Mercurial: Changelog

wireproto: separate commands tables for version 1 and 2 commands We can't easily reuse existing command handlers for version 2 commands because the response types will be different. e.g. many commands return nodes encoded as hex. Our new wire protocol is binary safe, so we'll wish to encode nodes as binary. We /could/ teach each command handler to look at the protocol handler and change behavior based on the version in use. However, this would make logic a bit unwieldy over time and would make it harder to design a unified protocol handler interface. I think it's better to create a clean break between version 1 and version 2 of commands on the server. What I imagine happening is we will have separate @wireprotocommand functions for each protocol generation. Those functions will parse the request, dispatch to a common function to process it, then generate the response in its own, transport-specific manner. This commit establishes a separate table for tracking version 1 commands from version 2 commands. The HTTP server pieces have been updated to use this new table. Most commands are marked as both version 1 and version 2, so there is little practical impact to this change. A side-effect of this change is we now rely on transport registration in wireprototypes.TRANSPORTS and certain properties of the protocol interface. So a test had to be updated to conform. Differential Revision: https://phab.mercurial-scm.org/D2982

wireproto: mark SSHv2 as a version 1 transport The version component is used for filtering/routing wire protocol commands to their proper handler. The actual version 2 of the wire protocol commands will use a different encoding of responses. We already have tests using the version 2 SSH transport and version 2 of the wire protocol commands won't be implemented atomically. This commit marks the SSHv2 transport as version 1 so it will still invoke the version 1 commands. Once the commands are all implemented in version 2, we can restore its proper behavior. Some tests had to be disabled as a result of this change. Differential Revision: https://phab.mercurial-scm.org/D2981

wireproto: stop aliasing wire protocol types (API) We generally shy away from aliasing module symbols. I think I was keeping this around for API compatibility. We've already made tons of other API breaks in the wire protocol code this release. What's one more? .. api:: ``wireproto`` module no longer re-exports various types used to define responses to wire protocol commands. Access these types from the ``wireprototypes`` module. Differential Revision: https://phab.mercurial-scm.org/D2979

wireproto: use CBOR for command requests Now that we're using CBOR in the new wire protocol, let's convert command requests to it. Before I wrote this patch and was even thinking about CBOR, I was thinking about how commands should be issued and came to the conclusion that we didn't need separate frames to represent the command name from its arguments. I already had a partially completed patch prepared to merge the frames. But with CBOR, it makes the implementation a bit simpler because we don't need to roll our own serialization. The changes here are a bit invasive. I tried to split this into multiple commits to make it easier to review. But it was just too hard. * "command name" and "command argument" frames have been collapsed into a "command request" frame. * The flags for this new frame are totally different. * Frame processing has been overhauled to reflect the new order of things. * Test fallout was significant. A handful of tests were removed. Altogether, I think the new code is simpler. We don't have complicated state around receiving commands. We're either receiving command request frames or command data frames. We /could/ potentially collapse command data frames into command request frames. Although I'd have to think a bit more about this before I do it. Differential Revision: https://phab.mercurial-scm.org/D2951

wireproto: define frame to represent progress updates Today, a long-running operation on a server may run without any sign of progress on the client. This can lead to the conclusion that the server has hung or the connection has dropped. In fact, connections can and do time out due to inactivity. And a long-running server operation can result in the connection dropping prematurely because no data is being sent! While we're inventing the new wire protocol, let's provide a mechanism for communicating progress on potentially expensive server-side events. We introduce a new frame type that conveys "progress" updates. This frame type essentially holds the data required to formulate a ``ui.progress()`` call. We only define the frame right now. Implementing it will be a bit of work since there is no analog to progress frames in the existing wire protocol. We'll need to teach the ui object to write to the wire protocol, etc. The use of a CBOR map may seem wasteful, as this will encode key names in every frame. This *is* wasteful. However, maps are extensible. And the intent is to always use compression via streams. Compression will make the overhead negligible since repeated strings will be mostly eliminated over the wire. Differential Revision: https://phab.mercurial-scm.org/D2902

wireproto: syntax for encoding CBOR into frames We just vendored a library for encoding and decoding the CBOR data format. While the intent of that vendor was to support state files, CBOR is really a nice data format. It is extensible and compact. I've been feeling dirty inventing my own data formats for frame payloads. While custom formats can always beat out a generic format, there is a cost to be paid in terms of implementation, comprehension, etc. CBOR is compact enough that I'm not too worried about efficiency loss. I think the benefits of using a standardized format outweigh rolling our own formats. So I plan to make heavy use of CBOR in the wire protocol going forward. This commit introduces support for encoding CBOR data in frame payloads to our function to make a frame from a human string. We do need to employ some low-level Python code in order to evaluate a string as a Python expression. But other than that, this should hopefully be pretty straightforward. Unit tests for this function have been added. Differential Revision: https://phab.mercurial-scm.org/D2948

