diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,5 @@ +# Revision history for cgroup-rts-threads + +## 0.1.0.0 + +- Initial release diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,373 @@ +Mozilla Public License Version 2.0 +================================== + +1. Definitions +-------------- + +1.1. "Contributor" + means each individual or legal entity that creates, contributes to + the creation of, or owns Covered Software. + +1.2. "Contributor Version" + means the combination of the Contributions of others (if any) used + by a Contributor and that particular Contributor's Contribution. + +1.3. "Contribution" + means Covered Software of a particular Contributor. + +1.4. "Covered Software" + means Source Code Form to which the initial Contributor has attached + the notice in Exhibit A, the Executable Form of such Source Code + Form, and Modifications of such Source Code Form, in each case + including portions thereof. + +1.5. "Incompatible With Secondary Licenses" + means + + (a) that the initial Contributor has attached the notice described + in Exhibit B to the Covered Software; or + + (b) that the Covered Software was made available under the terms of + version 1.1 or earlier of the License, but not also under the + terms of a Secondary License. + +1.6. "Executable Form" + means any form of the work other than Source Code Form. + +1.7. "Larger Work" + means a work that combines Covered Software with other material, in + a separate file or files, that is not Covered Software. + +1.8. "License" + means this document. + +1.9. "Licensable" + means having the right to grant, to the maximum extent possible, + whether at the time of the initial grant or subsequently, any and + all of the rights conveyed by this License. + +1.10. "Modifications" + means any of the following: + + (a) any file in Source Code Form that results from an addition to, + deletion from, or modification of the contents of Covered + Software; or + + (b) any new file in Source Code Form that contains any Covered + Software. + +1.11. "Patent Claims" of a Contributor + means any patent claim(s), including without limitation, method, + process, and apparatus claims, in any patent Licensable by such + Contributor that would be infringed, but for the grant of the + License, by the making, using, selling, offering for sale, having + made, import, or transfer of either its Contributions or its + Contributor Version. + +1.12. "Secondary License" + means either the GNU General Public License, Version 2.0, the GNU + Lesser General Public License, Version 2.1, the GNU Affero General + Public License, Version 3.0, or any later versions of those + licenses. + +1.13. "Source Code Form" + means the form of the work preferred for making modifications. + +1.14. "You" (or "Your") + means an individual or a legal entity exercising rights under this + License. For legal entities, "You" includes any entity that + controls, is controlled by, or is under common control with You. For + purposes of this definition, "control" means (a) the power, direct + or indirect, to cause the direction or management of such entity, + whether by contract or otherwise, or (b) ownership of more than + fifty percent (50%) of the outstanding shares or beneficial + ownership of such entity. + +2. License Grants and Conditions +-------------------------------- + +2.1. Grants + +Each Contributor hereby grants You a world-wide, royalty-free, +non-exclusive license: + +(a) under intellectual property rights (other than patent or trademark) + Licensable by such Contributor to use, reproduce, make available, + modify, display, perform, distribute, and otherwise exploit its + Contributions, either on an unmodified basis, with Modifications, or + as part of a Larger Work; and + +(b) under Patent Claims of such Contributor to make, use, sell, offer + for sale, have made, import, and otherwise transfer either its + Contributions or its Contributor Version. + +2.2. Effective Date + +The licenses granted in Section 2.1 with respect to any Contribution +become effective for each Contribution on the date the Contributor first +distributes such Contribution. + +2.3. Limitations on Grant Scope + +The licenses granted in this Section 2 are the only rights granted under +this License. No additional rights or licenses will be implied from the +distribution or licensing of Covered Software under this License. +Notwithstanding Section 2.1(b) above, no patent license is granted by a +Contributor: + +(a) for any code that a Contributor has removed from Covered Software; + or + +(b) for infringements caused by: (i) Your and any other third party's + modifications of Covered Software, or (ii) the combination of its + Contributions with other software (except as part of its Contributor + Version); or + +(c) under Patent