will be able to + avoid uploading entire snapshots of files that have changes since our last sharing session. + Instead, the server can report that last version vector that it has seen for a file, + and we can use that to construct a diff based on our history. + +## RPC implementation details + +Every client will have a single TCP connection to `zed.dev`. + +The API will consist of resources named with URL-like paths, for example: `/worktrees/1`. + +You'll be able to communicate with any resource in the following ways: + +* `send`: A "fire-and-forget" message with no reply. (We may not need this) +* `request`: A message that expects a reply message that is tagged with the same sequence number as the request. +* `request_stream`: A message that expects a series of reply messages that are tagged with the same sequence number as the request. Unsure if this is needed beyond `subscribe`. +* `subscribe`: Returns a stream that allows the resource to emit messages at any time in the future. When the stream is dropped, we unsubscribe automatically. + +Any resource you can subscribe to is considered a *channel*, and all of its processing needs to occur on a single machine. We'll recognize channels based on their URL pattern and handle them specially in our frontend servers. For any channel, the frontend will perform a lookup for the machine on which that channel exists. If no machine exists, we'll select one. Maybe it's always the frontend itself?. If a channel already exists on another server, we'll proxy the connection through the frontend and relay and broadcasts from this channel to the client. + +The client will interact with the server via a `api::Client` object. Model objects with remote behavior will interact directly with this client to communicate with the server. For example, `Worktree` will be changed to an enum type with `Local` and `Remote` variants. The local variant will have an optional `client` in order to stream local changes to the server when sharing. The remote variant will always have a client and implement all worktree operations in terms of it. + +```rs +enum Worktree { + Local { + remote: Option, + } + Remote { + remote: Client, + } +} + +impl Worktree { + async fn remote(client, id, cx) -> anyhow::Result { + // Subscribe to the stream of all worktree events going forward + let events = client.subscribe::(format!("/worktrees/{}", worktree_id)).await?; + // Stream the entries of the worktree + let entry_chunks = client.request_stream() + + // In the background, populate all worktree entries in the initial stream and process any change events. + // This is similar to what we do + let _handle = thread::spawn(smol::block_on(async move { + for chunk in entry_chunks { + // Grab the lock and fill in the new entries + } + + while let Some() = events.recv_next() { + // Update the tree + } + })) + + // The _handle depicted here won't actually work, but we need to terminate the thread and drop the subscription + // when the Worktree is dropped... maybe we use a similar approach to how we handle local worktrees. + + Self::Remote { + _handle, + client, + } + } +} +``` \ No newline at end of file