diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,5 @@ +# Revision history for co-log-json + +## 0.0.1.0 -- 2020-11-11 + +* First version. 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 +1,236 @@ +# co-log-json + +`co-log-json` allows writing structured logs in your application. + +The library allows adding additional machine-readable context to the log +messages. I.e. each log message is a JSON object with a predefined structure +where additional user context can be added. Such logs can be easily indexed +by external logs systems such as [Graylog](https://www.graylog.org) or +[Elastic search](https://www.elastic.co). The message logging is done using +a special context, that keeps the information about additional attributes. +Such contexts form a nested scope, and all messages in the score inherit provided +context: + +``` + scope [ user = "Joe"] + | + | ==> {"message":"user arrived", "data": { "user": "Joe"} + | + +------ scope [ tag = "human" ] + | + | ==> {"message": "user entered the door", "data": { "user": "Joe", "tag": "human"} +``` + + +In other words, this library takes two choices: + + 1. We write full context with each message. + This approach allows using external tools (like elastic-search) that can index message + without any additional work and information. + Any message can be lost without affecting the ability to decode other messages. An alternative + approach could be emitting a list of events (possibly as a bytecode), such an approach + is taken by the tracing libraries. It requires more works during reading and indexing + logs, and in the case in some logs are logs may render later ones unusable or lose some info. + + 2. We keep a state context so we don't need to attach context messages to each one. + An alternative approach is the extraction of the structure information from the message itself. + This approach is taken in some structured logging libraries, it can provide better error + messages. However, it requires to think about the message context all the time (and developer + user may not even know all interesting context where the message will be used). + + +# Using a library + +To to use a library you'll need to add `co-log-json` to the dependency list. + +``` +library.cabal + +library + build-depends: + base, + co-log-json ^>= 0.0 +``` + + +## Setting the library + + +```haskell +import Colog.Json -- Core API for structured logging +import Colog.Json.Action (logToHandle) -- Actions to store the message +import System.IO (stderr) + +main :: IO () +main = do + -- First, we need to set up log storing function: + -- To emit logs we need to create a context. + -- Context takes the action to store log and it's possible to + -- attach additional information to it. + + let context = mkLogger (logToHandle stderr) + -- ^ + -- | + -- +------ `LogAction IO Message` + -- (see discussion "Why IO below") + -- + -- Once 'context' is created it can be passed to the other parts + -- of the code or used to emit logs. + + logDebug context "Hi, there!" + -- ^ ^ + -- | | + -- | +----- `LogStr` type - is an efficient text builder. + -- | + -- | + -- +-- log context + + -- Will output: + -- + -- ``` + -- {"severity":"DEBUG", "thread": 1, "message": "Hi, there!"} + -- ``` + -- ^ ^ ^ + -- | | +------------ Message itself + -- | +----------------------------- Id of the thread that emitted the message + -- +----------------- Severity level: Debug, Info, Notice, Error, Critical, Alert, Emergency + -- + -- to the stderr. + + -- There are other helper functions list `logInfo`, `logNotice`, etc. +``` + +Now let's discuss `LogStr` type. It exists to efficiently generate message without +extra allocations that can be avoided. It's just a [Text.Builder](http://hackage.haskell.org/package/text-1.2.4.0/docs/Data-Text-Lazy-Builder.html) though internal +representation may evolve in the future. `LogStr` allows message concatenation without allocating +intermediate structures, so it allows efficient log building. For