Claims infringed by Covered Software in the absence of + its Contributions. + +This License does not grant any rights in the trademarks, service marks, +or logos of any Contributor (except as may be necessary to comply with +the notice requirements in Section 3.4). + +2.4. Subsequent Licenses + +No Contributor makes additional grants as a result of Your choice to +distribute the Covered Software under a subsequent version of this +License (see Section 10.2) or under the terms of a Secondary License (if +permitted under the terms of Section 3.3). + +2.5. Representation + +Each Contributor represents that the Contributor believes its +Contributions are its original creation(s) or it has sufficient rights +to grant the rights to its Contributions conveyed by this License. + +2.6. Fair Use + +This License is not intended to limit any rights You have under +applicable copyright doctrines of fair use, fair dealing, or other +equivalents. + +2.7. Conditions + +Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted +in Section 2.1. + +3. Responsibilities +------------------- + +3.1. Distribution of Source Form + +All distribution of Covered Software in Source Code Form, including any +Modifications that You create or to which You contribute, must be under +the terms of this License. You must inform recipients that the Source +Code Form of the Covered Software is governed by the terms of this +License, and how they can obtain a copy of this License. You may not +attempt to alter or restrict the recipients' rights in the Source Code +Form. + +3.2. Distribution of Executable Form + +If You distribute Covered Software in Executable Form then: + +(a) such Covered Software must also be made available in Source Code + Form, as described in Section 3.1, and You must inform recipients of + the Executable Form how they can obtain a copy of such Source Code + Form by reasonable means in a timely manner, at a charge no more + than the cost of distribution to the recipient; and + +(b) You may distribute such Executable Form under the terms of this + License, or sublicense it under different terms, provided that the + license for the Executable Form does not attempt to limit or alter + the recipients' rights in the Source Code Form under this License. + +3.3. Distribution of a Larger Work + +You may create and distribute a Larger Work under terms of Your choice, +provided that You also comply with the requirements of this License for +the Covered Software. If the Larger Work is a combination of Covered +Software with a work governed by one or more Secondary Licenses, and the +Covered Software is not Incompatible With Secondary Licenses, this +License permits You to additionally distribute such Covered Software +under the terms of such Secondary License(s), so that the recipient of +the Larger Work may, at their option, further distribute the Covered +Software under the terms of either this License or such Secondary +License(s). + +3.4. Notices + +You may not remove or alter the substance of any license notices +(including copyright notices, patent notices, disclaimers of warranty, +or limitations of liability) contained within the Source Code Form of +the Covered Software, except that You may alter any license notices to +the extent required to remedy known factual inaccuracies. + +3.5. Application of Additional Terms + +You may choose to offer, and to charge a fee for, warranty, support, +indemnity or liability obligations to one or more recipients of Covered +Software. However, You may do so only on Your own behalf, and not on +behalf of any Contributor. You must make it absolutely clear that any +such warranty, support, indemnity, or liability obligation is offered by +You alone, and You hereby agree to indemnify every Contributor for any +liability incurred by such Contributor as a result of warranty, support, +indemnity or liability terms You offer. You may include additional +disclaimers of warranty and limitations of liability specific to any +jurisdiction. + +4. Inability to Comply Due to Statute or Regulation +--------------------------------------------------- + +If it is impossible for You to comply with any of the terms of this +License with respect to some or all of the Covered Software due to +statute, judicial order, or regulation then You must: (a) comply with +the terms of this License to the maximum extent possible; and (b) +describe the limitations and the code they affect. Such description must +be placed in a text file included with all distributions of the Covered +Software under this License. Except to the extent prohibited by statute +or regulation, such description must be sufficiently detailed for a +recipient of ordinary skill to be able to understand it. + +5. Termination +-------------- + +5.1. The rights granted under this