Source file key_value_store.ml
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open Error_monad
type error +=
| Missing_stored_kvs_data of {filepath : string; index : int}
| Wrong_encoded_value_size of {
file : string;
index : int;
expected : int;
got : int;
}
| Closed of {action : string}
| Corrupted_data of {action : string; filepath : string; index : int}
| Encoding_failed of {filepath : string; index : int}
| Decoding_failed of {filepath : string; index : int}
let () =
register_error_kind
`Permanent
~id:"stdlib_unix.missing_kvs_data"
~title:"Missing stored data from KVS"
~description:"Failed to load stored data from KVS"
~pp:(fun ppf (path, index) ->
Format.fprintf
ppf
"Failed to load on-disk data: no corresponding data found in file %s \
at index %d."
path
index)
Data_encoding.(obj2 (req "filepath" string) (req "index" int31))
(function
| Missing_stored_kvs_data {filepath; index} -> Some (filepath, index)
| _ -> None)
(fun (filepath, index) -> Missing_stored_kvs_data {filepath; index}) ;
register_error_kind
`Permanent
~id:"stdlib_unix.wrong_encoded_value_size"
~title:"Wrong encoded value size"
~description:"Try to write a value that does not match the expected size"
~pp:(fun ppf (file, index, expected, got) ->
Format.fprintf
ppf
"While encoding a value with index '%d' on file '%s', the value size \
was expected to be '%d'. Got '%d'."
index
file
expected
got)
Data_encoding.(
obj4
(req "file" string)
(req "index" int31)
(req "expected_size " int31)
(req "got_size" int31))
(function
| Wrong_encoded_value_size {file; index; expected; got} ->
Some (file, index, expected, got)
| _ -> None)
(fun (file, index, expected, got) ->
Wrong_encoded_value_size {file; index; expected; got}) ;
register_error_kind
`Permanent
~id:"stdlib_unix.closed"
~title:"Key value stored was closed"
~description:"Action performed while the store is closed"
~pp:(fun ppf action ->
Format.fprintf
ppf
"Failed to performa action '%s' because the store was closed"
action)
Data_encoding.(obj1 (req "action" string))
(function Closed {action} -> Some action | _ -> None)
(fun action -> Closed {action}) ;
register_error_kind
`Permanent
~id:"stdlib_unix.corrupted_data"
~title:"key value store data is corrupted"
~description:"A data of the key value store was corrupted"
~pp:(fun ppf (action, file, index) ->
Format.fprintf
ppf
"Could not complete action '%s' because the data associated to file \
'%s' and key index '%d' because the data is corrupted. Likely the \
store was shutdown abnormally. If you see this message, please report \
it."
action
file
index)
Data_encoding.(
obj3 (req "action" string) (req "filepath" string) (req "index" int31))
(function
| Corrupted_data {action; filepath; index} ->
Some (action, filepath, index)
| _ -> None)
(fun (action, filepath, index) -> Corrupted_data {action; filepath; index}) ;
register_error_kind
`Permanent
~id:"stdlib_unix.encoding_failed"
~title:"key value store failed to encode the data"
~description:"A failure was triggered while encoding the data"
~pp:(fun ppf (file, index) ->
Format.fprintf
ppf
"While writing the data associated to file '%s' and key index '%d', a \
failure was triggered during the encoding"
file
index)
Data_encoding.(obj2 (req "filepath" string) (req "index" int31))
(function
| Encoding_failed {filepath; index} -> Some (filepath, index) | _ -> None)
(fun (filepath, index) -> Encoding_failed {filepath; index}) ;
register_error_kind
`Permanent
~id:"stdlib_unix.decoding_failed"
~title:"key value store failed to decode the data"
~description:"A failure was triggered while decoding the data"
~pp:(fun ppf (file, index) ->
Format.fprintf
ppf
"While reading the data associated to file '%s' and key index '%d', a \
failure was triggered during the decoding"
file
index)
Data_encoding.(obj2 (req "filepath" string) (req "index" int31))
(function
| Decoding_failed {filepath; index} -> Some (filepath, index) | _ -> None)
(fun (filepath, index) -> Decoding_failed {filepath; index})
module Events = struct
include Internal_event.Simple
let section = ["key value store"]
let warn_non_opened_file_descriptor =
declare_0
~section
~name:"bad_file_descriptor"
~level:Warning
~msg:
"Trying to unlock/close a non-open file descriptor, is the file \
already closed?\n"
()
end
type ('key, 'value) layout = {
encoding : 'value Data_encoding.t;
eq : 'value -> 'value -> bool;
index_of : 'key -> int;
filepath : string;
value_size : int;
number_of_keys_per_file : int;
}
let max_number_of_keys_per_file = 4096
let bitset_size = max_number_of_keys_per_file
(** The module [Files] handles writing and reading into memory-mapped files. A
virtual file is backed by a physical file and a key is just an index (from 0
to [max_number_of_keys_per_file - 1]). As values within a file have a fixed size, the
index encodes the position of the associated value within the physical file.
