docs(tvix): Begin documenting the Nix daemon protocol r/8154

This adds rough notes documenting the history of the Nix
daemon protocol, how logging works as well as begins
documenting inputs and outputs for all operations.

Change-Id: Id24a9a658c3e4e7c350ca1e4622f63ed96ccef5a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11594
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

1 files changed, 894 insertions, 0 deletions

diff --git a/tvix/docs/src/nix-daemon/operations.md b/tvix/docs/src/nix-daemon/operations.md
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+
+# TOC
+
+| Operation                                                   | Id |
+| ----------------------------------------------------------- | -- |
+| [IsValidPath](#isvalidpath)                                 | 1  |
+| [HasSubstitutes](#hassubstitutes)                           | 3  |
+| [QueryReferrers](#queryreferrers)                           | 6  |
+| [AddToStore](#addtostore)                                   | 7  |
+| [BuildPaths](#buildpaths)                                   | 9  |
+| [EnsurePath](#ensurepath)                                   | 10 |
+| [AddTempRoot](#addtemproot)                                 | 11 |
+| [AddIndirectRoot](#addindirectroot)                         | 12 |
+| [FindRoots](#findroots)                                     | 14 |
+| [SetOptions](#setoptions)                                   | 19 |
+| [CollectGarbage](#collectgarbage)                           | 20 |
+| [QuerySubstitutablePathInfo](#querysubstitutablepathinfo)   | 21 |
+| [QueryAllValidPaths](#queryallvalidpaths)                   | 23 |
+| [QueryPathInfo](#querypathinfo)                             | 26 |
+| [QueryPathFromHashPart](#querypathfromhashpart)             | 29 |
+| [QuerySubstitutablePathInfos](#querysubstitutablepathinfos) | 30 |
+| [QueryValidPaths](#queryvalidpaths)                         | 31 |
+| [QuerySubstitutablePaths](#querysubstitutablepaths)         | 32 |
+| [QueryValidDerivers](#queryvalidderivers)                   | 33 |
+| [OptimiseStore](#optimisestore)                             | 34 |
+| [VerifyStore](#verifystore)                                 | 35 |
+| [BuildDerivation](#buildderivation)                         | 36 |
+| [AddSignatures](#addsignatures)                             | 37 |
+| [NarFromPath](#narfrompath)                                 | 38 |
+| [AddToStoreNar](#addtostore)                                | 39 |
+| [QueryMissing](#querymissing)                               | 40 |
+| [QueryDerivationOutputMap](#queryderivationoutputmap)       | 41 |
+| [RegisterDrvOutput](#registerdrvoutput)                     | 42 |
+| [QueryRealisation](#queryrealisation)                       | 43 |
+| [AddMultipleToStore](#addmultipletostore)                   | 44 |
+| [AddBuildLog](#addbuildlog)                                 | 45 |
+| [BuildPathsWithResults](#buildpathswithresults)             | 46 |
+| [AddPermRoot](#addpermroot)                                 | 47 |
+
+
+## Obsolete operations
+
+| Operation                                                 | Id |
+| --------------------------------------------------------- | -- |
+| [QueryPathHash](#querypathhash)                           | 4  |
+| [QueryReferences](#queryreferences)                       | 5  |
+| [AddTextToStore](#addtexttostore)                         | 8  |
+| [SyncWithGC](#syncwithgc)                                 | 13 |
+| [ExportPath](#exportpath)                                 | 16 |
+| [QueryDeriver](#queryderiver)                             | 18 |
+| [QueryDerivationOutputs](#queryderivationoutputs)         | 22 |
+| [ImportPaths](#importpaths)                               | 27 |
+| [QueryDerivationOutputNames](#queryderivationoutputnames) | 28 |
+
+
+## Removed operations
+
+| Operation                                         | Id |
+| ------------------------------------------------- | -- |
+| [Quit](#quit-removed)                             | 0  |
+| [ImportPath](#importpath-removed)                 | 17 |
+| [Old CollectGarbage](#old-collectgarbage-removed) | 15 |
+| [QueryFailedPaths](#queryfailedpaths)             | 24 |
+| [ClearFailedPaths](#clearfailedpaths)             | 25 |
+
+
+
+## Quit (removed)
+
+**Id:** 0<br>
+**Introduced:** Nix 0.11<br>
+**Removed:** Became dead code in Nix 0.11 and removed in Nix 1.8
+
+
+## IsValidPath
+
+**Id:** 1<br>
+**Introduced:** Nix 0.11<br>
+
+As the name says checks that a store path is valid i.e. in the store.