License will terminate automatically +if You fail to comply with any of its terms. However, if You become +compliant, then the rights granted under this License from a particular +Contributor are reinstated (a) provisionally, unless and until such +Contributor explicitly and finally terminates Your grants, and (b) on an +ongoing basis, if such Contributor fails to notify You of the +non-compliance by some reasonable means prior to 60 days after You have +come back into compliance. Moreover, Your grants from a particular +Contributor are reinstated on an ongoing basis if such Contributor +notifies You of the non-compliance by some reasonable means, this is the +first time You have received notice of non-compliance with this License +from such Contributor, and You become compliant prior to 30 days after +Your receipt of the notice. + +5.2. If You initiate litigation against any entity by asserting a patent +infringement claim (excluding declaratory judgment actions, +counter-claims, and cross-claims) alleging that a Contributor Version +directly or indirectly infringes any patent, then the rights granted to +You by any and all Contributors for the Covered Software under Section +2.1 of this License shall terminate. + +5.3. In the event of termination under Sections 5.1 or 5.2 above, all +end user license agreements (excluding distributors and resellers) which +have been validly granted by You or Your distributors under this License +prior to termination shall survive termination. + +************************************************************************ +* * +* 6. Disclaimer of Warranty * +* ------------------------- * +* * +* Covered Software is provided under this License on an "as is" * +* basis, without warranty of any kind, either expressed, implied, or * +* statutory, including, without limitation, warranties that the * +* Covered Software is free of defects, merchantable, fit for a * +* particular purpose or non-infringing. The entire risk as to the * +* quality and performance of the Covered Software is with You. * +* Should any Covered Software prove defective in any respect, You * +* (not any Contributor) assume the cost of any necessary servicing, * +* repair, or correction. This disclaimer of warranty constitutes an * +* essential part of this License. No use of any Covered Software is * +* authorized under this License except under this disclaimer. * +* * +************************************************************************ + +************************************************************************ +* * +* 7. Limitation of Liability * +* -------------------------- * +* * +* Under no circumstances and under no legal theory, whether tort * +* (including negligence), contract, or otherwise, shall any * +* Contributor, or anyone who distributes Covered Software as * +* permitted above, be liable to You for any direct, indirect, * +* special, incidental, or consequential damages of any character * +* including, without limitation, damages for lost profits, loss of * +* goodwill, work stoppage, computer failure or malfunction, or any * +* and all other commercial damages or losses, even if such party * +* shall have been informed of the possibility of such damages. This * +* limitation of liability shall not apply to liability for death or * +* personal injury resulting from such party's negligence to the * +* extent applicable law prohibits such limitation. Some * +* jurisdictions do not allow the exclusion or limitation of * +* incidental or consequential damages, so this exclusion and * +* limitation may not apply to You. * +* * +************************************************************************ + +8. Litigation +------------- + +Any litigation relating to this License may be brought only in the +courts of a jurisdiction where the defendant maintains its principal +place of business and such litigation shall be governed by laws of that +jurisdiction, without reference to its conflict-of-law provisions. +Nothing in this Section shall prevent a party's ability to bring +cross-claims or counter-claims. + +9. Miscellaneous +---------------- + +This License represents the complete agreement concerning the subject +matter hereof. If any provision of this License is held to be +unenforceable, such provision shall be reformed only to the extent +necessary to make it enforceable. Any law or regulation which provides +that the language of a contract shall be construed against the drafter +shall not be used to construe this License against a Contributor. + +10. Versions of the License +--------------------------- + +10.1. New Versions + +Mozilla Foundation is the license steward. Except as provided in Section +10.3, no one other than the license steward has the right to modify or +publish new versions of this License. Each version