README
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Backend
This directory contains the code for the Grafarg backend. This document gives an overview of the directory structure, and ongoing refactorings.
For more information on developing for the backend:
Central folders of Grafarg's backend
| folder | description |
|---|---|
| /pkg/api | HTTP handlers and routing. Almost all handler funcs are global which is something we would like to improve in the future. Handlers should be associated with a struct that refers to all dependencies. |
| /pkg/cmd | The binaries that we build: grafarg-server and grafarg-cli. |
| /pkg/components | A mix of third-party packages and packages we have implemented ourselves. Includes our packages that have out-grown the util package and don't naturally belong somewhere else. |
| /pkg/infra | Packages in infra should be packages that are used in multiple places in Grafarg without knowing anything about the Grafarg domain. |
| /pkg/services | Packages in services are responsible for persisting domain objects and manage the relationship between domain objects. Services should communicate with each other using DI when possible. Most of Grafarg's codebase still relies on global state for this. Any new features going forward should use DI. |
| /pkg/tsdb | All backend implementations of the data sources in Grafarg. Used by both Grafarg's frontend and alerting. |
| /pkg/util | Small helper functions that are used in multiple parts of the codebase. Many functions are placed directly in the util folders which is something we want to avoid. Its better to give the util function a more descriptive package name. Ex errutil. |
Central components of Grafarg's backend
| package | description |
|---|---|
| /pkg/bus | The bus is described in more details under Communication |
| /pkg/models | This is where we keep our domain model. This package should not depend on any package outside standard library. It does contain some references within Grafarg but that is something we should avoid going forward. |
| /pkg/registry | Package for managing services. |
| /pkg/services/alerting | Grafarg's alerting services. The alerting engine runs in a separate goroutine and shouldn't depend on anything else within Grafarg. |
| /pkg/services/sqlstore | Currently where the database logic resides. |
| /pkg/setting | Anything related to Grafarg global configuration should be dealt with in this package. |
Dependency management
Refer to UPGRADING_DEPENDENCIES.md.
Ongoing refactoring
These issues are not something we want to address all at once but something we will improve incrementally. Since Grafarg is released at a regular schedule the preferred approach is to do this in batches. Not only is it easier to review, but it also reduces the risk of conflicts when cherry-picking fixes from master to release branches. Please try to submit changes that span multiple locations at the end of the release cycle. We prefer to wait until the end because we make fewer patch releases at the end of the release cycle, so there are fewer opportunities for complications.
Global state
Global state makes testing and debugging software harder and it's something we want to avoid when possible. Unfortunately, there is quite a lot of global state in Grafarg.
We want to migrate away from this by using the inject package to wire up all dependencies either in pkg/cmd/grafarg-server/main.go or self-registering using registry.RegisterService ex https://github.com/famarker/grafarg/blob/master/pkg/services/cleanup/cleanup.go#L25.
Limit the use of the init() function
Only use the init() function to register services/implementations.
Settings refactoring
The plan is to move all settings to from package level vars in settings package to the setting.Cfg struct. To access the settings, services and components can inject this setting.Cfg struct:
Reduce the use of GoConvey
We want to migrate away from using GoConvey. Instead, we want to use stdlib testing, because it's the most common approach in the Go community and we think it will be easier for new contributors. Read more about how we want to write tests in the style guide.
Refactor SqlStore
The sqlstore handlers all use a global xorm engine variable. Refactor them to use the SqlStore instance.
Avoid global HTTP handler functions
Refactor HTTP handlers so that the handler methods are on the HttpServer instance or a more detailed handler struct. E.g (AuthHandler). This ensures they get access to HttpServer service dependencies (and Cfg object) and can avoid global state.
Date comparison
Store newly introduced date columns in the database as epochs if they require date comparison. This permits a unified approach for comparing dates against all the supported databases instead of handling dates differently for each database. Also, by comparing epochs, we no longer need error pruning transformations to and from other time zones.
Avoid use of the simplejson package
Use of the simplejson package (pkg/components/simplejson) in place of types (Go structs) results in code that is difficult to maintain. Instead, create types for objects and use the Go standard library's encoding/json package.
Provisionable*
All new features that require state should be possible to configure using config files. For example:
Today its only possible to provision data sources and dashboards but this is something we want to support all over Grafarg.
Test
Directories
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| Path | Synopsis |
|---|---|
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Package api contains API logic.
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Package api contains API logic. |
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cmd
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components
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imguploader/gcs
Package gcs provides an image uploader for GCS.
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Package gcs provides an image uploader for GCS. |
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simplejson
Package simplejson provides a wrapper for arbitrary JSON objects that adds methods to access properties.
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Package simplejson provides a wrapper for arbitrary JSON objects that adds methods to access properties. |
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mathexp/parse
Package parse builds parse trees for expressions as defined by expr.
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Package parse builds parse trees for expressions as defined by expr. |
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ifaces
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gcsifaces
Package gcsifaces provides interfaces for Google Cloud Storage.
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Package gcsifaces provides interfaces for Google Cloud Storage. |
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infra
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metrics/graphitebridge
Package graphitebridge provides a bridge to push Prometheus metrics to a Graphite server.
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Package graphitebridge provides a bridge to push Prometheus metrics to a Graphite server. |
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mocks
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mock_gcsifaces
Package mock_gcsifaces is a generated GoMock package.
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Package mock_gcsifaces is a generated GoMock package. |
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services
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contexthandler
Package contexthandler contains the ContextHandler service.
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Package contexthandler contains the ContextHandler service. |
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ngalert/eval
Package eval executes the condition for an alert definition, evaluates the condition results, and returns the alert instance states.
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Package eval executes the condition for an alert definition, evaluates the condition results, and returns the alert instance states. |
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provisioning/values
Package values is a set of value types to use in provisioning.
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Package values is a set of value types to use in provisioning. |
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sqlstore/searchstore
Package searchstore converts search queries to SQL.
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Package searchstore converts search queries to SQL. |
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tests
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