wireproto: explicit API to create outgoing streams It is better to create outgoing streams through the reactor so the reactor knows about what streams are active and can track them accordingly. Test output changes slightly because frames from subsequent responses no longer have the "stream begin" stream flag set because the stream is now used across all responses. Differential Revision: https://phab.mercurial-scm.org/D2947

wireproto: add streams to frame-based protocol Previously, the frame-based protocol was just a series of frames, with each frame associated with a request ID. In order to scale the protocol, we'll want to enable the use of compression. While it is possible to enable compression at the socket/pipe level, this has its disadvantages. The big one is it undermines the point of frames being standalone, atomic units that can be read and written: if you add compression above the framing protocol, you are back to having a stream-based protocol as opposed to something frame-based. So in order to preserve frames, compression needs to occur at the frame payload level. Compressing each frame's payload individually will limit compression ratios because the window size of the compressor will be limited by the max frame size, which is 32-64kb as currently defined. It will also add CPU overhead, as it is more efficient for compressors to operate on fewer, larger blocks of data than more, smaller blocks. So compressing each frame independently is out. This means we need to compress each frame's payload as if it is part of a larger stream. The simplest approach is to have 1 stream per connection. This could certainly work. However, it has disadvantages (documented below). We could also have 1 stream per RPC/command invocation. (This is the model HTTP/2 goes with.) This also has disadvantages. The main disadvantage to one global stream is that it has the very real potential to create CPU bottlenecks doing compression. Networks are only getting faster and the performance of single CPU cores has been relatively flat. Newer compression formats like zstandard offer better CPU cycle efficiency than predecessors like zlib. But it still all too common to saturate your CPU with compression overhead long before you saturate the network pipe. The main disadvantage with streams per request is that you can't reap the benefits of the compression context for multiple requests. For example, if you send 1000 RPC requests (or HTTP/2 requests for that matter), the response to each would have its own compression context. The overall size of the raw responses would be larger because compression contexts wouldn't be able to reference data from another request or response. The approach for streams as implemented in this commit is to support N streams per connection and for streams to potentially span requests and responses. As explained by the added internals docs, this facilitates servers and clients delegating independent streams and compression to independent threads / CPU cores. This helps alleviate the CPU bottleneck of compression. This design also allows compression contexts to be reused across requests/responses. This can result in improved compression ratios and less overhead for compressors and decompressors having to build new contexts. Another feature that was defined was the ability for individual frames within a stream to declare whether that individual frame's payload uses the content encoding (read: compression) defined by the stream. The idea here is that some servers may serve data from a combination of caches and dynamic resolution. Data coming from caches may be pre-compressed. We want to facilitate servers being able to essentially stream bytes from caches to the wire with minimal overhead. Being able to mix and match with frames are compressed within a stream enables these types of advanced server functionality. This commit defines the new streams mechanism. Basic code for supporting streams in frames has been added. But that code is seriously lacking and doesn't fully conform to the defined protocol. For example, we don't close any streams. And support for content encoding within streams is not yet implemented. The change was rather invasive and I didn't think it would be reasonable to implement the entire feature in a single commit. For the record, I would have loved to reuse an existing multiplexing protocol to build the new wire protocol on top of. However, I couldn't find a protocol that offers the performance and scaling characteristics that I desired. Namely, it should support multiple compression contexts to facilitate scaling out to multiple CPU cores and compression contexts should be able to live longer than single RPC requests. HTTP/2 *almost* fits the bill. But the semantics of HTTP message exchange state that streams can only live for a single request-response. We /could/ tunnel on top of HTTP/2 streams and frames with HEADER and DATA frames. But there's no guarantee that HTTP/2 libraries and proxies would allow us to use HTTP/2 streams and frames without the HTTP message exchange semantics defined in RFC 7540 Section 8. Other RPC protocols like gRPC tunnel are built on top of HTTP/2 and thus preserve its semantics of stream per RPC invocation. Even QUIC does this. We could attempt to invent a higher-level stream that spans HTTP/2 streams. But this would be violating HTTP/2 because there is no guarantee that HTTP/2 streams are routed to the same server. The best we can do - which is what this protocol does - is shoehorn all request and response data into a single HTTP message and create streams within. At that point, we've defined a Content-Type in HTTP parlance. It just so happens our media type can also work as a standalone, stream-based protocol, without leaning on HTTP or similar protocol. Differential Revision: https://phab.mercurial-scm.org/D2907