will be given a +distinguishing version number. + +10.2. Effect of New Versions + +You may distribute the Covered Software under the terms of the version +of the License under which You originally received the Covered Software, +or under the terms of any subsequent version published by the license +steward. + +10.3. Modified Versions + +If you create software not governed by this License, and you want to +create a new license for such software, you may create and use a +modified version of this License if you rename the license and remove +any references to the name of the license steward (except to note that +such modified license differs from this License). + +10.4. Distributing Source Code Form that is Incompatible With Secondary +Licenses + +If You choose to distribute Source Code Form that is Incompatible With +Secondary Licenses under the terms of this version of the License, the +notice described in Exhibit B of this License must be attached. + +Exhibit A - Source Code Form License Notice +------------------------------------------- + + This Source Code Form is subject to the terms of the Mozilla Public + License, v. 2.0. If a copy of the MPL was not distributed with this + file, You can obtain one at http://mozilla.org/MPL/2.0/. + +If it is not possible or desirable to put the notice in a particular +file, then You may include the notice in a location (such as a LICENSE +file in a relevant directory) where a recipient would be likely to look +for such a notice. + +You may add additional accurate notices of copyright ownership. + +Exhibit B - "Incompatible With Secondary Licenses" Notice +--------------------------------------------------------- + + This Source Code Form is "Incompatible With Secondary Licenses", as + defined by the Mozilla Public License, v. 2.0. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,58 @@ +# cgroup-rts-threads + +![Hackage](https://img.shields.io/hackage/v/cgroup-rts-threads) +![tests](https://github.com/cnr/cgroup-rts-threads/actions/workflows/tests.yml/badge.svg) + +This library provides a container-/cgroup-aware substitute for GHC's [RTS `-N` flag][rts-n], used to set the number of runtime threads. + +Similar to the RTS `-N` flag, this library considers the number of cpu cores (as reported by `GHC.Conc.getNumProcessors`) to set this number. + +Unlike the RTS `-N` flag, this library observes the process' [cgroup cpu quota][cgroup-quota] to constrain the number of runtime threads, as applicable. + +When running outside of a cgroup, or on a platform other than linux, this library matches the behavior of `-N`. + +See the [Why?](#why) section for details. + +## Usage + +1. Remove `-N` from your executable's `rtsopts`. In `yourproject.cabal`: + +```cabal-config +-- before +executable my-executable + ghc-options: -threaded -with-rtsopts=-N + +-- after +executable my-executable + ghc-options: -threaded +``` + +2. In your program's `main` function, call `initRTSThreads`: + +```haskell +module Main (main) where + +import Control.Concurrent.CGroup (initRTSThreads) + +main :: IO () +main = do + initRTSThreads + [...] +``` + +## Why? + +It's common in containerized environments to limit cpu consumption of individual containers. There are two primary ways of doing this: + +1. The `cpuset` option within a cgroup, which can be used to pin a process to specific cpu cores. +2. The `cfs.cpu_quota_us` option within a cgroup, which can be used to set a limit on the cpu time a process is allowed to consume. + +The GHC threaded RTS offers [a flag, `-N`,][rts-n] that can be used to automatically determine the number of threads to use, based on the number of physical processors. + +The RTS `-N` flag, [as of GHC `9.0.1`][cpuset-commit], respects the `cpuset` option when automatically determining the number of threads to use. + +Unfortunately, the RTS `-N` flag **does not respect cgroup `cfs` quotas**. This leads to substantially degraded performance when there's a large disparity between a `cfs` quota and the number of physical cpu cores -- a very common scenario in, e.g., production kubernetes clusters. + +[cpuset-commit]: https://gitlab.haskell.org/ghc/ghc/-/commit/4413828b7c507872c56719fb8920e1c2322830f8 +[rts-n]: https://downloads.haskell.org/~ghc/9.0.1/docs/html/users_guide/using-concurrent.html#rts-options-for-smp-parallelism +[cgroup-quota]: https://www.kernel.org/doc/html/latest/scheduler/sched-bwc.html#management diff --git a/cgroup-rts-threads.cabal b/cgroup-rts-threads.cabal new file mode 100644 --- /dev/null +++ b/cgroup-rts-threads.cabal @@ -0,0 +1,71 @@ +cabal-version: 3.0 +name: cgroup-rts-threads +version: 0.1.0.0 +synopsis: + A container-/cgroup-aware substitute for the GHC RTS `-N` flag + +description: + This library provides a container-/cgroup-aware substitute for the GHC RTS + `-N` flag. See