vatel

vatel

vatel is a REST framework built on fasthttp and fasthttp/router. An endpoint is a method, a path and a controller factory; vatel decodes path parameters, query string and JSON body into the controller, calls it, serializes the result to JSON and handles errors, logging (with masking of sensitive fields), metrics, authentication and authorization.

go get github.com/axkit/vatel@latest

Requires Go 1.26, fasthttp v1.77.0+ and fasthttp/router v1.5.4+ and, for WebSocket, regorov/websocket v0.1.4+ (Go modules raise them in your project automatically). Errors are built with github.com/axkit/errors v1.1.0+. Upgrading from v0.14? See MIGRATION.md.

Contents

• Quick start
• Endpoints
• Controllers and carriers
• Input decoding and validation
• Middleware
• Authentication and authorization (vatel/auth)
• Errors
• Logging
• Masking sensitive data
• Request context, timeouts and shutdown
• HEAD, OPTIONS and CORS
• WebSocket
• Other options

Quick start

A complete runnable application is in example/ (ADDR=:18080 go run ./example). It verifies HS256 JWTs signed with the JWT_SECRET environment variable (without it, a public development key is used and a warning is logged). To call the protected endpoints, mint a development token (user 100, every permission, valid 24 hours) with the same JWT_SECRET:

TOKEN=$(go run ./example token)
curl -H "Authorization: Bearer $TOKEN" localhost:18080/orders

go run ./example token 2 mints the token for organization 2 (default 1). The order endpoints serve only the orders of the token's organization: GET /orders lists them, GET, PUT and DELETE of /orders/{id} give 404 for an order of another organization, and POST /orders creates the order in the token's organization. The example also serves WebSocket on /ws: send {"path":"updateAccessToken","data":{"mid":"<uuid>","at":"<token>"}} within 10 seconds, then {"path":"orders.watch","data":{"id":1}} (see Security context and closing connections).

The minimal version:

package main

import (
	"context"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/axkit/errors"
	"github.com/axkit/vatel"
	"github.com/axkit/vatel/auth"
	"github.com/fasthttp/router"
	"github.com/rs/zerolog"
)

type Order struct {
	ID      int    `json:"id"`
	Product string `json:"product"`
}

var errOrderNotFound = errors.Template("order not found").Code("APP-0001").StatusCode(404)

// GET /orders/{id}
type GetOrder struct {
	vatel.PathParams[struct {
		ID int `param:"id"`
	}]
	vatel.Output[Order]
}

func (c *GetOrder) Handle(ctx vatel.Context) error {
	if c.Params.ID != 1 {
		return errOrderNotFound.New().Set("id", c.Params.ID)
	}
	c.Out = Order{ID: 1, Product: "Widget"}
	return nil
}

// POST /orders
type CreateOrderInput struct {
	Product string `json:"product"`
}

// Validate is called by vatel after decoding, before Handle.
func (in *CreateOrderInput) Validate() error {
	if in.Product == "" {
		return vatel.ErrValidationFailed.New().Set("reason", "product is required")
	}
	return nil
}

type CreateOrder struct {
	vatel.Body[CreateOrderInput]
	vatel.Output[Order]
}

func (c *CreateOrder) Handle(ctx vatel.Context) error {
	c.Out = Order{ID: 2, Product: c.In.Product}
	return nil
}

func OrderEndpoints(cfg *auth.Config) vatel.Endpoints {
	read := cfg.RequirePerms(map[string]uint{"orders:read": 0}) // name -> bit position
	write := cfg.RequirePerms(map[string]uint{"orders:write": 1})

	return vatel.Endpoints{
		vatel.GET("/orders/{id}", func() vatel.Handler { return &GetOrder{} }, read),
		vatel.POST("/orders", func() vatel.Handler { return &CreateOrder{} }, write,
			vatel.WithSuccessStatusCode(201)),
		vatel.GET("/healthcheck", vatel.Func(func(ctx vatel.Context) error {
			ctx.SetStatusCode(204)
			return nil
		})),
	}
}

func main() {
	log := zerolog.New(os.Stdout).With().Timestamp().Logger()

	authCfg := &auth.Config{
		Decoder:    &JWTDecoder{Secret: []byte(os.Getenv("JWT_SECRET"))}, // your vatel.TokenDecoder
		Authorizer: &BitsetAuthorizer{},                                  // your auth.Authorizer
	}