Added signature for changeset 7de7bd407251

Added tag 4.5.3 for changeset 7de7bd407251

wireproto: start to associate frame generation with a stream An upcoming commit will introduce "streams" into the frame-based wire protocol. In preparation for this invasive change, we introduce a basic "stream" class and have all operations that create frames also operate alongside a stream instance. Differential Revision: https://phab.mercurial-scm.org/D2906

tests: fix duplicate and failing test There were two "testconflictingrequestid" methods. Naturally this isn't an error in Python. And by our luck, the test was failing. So we rename the test and fix it to pass. As part of this, _sendsingleframe() now takes a frame, not a string describing the frame. This is better because action at a distance can be confusing. Differential Revision: https://phab.mercurial-scm.org/D2950

debugcommands: drop offset and length from debugindex by default These fields are an implementation detail of revlog storage. As such, they are not part of the generic storage "index" interface and shouldn't be displayed by default. Because we don't have another way to display these fields, we've retained support for printing these fields via --verbose. Yes, I know we should probably be doing all this formatting using modern formatting/templater APIs. I didn't feel like scope bloating this patch. Differential Revision: https://phab.mercurial-scm.org/D3028

debugcommands: drop base revision from debugindex Revlog index data consists of generic index metadata that will likely be implemented across all storage engines and revlog-specifc metadata. Most tests printing index data only care about the generic fields. This commit drops the printing of the base revision from `hg debugindex`. This value is an implementation detail of revlogs / delta chains. If tests are interested in verifying this implementation detail, `hg debugdeltachain` is a better command. Most tests were skipping over this field anyway. Tests that weren't looked like they were newer. So my guess is we forgot to make them skip the field to match the style of the older tests. This reinforces my belief that the base revision is not worth having in `hg debugindex`. Differential Revision: https://phab.mercurial-scm.org/D3027

tests: use debugdeltachain where appropriate Some tests are verifying delta chain type things. This metadata has more to do with a revlog implementation details than index data, which is theoretically generic. This commit ports some tests to `hg debugdeltachain`, as it is the more appropriate debug command for looking at delta metadata. Differential Revision: https://phab.mercurial-scm.org/D3026

tests: don't use revlog paths in tests Debug commands operating on revlogs don't need the full revlog path: they can accept the relative path to a tracked file or use -c/-m to specify a changelog or manifest. Not using the revlog path makes tests more resilient to cases where revlogs aren't being used for storage. Differential Revision: https://phab.mercurial-scm.org/D3025

templater: define interface for objects requiring unwrapvalue() unwrapvalue() is changed to not return a lazy bytes generator for "wrapped" types because I want to define the tovalue() interface as such. It's a baby step to unify unwrapvalue() and _unwrapvalue().

templater: extract private function to evaluate generator to byte string

templater: pass (context, mapping) down to unwrapvalue() The same reason as why I made unwraphybrid() take a (context, mapping) pair.

templater: drop unneeded generator from mappable object Per the definition of the show() interface, it can return a bytes.

templater: mark .gen as a private attribute

templatekw: do not directly call .gen

templater: define interface for objects requiring unwraphybrid() Prepares for introducing another hybrid-like data type. show() takes context as an argument so a wrapper class may render its items by pre-configured template: def show(self, context, mapping): return (context.expand(self._tmpl, mapping + lm) for lm in self._mappings)

templater: pass (context, mapping) down to unwraphybrid() See the subsequent patches for why. I initially thought it would be wrong to pass a mapping to flatten() and stringify() since these functions may be applied to a tree of generators, where each node should be bound to the mapping when it was evaluated. But, actually that isn't a problem. If an intermediate node has to override a mapping dict, it can do on unwraphybrid() and yield "unwrapped" generator of byte strings: "{f(g(v))}" # literal template example. ^^^^ # g() want to override a mapping, so it returns a wrapped # object 'G{V}' with partial mapping 'lm' attached. ^^^^^^^ # f() stringifies 'G{V}', starting from a mapping 'm'. # when unwrapping 'G{}', it updates 'm' with 'lm', and # passes it to 'V'. This structure is important for the formatter (and the hgweb) to build a static template keyword, which can't access a mapping dict until evaluation phase.

scmutil: add method for looking up a context given a revision symbol changectx's constructor currently supports a mix if inputs: * integer revnums * binary nodeids * '.', 'tip', 'null' * stringified revnums * namespaced identifiers (e.g. bookmarks and tags) * hex nodeids * partial hex nodeids The first two are always internal [1]. The other five can be specified by the user. The third type ('.', 'tip', 'null') often comes from either the user or internal callers. We probably have some internal callers that pass hex nodeids too, perhaps even partial ones (histedit?). There are only a few callers that pass user-supplied strings: revsets.stringset, peer.lookup, webutil.changeidctx, and maybe one or two more. Supporting this mix of things in the constructor is convenient, but a bit strange, IMO. For example, if repo[node] is given a node that's not in the repo, it will first check if it's bookmark etc before raising an exception. Of course, the risk of it being a bookmark is extremely small, but it just feels ugly. Also, a problem with having this code in the constructor (whether it supports a mix of types or not) is that it's harder to override (I'd like to override it, and that's how this series started). This patch starts moving out the handling of user-supplied strings by introducing scmutil.revsymbol(). So far, that just checks that the input is indeed a string, and then delegates to repo[symbol]. The patch also calls it from revsets.stringset to prove that it works. [1] Well, you probably can enter a 20-byte binary nodeid on the command line, but I don't think we should care to preserve support for that. Differential Revision: https://phab.mercurial-scm.org/D3024