This module basically implements the key-value store, by grouping sets of
key-value pairs in files. Each file comes with its own layout, specifying in
particular the value size.
This module must properly handle resource utilization, especially file
descriptors.
The structure {!Files.t} guarantees that no more than the specified
[lru_size] file descriptors can be open at the same time.
*)
module Files : sig
type 'value t
val init : lru_size:int -> 'value t
val close : 'value t -> unit Lwt.t
val write :
?override:bool ->
'value t ->
('key, 'value) layout ->
'key ->
'value ->
unit tzresult Lwt.t
val read : 'value t -> ('key, 'value) layout -> 'key -> 'value tzresult Lwt.t
val value_exists :
'value t -> ('key, 'value) layout -> 'key -> bool tzresult Lwt.t
val count_values : 'value t -> ('key, 'value) layout -> int tzresult Lwt.t
val remove : 'value t -> ('key, 'value) layout -> unit tzresult Lwt.t
end = struct
module LRU = Ringo.LRU_Collection
module Table = Hashtbl.Make (struct
include String
let hash = Hashtbl.hash
end)
module Cache = Hashtbl.Make (struct
type t = int
let equal = Int.equal
let hash n = n
end)
type 'value opened_file = {
fd : Lwt_unix.file_descr;
bitset : Lwt_bytes.t;
count : int;
cache : 'value Cache.t;
lru_node : string LRU.node;
}
let number_of_set_bits (bitset : Lwt_bytes.t) size : int =
let count = ref 0 in
for i = 0 to size - 1 do
if bitset.{i} = '\001' then count := !count + 1
done ;
!count
type 'value file =
| Opening of 'value opened_file Lwt.t
| Closing of unit Lwt.t
type 'value action_output =
| Close of unit Lwt.t
| Read of ('value opened_file option * 'value tzresult) Lwt.t
| Write of ('value opened_file * unit tzresult) Lwt.t
| Value_exists of ('value opened_file option * bool tzresult) Lwt.t
| Count_values of ('value opened_file option * int tzresult) Lwt.t
| Remove of unit Lwt.t
type 'value t = {
closed : bool ref;
last_actions : 'value action_output Table.t;
files : 'value file Table.t;
lru : string LRU.t;
}
let init ~lru_size =
let last_actions = Table.create lru_size in
let files = Table.create lru_size in
let lru = LRU.create lru_size in
let closed = ref false in
{closed; last_actions; files; lru}
let wait_last_action =
let open Lwt_syntax in
function
| Read p ->
let* file, _ = p in
return file
| Close p ->
let* () = p in
return_none
| Write p ->
let* file, _ = p in
return_some file
| Value_exists p ->
let* file, _ = p in
return file
| Count_values p ->
let* file, _ = p in
return file
| Remove p ->
let* () = p in
return_none
let close_opened_file opened_file = Lwt_unix.close opened_file.fd
let key_exists handle index =
let bit = handle.bitset.{index} in
if bit = '\000' then `Not_found
else if bit = '\001' then `Found
else `Corrupted
let position_of layout index =
bitset_size + (index * layout.value_size) |> Int64.of_int
let read_with_opened_file layout opened_file key =
let open Lwt_syntax in
let index = layout.index_of key in
let filepath = layout.filepath in
match key_exists opened_file index with
| `Not_found ->
return
( Some opened_file,
Error
(Error_monad.TzTrace.make
(Missing_stored_kvs_data {filepath = layout.filepath; index}))
)
| `Corrupted ->
return
( Some opened_file,
Error
(Error_monad.TzTrace.make
(Corrupted_data {action = "read"; filepath; index})) )
| `Found -> (
match Cache.find opened_file.cache index with
| None -> (
let pos = position_of layout index in
let mmap =
Lwt_bytes.map_file
~fd:(Lwt_unix.unix_file_descr opened_file.fd)
~pos
~size:layout.value_size
~shared:true
()
in
let bytes = Bytes.make layout.value_size '\000' in
Lwt_bytes.blit_to_bytes mmap 0 bytes 0 layout.value_size ;