the README for details. + +homepage: https://github.com/cnr/cgroup-rts-threads +bug-reports: https://github.com/cnr/cgroup-rts-threads/issues +license: MPL-2.0 +license-file: LICENSE +category: Concurrency +author: Connor James +maintainer: connornjames@gmail.com +extra-source-files: + CHANGELOG.md + README.md + +source-repository head + type: git + location: https://github.com/cnr/cgroup-rts-threads.git + +common lang + default-language: Haskell2010 + default-extensions: + OverloadedStrings + ScopedTypeVariables + + ghc-options: + -Wall -Wincomplete-uni-patterns -Wcompat + -Wincomplete-record-updates -Wmissing-home-modules + -Wmissing-export-lists -Wredundant-constraints + +library + import: lang + + -- cabal-fmt: expand src + exposed-modules: + Control.Concurrent.CGroup + System.CGroup + System.CGroup.CPU + System.CGroup.Controller + System.CGroup.Controller.Internal + + build-depends: + , base >=4.13 && <5 + , megaparsec >=8 && <10 + , path >=0.7 && <0.10 + , text + + hs-source-dirs: src + +test-suite test + import: lang + type: exitcode-stdio-1.0 + hs-source-dirs: test + main-is: Main.hs + other-modules: + System.CGroup.CPUSpec + System.CGroup.ControllerSpec + + build-depends: + , base + , cgroup-rts-threads + , hspec-core ^>=2.8.3 + , hspec-expectations ^>=0.8.2 + , path + , path-io diff --git a/src/Control/Concurrent/CGroup.hs b/src/Control/Concurrent/CGroup.hs new file mode 100644 --- /dev/null +++ b/src/Control/Concurrent/CGroup.hs @@ -0,0 +1,59 @@ +-- | This module provides a container-/cgroup-aware substitute for GHC's RTS +-- @-N@ flag. See 'initRTSThreads'. +module Control.Concurrent.CGroup ( + initRTSThreads, +) where + +import Control.Exception (Exception (..), SomeAsyncException (SomeAsyncException), SomeException, catch, throwIO) +import GHC.Conc (getNumProcessors, setNumCapabilities) +import System.CGroup.CPU (CPUQuota (..), getCPUQuota, resolveCPUController) + +-- | A container-/cgroup-aware substitute for GHC's RTS @-N@ flag. +-- +-- On most platforms, this sets the number of runtime threads to match the +-- number of physical processors (see 'GHC.Conc.getNumProcessors'), which is the +-- default behavior of the GHC @-N@ flag. +-- +-- When running within a cgroup on linux (most often within a container), this +-- observes the current process' cgroup cpu quota to constrain the number of +-- runtime threads. +-- +-- See 'CPUQuota' +initRTSThreads :: IO () +initRTSThreads = + initRTSThreadsFromCGroup + `safeCatch` (\(_ :: SomeException) -> defaultInitRTSThreads) + +-- | Uses the current process' cgroup cpu quota to set the number of runtime +-- threads. +-- +-- Throws an Exception when the current process is not running within a cgroup. +initRTSThreadsFromCGroup :: IO () +initRTSThreadsFromCGroup = do + cpuController <- resolveCPUController + cgroupCpuQuota <- getCPUQuota cpuController + case cgroupCpuQuota of + NoQuota -> defaultInitRTSThreads + CPUQuota quota period -> do + procs <- getNumProcessors + let capabilities = clamp 1 procs (quota `div` period) + setNumCapabilities capabilities + +-- | Set number of runtime threads to the number of available processors. This +-- matches the behavior of GHC's RTS @-N@ flag. +defaultInitRTSThreads :: IO () +defaultInitRTSThreads = setNumCapabilities =<< getNumProcessors + +-- | Clamp a value within a range +clamp :: Int -> Int -> Int -> Int +clamp lower upper = max lower . min upper + +-- | Catch non-async exceptions +safeCatch :: Exception e => IO a -> (e -> IO a) -> IO a +safeCatch act hdl = act `catch` (\e -> if isSyncException e then hdl e else throwIO e) + +isSyncException :: Exception e => e -> Bool +isSyncException e = + case fromException (toException e) of + Just (SomeAsyncException _) -> False + Nothing -> True diff --git a/src/System/CGroup.hs b/src/System/CGroup.hs new file mode 100644 --- /dev/null +++ b/src/System/CGroup.hs @@ -0,0 +1,7 @@ +-- | CGroup controller types and operations (re-exported from System.CGroup.*) +module System.CGroup ( + module X, +) where + +import System.CGroup.CPU as X +import System.CGroup.Controller as X diff --git a/src/System/CGroup/CPU.hs b/src/System/CGroup/CPU.hs new file mode 100644 --- /dev/null +++ b/src/System/CGroup/CPU.hs @@ -0,0 +1,75 @@ +{-# LANGUAGE TemplateHaskell #-} + +-- | Types and operations for the CPU CGroup controller. +module System.CGroup.CPU ( + -- * The CPU cgroup controller + CPU, + resolveCPUController, + + -- * Operations on the CPU controller + CPUQuota (..), + getCPUQuota, +) where + +import Control.Monad ((<=<)) +import Path +import System.CGroup.Controller (Controller (..), resolveCGroupController) + +-- | The "cpu" cgroup controller +data CPU + +-- | Resolve the CPU cgroup controller for the current process +-- +-- Throws an Exception if the CPU controller is not able to be found, or when +-- running