co-log-json (empty) → 0.0.1.0
raw patch · 9 files changed
+1146/−0 lines, 9 filesdep +aesondep +basedep +bytestringsetup-changed
Dependencies added: aeson, base, bytestring, co-log-core, containers, string-conv, text
Files
- CHANGELOG.md +5/−0
- LICENSE +373/−0
- Readme.md +236/−0
- Setup.hs +2/−0
- co-log-json.cabal +76/−0
- src/Colog/Json.hs +205/−0
- src/Colog/Json/Action.hs +109/−0
- src/Colog/Json/Internal/Structured.hs +129/−0
- src/Colog/Json/Message.hs +11/−0
+ CHANGELOG.md view
@@ -0,0 +1,5 @@+# Revision history for co-log-json++## 0.0.1.0 -- 2020-11-11++* First version.
+ LICENSE view
@@ -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.
+ Readme.md view
@@ -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.
+ Setup.hs view
@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain
+ co-log-json.cabal view
@@ -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
+ src/Colog/Json.hs view
@@ -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 () #-}
+ src/Colog/Json/Action.hs view
@@ -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+ ]++
+ src/Colog/Json/Internal/Structured.hs view
@@ -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
+ src/Colog/Json/Message.hs view
@@ -0,0 +1,11 @@+module Colog.Json.Message+ ( -- * Message+ LogStr+ , ls+ , showLS+ -- * Context+ , PushContext+ , sl+ ) where++import Colog.Json.Internal.Structured as Internal