+
+This is a pretty core operation used everywhere.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+isValid :: [Bool][se-Bool]
+
+
+## HasSubstitutes
+
+**Id:** 3<br>
+**Introduced:** Nix 0.11<br>
+
+Checks if we can substitute the input path from a substituter. Uses
+QuerySubstitutablePaths under the hood :/
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+hasSubstitutes :: [Bool][se-Bool]
+
+
+## QueryPathHash
+
+**Id:** 4<br>
+**Introduced:** Nix 0.11<br>
+**Obsolete:** Protocol 1.16, Nix 2.0<br>
+
+Retrieves the base16 NAR hash of a given store path.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+hash :: [String][se-String] (base16-encoded NAR hash without algorithm prefix)
+
+
+## QueryReferences
+
+**Id:** 5<br>
+**Introduced:** Nix 0.11<br>
+**Obsolete:** Protocol 1.16, Nix 2.0<br>
+
+Retrieves the references of a given path
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+references :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## QueryReferrers
+
+**Id:** 6<br>
+**Introduced:** Nix 0.11<br>
+
+Retrieves the referrers of a given path.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+referrers :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## AddToStore
+
+**Id:** 7<br>
+**Introduced:** Nix 0.11<br>
+
+Add a new path to the store.
+
+### Before protocol version 1.25
+#### Inputs
+- baseName :: [String][se-String]
+- fixed :: [Bool64][se-Bool64]
+- recursive :: [FileIngestionMethod][se-FileIngestionMethod]
+- hashAlgo :: [String][se-String]
+- NAR dump
+
+If fixed is `true`, hashAlgo is forced to `sha256` and recursive is forced to
+`Recursive`.
+
+Only `Flat` and `Recursive` values are supported for the recursive input
+parameter.
+
+#### Outputs
+path :: [StorePath][se-StorePath]
+
+### Protocol version 1.25 or newer
+#### Inputs
+- name :: [String][se-String]
+- camStr :: [ContentAddressMethodWithAlgo][se-ContentAddressMethodWithAlgo]
+- refs :: [List][se-List] of [StorePath][se-StorePath]
+- repairBool :: [Bool64][se-Bool64]
+- [Framed][se-Framed] NAR dump
+
+#### Outputs
+info :: [ValidPathInfo][se-ValidPathInfo]
+
+
+## AddTextToStore
+
+**Id:** 8<br>
+**Introduced:** Nix 0.11<br>
+**Obsolete:** Protocol 1.25, Nix 2.4
+
+Add a text file as a store path.
+
+This was obsoleted by adding the functionality implemented by this operation
+to [AddToStore](#addtostore). And so this corresponds to calling
+[AddToStore](#addtostore) with `camStr` set to `text:sha256` and `text`
+wrapped as a NAR.
+
+### Inputs
+- suffix :: [String][se-String]
+- text :: [Bytes][se-Bytes]
+- refs :: [List][se-List] of [StorePath][se-StorePath]
+
+### Outpus
+path :: [StorePath][se-StorePath]
+
+
+## BuildPaths
+
+**Id:** 9<br>
+****Introduced:**** Nix 0.11<br>
+
+Build (or substitute) a list of derivations.
+
+### Inputs
+paths :: [List][se-List] of [DerivedPath][se-DerivedPath]
+
+#### Protocol 1.15 or newer
+mode :: [BuildMode][se-BuildMode]
+
+Check that connection is trusted before allowing Repair mode.
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## EnsurePath
+
+**Id:** 10<br>
+**Introduced:** Nix 0.11<br>
+
+Checks if a path is valid. Note: it may be made valid by running a substitute.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## AddTempRoot
+
+**Id:** 11<br>
+**Introduced:** Nix 0.11<br>
+
+Creates a temporary GC root for the given store path.