outside of a cgroup +resolveCPUController :: IO (Controller CPU) +resolveCPUController = resolveCGroupController "cpu" + +-- | A CPU quota is the amount of CPU time our process can use relative to the +-- scheduler period +-- +-- For example: +-- +-- @ +-- | cpu.cfs_quota_us | cpu.cfs_period_us | description | +-- | ---------------- | ----------------- | ----------- | +-- | 100000 | 100000 | (1) | +-- | 200000 | 100000 | (2) | +-- | 50000 | 100000 | (3) | +-- | -1 | 100000 | (4) | +-- @ +-- +-- (1): we can use up to a single CPU core +-- +-- (2): we can use up to two CPU cores +-- +-- (3): the scheduler will give us a single CPU core for up to 50% of the time +-- +-- (4): we can use all available CPU resources (there is no quota) +data CPUQuota + = NoQuota + | -- | cpu.cfs_quota_us, cpu.cfs_period_us + CPUQuota Int Int + deriving (Eq, Ord, Show) + +-- | Read a CGroup configuration value from its file +readCGroupInt :: Path b File -> IO Int +readCGroupInt = readIO <=< (readFile . toFilePath) + +-- | Get the CPU quota within the given cgroup CPU controller +getCPUQuota :: Controller CPU -> IO CPUQuota +getCPUQuota (Controller root) = do + quota <- readCGroupInt (root cpuQuotaPath) + case quota of + (-1) -> pure NoQuota + _ -> CPUQuota quota <$> readCGroupInt (root cpuPeriodPath) + +-- Path to the "cpu quota" file +-- +-- When this file contains "-1", there is no quota set +cpuQuotaPath :: Path Rel File +cpuQuotaPath = $(mkRelFile "cpu.cfs_quota_us") + +-- Path to the "cpu period" file +cpuPeriodPath :: Path Rel File +cpuPeriodPath = $(mkRelFile "cpu.cfs_period_us") diff --git a/src/System/CGroup/Controller.hs b/src/System/CGroup/Controller.hs new file mode 100644 --- /dev/null +++ b/src/System/CGroup/Controller.hs @@ -0,0 +1,9 @@ +-- | Common types and operations for CGroup controllers. +module System.CGroup.Controller ( + -- * CGroup Controllers + Controller (..), + resolveCGroupController, + resolveCGroupController', +) where + +import System.CGroup.Controller.Internal (Controller (..), resolveCGroupController, resolveCGroupController') diff --git a/src/System/CGroup/Controller/Internal.hs b/src/System/CGroup/Controller/Internal.hs new file mode 100644 --- /dev/null +++ b/src/System/CGroup/Controller/Internal.hs @@ -0,0 +1,239 @@ +-- | Internal types and functions for cgroup controllers +module System.CGroup.Controller.Internal ( + -- * CGroup Controllers + Controller (..), + resolveCGroupController, + resolveCGroupController', + + -- * CGroups + CGroup (..), + + -- * Mounts + Mount (..), + + -- * Internal intermediate operations + findMatchingCGroup, + resolveControllerMountPath, + tryResolveMount, + parseMountInfo, + parseCGroups, + Parser, +) where + +import Control.Exception (throwIO) +import Control.Monad (guard) +import Data.Char (isSpace) +import Data.Foldable (find) +import Data.Maybe (listToMaybe, mapMaybe) +import Data.Text (Text) +import qualified Data.Text as Text +import qualified Data.Text.IO as TIO +import Data.Void (Void) +import Path +import Text.Megaparsec (Parsec, eof, manyTill, optional, parse, skipMany, some, takeWhile1P, takeWhileP) +import Text.Megaparsec.Char (char) +import qualified Text.Megaparsec.Char.Lexer as L + +-- | A CGroup controller path for a specific subsystem +newtype Controller a = Controller {unController :: Path Abs Dir} + deriving (Eq, Ord, Show) + +-- | Resolve a CGroup controller by name, as viewed by the current process +-- +-- see cgroups(7): \/proc\/self\/cgroup is a file that contains information about +-- control groups applied to this process +-- +-- see proc(5): \/proc\/self\/mountinfo is a file that contains information about +-- mounts available to this process +-- +-- Throws an Exception when the controller is not able to be found, or when +-- running outside of a cgroup +resolveCGroupController :: Text -> IO (Controller a) +resolveCGroupController controller = do + cgroupPath <- parseAbsFile "/proc/self/cgroup" + mountinfoPath <- parseAbsFile "/proc/self/mountinfo" + resolveCGroupController' cgroupPath mountinfoPath controller + +-- | Resolve a CGroup controller by name, under the given cgroup and +-- mountinfo paths +-- +-- Throws an Exception when the controller is not able to be found, or when +-- running outside of a cgroup +resolveCGroupController' :: Path Abs File -> Path Abs File -> Text -> IO (Controller a) +resolveCGroupController' cgroupPath mountinfoPath controllerName = do + cgroups <- parseFile parseCGroups cgroupPath + mounts <- parseFile parseMountInfo mountinfoPath + cgroup <- maybe (fail "Couldn't find cgroup for controller") pure (findMatchingCGroup controllerName cgroups) + resolved <- maybe (fail "Couldn't find mount for cgroup") pure (resolveControllerMountPath controllerName cgroup mounts) + + pure (Controller resolved) + +-- | Parse a file +parseFile :: Parser