example line: + +```haskell + logDebug context $ "a" <> "b" <> "c" +``` + +will write all text string "a", "b", "c" directly to the buffer, and can do more optimizations. +So it's quite safe to use the library even with a large number of logs. + +The 'LogStr' type implement [IsString](http://hackage.haskell.org/package/base-4.14.0.0/docs/Data-String.html#t:IsString) instance it means that you can just write string literals +and they will be treated as 'LogStr'. To concatenate two 'LogStr' you can use [`<>`](https://hackage.haskell.org/package/base-4.14.0.0/docs/Data-Semigroup.html#t:Semigroup) operation. + +In addition you can convert any string lines that has [StringConv a T.Text](https://hackage.haskell.org/package/string-conv-0.1.2/docs/Data-String-Conv.html), i.e. can be converted +to LogStr using `ls :: StringConv a T.Text => a -> LogStr`. +Efficiency and safety of this conversion depends on the concrete instance implementation and is out +of control of the package. + +```haskell + logDebug context $ "foo is " <> ls ("ы":: ByteString) +``` + +In case your data structure does not implement `StringConv a` it's possible to use not efficient but +very general `showLS :: Show a => a -> LogStr` method that will work for any type that has Show instance. + +## Adding context. + +But just writing JSON messages is not very interesting, we want to control the context of the message. +In order to add user data to the context we can use `addContext :: PushContext -> LoggerEnv -> LoggerEnv` +method. + +```haskell + + let context1 = addContext (sl "user_id" (1::Int)) context + -- ^ ^ ^ ^ ^ + -- | | | | +--- old context + -- | | | +------------ user data + -- | | +---------------------- key for the user data + -- | +---------------------------- function that generates an entry + -- +------------------------------------------------- new context that has data attached + + logDebug context1 "Hi again!" + + -- Will emit to the stderr: + -- + -- ``` + -- {"severity":"DEBUG", "thread": 1, "message": "Hi, there!", "data": {"user_id":1}} + -- ``` + -- ^ ^ ^ + -- | | +-- value + -- | +------- key + -- +--- all user data is kept under 'data' key +``` + +Sidenote: 'sl' function looks redundant, but it's needed in order to provide a future +compatibility for a case when internal structure of user data is changing. Historically +it came from [katip](https://hackage.haskell.org/package/katip) library, there are more functions that allows context creation but + +Function `sl :: ToJSON a => T.Text -> a -> PushContext` prepares update to the context. +It encodes user data to JSON. This is why we had to add type annotation to `1` otherwise GHC had +no means to infer the type). + +It's important that the library does not perform any compaction of key-values, i.e.: + +```haskell + logDebug (addContext (sl "user_id" 2) context1) "Who am I?" + -- Will emit: + -- ``` + -- {"severity":"DEBUG", "thread": 1, "message": "Hi, there!", "data": {"user_id":1, "user_id": 2}} + -- ``` +``` + +This is done for purpose, but may be a subject to change in the future major versions. + +`addContext` is not the only function that allows to modify context, there is the other one +`addNamespace :: Text -> LoggerEnv -> LoggerEnv`, this function adds an entry about the +current namespace. Namespace is a nested list of strings that tells the logical part of +the codebase the log belongs to. It's kept separate fom the data, and it's possible to +use in library filtering (using [cfilter](https://kowainik.github.io/posts/2018-09-25-co-log#cfilter)) or filtering in external system. + + +The described functionality is enough to perform logging. However, it may worth discussing +interoperability with the rest of co-log ecosystem and ergonomics. + +## co-log interoperability + +The co-log ecosystem works with "LogAction m a" and in the package, we use "LogEnv" it means +that we are losing most of the benefits of the library and can't use a lot of utility +functions. To improve the