	v := vatel.NewVatel(
		vatel.WithDefaultLogOption(vatel.LogFullOnExit),
		vatel.WithRequestID(),
		vatel.WithClientErrorFields("reason"),
	)
	v.AddMiddleware(vatel.OnAuthentication, authCfg.Middleware())
	v.Add(OrderEndpoints(authCfg))

	mux := router.New()
	if err := v.BuildHandlers(mux, &log); err != nil {
		log.Fatal().Err(err).Msg("build handlers")
	}

	go func() {
		// nil after Shutdown; ErrServerClosed if Shutdown ran first.
		if err := v.ListenAndServe(":8080", mux, &log); err != nil && !errors.Is(err, vatel.ErrServerClosed) {
			log.Fatal().Err(err).Msg("server stopped")
		}
	}()

	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
	<-quit

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	if err := v.Shutdown(ctx); err != nil {
		log.Error().Err(err).Msg("shutdown")
	}
}

JWTDecoder and BitsetAuthorizer are application types; see example/claims.go for a sample implementation (HS256 signature and exp check with the standard library; a JWT library such as github.com/golang-jwt/jwt/v5 adds key rotation and other algorithms).

Responses:

GET /orders/1   (token with orders:read)  -> 200 {"id":1,"product":"Widget"}
GET /orders/5   (token with orders:read)  -> 404 {"msg":"order not found","severity":"unknown","code":"APP-0001","statusCode":404}
GET /orders/1   (no token)                -> 401 {"msg":"authentication required","severity":"medium","code":"VTL-0004","statusCode":401}
POST /orders    {"product":""}            -> 400 {"msg":"validation failed","severity":"tiny","code":"VTL-0006","statusCode":400,"reason":"product is required"}

GET / (under WithUrlPrefix, if set) is registered automatically and returns an HTML list of all endpoints, WS endpoints included. It is public and cannot be replaced: your own GET / makes BuildHandlers fail. Keep in mind that it exposes the route list.

Endpoints

An endpoint is created with a builder function: method, path template, controller factory and options.

vatel.GET(path, ctrl, opts...)     // also POST, PUT, PATCH, DELETE, HEAD, OPTIONS
vatel.WS(path, wsCtrl, opts...)    // WebSocket message endpoint, see below

ctrl is a func() vatel.Handler. It is called once per request, so each request gets its own controller value, and once more during BuildHandlers to inspect the controller type. Keep it cheap and free of side effects. vatel.Func(f) turns a plain func(vatel.Context) error into a factory.

Path templates use fasthttp/router syntax: /orders/{id}, /files/{path:*}, /items/{id:[0-9]+}.

Group endpoints with vatel.Endpoints (a []Endpoint that implements Endpointer) or with your own type that has an Endpoints() []vatel.Endpoint method, and register them with v.Add(...).

Endpoint options

An EndpointOption is a func(*vatel.Endpoint), so you can write your own; it may add per-endpoint middleware with e.AddMiddleware(pos, f).

Building handlers

v.BuildHandlers(mux, &log) validates every endpoint and registers it with the router. It returns an error for, among others: a path with {params} and a controller that is not a Paramer (or the reverse; a vatel.Func handler may have {params} and reads them with ctx.PathValue), a Param(), QueryInput() or GET/DELETE/HEAD/OPTIONS Input() that does not return a pointer to a struct, a path that does not begin with /, a route the router rejects (a duplicate or conflicting path, your own GET /), WithOptionalBody on GET/DELETE/HEAD/OPTIONS, an unknown method, a WS endpoint without WithWebsocketSupport, a duplicate WS path, WS Perms without WithWsAuthFunc. MustBuildHandlers panics instead.

Add endpoints (v.Add) and middleware (v.AddMiddleware) before BuildHandlers: it copies them, later additions have no effect.

BuildHandlers may be called once. Registration is not transactional: after a failed build the router may hold part of the routes, so the Vatel is unusable; further BuildHandlers/ListenAndServe calls return a "previous build failed" error. Create a new Vatel and router.

v.ListenAndServe(addr, mux, &log) builds the handlers if that has not been done yet and starts a fasthttp.Server with IdleTimeout = vatel.DefaultIdleTimeout (90 s) and CloseOnShutdown. vatel.WithServerConfig(func(*fasthttp.Server)) changes it (e.g. ReadTimeout, MaxRequestBodySize, MaxConnsPerIP, a ConnState hook; do not replace Handler). After Shutdown it returns nil; called after Shutdown, it returns vatel.ErrServerClosed. You can also serve mux.Handler with your own server; then Shutdown only cancels request contexts and closes WebSocket connections (waiting, within its ctx, until they have closed).