+
+Temporary GC roots are valid only for the life of the connection and are used
+primarily to prevent the GC from pulling the rug out from under the client and
+deleting store paths that the client is actively doing something with.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## AddIndirectRoot
+
+**Id:** 12<br>
+**Introduced:** Nix 0.11<br>
+
+Add an indirect root, which is a weak reference to the user-facing symlink
+created by [AddPermRoot](#addpermroot).
+
+Only ever sent on the local unix socket nix daemon.
+
+### Inputs
+path :: [String][se-String]
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## SyncWithGC
+
+**Id:** 13<br>
+**Introduced:** Nix 0.11<br>
+**Obsolete:** Protocol 1.32, Nix 2.5.0
+
+Acquire the global GC lock, then immediately release it.  This function must be
+called after registering a new permanent root, but before exiting.  Otherwise,
+it is possible that a running garbage collector doesn't see the new root and
+deletes the stuff we've just built.  By acquiring the lock briefly, we ensure
+that either:
+
+- The collector is already running, and so we block until the
+    collector is finished.  The collector will know about our
+    *temporary* locks, which should include whatever it is we
+    want to register as a permanent lock.
+- The collector isn't running, or it's just started but hasn't
+    acquired the GC lock yet.  In that case we get and release
+    the lock right away, then exit.  The collector scans the
+    permanent root and sees ours.
+
+In either case the permanent root is seen by the collector.
+
+Was made obsolete by using [AddTempRoot](#addtemproot) to accomplish the same
+thing.
+
+
+## FindRoots
+
+**Id:** 14<br>
+**Introduced:** Nix 0.11<br>
+
+Find the GC roots.
+
+### Outputs
+roots :: [Map][se-Map] of [String][se-String] to [StorePath][se-StorePath]
+
+The key is the link pointing to the given store path.
+
+
+## Old CollectGarbage (removed)
+
+**Id:** 15<br>
+**Introduced:** Nix 0.11<br>
+**Removed:** Protocol 1.02, Nix 0.12<br>
+
+
+## ExportPath
+
+**Id:** 16<br>
+**Introduced:** Nix 0.11<br>
+**Obsolete:** Protocol 1.17, Nix 2.0<br>
+
+Export a store path in the binary format nix-store --import expects. See implementation there https://github.com/NixOS/nix/blob/db3bf180a569cb20db42c5e4669d2277be6f46b6/src/libstore/export-import.cc#L29 for more details.
+
+### Inputs
+- path :: [StorePath][se-StorePath]
+- sign :: [Int][se-Int] (ignored and hardcoded to 0 in client)
+
+### Outputs
+Uses `STDERR_WRITE` to send dump in export format
+
+After dump it outputs.
+
+1 :: [Int][se-Int] (hardcoded)
+
+
+## ImportPath (removed)
+
+**Id:** 17<br>
+**Introduced:** Nix 0.11<br>
+**Removed:** Protocol 1.09, Nix 1.0<br>
+
+
+## QueryDeriver
+
+**Id:** 18<br>
+**Introduced:** Nix 0.11<br>
+**Obsolete:** Protocol 1.16, Nix 2.0<br>
+
+Returns the store path of the derivation for a given store path.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+deriver :: [OptStorePath][se-OptStorePath]
+
+
+## SetOptions
+
+**Id:** 19<br>
+**Introduced:** Nix 0.11<br>
+
+Sends client options to the remote side.
+
+Only ever used right after the handshake.