situation it's possible to convert LogEnv into +`LogAction m (Severity,LogStr)` using function `unLogger`. Then we will have log action +that will emit a message with the current context, but the context will no longer be modifiable. + +# Ergonomics + +The package provides no ergonomic tools by default and it's important that `addContext` is a pure +function. On the one han,d it introduces a log of boilerplate code but on the other. + +It allows to modify context even outside of the effectful computation for example with servant you may have: + +```haskell +-- | Catalogue of items +data CatalogueApi route = CatalogueApi + { _the_catalogue :: route :- Capture "catalogue_id" CatalogueId :> ToServantAPI Bar + , ... + } + +-- Item +data ItemApi route = ItemApi + { _items :: route :- "items" :> Get '[JSON] (Vector Item) + , ... + } + +handleCatalogue :: LoggerEnv -> ToServant CatalogueApi AsServer +handleCatalogue ctx' = CatalogueApi + { _the_catalogue = \catalogue_id -> + handleItem (addContext "catalogue_id" catalogue_id) ctx) catalogue_id + , ... + } + where + ctx = addNamespace "catalogue" ctx' + +handleItem :: LoggerEnv -> CatalogueId -> ToServant ItemApi AsServer +handleItem ctx' catalogue_id = ItemApi ... + where ctx = addNamespace "item" ctx' +``` + +So we can build computation that we will execute later while modifying the context. + +On the other hand, we can always wrap this pure function into an effect system +of choice be it either handle pattern or readert or MTL or effect system. +This library does not target any particular solution and want to introduce +neither additional dependencies nor additional restrictions on the user. diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/co-log-json.cabal b/co-log-json.cabal new file mode 100644 --- /dev/null +++ b/co-log-json.cabal @@ -0,0 +1,76 @@ +cabal-version: 3.0 +name: co-log-json +version: 0.0.1.0 +synopsis: Structured messages support in co-log ecosystem. +description: + + The library implements of a very simple approach to structured logging, that + ca be used with the [co-log](https://hackage.haskell.org/package/co-log) + ecosystem or on it's own see [cheops-logger](https://github.com/cheopslab/cheops-logger). + + It provides: + + * "Colog.Json" — API for adding structured context to the log messages + * "Colog.Json.Action" — efficient function for dumping logs in the + following format. + + By default it emits logs in the following format (pretty-printed for convenience): + + @ + { "namespace":"server.package" -- namespace for the component + , "severity": \"DEBUG\" -- severity level + , "thread":19 -- id of the thread that emitted the message + , "message":"some long text " -- textual message itself + , "data": -- user data + { "ip":"8.8.8.8" + , "http.request_id":"b362cd5db5c193c05312af4d3a399955" + , "http.method":\"DELETE\" + , "http.path":"\/url\/" + , "user_id":"123" + } + } + @ + + The most interesting thing here is the field @data@ that can be used by the user + to add additional structured info to the message. + +bug-reports: https://github.com/cheopslab/cheops-logger/issues/new?labels=co-log-json +license: MPL-2.0 +license-file: LICENSE +author: Alexander Vershilov +maintainer: alexander.vershilov@sirius.online +copyright: (C) 2019-2020 Фонд Талант и Успех +category: System +extra-source-files: + CHANGELOG.md + Readme.md + +library + exposed-modules: + Colog.Json + Colog.Json.Action + Colog.Json.Message + Colog.Json.Internal.Structured + default-extensions: + BlockArguments + DerivingStrategies + FlexibleContexts + GeneralizedNewtypeDeriving + LambdaCase + OverloadedStrings + RecordWildCards + other-extensions: + UnliftedFFITypes + MagicHash + FlexibleContexts + build-depends: + base >=4.11 && <5 + , aeson ^>= 1.5 + , bytestring ^>=0.10 + , text ^>=1.2 + , containers ^>=0.6 + , co-log-core ^>=0.2 + , string-conv ^>=0.1 + hs-source-dirs: src + ghc-options: -Wall + default-language: Haskell2010 diff --git a/src/Colog/Json.hs b/src/Colog/Json.hs new