Controllers and carriers

A controller implements Handle(vatel.Context) error. Capability interfaces tell vatel what to decode and what to send back:

The returned pointers must point into the controller (not to a local variable).

Instead of writing these methods, embed the generic carriers:

// POST /customers/{customerId}/orders/search?limit=50
type SearchFilter struct {
	Limit int `param:"limit"`
}

type SearchOrders struct {
	vatel.PathParams[struct {
		CustomerID int `param:"customerId"`
	}]
	vatel.QueryParams[SearchFilter]
	vatel.Body[struct {
		Products []string `json:"products"`
	}]
	vatel.Output[[]Order]
}

func (c *SearchOrders) Handle(ctx vatel.Context) error {
	// c.Params.CustomerID, c.Query.Limit, c.In.Products
	return nil
}

File upload:

type ImportController struct {
	vatel.Upload
	vatel.Output[ImportResult]
}

func (c *ImportController) Handle(ctx vatel.Context) error {
	if err := c.BindFile(ctx); err != nil {
		return err
	}
	f, err := c.Open() // or c.SaveTo(ctx, path), c.StreamTo(w)
	if err != nil {
		return err
	}
	defer f.Close()
	// ...
	return nil
}

vatel.POST("/import", func() vatel.Handler {
	return &ImportController{Upload: vatel.Upload{Key: "file"}}
})

BindFile returns 400 VTL-0007 (ErrInvalidRequestBody) with field field (the Key) when the request is not a multipart form or has no such file field.

Context

vatel.Context gives the handler access to the request and the response without exposing fasthttp: Header, RequestBody, PathValue, QueryValue, FormFile, FormValue, RemoteAddr (real IP), RequestTime, SetStatusCode, SetHeader, SetContentType, BodyWriter, TokenPayload, Context (Go context), and a per-request key-value store Set/Get. Values stored with Set are written to the request log.

SetValue(key, val any) stores a value under any comparable key, typically an unexported typed key, for code that only gets the Go context: ctx.Context().Value(key) returns it. A string key is the same as Set; a value under a non-string key is not returned by Get and is not written to the log.

type patKey struct{}

// middleware (OnAuthorization, OnHandle, ...)
ctx.SetValue(patKey{}, patID)

// business code that receives ctx.Context()
func viaPAT(ctx context.Context) bool { _, ok := ctx.Value(patKey{}).(int64); return ok }

The token payload set by the auth middleware is type-asserted to your claims type:

claims := ctx.TokenPayload().(*Claims)

Input decoding and validation

Order of steps for a request: path parameters (Paramer), query (Querier), query or body (Inputer), then validation: Validate() of the Querier input, then Validate() of the Inputer input. The first error rejects the request with 400.

• Path parameters and query: int*, uint*, string, bool, float* fields, pointers to them, github.com/axkit/date.Date and *date.Date; fields of nested structs (embedded or untagged) are flattened. A nested struct of a type already being flattened (a cycle such as Parent *Filter) is skipped. A missing query variable leaves the field as is.
• A value that cannot be parsed gives 400 VTL-0006 (ErrValidationFailed) with field param, and so does an empty date (?from=). So does an integer that does not fit the field (300 for a uint8, 2147483648 for an int32): integers are parsed at the size of the field, never truncated.
• Param(), QueryInput() and the GET/DELETE/HEAD/OPTIONS Input() must return a non-nil pointer to a struct; anything else, a typed nil included, is a BuildHandlers error.
• Body: encoding/json into the Inputer value. An empty or whitespace-only body gives 400 VTL-0007 "empty request body, JSON expected"; invalid JSON gives 400 VTL-0007 "request body is not valid JSON". For an input type with mask tags the encoding/json error is not wrapped, because it may quote a value (a number that does not fit the field, a time.Time); the error carries only the fields field, type and offset.
• A request body on DELETE is not supported (RFC 9110 leaves its semantics undefined); use query parameters (QueryParams).