+
+### Inputs
+
+- keepFailed :: [Int][se-Int]
+- keepGoing :: [Int][se-Int]
+- tryFallback :: [Int][se-Int]
+- verbosity :: [Verbosity][se-Verbosity]
+- maxbuildJobs :: [Int][se-Int]
+- maxSilentTime :: [Int][se-Int]
+- useBuildHook :: [Bool][se-Bool] (ignored and hardcoded to true in client)
+- verboseBuild :: [Verbosity][se-Verbosity]
+- logType :: [Int][se-Int] (ignored and hardcoded to 0 in client)
+- printBuildTrace :: [Int][se-Int] (ignored and hardcoded to 0 in client)
+- buildCores :: [Int][se-Int]
+- useSubstitutes :: [Int][se-Int]
+
+### Protocol 1.12 or newer
+otherSettings :: [Map][se-Map] of [String][se-String] to [String][se-String]
+
+
+## CollectGarbage
+
+**Id:** 20<br>
+**Introduced:** Protocol 1.02, Nix 0.12<br>
+
+Find the GC roots.
+
+### Inputs
+- action :: [GCAction][se-GCAction]
+- pathsToDelete :: [List][se-List] of [StorePath][se-StorePath]
+- ignoreLiveness :: [Bool64][se-Bool64]
+- maxFreed :: [UInt64][se-UInt64]
+- removed :: [Int][se-Int] (ignored and hardcoded to 0 in client)
+- removed :: [Int][se-Int] (ignored and hardcoded to 0 in client)
+- removed :: [Int][se-Int] (ignored and hardcoded to 0 in client)
+
+### Outputs
+- pathsDeleted :: [List][se-List] of [String][se-String]
+- bytesFreed :: [UInt64][se-UInt64]
+- 0 :: [UInt64][se-UInt64] (hardcoded)
+
+Depending on the action pathsDeleted is, the GC roots, or the paths that would
+be or have been deleted.
+
+
+## QuerySubstitutablePathInfo
+
+**Id:** 21<br>
+**Introduced:** Protocol 1.02, Nix 0.12<br>
+
+Retrieves the various substitutable paths infos for a given path.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+found :: [Bool][se-Bool]
+
+#### If found is true
+- deriver :: [OptStorePath][se-OptStorePath]
+- references :: [List][se-List] of [StorePath][se-StorePath]
+- downloadSize :: [UInt64][se-UInt64]
+- narSize :: [UInt64][se-UInt64]
+
+
+## QueryDerivationOutputs
+
+**Id:** 22<br>
+**Introduced:** Protocol 1.05, Nix 1.0<br>
+**Obsolete:** Protocol 1.22*, Nix 2.4<br>
+
+Retrieves all the outputs paths of a given derivation.
+
+### Inputs
+path :: [StorePath][se-StorePath] (must point to a derivation)
+
+### Outputs
+derivationOutputs :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## QueryAllValidPaths
+
+**Id:** 23<br>
+**Introduced:** Protocol 1.05, Nix 1.0<br>
+
+Retrieves all the valid paths contained in the store.
+
+### Outputs
+paths :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## QueryFailedPaths (removed)
+
+**Id:** 24<br>
+**Introduced:** Protocol 1.05, Nix 1.0<br>
+**Removed:** Protocol 1.16, Nix 2.0<br>
+
+Failed build caching API only ever used by Hydra.
+
+
+## ClearFailedPaths (removed)
+
+**Id:** 25<br>
+**Introduced:** Protocol 1.05, Nix 1.0<br>
+**Removed:** Protocol 1.16, Nix 2.0<br>
+
+Failed build caching API only ever used by Hydra.
+
+
+## QueryPathInfo
+
+**Id:** 26<br>
+**Introduced:** Protocol 1.06, Nix 1.0<br>
+
+Retrieves the pathInfo for a given path.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+
+#### If protocol version is 1.17 or newer
+success :: [Bool64][se-Bool64]
+
+##### If success is true
+pathInfo :: [UnkeyedValidPathInfo][se-UnkeyedValidPathInfo]
+
+#### If protocol version is older than 1.17
+If info not found return error with `STDERR_ERROR`
+
+pathInfo :: [UnkeyedValidPathInfo][se-UnkeyedValidPathInfo]
+
+
+## ImportPaths
+
+**Id:** 27<br>
+**Introduced:** Protocol 1.09, Nix 1.0<br>
+**Obsolete:** Protocol 1.17, Nix 2.0<br>
+
+Older way of adding a store path to the remote store.
