At a high level, this is what I've done and why:
- I'm moving the protobuf generation for the `protocol`, `discovery` and
`db` packages to the modern alternatives, and using `buf` to generate
because it's nice and simple.
- After trying various approaches on how to integrate the new types with
the existing code, I opted for splitting off our own data model types
from the on-the-wire generated types. This means we can have a
`FileInfo` type with nicer ergonomics and lots of methods, while the
protobuf generated type stays clean and close to the wire protocol. It
does mean copying between the two when required, which certainly adds a
small amount of inefficiency. If we want to walk this back in the future
and use the raw generated type throughout, that's possible, this however
makes the refactor smaller (!) as it doesn't change everything about the
type for everyone at the same time.
- I have simply removed in cold blood a significant number of old
database migrations. These depended on previous generations of generated
messages of various kinds and were annoying to support in the new
fashion. The oldest supported database version now is the one from
Syncthing 1.9.0 from Sep 7, 2020.
- I changed config structs to be regular manually defined structs.
For the sake of discussion, some things I tried that turned out not to
work...
### Embedding / wrapping
Embedding the protobuf generated structs in our existing types as a data
container and keeping our methods and stuff:
```
package protocol
type FileInfo struct {
*generated.FileInfo
}
```
This generates a lot of problems because the internal shape of the
generated struct is quite different (different names, different types,
more pointers), because initializing it doesn't work like you'd expect
(i.e., you end up with an embedded nil pointer and a panic), and because
the types of child types don't get wrapped. That is, even if we also
have a similar wrapper around a `Vector`, that's not the type you get
when accessing `someFileInfo.Version`, you get the `*generated.Vector`
that doesn't have methods, etc.
### Aliasing
```
package protocol
type FileInfo = generated.FileInfo
```
Doesn't help because you can't attach methods to it, plus all the above.
### Generating the types into the target package like we do now and
attaching methods
This fails because of the different shape of the generated type (as in
the embedding case above) plus the generated struct already has a bunch
of methods that we can't necessarily override properly (like `String()`
and a bunch of getters).
### Methods to functions
I considered just moving all the methods we attach to functions in a
specific package, so that for example
```
package protocol
func (f FileInfo) Equal(other FileInfo) bool
```
would become
```
package fileinfos
func Equal(a, b *generated.FileInfo) bool
```
and this would mostly work, but becomes quite verbose and cumbersome,
and somewhat limits discoverability (you can't see what methods are
available on the type in auto completions, etc). In the end I did this
in some cases, like in the database layer where a lot of things like
`func (fv *FileVersion) IsEmpty() bool` becomes `func fvIsEmpty(fv
*generated.FileVersion)` because they were anyway just internal methods.
Fixes#8247
This is a refactor of the protocol/model interface to take the actual
message as the parameter, instead of the broken-out fields:
```diff
type Model interface {
// An index was received from the peer device
- Index(conn Connection, folder string, files []FileInfo) error
+ Index(conn Connection, idx *Index) error
// An index update was received from the peer device
- IndexUpdate(conn Connection, folder string, files []FileInfo) error
+ IndexUpdate(conn Connection, idxUp *IndexUpdate) error
// A request was made by the peer device
- Request(conn Connection, folder, name string, blockNo, size int32, offset int64, hash []byte, weakHash uint32, fromTemporary bool) (RequestResponse, error)
+ Request(conn Connection, req *Request) (RequestResponse, error)
// A cluster configuration message was received
- ClusterConfig(conn Connection, config ClusterConfig) error
+ ClusterConfig(conn Connection, config *ClusterConfig) error
// The peer device closed the connection or an error occurred
Closed(conn Connection, err error)
// The peer device sent progress updates for the files it is currently downloading
- DownloadProgress(conn Connection, folder string, updates []FileDownloadProgressUpdate) error
+ DownloadProgress(conn Connection, p *DownloadProgress) error
}
```
(and changing the `ClusterConfig` to `*ClusterConfig` for symmetry;
we'll be forced to use all pointers everywhere at some point anyway...)
The reason for this is that I have another thing cooking which is a
small troubleshooting change to check index consistency during transfer.
This required adding a field or two to the index/indexupdate messages,
and plumbing the extra parameters in umpteen changes is almost as big a
diff as this is. I figured let's do it once and avoid having to do that
in the future again...
The rest of the diff falls out of the change above, much of it being in
test code where we run these methods manually...
This adds error returns to model methods called by the protocol layer.
Returning an error will cause the connection to be torn down as the
message couldn't be handled. Using this to signal that a folder isn't
currently available will then cause a reconnection a few moments later,
when it'll hopefully work better.
Tested manually by running with STRECHECKDBEVERY=0 on a nontrivially
sized setup. This panics reliably before this patch, but just causes a
disconnect/reconnect now.
So there were some issues here. The main problem was that
model.Close(deviceID) was overloaded to mean "the connection was closed
by the protocol layer" and "i want to close this connection". That meant
it could get called twice - once *to* close the connection and then once
more when the connection *was* closed.
After this refactor there is instead a Closed(conn) method that is the
callback. I didn't need to change the parameter in the end, but I think
it's clearer what it means when it takes the connection that was closed
instead of a device ID. To close a connection, the new close(deviceID)
method is used instead, which only closes the underlying connection and
leaves the cleanup to the Closed() callback.
I also changed how we do connection switching. Instead of the connection
service calling close and then adding the connection, it just adds the
new connection. The model knows that it already has a connection and
makes sure to close and clean out that one before adding the new
connection.
To make sure to sequence this properly I added a new map of channels
that get created on connection add and closed by Closed(), so that
AddConnection() can do the close and wait for the cleanup to happen
before proceeding.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3490
This changes the BEP protocol to use protocol buffer serialization
instead of XDR, and therefore also the database format. The local
discovery protocol is also updated to be protocol buffer format.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3276
LGTM: AudriusButkevicius