Declare Validate() on a named type. An anonymous struct (vatel.Body[struct{...}]) cannot have methods, so its Validate() never exists. The method may have a pointer receiver; it may also set default values.

type SearchFilter struct {
	Limit int `param:"limit"`
}

func (f *SearchFilter) Validate() error {
	if f.Limit == 0 {
		f.Limit = 20
	}
	if f.Limit > 100 {
		return vatel.ErrValidationFailed.New().Set("reason", "limit must be <= 100")
	}
	return nil
}

The client sees ErrValidationFailed: the message "validation failed", status 400 and code VTL-0006. Any status of the returned error (409, 422, ...) is replaced by 400; the code of a returned *errors.Error, if it has one, replaces VTL-0006, and its fields are kept. A plain errors.New("...") text from Validate() reaches the client only with verbose errors; to show a reason, set an error field and list it in WithClientErrorFields (see Errors). Validate() is called on Querier and Inputer input only, not on a PathParams struct. On a WebSocket endpoint it is called on the Inputer input after the message data is decoded.

Optional request body

By default POST/PUT/PATCH with an Inputer require a JSON body. With vatel.WithOptionalBody() an empty or whitespace-only body is accepted: decoding is skipped, the input stays zero and Validate() is not called, so a Validate() that fills in defaults does not run. A non-empty body is decoded and validated as usual.

vatel.POST("/orders/{id}/ticket", func() vatel.Handler { return &CreateTicket{} },
	vatel.WithOptionalBody())

Middleware

Middleware has the signature func(vatel.Context, vatel.EndpointMeta) error and runs at a position in the pipeline:

Global middleware is added with v.AddMiddleware(pos, f...), per-endpoint middleware with e.AddMiddleware(pos, f...) inside an EndpointOption. At each position global middleware runs first, then per-endpoint, in the order added. An error returned at OnRequest..OnHandle stops the request and is written as the error response.

EndpointMeta carries the endpoint's Method, Path (template, with URL prefix), Perms and LogOptions; every position, including OnErrorResponse, receives it.

func audit(ctx vatel.Context, meta vatel.EndpointMeta) error {
	if len(meta.Perms) > 0 {
		ctx.Set("perms", meta.Perms) // written to the request log
	}
	return nil
}

v.AddMiddleware(vatel.OnHandle, audit)

// Per-endpoint middleware as an option.
func RateLimit(perMinute int) vatel.EndpointOption {
	return func(e *vatel.Endpoint) {
		e.AddMiddleware(vatel.OnHandle, func(ctx vatel.Context, meta vatel.EndpointMeta) error {
			// ...
			return nil
		})
	}
}

Authentication and authorization (vatel/auth)

vatel itself does not check tokens. The github.com/axkit/vatel/auth package provides middleware for a JWT-like token with a bitset of permissions.

cfg := &auth.Config{
	Decoder:     myDecoder,     // vatel.TokenDecoder: Decode([]byte) (vatel.Tokener, error)
	Authorizer:  myAuthorizer,  // auth.Authorizer: IsAllowed(requestPerms []byte, bits ...uint) (bool, error)
	RevokeCheck: myRevokeCheck, // optional vatel.RevokeTokenChecker
}

v.AddMiddleware(vatel.OnAuthentication, cfg.Middleware())

v.Add(vatel.Endpoints{
	vatel.GET("/healthcheck", healthCtrl),                                   // public
	vatel.GET("/users/me", meCtrl, cfg.RequireAuth()),                       // any valid token
	vatel.GET("/orders", listCtrl, cfg.RequirePerms(map[string]uint{"orders:read": 0})),
})

• Middleware() reads the Authorization header, checks revocation, decodes the token and stores Tokener.ApplicationPayload() with ctx.SetTokenPayload. If the payload's Debug() is true, verbose errors are enabled for the request. A missing, invalid, expired or revoked token does not fail the request here: public endpoints serve it as unauthenticated.
• RequireAuth() rejects a request without a valid token (401; the token error if the token was bad).
• RequirePerms(map[string]uint) maps permission names to bit positions. It rejects a request without a valid token (401) or without all bits (403 VTL-0003). The names are appended, sorted, to EndpointMeta.Perms. A nil Authorizer gives 500 instead of a panic.
• Config.Decoder is required with Middleware(). It and RevokeCheck receive the raw Authorization header value; nothing strips a Bearer prefix, so strip it in the decoder. A nil Decoder or a RevokeCheck error fails RequireAuth/RequirePerms endpoints with 500 VTL-0005; public endpoints serve the request as unauthenticated. A Decoder returning neither a token nor an error counts as a bad token (401).
• Config.Disabled = true turns all checks off; it is read on every request without synchronisation, so set it before the server starts serving.