file mode 100644 --- /dev/null +++ b/src/Colog/Json.hs @@ -0,0 +1,205 @@ +-- | +-- Top-level module for structured logging support. Structured logging provides messages in +-- a machine-readable format and passing an additional user data to the messages (context) +-- to the log messages, and tooling that allows keep track of the current context and attach +-- it to all the messages. +-- +-- Short example: +-- +-- @ +-- logic :: LoggerEnv -> Int -> IO () +-- logic ctx' entity_id = do -- (1) +-- 'logInfo' ctx "start processing entity" -- (2) +-- internal ctx entity_id -- (3) +-- 'logInfo' ctx "finish processing +-- where +-- ctx = 'addNamespace' "logic" -- (4) +-- . 'addContext' (sl "id" entity_id) -- (5) +-- $ ctx' +-- @ +-- Here we: +-- +-- * @(1)@ pass initial context (@ctx'@ :: 'LoggerEnv') +-- * @(2)@ log message on 'InfoS' severtity level with new context attached +-- * @(3)@ start internal fuction with new context +-- * @(4)@ extend initial context with a new namespace +-- * @(5)@ extend initial context with a new user data +-- +-- __NOTE__ You may notice a bit of an extra boilerplate code here. It can be removed +-- by using any effect handling approach, like ReaderT, MTL, various effects +-- system or service pattern. However this library does not commit to any of +-- those approaches and provides simple @IO@ interface, so there can be a light +-- wrapper with the system of your choice. E.g. The library author prefer to use +-- @ImplicitParams@ extension, as you can see in cheops-logger package. +-- +-- +module Colog.Json + ( -- $logger-env + LoggerEnv + , mkLogger + , emptyLogger + , unLogger + -- * Writing logs + -- $writing-logs + , ls + , showLS + , LogStr + -- $writing-helpers + , logDebug + , logNotice + , logInfo + , logErr + , logWarn + , logAlert + , logCrit + , logEmergency + , Severity(..) + + -- * Adding context + -- $adding-context + , addContext + , sl + , addNamespace + ) where + +import Colog.Core hiding (Severity) +import Colog.Json.Internal.Structured +import Control.Concurrent +import Control.Monad.IO.Class +import qualified Data.Sequence as Seq +import qualified Data.Text as T + +-- $logger-env +-- +-- For each message we attach additional information +-- +-- * @thread id@ — it can be useful to group messages by the +-- thread when debugging, especially in a case if a thread +-- can be associated with the request processing. +-- +-- * @namespace@ — '.' delimited text that describes the component +-- that the log was emitted from. It allows simple logs +-- filtering in an external system, or in the logger action. +-- +-- * @severity@ — information how urgent the message is. +-- +-- * @user_data@ - any user data in a key-value form, the key is a +-- text value, and the value is a JSON-encoded value. +-- +-- In order to keep track of that information we introduce 'LoggerEnv' handle. +-- It can be used to emit messages with additional information, +-- see writing logs section, and modify current context, see adding context section. + +-- | Logger environment is used to keep information about +-- the current context and modify it. When any log message +-- is emitted the current context is added to the message. +data LoggerEnv = LoggerEnv + { action :: LogAction IO Message -- ^ Internal log action. + , context :: Seq.Seq Structured -- ^ Current context. + } + +-- | Logger that does nothing. Useful for the testing purpose. +emptyLogger :: LoggerEnv +emptyLogger = LoggerEnv (LogAction $ \_ -> pure ()) Seq.empty + +-- | Covert ordinary colog action into 'LoggerEnv' this way +-- we can keep track of the current context and modify it. +-- +-- @ +-- let ctx = 'mkLogger' ('Colog.Json.Action.logToHandle' 'System.IO.stderr') +-- in 'logDebug' ctx "message" +-- @ +-- +mkLogger :: LogAction IO Message -> LoggerEnv +mkLogger action = LoggerEnv action Seq.empty + +-- | Covert 'LoggerEnv' back into colog 'LogAction', so we can +-- combie it with the rest of the colog ecosystem. +-- +-- @ +-- 'Colog.Core.Action.cfilter' (\\(sev, _) -> sev > 'Colog.Json.DebugS') 'unLogger' ctx +-- @ +unLogger :: LoggerEnv -> LogAction IO (Severity, LogStr) +unLogger (LoggerEnv action st) = LogAction $ \(lvl, msg) -> do + tid <- myThreadId + unLogAction action $ Message lvl (mkThreadId tid) st msg + +-- $adding-context +-- +-- Messages in the library forms a stack, and you can attach 2 kinds of data to it: +-- +-- 1. @namespace@ - a list of locations, that allows to tell that the component +-- is it. +-- 2. @context@ - context is a list of key-value pairs, where key is a text and +-- a value is any JSON value. +-- +-- When you attach that information to the 'LoggerContext' it will be added to +-- each message that is written in that context. Allowing to analyze data in the +-- external systems. User data is pushed as using 'PushContext' wrapper, that +-- can be created using 'sl'. +-- + +-- | Helper to update context, by appending another item to the log. +-- +-- @ +-- local ('addContext' ('sl' "key" "value")) $ do +-- ... +-- @ +addContext + :: PushContext -- ^ New data to store + -> LoggerEnv -- ^ Old context. + -> LoggerEnv +addContext (PushContext f) LoggerEnv{..} = LoggerEnv{context = f context, ..} + +-- | Helper to extend current namespace by appending sub-namespace. +-- +-- @ +-- local ('addNamespace' "subcomponent") $ do +-- ... +-- @ +addNamespace :: T.Text -> LoggerEnv -> LoggerEnv +addNamespace ns LoggerEnv{..} = LoggerEnv{context=context Seq.|> Segment ns, ..} + +-- $writing-logs +-- Logs can we written using one of the following helpers. The general pattern is +-- +-- @ +-- 'logDebug' logger "message" +-- @ +-- +-- Messages has type 'LogStr'. This is an abstraction over a data-type for efficient +-- log concatenation. Currently it uses 'Data.Text.Lazy.Builder' but it's an implementation +-- detail and may change in the future. +-- +-- 'LogStr' can be created is several ways: +-- +-- * From the string literal using 'Data.String.IsString' interface +-- * From the string like data that can be converted to text, using 'ls' function +-- * From the type that has a 'Show' instance using 'showLS' +-- + +-- $writing-helpers +-- Library provides helper for each 'Severity' level. + +logDebug, logNotice, logInfo, logWarn, + logErr, logAlert, logCrit, logEmergency + :: MonadIO m => LoggerEnv -> LogStr -> m () +logDebug x = logSay x DebugS +logNotice x = logSay x InfoS +logInfo x = logSay x InfoS +logWarn x = logSay x WarningS +logErr x = logSay x ErrorS +logCrit x = logSay x CriticalS +logAlert x = logSay x AlertS +logEmergency x = logSay x EmergencyS + +-- | Internal logger function. +logSay :: MonadIO m + => LoggerEnv -- ^ Logger handle. + -> Severity -- ^ Message severity. + -> LogStr -- ^ Message itself. + -> m () +logSay (LoggerEnv action context) lvl msg = liftIO $ do + tid <- myThreadId + unLogAction action $ Message lvl (mkThreadId tid) context msg +{-# SPECIALIZE logSay :: LoggerEnv -> Severity -> LogStr -> IO () #-} diff --git a/src/Colog/Json/Action.hs b/src/Colog/Json/Action.hs new file mode 100644 --- /dev/null +++ b/src/Colog/Json/Action.hs @@ -0,0 +1,109 @@ +-- | +-- Action that allows to write structured log message. +-- +module Colog.Json.Action + ( logToHandle + , encodeMessage + ) where + +import Colog.Core +import Colog.Json.Internal.Structured +import Control.Exception +import Data.Aeson.Encoding as Aeson +import qualified Data.ByteString.Builder as Builder +import Data.Coerce +import Data.Foldable +import qualified Data.List.NonEmpty as NE +import qualified Data.Text.Lazy as TL +import qualified Data.Text.Lazy.Builder as TLB +import System.IO + +-- | Dump logs to the output. On the contrary to the usual co-log functions this one +-- embeds all the functionality inside. However all internals are exposed and in the +-- case if you need any special functionality you can build your own function. +-- +-- This function serializes a message to a temporary buffer and dumps buffer contents +-- to the handle as soon as it's filled. See 