let data =
catch_f
(fun () ->
Data_encoding.Binary.of_bytes_exn layout.encoding bytes)
(fun _ -> Encoding_failed {filepath; index})
in
match data with
| Error err -> Lwt.return (Some opened_file, Error err)
| Ok data ->
Cache.add opened_file.cache index data ;
return (Some opened_file, Ok data))
| Some v -> return (Some opened_file, Ok v))
let write_with_opened_file ~override layout opened_file key data =
let open Lwt_syntax in
let index = layout.index_of key in
let filepath = layout.filepath in
let key_already_present = key_exists opened_file index in
match (key_already_present, override) with
| `Corrupted, false ->
Lwt.return
( opened_file,
Error
(Error_monad.TzTrace.make
(Corrupted_data {action = "write"; filepath; index})) )
| `Found, false -> Lwt.return (opened_file, Ok ())
| `Corrupted, true | `Found, true | `Not_found, _ -> (
let pos = position_of layout index in
let mmap =
Lwt_bytes.map_file
~fd:(Lwt_unix.unix_file_descr opened_file.fd)
~pos
~size:layout.value_size
~shared:true
()
in
let bytes =
catch_f
(fun () -> Data_encoding.Binary.to_bytes_exn layout.encoding data)
(fun _ -> Encoding_failed {filepath; index})
in
match bytes with
| Error err -> return (opened_file, Error err)
| Ok bytes ->
let encoded_size = Bytes.length bytes in
if encoded_size <> layout.value_size then
Lwt.return
( opened_file,
Error
(Error_monad.TzTrace.make
(Wrong_encoded_value_size
{
file = layout.filepath;
index;
expected = layout.value_size;
got = encoded_size;
})) )
else (
opened_file.bitset.{index} <- '\002' ;
Lwt_bytes.blit_from_bytes bytes 0 mmap 0 layout.value_size ;
Cache.replace opened_file.cache index data ;
opened_file.bitset.{index} <- '\001' ;
let opened_file =
if key_already_present = `Not_found then
{opened_file with count = opened_file.count + 1}
else opened_file
in
return (opened_file, Ok ())))
let remove_with_opened_file files lru filepath opened_file =
let open Lwt_syntax in
let* () = close_opened_file opened_file in
(try LRU.remove lru opened_file.lru_node with _ -> ()) ;
Table.remove files filepath ;
Lwt_unix.unlink filepath
module Action = struct
let get_file_from_last_action files last_actions filepath =
let open Lwt_syntax in
let last_or_concurrent_action = Table.find_opt last_actions filepath in
match last_or_concurrent_action with
| None -> (
let file_cached = Table.find_opt files filepath in
match file_cached with
| None -> Lwt.return_none
| Some (Closing p) ->
let* () = p in
Lwt.return_none
| Some (Opening p) ->
let* opened_file = p in
Lwt.return_some opened_file)
| Some action -> wait_last_action action
let generic_action files last_actions filepath ~on_file_closed
~on_file_opened =
let open Lwt_syntax in
let* opened_file_opt =
get_file_from_last_action files last_actions filepath
in
match opened_file_opt with
| None -> on_file_closed ~on_file_opened
| Some opened_file -> on_file_opened opened_file
let close_file files last_actions filepath =
let on_file_closed ~on_file_opened:_ = Lwt.return_unit in
let on_file_opened opened_file = close_opened_file opened_file in
generic_action files last_actions filepath ~on_file_closed ~on_file_opened
let read ~on_file_closed files last_actions layout key =
let on_file_opened opened_file =
read_with_opened_file layout opened_file key
in
generic_action
files
last_actions
layout.filepath
~on_file_closed
~on_file_opened
let value_exists ~on_file_closed files last_actions layout key =
let on_file_opened opened_file =
let index = layout.index_of key in
let filepath = layout.filepath in
match key_exists opened_file index with
| `Corrupted ->
Lwt.return
( Some opened_file,
Error