The payload must implement vatel.AuthPayload (Perms() []byte, Debug() bool; the vatel core does not call them, vatel/auth does); handlers type-assert ctx.TokenPayload() to the concrete type. vatel.Perms(...) alone does not protect an HTTP endpoint.

Errors

Return any error from Handle, Validate or middleware. Errors from github.com/axkit/errors carry an HTTP status, a code and a severity:

var ErrOrderLocked = errors.Template("order is locked").
	Code("APP-0042").StatusCode(409).Severity(errors.Medium)

return ErrOrderLocked.New().Set("orderId", id).Set("reason", "payment in progress")
return ErrOrderLocked.Wrap(err)

The client receives the message, severity, code and status of the first *errors.Error (or *errors.ErrorTemplate) in the error chain; a fmt.Errorf("...: %w", err) wrapper keeps its status and the wrapper text is not sent:

{"msg":"order is locked","severity":"medium","code":"APP-0042","statusCode":409}

Fields (Set), wrapped errors and the stack are written to the server log only. To show selected fields to the client, list them once:

v := vatel.NewVatel(vatel.WithClientErrorFields("reason", "suggestedName"))
// -> {"msg":"order is locked",...,"statusCode":409,"reason":"payment in progress"}

The listed fields are written at the root of the error JSON. Do not list fields that may contain internal data.

Verbose errors (stack, all fields, wrapped errors in the response) are enabled for all requests by vatel.WithVerboseError(true), or per request by a token whose payload Debug() returns true (or by middleware calling ctx.SetVerboseError(true)). Use them in development only.

An error chain without *errors.Error (a driver error, errors.New, fmt.Errorf) may carry internal text, so the client gets a generic error instead: {"msg":"internal error",...,"code":"VTL-0005","statusCode":500}, or "service unavailable" / "gateway timeout" for 503/504. The original error is logged. With verbose errors the client gets the original text.

Status of an error without its own status (a plain error, or an *errors.Error with status 0): 504 if the chain contains context.DeadlineExceeded, 503 for context.Canceled, 500 otherwise. An error with status 429 and a Retry-After field sets the Retry-After header. Errors with status >= 500 are passed to the Alarmer (vatel.WithAlarmer).

Panics

vatel recovers a panic anywhere in the pipeline of an HTTP request (middleware, path/query/body decoding, the handler, response serialization, OnSuccessResponse and OnErrorResponse middleware) and in a WebSocket message handler; the server keeps running. The response written so far (status, headers, body) is dropped and the client gets ErrInternalError: 500, VTL-0005, "internal error" (the panic value only with verbose errors). The panic value is logged under panic and the stack under stack, whatever the log level; the request is reported to the metrics once, the Alarmer is called and OnErrorResponse middleware runs (not when the panic came from a middleware that runs after the response is written). A WebSocket client gets the error frame and its connection keeps serving messages. A panic in the WebSocket OnOpen or OnClose callback is recovered too: it is logged (panic, stack, callback) and the Alarmer is called; after an OnOpen panic the connection is closed with status 1011 (OnClose is still called for it).

Predefined errors:

Logging

vatel logs with zerolog. Each endpoint logger carries method, path and client (real IP); WithRequestID() adds reqId. path is the path as registered, without the WithUrlPrefix prefix (EndpointMeta.Path and metrics include it). The "new request" and exit lines are logged at debug level, so a logger at info level hides them; errors are logged at error level.

What is logged is a bitmask (LogOption):

Presets: LogFull (enter, exit, request body and input, response body), LogFullOnExit (the same without enter), LogConfidential (exit only).

• The default level is 0: only errors are logged. Set a default with vatel.WithDefaultLogOption(lo) and override it per endpoint with vatel.WithLogOption(lo).
• Errors are logged at error level with the full error (fields, wrapped errors, stack), the path and query parameters decoded so far and context values. With LogSilent only 5xx errors are logged.
• Path and query parameters are logged by name; values stored with ctx.Set are logged as well. A value stored with ctx.Set("message", v) replaces the exit line message (a path parameter named message does not).
• The X-Set-Log-Level request header (X-Set-Log-Level: exit,req-body) replaces the endpoint level for that one request. It cannot switch off LogSilent of an endpoint; silent in the header silences the request. vatel.WithStaticLoggingLevel() ignores the header. Any client can send this header; use WithStaticLoggingLevel() in production unless every secret in request and response types is tagged with mask.

