This is the more typically way to do [Argument-dependent
lookup](https://en.cppreference.com/w/cpp/language/adl)-leveraging
generic serializers in C++. It makes the relationship between the `read`
and `write` methods more clear and rigorous, and also looks more
familiar to users coming from other languages that do not have C++'s
libertine ad-hoc overloading.
I am returning to this because during the review in
https://github.com/NixOS/nix/pull/6223, it came up as something that
would make the code easier to read --- easier today hopefully already,
but definitely easier if we were have multiple codified protocols with
code sharing between them as that PR seeks to accomplish.
If I recall correctly, the main criticism of this the first time around
(in 2020) was that having to specify the type when writing, e.g.
`WorkerProto<MyType>::write`, was too verbose and cumbersome. This is
now addressed with the `workerProtoWrite` wrapper function.
This method is also the way `nlohmann::json`, which we have used for a
number of years now, does its serializers, for what its worth.
This reverts commit 45a0ed82f0. That
commit in turn reverted 9ab07e99f5.
In many cases we are dealing with a collection of realisations, they are
all outputs of the same derivation. In that case, we don't need
"derivation hashes modulos" to be part of our map key, because the
output names alone will be unique. Those hashes are still part of the
realisation proper, so we aren't loosing any information, we're just
"normalizing our schema" by narrowing the "primary key".
Besides making our data model a bit "tighter" this allows us to avoid a
double `for` loop in `DerivationGoal::waiteeDone`. The inner `for` loop
was previously just to select the output we cared about without knowing
its hash. Now we can just select the output by name directly.
Note that neither protocol is changed as part of this: we are still
transferring `DrvOutputs` over the wire for `BuildResult`s. I would only
consider revising this once #6223 is merged, and we can mention protocol
versions inside factored-out serialization logic. Until then it is
better not change anything because it would come a the cost of code
reuse.
In https://github.com/NixOS/nix/pull/6311#discussion_r834863823, I
realized since derivation goals' wanted outputs can "grow" due to
overlapping dependencies (See `DerivationGoal::addWantedOutputs`, called
by `Worker::makeDerivationGoalCommon`), the previous bug fix had an
unfortunate side effect of causing more pointless rebuilds.
In paticular, we have this situation:
1. Goal made from `DerivedPath::Built { foo, {a} }`.
2. Goal gives on on substituting, starts building.
3. Goal made from `DerivedPath::Built { foo, {b} }`, in fact is just
modified original goal.
4. Though the goal had gotten as far as building, so all outputs were
going to be produced, `addWantedOutputs` no longer knows that and so
the goal is flagged to be restarted.
This might sound far-fetched with input-addressed drvs, where we usually
basically have all our goals "planned out" before we start doing
anything, but with CA derivation goals and especially RFC 92, where *drv
resolution* means goals are created after some building is completed, it
is more likely to happen.
So the first thing to do was restore the clearing of `wantedOutputs` we
used to do, and then filter the outputs in `buildPathsWithResults` to
only get the ones we care about.
But fix also has its own side effect in that the `DerivedPath` in the
`BuildResult` in `DerivationGoal` cannot be trusted; it is merely the
*first* `DerivedPath` for which this goal was originally created.
To remedy this, I made `BuildResult` be like it was before, and instead
made `KeyedBuildResult` be a subclass wit the path. Only
`buildPathsWithResults` returns `KeyedBuildResult`s, everything else
just becomes like it was before, where the "key" is unambiguous from
context.
I think separating the "primary key" field(s) from the other fields is
good practical in general anyways. (I would like to do the same thing
for `ValidPathInfo`.) Among other things, it allows constructions like
`std::map<Key, ThingWithKey>` where doesn't contain duplicate keys and
just precludes the possibility of those duplicate keys being out of
sync.
We might leverage the above someday to overload `buildPathsWithResults`
to take a *set* of return a *map* per the above.
-----
Unfortunately, we need to avoid C++20 strictness on designated
initializers.
(BTW
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2287r1.html
this offers some new syntax for this use-case. Hopefully this will be
adopted and we can eventually use it.)
No having that yet, maybe it would be better to not make
`KeyedBuildResult` a subclass to just avoid this.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
More progress on issue #5729
The method trivially generalizes to be store-implementation-agnostic, in
fact.