+
+It was obsoleted and replaced by AddToStoreNar because it sends the NAR
+before the metadata about the store path and so you would typically have
+to store the NAR in memory or temporarily on disk before processing it.
+
+### Inputs
+List of NAR dumps coming from the ExportPaths operations.
+
+### Outputs
+importedPaths :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## QueryDerivationOutputNames
+
+**Id:** 28<br>
+**Introduced:** Protocol 1.08, Nix 1.0<br>
+**Obsolete:** Protocol 1.21, Nix 2.4<br>
+
+Retrieves the name of the outputs of a given derivation. EG. out, dev, etc.
+
+### Inputs
+path :: [StorePath][se-StorePath] (must be a derivation path)
+
+### Outputs
+names :: [List][se-List] of [String][se-String]
+
+
+## QueryPathFromHashPart
+
+**Id:** 29<br>
+**Introduced:** Protocol 1.11, Nix 1.1<br>
+
+Retrieves a store path from a base16 (input) hash. Returns "" if no path was
+found.
+
+### Inputs
+hashPart :: [String][se-String]  (must be a base-16 hash)
+
+### Outputs
+path :: [OptStorePath][se-OptStorePath]
+
+
+## QuerySubstitutablePathInfos
+
+**Id:** 30<br>
+**Introduced:** Protocol 1.12*, Nix 1.2<br>
+
+Retrieves the various substitutable paths infos for set of store paths.
+
+### Inputs
+#### If protocol version is 1.22 or newer
+paths :: [Map][se-Map] of [StorePath][se-StorePath] to [OptContentAddress][se-OptContentAddress] 
+
+#### If protocol version older than 1.22
+paths :: [List][se-List] of [StorePath][se-StorePath]
+
+### Outputs
+infos :: [List][se-List] of [SubstitutablePathInfo][se-SubstitutablePathInfo]
+
+
+## QueryValidPaths
+
+**Id:** 31<br>
+**Introduced:** Protocol 1.12, Nix 1.2<br>
+
+Takes a list of store paths and returns a new list only containing the valid store paths
+
+## Inputs
+paths :: [List][se-List] of [StorePath][se-StorePath]
+
+### If protocol version is 1.27 or newer
+substitute :: [Bool][se-Bool] (defaults to false if not sent)
+
+## Outputs
+paths :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## QuerySubstitutablePaths
+
+**Id:** 32<br>
+**Introduced:** Protocol 1.12, Nix 1.2<br>
+
+Takes a set of store path, returns a filtered new set of paths that can be
+substituted.
+
+In versions of the protocol prior to 1.12 [HasSubstitutes](#hassubstitutes)
+is used to implement the functionality that this operation provides.
+
+### Inputs
+paths :: [List][se-List] of [StorePath][se-StorePath]
+
+### Outputs
+paths :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## QueryValidDerivers
+
+**Id:** 33<br>
+**Introduced:** Protocol 1.13*, Nix 1.3<br>
+
+Retrieves the derivers of a given path.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+derivers :: [List][se-List] of [StorePath][se-StorePath]
+
+
+## OptimiseStore
+
+**Id:** 34<br>
+**Introduced:** Protocol 1.14, Nix 1.8<br>
+
+Optimise store by hardlinking files with the same content.
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## VerifyStore
+
+**Id:** 35<br>
+**Introduced:** Protocol 1.14, Nix 1.9<br>
+
+Verify store either only db and existence of path or entire contents of store
+paths against the NAR hash. 
+
+### Inputs
+- checkContents :: [Bool64][se-Bool64]
+- repair :: [Bool64][se-Bool64]
+
+### Outputs
+errors :: [Bool][se-Bool]
+
+
+## BuildDerivation
+
+**Id:** 36<br>
+**Introduced:** Protocol 1.14, Nix 1.10<br>
+
+Main build operation used when remote building.
+
+When functioning as a remote builder this operation is used instead of
+BuildPaths so that it doesn't have to send the entire tree of derivations
+to the remote side first before it can start building. What this does
+instead is have a reduced version of the derivation to be built sent as
+part of its input and then only building that derivation.