Masking sensitive data

Tag fields with mask and they are masked in the log. The response sent to the client is not changed.

type LoginInput struct {
	Login    string `json:"login"`
	Password string `json:"password" mask:"-"`      // removed from the log
	Card     string `json:"card"     mask:"secret"` // "***"
	Phone    string `json:"phone"    mask:"phone"`  // custom function
}

• mask:"-" removes the field; any other value names a masking function. A name not registered with AddFunc gives "***" (jsonmask.DefaultMask).

• Without vatel.WithJsonMasker a default jsonmask.New() is used, so tagged fields are always masked. Register functions with your own masker:

  jm := jsonmask.New()
  jm.AddFunc("phone", func(s string) string {
      if len(s) < 4 {
          return jsonmask.DefaultMask
      }
      return strings.Repeat("*", len(s)-4) + s[len(s)-4:]
  })
  v := vatel.NewVatel(vatel.WithJsonMasker(jm))
  

• Masked log keys: requestBody, reqInput, reqQuery, respBody, result, including elements of arrays (Body[[]T], Output[[]T]) and OptionalOutput[T]. A result is masked by the rules of the type Result() returns for the request. If masking fails only the error is logged (requestBodyMaskingFailed, reqInputMaskingFailed, respBodyMaskingFailed or resultMaskingFailed), never the unmasked value.

• The request body of an input type with mask tags is logged as the decoded input, not as the raw body: encoding/json also decodes keys in another letter case ("Password") and the last of duplicate keys, which a path-based masker would miss. A body that cannot be decoded is then not logged (requestBodyLoggingFailed).

• Tags are honoured in nested structs, *Struct, []Struct, []*Struct and recursive types. A tagged field is a leaf: a tagged struct, pointer or slice (e.g. time.Time) is masked or removed as a whole. A tag on an embedded struct applies to each promoted field without a tag of its own. Maps and any (interface) values are not visited. Fields absent from the JSON (omitempty) are not added.

• Path and query parameters: mask:"-" omits the parameter from the log, any other non-empty mask logs "***". Masking functions are not applied to parameters. A mask tag on a nested struct of a query input applies to its fields without their own tag. An invalid value of a masked parameter gives 400 without the value in the error (not even in verbose responses). The same holds for a JSON body (HTTP or WS data) of an input type with mask tags that cannot be decoded.

type ResetPassword struct {
	vatel.PathParams[struct {
		Token string `param:"token" mask:"secret"` // logged as "***"
	}]
	vatel.QueryParams[struct {
		Email string `param:"email" mask:"-"` // not logged
	}]
}

Types without mask tags are logged unchanged.

Request context, timeouts and shutdown

ctx.Context() returns a Go context for the request; pass it to database and HTTP calls.

• It is a child of a base context owned by the Vatel. v.Shutdown(ctx):

  1. starts closing WebSocket connections and stops accepting new connections;
  2. waits until no request is in flight and every WebSocket connection has closed: requests being handled and requests still being received (headers or body) finish normally, and their responses carry Connection: close. Idle keep-alive connections do not hold it up: they are closed. A new connection that has sent nothing yet gets about 5 seconds to start its request (as in net/http), then it is closed too. A WebSocket message being handled is finished;
  3. cancels the base context and returns nil.

  When ctx is done first, the base context is cancelled at once, so handlers still running get context.Canceled (503); Shutdown waits up to one more second for them to finish and returns ctx.Err(); requests still running after that are not interrupted, and their connections are closed when they finish. Requests that start after Shutdown get a cancelled context. Without a server started by ListenAndServe, the base context is cancelled at once and Shutdown waits, within ctx, only for the WebSocket connections. Calling Shutdown again, also concurrently, is safe: each call waits for the server with its own ctx.

• vatel.WithTimeout(d) (endpoint) and vatel.WithDefaultTimeout(d) (Vatel, for endpoints without their own timeout) add a deadline. Such a context is also cancelled when the request ends.

• The timeout does not interrupt the handler by itself. Only code that listens to the context stops (database drivers, http.NewRequestWithContext, select on Done()).