However, we force it to continue to be unimplemented with `RemoteStore`
and `LegacySSHStore` because the implementation we'd get via the
generalization is probably not the one users expect. This keeps our
hands untied to do it right going forward.
For more about the tension between the scheduler logic being
store-type-agnostic and remote stores doing their own scheduling, see
issues #5025 and #5056.
More progress on issue #5729.
Instead of having it by the default method in `Store` itself, have it be
the implementation in `DummyStore` and `LegacySSHStore`. Then just the
implementations which fail to provide the method pay the "penalty" of
dealing with the icky `unimplemented` function for non-compliance.
Combined with my other recent PRs, this finally makes `Store` have no
`unsupported` calls!
This function returns true or false depending on whether the Nix client
is trusted or not. Mostly relevant when speaking to a remote store with
a daemon.
We include this information in `nix ping store` and `nix doctor`
Co-Authored-By: John Ericson <John.Ericson@Obsidian.Systems>
The references set seems to have been unused since `LegacySSHStore`
references were first created in
caa5793b4a.
The method decls never were upstream, and accidentally added by me in
062533f7cd (probably due to `git rerere`).
Sorry!
This reduces the diff from #3746.
These only functioned if a very narrow combination of conditions held:
- The result path does not yet exist (--check did not result in
repeated builds), AND
- The result path is not available from any configured substituters, AND
- No remote builders that can build the path are available.
If any of these do not hold, a derivation would be built 0 or 1 times
regardless of the repeat option. Thus, remove it to avoid confusion.
I had started the trend of doing `std::visit` by value (because a type
error once mislead me into thinking that was the only form that
existed). While the optomizer in principle should be able to deal with
extra coppying or extra indirection once the lambdas inlined, sticking
with by reference is the conventional default. I hope this might even
improve performance.
This is important if the remote side *does* execute
nix-store/nix-daemon successfully, but stdout is polluted
(e.g. because the remote user's bashrc script prints something to
stdout). In that case we have to shutdown the write side to force the
remote nix process to exit.
Instead of
error: serialised integer 7161674624452356180 is too large for type 'j'
we now get
error: 'nix-store --serve' protocol mismatch from 'sshtest@localhost', got 'This account is currently not available.'
Fixes https://github.com/NixOS/nixpkgs/issues/37287.
When doing e.g.
nix-build -A package --keep-failed --option \
builders \
'ssh://mfhydra?remote-store=/home/bosch/store x86_64-linux - 10 4 big-parallel'
this doesn't work properly because this build-setting is ignored.
I changed this behavior by passing the `settings.keepFailed` through the
serve-protocol to remote machines to make sure that I can introspect the
build-directory (which is particularly helpful when I have to look at a
`config.log` from a failed build for instance).
With this, we don't have to copy the entire .drv closure to the
destination store ahead of time (or at all). Instead, buildPaths()
reads .drv files from the eval store and copies inputSrcs to the
destination store if it needs to build a derivation.
Issue #5025.
This avoids an ambiguity where the `StorePathWithOutputs { drvPath, {}
}` could mean "build `brvPath`" or "substitute `drvPath`" depending on
context.
It also brings the internals closer in line to the new CLI, by
generalizing the `Buildable` type is used there and makes that
distinction already.
In doing so, relegate `StorePathWithOutputs` to being a type just for
backwards compatibility (CLI and RPC).
This is already used by Hydra, and is very useful when materializing
a remote builder list from service discovery. This allows the service
discovery tool to only sync one file instead of two.
We embrace virtual the rest of the way, and get rid of the
`assert(false)` 0-param constructors.
We also list config base classes first, so the constructor order is
always:
1. all the configs
2. all the stores
Each in the same order
For each known realisation, store:
- its output
- its output path
This comes with a set of needed changes:
- New `realisations` module declaring the types needed for describing
these mappings
- New `Store::registerDrvOutput` method registering all the needed informations
about a derivation output (also replaces `LocalStore::linkDeriverToPath`)
- new `Store::queryRealisation` method to retrieve the informations for a
derivations
This introcudes some redundancy on the remote-store side between
`wopQueryDerivationOutputMap` and `wopQueryRealisation`.
However we might need to keep both (regardless of backwards compat)
because we sometimes need to get some infos for all the outputs of a
derivation (where `wopQueryDerivationOutputMap` is handy), but all the
stores can't implement it − because listing all the outputs of a
derivation isn't really possible for binary caches where the server
doesn't allow to list a directory.