'encodeMessage' for encoding details. +-- +-- Notes: +-- +-- 1. In case of exception this function tries to dump information about exception +-- in the handle once. But if another exception arrives while storing info, +-- function rethorws the second exception. +-- +-- 2. During log dumping this function captures all exceptions (@SomeException@) including +-- asynchronous ones. So it should be run under a mask. +-- +-- 3. Running a function under interruptible mask is safe as long no other thread +-- is using a @Handle@. +-- +-- 4. This function does not add timestamp to the message. This is done because +-- we can always rely on external tools to add timestamp, whether it would be @ts@ +-- or @journald@ or docker-logger. +-- However if timestamp from the program is strictly needed it's possible to add +-- it to the user data. +-- +-- 5. If user data contains multiple values with the equal keys all the values will +-- be stored. In case if it's unbearable you should remove duplicates when generating +-- a @Message@ +-- +-- 6. While dumping the message to the @Handle@ no lock is obtained, so the user +-- is responsible for running this function in a race free context. It can be done +-- either from a single thread, or using additional locking mechanisms. +-- +-- 8. This function relies on the line bufferring in order to dump logs promptly. It's +-- up to the user to decide how to setup it but in case of block buffering during +-- low activity logs may be delayed a lot. +-- +logToHandle :: Handle -> LogAction IO Message +logToHandle h = LogAction \m -> + let msg = encodeMessage m + in try (Builder.hPutBuilder h $ Aeson.fromEncoding msg <> Builder.char7 '\n') >>= \case + Left e -> do + Builder.hPutBuilder h $ Aeson.fromEncoding (Aeson.pairs + $ mconcat + [ Aeson.pair "namespace" (Aeson.text "logger") + , Aeson.pair "exception" (Aeson.string (show (e::SomeException))) + ]) + <> Builder.char7 '\n' + Right _ -> pure () + + +-- | Efficiently convert a message into JSON encoding. +-- +-- Message structure: +-- +-- @ +-- { "namespace": "segment1.segment2" +-- , "severity": "DEBUG" +-- , "thread": 123121 +-- , "data": { ... } +-- , "message": "text message" +-- } +-- @ +-- +-- In case if there are no user attributes "data" key is omitted. +encodeMessage :: Message -> Encoding +{-# INLINE encodeMessage #-} +encodeMessage Message{..} = Aeson.pairs $ mconcat fields where + fields = + [ case namespace of + Nothing -> mempty + Just xs -> Aeson.pair "namespace" $ Aeson.lazyText xs + , Aeson.pair "severity" $ encodeSeverity message_severity + , Aeson.pair "thread" $ Aeson.int thread_id + , case user_data of + Nothing -> mempty + Just xs -> Aeson.pair "data" $ Aeson.pairs xs + , Aeson.pair "message" $ lazyText $ coerce TLB.toLazyText message + ] + namespace = TL.intercalate ".". toList <$> NE.nonEmpty + [ TL.fromStrict tm + | Segment tm <- toList attributes + ] + user_data = fold <$> NE.nonEmpty + [ pair key attributeValue + | Attr key attributeValue <- toList attributes + ] + + diff --git a/src/Colog/Json/Internal/Structured.hs b/src/Colog/Json/Internal/Structured.hs new file mode 100644 --- /dev/null +++ b/src/Colog/Json/Internal/Structured.hs @@ -0,0 +1,129 @@ +{-# LANGUAGE UnliftedFFITypes #-} +{-# LANGUAGE MagicHash #-} +{-# OPTIONS_HADDOCK not-home #-} +-- | +-- +-- Structure for tracing context. +-- +-- We assume that each message ('Message') can be tagged with two types of values: +-- +-- * @segment@ - path that tells where are we in the codebase. +-- * @attrbibutes@ - additional key-value tags, where value is an arbitrary json object. +-- +-- Segment is needed in a case if we want to apply differrent logging rules to the differrent +-- parts of the codebase. For example we may way to log all the messages in the component one +-- but not all the rest. +-- +-- In addition each @Message@ provides some common fields: +-- +-- * "thread" - id of the thread that emits message +-- * "severity" - message severity +-- +-- All messages in the