(Error_monad.TzTrace.make
(Corrupted_data {action = "value_exists"; filepath; index}))
)
| `Found -> Lwt.return (Some opened_file, Ok true)
| `Not_found -> Lwt.return (Some opened_file, Ok false)
in
generic_action
files
last_actions
layout.filepath
~on_file_closed
~on_file_opened
let count_values ~on_file_closed files last_actions layout =
let on_file_opened opened_file =
Lwt.return (Some opened_file, Ok opened_file.count)
in
generic_action
files
last_actions
layout.filepath
~on_file_closed
~on_file_opened
let write ~on_file_closed ~override files last_actions layout key data =
let on_file_opened opened_file =
write_with_opened_file ~override layout opened_file key data
in
generic_action
files
last_actions
layout.filepath
~on_file_closed
~on_file_opened
let remove_file ~on_file_closed files last_actions lru filepath =
let on_file_opened opened_file =
remove_with_opened_file files lru filepath opened_file
in
generic_action files last_actions filepath ~on_file_closed ~on_file_opened
end
let close_file files last_actions filepath =
let open Lwt_syntax in
let p = Action.close_file files last_actions filepath in
Table.replace files filepath (Closing p) ;
Table.replace last_actions filepath (Close p) ;
let* () = p in
Table.remove files filepath ;
(match Table.find_opt last_actions filepath with
| Some (Close p) -> (
match Lwt.state p with
| Lwt.Return _ -> Table.remove last_actions filepath
| _ -> ())
| _ -> ()) ;
Lwt.return_unit
let close {last_actions; files; lru; closed} =
let open Lwt_syntax in
if !closed then return_unit
else (
closed := true ;
let* () =
Table.iter_s
(fun filename _ -> close_file files last_actions filename)
files
in
LRU.clear lru ;
return_unit)
let add_lru files last_actions lru filename =
let open Lwt_syntax in
let lru_node, remove = LRU.add_and_return_erased lru filename in
match remove with
| None -> return lru_node
| Some filepath ->
let* () = close_file files last_actions filepath in
return lru_node
let load_file files last_actions lru filename =
let open Lwt_syntax in
let* lru_node = add_lru files last_actions lru filename in
let* fd = Lwt_unix.openfile filename [O_RDWR; O_CLOEXEC] 0o660 in
let bitset =
Lwt_bytes.map_file
~fd:(Lwt_unix.unix_file_descr fd)
~shared:true
~size:bitset_size
()
in
return
{
fd;
bitset;
count = number_of_set_bits bitset bitset_size;
cache = Cache.create 101;
lru_node;
}
let initialize_file files last_actions lru layout =
let open Lwt_syntax in
let* lru_node = add_lru files last_actions lru layout.filepath in
let* fd =
Lwt_unix.openfile
layout.filepath
[O_RDWR; O_CREAT; O_EXCL; O_CLOEXEC]
0o660
in
let total_size =
bitset_size + (layout.number_of_keys_per_file * layout.value_size)
in
let* () = Lwt_unix.ftruncate fd total_size in
let unix_fd = Lwt_unix.unix_file_descr fd in
let bitset =
Lwt_bytes.map_file ~fd:unix_fd ~shared:true ~size:bitset_size ()
in
return {fd; bitset; count = 0; cache = Cache.create 101; lru_node}
let may_load_file files last_actions lru filepath =
let open Lwt_syntax in
let* b = Lwt_unix.file_exists filepath in
if b then Lwt.return_some (load_file files last_actions lru filepath)
else Lwt.return_none
let may_remove_file filepath =
let open Lwt_syntax in
let* b = Lwt_unix.file_exists filepath in
if b then Lwt_unix.unlink filepath else Lwt.return_unit
let load_or_initialize_file files last_actions lru layout =
let open Lwt_syntax in
let* b = Lwt_unix.file_exists layout.filepath in
if b then load_file files last_actions lru layout.filepath
else initialize_file files last_actions lru layout
let read {files; last_actions; lru; closed} layout key =
let open Lwt_syntax in