+
+The paths required by the build need to be part of the remote store
+(by copying with AddToStoreNar or substituting) before this operation is
+called.
+
+### Inputs
+- drvPath :: [StorePath][se-StorePath]
+- drv :: [BasicDerivation][se-BasicDerivation]
+- buildMode :: [BuildMode][se-BuildMode]
+
+### Outputs
+buildResult :: [BuildResult][se-BuildResult]
+
+
+## AddSignatures
+
+**Id:** 37<br>
+**Introduced:** Protocol 1.16, Nix 2.0<br>
+
+Add the signatures associated to a given path.
+
+### Inputs
+- path :: [StorePath][se-StorePath]
+- signatures :: [List][se-List] of [String][se-String]
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## NarFromPath
+
+**Id:** 38<br>
+**Introduced:** Protocol 1.17, Nix 2.0<br>
+
+Main way of getting the contents of a store path to the client.
+
+As the name suggests this is done by sending a NAR file.
+
+It replaced the now obsolete ExportPath operation and is used by newer clients to
+implement the export functionality for cli. It is also used when remote building
+to transfer build results from remote builder to client.
+
+### Inputs
+path :: [StorePath][se-StorePath]
+
+### Outputs
+NAR dumped straight to the stream.
+
+
+## AddToStoreNar
+
+**Id:** 39<br>
+**Introduced:** Protocol 1.17, Nix 2.0<br>
+
+Dumps a path as a NAR
+
+### Inputs
+- path :: [StorePath][se-StorePath]
+- deriver :: [OptStorePath][se-OptStorePath]
+- narHash :: [String][se-String] SHA256 NAR hash base 16
+- references :: [List][se-List] of [StorePath][se-StorePath]
+- registrationTime :: [Time][se-Time]
+- narSize :: [UInt64][se-UInt64]
+- ultimate :: [Bool64][se-Bool64]
+- signatures :: [List][se-List] of [String][se-String]
+- ca :: [OptContentAddress][se-OptContentAddress]
+- repair :: [Bool64][se-Bool64]
+- dontCheckSigs :: [Bool64][se-Bool64]
+
+#### If protocol version is 1.23 or newer
+[Framed][se-Framed] NAR dump
+
+#### If protocol version is between 1.21 and 1.23
+NAR dump sent using `STDERR_READ`
+
+#### If protocol version is older than 1.21
+NAR dump sent raw on stream
+
+
+## QueryMissing
+
+**Id:** 40<br>
+**Introduced:** Protocol 1.19*, Nix 2.0<br>
+
+### Inputs
+targets :: [List][se-List] of [DerivedPath][se-DerivedPath]
+
+### Outputs
+- willBuild :: [List][se-List] of [StorePath][se-StorePath]
+- willSubstitute :: [List][se-List] of [StorePath][se-StorePath]
+- unknown :: [List][se-List] of [StorePath][se-StorePath]
+- downloadSize :: [UInt64][se-UInt64]
+- narSize :: [UInt64][se-UInt64]
+
+
+## QueryDerivationOutputMap
+
+**Id:** 41<br>
+**Introduced:** Protocol 1.22*, Nix 2.4<br>
+
+Retrieves an associative map outputName -> storePath for a given derivation.
+
+### Inputs
+path :: [StorePath][se-StorePath]  (must be a derivation path)
+
+### Outputs
+outputs :: [Map][se-Map] of [String][se-String] to [OptStorePath][se-OptStorePath]
+
+
+## RegisterDrvOutput
+
+**Id:** 42<br>
+**Introduced:** Protocol 1.27, Nix 2.4<br>
+
+Registers a DRV output
+
+### Inputs
+#### If protocol is 1.31 or newer
+realisation :: [Realisation][se-Realisation]
+
+#### If protocol is older than 1.31
+- outputId :: [DrvOutput][se-DrvOutput]
+- outputPath :: [StorePath][se-StorePath]
+
+
+## QueryRealisation
+
+**Id:** 43<br>
+**Introduced:** Protocol 1.27, Nix 2.4<br>
+
+Retrieves the realisations attached to a drv output id realisations.