same context share segment and attributes. So when exported to the log +-- analytics systems it's easy to load all the information associated with it. +-- +-- **Compatibility note** internal structure of the message may be changed in the future in case +-- if it's proven that another implementation is faster or more memory efficient. However the +-- higher level API is likely to be stable. +module Colog.Json.Internal.Structured + ( -- * Log datastructure. + Structured(..) + , Message(..) + , LogStr(..) + , PushContext(..) + -- * Internals. + , Severity(..) + , encodeSeverity + , showLS + , ls + , sl + , mkThreadId + ) where + +import Control.Concurrent +import Data.Aeson +import Data.Aeson.Encoding as Aeson +import Data.Sequence +import Data.String +import Data.String.Conv +import qualified Data.Text as T +import qualified Data.Text.Lazy.Builder as TLB +import Foreign.C +import GHC.Conc +import GHC.Exts hiding (toList) + +-- | Part of the structured message. +data Structured + = Segment T.Text -- ^ Part of the message that is associated this the context of code. + | Attr T.Text Encoding -- ^ Add attribute to the list. + +-- | Log message. +data Message = Message + { message_severity :: Severity -- ^ Message severity. + , thread_id :: Int -- ^ Thread that emitted message. + , attributes :: Seq Structured -- ^ List of attributes associated with the context. + , message :: LogStr -- ^ Message to log. + } + + +-- | Efficient message builder. +newtype LogStr = LogStr TLB.Builder + deriving newtype IsString + deriving newtype Semigroup + deriving newtype Monoid + +-- | Logger severity. +data Severity + = DebugS -- ^ Debug level, intended for internal information + | InfoS -- ^ Info level, that may be interesting to the user + | NoticeS -- ^ Notice, information that + | WarningS -- ^ Warning, information possible problem problem of some sort + | ErrorS -- ^ Error, information about a problem + | CriticalS -- ^ Critical error, intended for error that may break the system + | AlertS -- ^ Critical error where immediate actions should be taken + | EmergencyS -- ^ System wide emergency + deriving (Show, Bounded, Eq, Ord, Enum) + +-- | Convert severity into the one accepted by the loger. +encodeSeverity :: Severity -> Aeson.Encoding +{-# INLINE encodeSeverity #-} +encodeSeverity DebugS = Aeson.text "DEBUG" +encodeSeverity InfoS = Aeson.text "INFO" +encodeSeverity NoticeS = Aeson.text "NOTICE" +encodeSeverity WarningS = Aeson.text "WARNING" +encodeSeverity ErrorS = Aeson.text "ERROR" +encodeSeverity CriticalS = Aeson.text "CRITICAL" +encodeSeverity AlertS = Aeson.text "ALERT" +encodeSeverity EmergencyS = Aeson.text "EMERGENCY" + +-- | Wrapper over the structured message builder. +newtype PushContext = PushContext (Seq Structured -> Seq Structured) + +-- | "Simple logger" adds a key value to the context: +-- +-- @sl "foo" 123@ +-- +-- Will add @"foo":123@ key pair to the current list of the attributes. +-- Submitted value is stored with json encoding. +sl :: ToJSON a => T.Text -> a -> PushContext +sl label msg = PushContext \x -> + x |> Attr label (toEncoding msg) + +-- | Log any message. +logStr :: StringConv a T.Text => a -> LogStr +logStr t = LogStr (TLB.fromText $ toS t) + +-- | Convert message can be converted. +ls :: StringConv a T.Text => a -> LogStr +ls = logStr + +-- | Convert loggable value from any message that has show instance. +showLS :: Show a => a -> LogStr +showLS = ls . show + +-- | Helper function to get id of the thread. +mkThreadId :: ThreadId -> Int +{-# NOINLINE mkThreadId #-} +mkThreadId (ThreadId tid) = fromIntegral (getThreadId tid) + +foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> CInt diff --git a/src/Colog/Json/Message.hs b/src/Colog/Json/Message.hs new file mode 100644 --- /dev/null +++ b/src/Colog/Json/Message.hs @@ -0,0 +1,11 @@ +module Colog.Json.Message + ( -- * Message + LogStr + , ls + , showLS + -- * Context + , PushContext + , sl + ) where + +import Colog.Json.Internal.Structured as Internal