if !closed then
Lwt.return (Error (Error_monad.TzTrace.make (Closed {action = "read"})))
else
let on_file_closed ~on_file_opened =
let* r = may_load_file files last_actions lru layout.filepath in
match r with
| None ->
let index = layout.index_of key in
Lwt.return
( None,
Error
(Error_monad.TzTrace.make
(Missing_stored_kvs_data
{filepath = layout.filepath; index})) )
| Some opened_file_promise ->
Table.replace files layout.filepath (Opening opened_file_promise) ;
let* opened_file = opened_file_promise in
on_file_opened opened_file
in
let p = Action.read ~on_file_closed files last_actions layout key in
Table.replace last_actions layout.filepath (Read p) ;
let+ _file, value = p in
value
let value_exists {files; last_actions; lru; closed} layout key =
let open Lwt_syntax in
if !closed then
Lwt.return
(Error (Error_monad.TzTrace.make (Closed {action = "value_exists"})))
else
let on_file_closed ~on_file_opened =
let* r = may_load_file files last_actions lru layout.filepath in
match r with
| None -> return (None, Ok false)
| Some opened_file_promise ->
Table.replace files layout.filepath (Opening opened_file_promise) ;
let* opened_file = opened_file_promise in
on_file_opened opened_file
in
let p =
Action.value_exists ~on_file_closed files last_actions layout key
in
Table.replace last_actions layout.filepath (Value_exists p) ;
let+ _, exists = p in
exists
let count_values {files; last_actions; lru; closed} layout =
let open Lwt_syntax in
if !closed then
Lwt.return
(Error (Error_monad.TzTrace.make (Closed {action = "count_values"})))
else
let on_file_closed ~on_file_opened =
let* r = may_load_file files last_actions lru layout.filepath in
match r with
| None -> return (None, Ok 0)
| Some opened_file_promise ->
Table.replace files layout.filepath (Opening opened_file_promise) ;
let* opened_file = opened_file_promise in
on_file_opened opened_file
in
let p = Action.count_values ~on_file_closed files last_actions layout in
Table.replace last_actions layout.filepath (Count_values p) ;
let+ _, count = p in
count
let write ?(override = false) {files; last_actions; lru; closed} layout key
data =
let open Lwt_syntax in
if !closed then
Lwt.return (Error (Error_monad.TzTrace.make (Closed {action = "write"})))
else
let on_file_closed ~on_file_opened =
let opened_file_promise =
load_or_initialize_file files last_actions lru layout
in
Table.replace files layout.filepath (Opening opened_file_promise) ;
let* opened_file = opened_file_promise in
on_file_opened opened_file
in
let p =
Action.write
~on_file_closed
~override
files
last_actions
layout
key
data
in
Table.replace last_actions layout.filepath (Write p) ;
let+ _file, result = p in
result
let remove {files; last_actions; lru; closed} layout =
let open Lwt_syntax in
if !closed then
Lwt.return (Error (Error_monad.TzTrace.make (Closed {action = "remove"})))
else
let on_file_closed ~on_file_opened:_ = may_remove_file layout.filepath in
let p =
Action.remove_file
~on_file_closed
files
last_actions
lru
layout.filepath
in
Table.replace last_actions layout.filepath (Remove p) ;
Table.replace files layout.filepath (Closing p) ;
let* () = p in
(match Table.find_opt last_actions layout.filepath with
| Some (Close p) -> (
match Lwt.state p with
| Lwt.Return _ -> Table.remove last_actions layout.filepath
| _ -> ())
| _ -> ()) ;
return_ok ()
end
let layout ?encoded_value_size ~encoding ~filepath ~eq ~index_of
~number_of_keys_per_file () =
if number_of_keys_per_file > max_number_of_keys_per_file then
invalid_arg
@@ Format.sprintf
"Key_value_store.layout: cannot have more than %d keys per file. \
Given %d."