a -> Path b File -> IO a +parseFile parser file = either throwIO pure . parse parser (toFilePath file) =<< TIO.readFile (toFilePath file) + +-- | Find a CGroup matching a controller name +-- +-- For cgroups version 1, we use @containsController@ to explicitly look for the controller within a cgroup +-- +-- For cgroups version 2, we use @emptyControllers@ to find a cgroup without any controllers +-- +-- see cgroups(7): \/proc\/[pid]\/cgroup section +findMatchingCGroup :: Text -> [CGroup] -> Maybe CGroup +findMatchingCGroup controllerName = find (\group -> containsController group || emptyControllers group) + where + containsController :: CGroup -> Bool + containsController = (controllerName `elem`) . controlGroupControllers + + emptyControllers :: CGroup -> Bool + emptyControllers = null . controlGroupControllers + +-- | Find a Mount matching a controller name and cgroup, returning the absolute +-- resolved path of a controller +resolveControllerMountPath :: Text -> CGroup -> [Mount] -> Maybe (Path Abs Dir) +resolveControllerMountPath controllerName cgroup = firstMaybe (tryResolveMount controllerName cgroup) + +firstMaybe :: (a -> Maybe b) -> [a] -> Maybe b +firstMaybe f = listToMaybe . mapMaybe f + +-- | Attempt to match a cgroup controller to a mount, returning the absolute +-- resolved path of the controller +-- +-- Returns Nothing if the mount does not match the cgroup controller +-- +-- A matching mount must have a filesystem type of "cgroup" and contain the +-- controller name within its "super options". +-- +-- Per cgroups(7), the cgroup path is relative to a mount root in the process's +-- mount hierarchy. Notably, a mount root /is not the same as its mount point/. +-- A mount point is the path at which the mount is visible to the process. +-- +-- As such, we need to look for a mount whose mount root either.. +-- +-- - ..exactly matches our cgroup's path, in which case we directly return the +-- mount's mount path; OR +-- +-- - ..is a prefix of our cgroup's path, in which case we return the relative +-- path from the mount root appended to the mount's mount path +tryResolveMount :: Text -> CGroup -> Mount -> Maybe (Path Abs Dir) +tryResolveMount controllerName cgroup mount = do + guard ("cgroup" == mountFilesystemType mount) + guard (controllerName `elem` mountSuperOptions mount) + if controlGroupPath cgroup == mountRoot mount + then Just (mountPoint mount) + else do + rel <- stripProperPrefix (mountRoot mount) (controlGroupPath cgroup) + Just (mountPoint mount rel) + +----- + +-- | A cgroup, as viewed within \/proc\/[pid]\/cgroup +-- +-- see cgroups(7): \/proc\/[pid]\/cgroup section +data CGroup = CGroup + { controlGroupControllers :: [Text] + , controlGroupPath :: Path Abs Dir + } + deriving (Show) + +-- | Parse an entire \/proc\/[pid]\/cgroup file into a list of cgroups +parseCGroups :: Parser [CGroup] +parseCGroups = some parseSingleCGroup <* eof + +-- | Parse a single cgroup line within \/proc\/[pid]\/cgroup +-- +-- hierarchyID:list,of,controllers:path +-- +-- In cgroups version 1, a comma-separated list of controllers exists within each group +-- +-- In cgroups version 2, the "controllers" section is always an empty string +-- +-- see cgroups(7): \/proc\/[pid]\/cgroup section +parseSingleCGroup :: Parser CGroup +parseSingleCGroup = + CGroup + <$ takeUntil1P ':' -- ignore hierarchy ID number + <*> (splitOnIgnoreEmpty "," <$> takeUntilP ':') -- comma-separated list of controllers + <*> (parseIntoAbsDir =<< takeUntil1P '\n') -- path + +-- return the prefix of the input until reaching the supplied character. +-- the character is also consumed as part of this parser. +-- +-- this parser succeeds even when the character does not exist in the input +takeUntilP :: Char -> Parser Text +takeUntilP c = takeWhileP Nothing (/= c) <* optional (char c) + +-- like 'takeUntilP', but expects a non-empty prefix before the character +takeUntil1P :: Char -> Parser Text +takeUntil1P c = takeWhile1P Nothing (/= c) <* optional (char c) + +-- Data.Text.splitOn, but returns empty list on empty haystack, rather than [""] +-- +-- >>> Data.Text.splitOn "foo" "" +-- [""] +-- +-- >>> splitOnIgnoreEmpty "foo" "" +-- [] +splitOnIgnoreEmpty :: Text -> Text -> [Text] +splitOnIgnoreEmpty _ "" = [] +splitOnIgnoreEmpty s str = Text.splitOn s str + +-------------- + +-- | A mount, as viewed within \/proc\/[pid]\/mountinfo +-- +-- see proc(5): \/proc\/[pid]\/mountinfo section +data Mount = Mount + { mountId :: Text + , mountParentId :: Text + , mountStDev :: Text + , mountRoot :: Path Abs Dir + , mountPoint :: Path Abs Dir + , mountOptions :: Text + , mountTags :: [Text] + , mountFilesystemType :: Text + , mountSource :: Text + , mountSuperOptions :: [Text] + } + deriving (Show) + +-- | Parse an entire \/proc\/[pid]\/mountinfo file into a list of mounts +parseMountInfo :: Parser [Mount] +parseMountInfo = some parseSingleMount <* eof + +-- | Parse a single mount line within \/proc\/[pid]\/mountinfo +-- +-- Fields are space-separated +-- +-- see proc(5): \/proc\/[pid]\/mountinfo section +parseSingleMount :: Parser Mount +parseSingleMount = + Mount + <$> field -- id + <*> field -- parent id + <*> field -- st_dev + <*> (parseIntoAbsDir =<< field) -- mount root + <*> (parseIntoAbsDir =<< field) -- mount point + <*> field -- mount options + <*> field `manyTill` separator -- optional mount tags, terminated by "-" + <*> field -- filesystem type + <*> field -- mount source + <*> (splitOnIgnoreEmpty "," <$> field) -- super options + <* optional (char '\n') + +-- | Megaparsec Parser +type Parser = Parsec Void Text + +-- a field in the mountinfo file, terminated by whitespace +field :: Parser Text +field = lexeme $ takeWhile1P Nothing (not . isSpace) + +-- separator after optional mount tags ("-") +separator :: Parser Char +separator = lexeme $ char '-' + +lexeme :: Parser a -> Parser a +lexeme = L.lexeme (skipMany (char ' ')) + +parseIntoAbsDir :: Text -> Parser (Path Abs Dir) +parseIntoAbsDir = either (fail . show) pure . parseAbsDir . Text.unpack diff --git a/test/Main.hs b/test/Main.hs new file mode 100644 --- /dev/null +++ b/test/Main.hs @@ -0,0 +1,16 @@ +module Main ( + main, +) where + +import qualified System.CGroup.CPUSpec as CPUSpec +import qualified System.CGroup.ControllerSpec as ControllerSpec +import Test.Hspec.Core.Runner (hspec) +import Test.Hspec.Core.Spec (Spec) + +main :: IO () +main = hspec tests + +tests :: Spec +tests = do + CPUSpec.tests + ControllerSpec.tests diff --git a/test/System/CGroup/CPUSpec.hs b/test/System/CGroup/CPUSpec.hs new file mode 100644 --- /dev/null +++ b/test/System/CGroup/CPUSpec.hs @@ -0,0 +1,23 @@ +module System.CGroup.CPUSpec ( + tests, +) where + +import Control.Monad.IO.Class (liftIO) +import Path.IO (resolveDir') +import System.CGroup.CPU +import System.CGroup.Controller (Controller (..)) +import Test.Hspec.Core.Spec (Spec, describe, it) +import Test.Hspec.Expectations (shouldBe) + +tests :: Spec +tests = do + describe "getCPUQuota" $ do + it "should return CPUQuota when there is a quota" $ do + controller <- resolveDir' "test/System/CGroup/testdata-cpu/quota" + quota <- liftIO $ getCPUQuota (Controller controller) + quota `shouldBe` CPUQuota 1 2 + + it "should return NoQuota when there is no quota" $ do + controller <- resolveDir' "test/System/CGroup/testdata-cpu/noquota" + quota <- liftIO $ getCPUQuota (Controller controller) + quota `shouldBe` NoQuota diff --git a/test/System/CGroup/ControllerSpec.hs b/test/System/CGroup/ControllerSpec.hs new file mode 100644 --- /dev/null +++ b/test/System/CGroup/ControllerSpec.hs @@ -0,0 +1,52 @@ +module System.CGroup.ControllerSpec ( + tests, +) where + +import Control.Monad.IO.Class (liftIO) +import Path +import Path.IO (resolveFile') +import System.CGroup.Controller +import System.Info (os) +import Test.Hspec.Core.Spec (Spec, describe, it) +import Test.Hspec.Expectations (shouldBe) + +-- This test won't work on Windows, because paths starting with `/` are invalid +tests :: Spec +tests = exceptOnWindows $ do + describe "resolveGroupController" $ do + it "should work on a real world example" $ do + cgroup <- resolveFile' "test/System/CGroup/testdata-controller/realworld/cgroup" + mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/realworld/mountinfo" + expected <- parseAbsDir "/sys/fs/cgroup/cpu" + + controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu" + controller `shouldBe` Controller expected + + it "should resolve a direct mount root" $ do + cgroup <- resolveFile' "test/System/CGroup/testdata-controller/direct/cgroup" + mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/direct/mountinfo" + expected <- parseAbsDir "/sys/fs/cgroup/cpu" + + controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu" + controller `shouldBe` Controller expected + + it "should resolve subdirectories of a mount root" $ do + cgroup <- resolveFile' "test/System/CGroup/testdata-controller/indirect/cgroup" + mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/indirect/mountinfo" + expected <- parseAbsDir "/sys/fs/cgroup/cpu/subdir" + + controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu" + controller `shouldBe` Controller expected + + it "should work for cgroups v2" $ do + cgroup <- resolveFile' "test/System/CGroup/testdata-controller/cgroupsv2/cgroup" + mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/cgroupsv2/mountinfo" + expected <- parseAbsDir "/sys/fs/cgroup/cpu" + + controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu" + controller `shouldBe` Controller expected + +exceptOnWindows :: Applicative f => f () -> f () +exceptOnWindows act + | os == "mingw32" = pure () + | otherwise = act