Add package level documentation for db, historydb, l2db and api/...

api/api.go

@@ -1,3 +1,27 @@
+/*
+Package api implements the public interface of the hermez-node using a HTTP REST API.
+There are two subsets of endpoints:
+- coordinatorEndpoints: used to receive L2 transactions and account creation authorizations. Targeted for wallets.
+- explorerEndpoints: used to provide all sorts of information about the network. Targeted for explorers and similar services.
+
+About the configuration of the API:
+- The API is supposed to be launched using the cli found at the package cli/node, and configured through the configuration file.
+- The mentioned configuration file allows exposing any combination of the endpoint subsets.
+- Although the API can run in a "standalone" manner using the serveapi command, it won't work properly
+unless another process acting as a coord or sync is filling the HistoryDB.
+
+Design principles and considerations:
+- In order to decouple the API process from the rest of the node, all the communication between this package and the rest of
+the system is done through the SQL database. As a matter of fact, the only public function of the package is the constructor NewAPI.
+All the information needed for the API to work should be obtained through the configuration file of the cli or the database.
+- The format of the requests / responses doesn't match directly with the common types, and for this reason, the package api/apitypes is used
+to facilitate the format conversion. Most of the time, this is done directly at the db level.
+- The API endpoints are fully documented using OpenAPI aka Swagger. All the endpoints are tested against the spec to ensure consistency
+between implementation and specification. To get a sense of which endpoints exist and how they work, it's strongly recommended to check this specification.
+The specification can be found at api/swagger.yml.
+- In general, all the API endpoints produce queries to the SQL database in order to retrieve / insert the requested information. The most notable exceptions to this are
+the /config endpoint, which returns a static object generated at construction time, and the /state, which also is retrieved from the database, but it's generated by API/stateapiupdater package.
+*/
 package api
 
 import (
@@ -27,7 +51,6 @@ func NewAPI(
 	l2db *l2db.L2DB,
 ) (*API, error) {
 	// Check input
-	// TODO: is stateDB only needed for explorer endpoints or for both?
 	if coordinatorEndpoints && l2db == nil {
 		return nil, tracerr.Wrap(errors.New("cannot serve Coordinator endpoints without L2DB"))
 	}
@@ -54,7 +77,7 @@ func NewAPI(
 
 	// Add coordinator endpoints
 	if coordinatorEndpoints {
-		// Account
+		// Account creation authorization
 		v1.POST("/account-creation-authorization", a.postAccountCreationAuth)
 		v1.GET("/account-creation-authorization/:hezEthereumAddress", a.getAccountCreationAuth)
 		// Transaction
@@ -72,17 +95,23 @@ func NewAPI(
 		// Transaction
 		v1.GET("/transactions-history", a.getHistoryTxs)
 		v1.GET("/transactions-history/:id", a.getHistoryTx)
-		// Status
+		// Batches
 		v1.GET("/batches", a.getBatches)
 		v1.GET("/batches/:batchNum", a.getBatch)
 		v1.GET("/full-batches/:batchNum", a.getFullBatch)
+		// Slots
 		v1.GET("/slots", a.getSlots)
 		v1.GET("/slots/:slotNum", a.getSlot)
+		// Bids
 		v1.GET("/bids", a.getBids)
+		// State
 		v1.GET("/state", a.getState)
+		// Config
 		v1.GET("/config", a.getConfig)
+		// Tokens
 		v1.GET("/tokens", a.getTokens)
 		v1.GET("/tokens/:id", a.getToken)
+		// Coordinators
 		v1.GET("/coordinators", a.getCoordinators)
 	}
 

api/apitypes/apitypes.go

@@ -1,3 +1,11 @@
+/*
+Package apitypes is used to map the common types used across the node with the format expected by the API.
+
+This is done using different strategies:
+- Marshallers: they get triggered when the API marshals the response structs into JSONs
+- Scanners/Valuers: they get triggered when a struct is sent/received to/from the SQL database
+- Adhoc functions: when the already mentioned strategies are not suitable, functions are added to the structs to facilitate the conversions
+*/
 package apitypes
 
 import (

api/stateapiupdater/stateapiupdater.go

@@ -1,3 +1,10 @@
+/*
+Package stateapiupdater is responsible for generating and storing the object response of the GET /state endpoint exposed through the api package.
+This object is extensively defined at the OpenAPI spec located at api/swagger.yml.
+
+Deployment considerations: in a setup where multiple processes are used (dedicated api process, separated coord / sync, ...), only one process should care
+of using this package.
+*/
 package stateapiupdater
 
 import (

db/historydb/historydb.go

@@ -1,3 +1,24 @@
+/*
+Package historydb is responsible for storing and retrieving the historic data of the Hermez network.
+It's mostly but not exclusively used by the API and the synchronizer.
+
+Apart from the logic defined in this package, it's important to notice that there are some triggers defined in the
+migration files that have to be taken into consideration to understanding the results of some queries. This is especially true
+for reorgs: all the data is directly or indirectly related to a block, this makes handling reorgs as easy as deleting the
+reorged blocks from the block table, and all related items will be dropped in cascade. This is not the only case, in general
+functions defined in this package that get affected somehow by the SQL level defined logic has a special mention on the function description.
+
+Some of the database tooling used in this package such as meddler and migration tools is explained in the db package.
+
+This package is spitted in different files following these ideas:
+- historydb.go: constructor and functions used by packages other than the api.
+- apiqueries.go: functions used by the API, the queries implemented in this functions use a semaphore
+to restrict the maximum concurrent connections to the database.
+- views.go: structs used to retrieve/store data from/to the database. When possible, the common structs are used, however
+most of the time there is no 1:1 relation between the struct fields and the tables of the schema, especially when joining tables.
+In some cases, some of the structs defined in this file also include custom Marshallers to easily match the expected api formats.
+- nodeinfo.go: used to handle the interfaces and structs that allow communication across running in different machines/process but sharing the same database.
+*/
 package historydb
 
 import (

db/l2db/l2db.go

@@ -1,3 +1,20 @@
+/*
+Package l2db is responsible for storing and retrieving the data received by the coordinator through the api.
+Note that this data will be different for each coordinator in the network, as this represents the L2 information.
+
+The data managed by this package is fundamentally PoolL2Tx and AccountCreationAuth. All this data come from
+the API sent by clients and is used by the txselector to decide which transactions are selected to forge a batch.
+
+Some of the database tooling used in this package such as meddler and migration tools is explained in the db package.
+
+This package is spitted in different files following these ideas:
+- l2db.go: constructor and functions used by packages other than the api.
+- apiqueries.go: functions used by the API, the queries implemented in this functions use a semaphore
+to restrict the maximum concurrent connections to the database.
+- views.go: structs used to retrieve/store data from/to the database. When possible, the common structs are used, however
+most of the time there is no 1:1 relation between the struct fields and the tables of the schema, especially when joining tables.
+In some cases, some of the structs defined in this file also include custom Marshallers to easily match the expected api formats.
+*/
 package l2db
 
 import (

db/utils.go

@@ -1,3 +1,10 @@
+/*
+Package db have some common utilities shared by db/l2db and db/historydb, the most relevant ones are:
+- SQL connection utilities
+- Managing the SQL schema: this is done using migration files placed under db/migrations. The files are executed by
+order of the file name.
+- Custom meddlers: used to easily transform struct <==> table
+*/
 package db
 
 import (