max_number_of_keys_per_file
number_of_keys_per_file ;
match encoded_value_size with
| Some value_size ->
{filepath; eq; encoding; index_of; value_size; number_of_keys_per_file}
| None -> (
match Data_encoding.classify encoding with
| `Fixed value_size ->
{
filepath;
eq;
encoding;
index_of;
value_size;
number_of_keys_per_file;
}
| `Dynamic | `Variable ->
invalid_arg
"Key_value_store.layout: encoding does not have fixed size")
type ('file, 'key, 'value) t = {
files : 'value Files.t;
root_dir : string;
lockfile : Lwt_unix.file_descr;
}
type ('file, 'key, 'value) file_layout =
root_dir:string -> 'file -> ('key, 'value) layout
let with_lockfile_lock fn f =
let open Lwt_result_syntax in
let* fd =
Lwt.catch
(fun () ->
let*! fd =
Lwt_unix.openfile fn [Unix.O_CLOEXEC; O_CREAT; O_RDWR] 0o644
in
Lwt.return_ok fd)
(function
| Unix.Unix_error (unix_code, caller, arg) ->
tzfail
(Lwt_utils_unix.Io_error {action = `Open; unix_code; caller; arg})
| exn -> Lwt.reraise exn)
in
Lwt.catch
(fun () ->
let*! () = Lwt_unix.lockf fd F_TLOCK 0 in
f fd)
(function
| Unix.Unix_error (unix_code, caller, arg) ->
let* () =
Lwt.catch
(fun () ->
let*! () = Lwt_unix.close fd in
return_unit)
(function
| Unix.Unix_error (unix_code, caller, arg) ->
tzfail
(Lwt_utils_unix.Io_error
{action = `Close; unix_code; caller; arg})
| exn -> Lwt.reraise exn)
in
tzfail
(Lwt_utils_unix.Io_error {action = `Lock; unix_code; caller; arg})
| exn -> Lwt.reraise exn)
let lockfile_unlock fd =
let open Lwt_result_syntax in
let* () =
Lwt.catch
(fun () ->
let*! () = Lwt_unix.lockf fd Unix.F_ULOCK 0 in
return_unit)
(function
| Unix.Unix_error (Unix.EBADF, _, _) ->
let*! () = Events.(emit warn_non_opened_file_descriptor ()) in
return_unit
| Unix.Unix_error (unix_code, caller, arg) ->
tzfail
(Lwt_utils_unix.Io_error {action = `Lock; unix_code; caller; arg})
| exn -> Lwt.reraise exn)
in
Lwt.catch
(fun () ->
let*! () = Lwt_unix.close fd in
return_unit)
(function
| Unix.Unix_error (Unix.EBADF, _, _) ->
let*! () = Events.(emit warn_non_opened_file_descriptor ()) in
return_unit
| Unix.Unix_error (unix_code, caller, arg) ->
tzfail
(Lwt_utils_unix.Io_error {action = `Close; unix_code; caller; arg})
| exn -> Lwt.reraise exn)
let init ~lru_size ~root_dir =
let open Lwt_result_syntax in
let*! () =
if not (Sys.file_exists root_dir) then Lwt_utils_unix.create_dir root_dir
else Lwt.return_unit
in
with_lockfile_lock (Filename.concat root_dir ".lock") @@ fun fd ->
return {files = Files.init ~lru_size; root_dir; lockfile = fd}
let close t =
let open Lwt_result_syntax in
let*! () = Files.close t.files in
lockfile_unlock t.lockfile
let write_value :
type file key value.
?override:bool ->
(file, key, value) t ->
(file, key, value) file_layout ->
file ->
key ->
value ->
unit tzresult Lwt.t =
fun ?override {files; root_dir; _} file_layout file key value ->
let layout = file_layout ~root_dir file in
Files.write ?override files layout key value
let read_value :
type file key value.
(file, key, value) t ->
(file, key, value) file_layout ->
file ->
key ->
value tzresult Lwt.t =
fun {files; root_dir; _} file_layout file key ->
let layout = file_layout ~root_dir file in
Files.read files layout key
let value_exists :
type file key value.
(file, key, value) t ->
(file, key, value) file_layout ->
file ->
key ->
bool tzresult Lwt.t =
fun {files; root_dir; _} file_layout file key ->
let layout = file_layout ~root_dir file in
Files.value_exists files layout key
let count_values :
type file key value.
(file, key, value) t ->
(file, key, value) file_layout ->
file ->
int tzresult Lwt.t =
fun {files; root_dir; _} file_layout file ->
let layout = file_layout ~root_dir file in
Files.count_values files layout
let write_values ?override t file_layout seq =
Seq.ES.iter
(fun (file, key, value) ->
write_value ?override t file_layout file key value)
seq
let read_values t file_layout seq =
let open Lwt_syntax in
Seq_s.of_seq seq
|> Seq_s.S.map (fun (file, key) ->
let* maybe_value = read_value t file_layout file key in
return (file, key, maybe_value))
let values_exist t file_layout seq =
let open Lwt_syntax in
Seq_s.of_seq seq
|> Seq_s.S.map (fun (file, key) ->
let* maybe_value = value_exists t file_layout file key in
return (file, key, maybe_value))
let remove_file {files; root_dir; _} file_layout file =
let layout = file_layout ~root_dir file in
Files.remove files layout