+
+### Inputs
+outputId :: [DrvOutput][se-DrvOutput]
+
+### Outputs
+#### If protocol is 1.31 or newer
+realisations :: [List][se-List] of [Realisation][se-Realisation]
+
+#### If protocol is older than 1.31
+outPaths :: [List][se-List] of [BaseStorePath][se-BaseStorePath]
+
+
+## AddMultipleToStore
+
+**Id:** 44<br>
+**Introduced:** Protocol 1.32*, Nix 2.4<br>
+
+A pipelined version of [AddToStoreNar](#addtostorenar) where you can add
+multiple paths in one go.
+
+Added because the protocol doesn't support pipelining and so on a low latency
+connection waiting for the request/response of [AddToStoreNar](#addtostorenar)
+for each small NAR was costly.
+
+### Inputs
+- repair :: [Bool64][se-Bool64]
+- dontCheckSigs :: [Bool64][se-Bool64]
+- [Framed][se-Framed] stream of add multiple NAR dump
+
+
+## AddBuildLog
+
+**Id:** 45<br>
+**Introduced:** Protocol 1.32, Nix 2.6.0<br>
+
+Attach some build logs to a given build.
+
+### Inputs
+- path :: [String][se-String] (might be [BaseStorePath][se-BaseStorePath])
+- [Framed][se-Framed] stream of log lines
+
+### Outputs
+1 :: [Int][se-Int] (hardcoded)
+
+
+## BuildPathsWithResults
+
+**Id:** 46<br>
+**Introduced:** Protocol 1.34*, Nix 2.8.0<br>
+
+Build (or substitute) a list of derivations and returns a list of results.
+
+### Inputs
+- drvs :: [List][se-List] of [DerivedPath][se-DerivedPath]
+- mode :: [BuildMode][se-BuildMode]
+
+### Outputs
+results :: [List][se-List] of [KeyedBuildResult][se-KeyedBuildResult]
+
+
+## AddPermRoot
+
+**Id:** 47<br>
+**Introduced:** Protocol 1.36*, Nix 2.20.0<br>
+
+### Inputs
+- storePath :: [StorePath][se-StorePath]
+- gcRoot :: [String][se-String]
+
+### Outputs
+gcRoot :: [String][se-String]
+
+
+
+[se-Int]: ./serialization.md#int
+[se-UInt8]: ./serialization.md#uint8
+[se-UInt64]: ./serialization.md#uint64
+[se-Bool]: ./serialization.md#bool
+[se-Bool64]: ./serialization.md#bool64
+[se-Time]: ./serialization.md#time
+[se-FileIngestionMethod]: ./serialization.md#fileingestionmethod
+[se-BuildMode]: ./serialization.md#buildmode
+[se-Verbosity]: ./serialization.md#verbosity
+[se-GCAction]: ./serialization.md#gcaction
+[se-Bytes]: ./serialization.md#bytes
+[se-String]: ./serialization.md#string
+[se-StorePath]: ./serialization.md#storepath
+[se-BaseStorePath]: ./serialization.md#basestorepath
+[se-OptStorePath]: ./serialization.md#optstorepath
+[se-ContentAddressMethodWithAlgo]: ./serialization.md#contentaddressmethodwithalgo
+[se-OptContentAddress]: ./serialization.md#optcontentaddress
+[se-DerivedPath]: ./serialization.md#derivedpath
+[se-DrvOutput]: ./serialization.md#drvoutput
+[se-Realisation]: ./serialization.md#realisation
+[se-List]: ./serialization.md#list-of-x
+[se-Map]: ./serialization.md#map-of-x-to-y
+[se-SubstitutablePathInfo]: ./serialization.md#substitutablepathinfo
+[se-ValidPathInfo]: ./serialization.md#validpathinfo
+[se-UnkeyedValidPathInfo]: ./serialization.md#unkeyedvalidpathinfo
+[se-BuildResult]: ./serialization.md#buildmode
+[se-KeyedBuildResult]: ./serialization.md#keyedbuildresult
+[se-BasicDerivation]: ./serialization.md#basicderivation
+[se-Framed]: ./serialization.md#framed
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