• A handler error whose chain contains context.DeadlineExceeded gives 504, context.Canceled gives 503, unless the error carries its own status.

• fasthttp does not report a client disconnect, so the context is not cancelled when the client goes away.

• Value(key) returns the request values first (Set, SetValue, path params, reqId), then the values of the parent context, looked up at call time: a context obtained before a value is stored sees it. It is safe to call from another goroutine. After the request has ended it returns the parent values only (fasthttp reuses the request object for the next request).

• vatel.NewContext(fctx) (for tests) returns a Context with context.Background().

func (c *Report) Handle(ctx vatel.Context) error {
	rows, err := c.db.QueryContext(ctx.Context(), query)
	if err != nil {
		return err // DeadlineExceeded -> 504
	}
	defer rows.Close()
	// ...
}

vatel.GET("/reports/sales", reportCtrl, vatel.WithTimeout(5*time.Second))

HEAD, OPTIONS and CORS

vatel.HEAD and vatel.OPTIONS work like vatel.GET: an Inputer is filled from the query string, WithOptionalBody is not allowed. On HEAD the fasthttp server drops the response body, so only the status and headers reach the client.

For CORS preflight use the router's GlobalOPTIONS handler. The router calls it only for registered paths (an unknown path gets 404) and sets the Allow header before calling it. An explicit vatel.OPTIONS endpoint on a path replaces GlobalOPTIONS for that path. Do not put RequireAuth/RequirePerms on an OPTIONS endpoint: browsers send the preflight without the Authorization header.

mux := router.New()
mux.GlobalOPTIONS = func(fctx *fasthttp.RequestCtx) {
	h := &fctx.Response.Header
	h.Set("Access-Control-Allow-Origin", allowedOrigin(fctx.Request.Header.Peek("Origin")))
	h.Set("Access-Control-Allow-Methods", string(h.Peek("Allow")))
	h.Set("Access-Control-Allow-Headers", "Authorization, Content-Type")
	h.Set("Access-Control-Max-Age", "600")
	h.Add("Vary", "Origin")
	fctx.SetStatusCode(fasthttp.StatusNoContent)
}

// Allow-Origin on actual responses, including errors.
v.AddMiddleware(vatel.OnRequest, func(ctx vatel.Context, _ vatel.EndpointMeta) error {
	ctx.SetHeader([]byte("Access-Control-Allow-Origin"), []byte(allowedOrigin(ctx.Header("Origin"))))
	ctx.SetHeader([]byte("Vary"), []byte("Origin"))
	return nil
})

See example/cors.go.

WebSocket

WebSocket endpoints share the endpoint model. A client sends JSON messages {"path": "<endpoint path>", "data": {...}}; data is decoded into the handler's Inputer, the Resulter value is sent back as JSON.

type Ping struct {
	in struct {
		Seq int `json:"seq"`
	}
	out struct {
		Seq int `json:"seq"`
	}
}

func (h *Ping) Input() any { return &h.in }
func (h *Ping) Result() any { return &h.out }
func (h *Ping) Handle(ctx vatel.WebsocketContext) error {
	h.out.Seq = h.in.Seq
	return nil
}

wv := vatel.NewWebsocketVatel(
	vatel.WithTokenDecoder(myDecoder),
	vatel.WithWsAuthFunc(func(ctx vatel.WebsocketContext, path string, perms []string) error {
		if len(perms) > 0 && ctx.TokenPayload() == nil {
			return vatel.ErrUnauthorized.New()
		}
		return nil // check perms against ctx.TokenPayload()
	}),
)
wv.OnTokenUpdate(func(cid uint64, prev, next vatel.AuthPayload) error { return nil })

v := vatel.NewVatel(vatel.WithWebsocketSupport(wv))
v.Add(vatel.Endpoints{
	vatel.WS("ping", func() vatel.WebsocketHandler { return &Ping{} }),
	vatel.WS("orders.watch", watchCtrl, vatel.Perms("orders:read")),
})

mux := router.New()
mux.GET("/ws", wv.Upgrade) // the HTTP route that upgrades to WebSocket

• The built-in endpoint updateAccessToken (data: {"mid": "<uuid>", "at": "<token>"}) decodes the token with WithTokenDecoder and calls the OnTokenUpdate callback with the payload stored so far (prev, nil for the first token) and the new one (next); unless the callback returns an error, it stores next for the connection. An error from the callback rejects the token (the connection keeps its previous payload) and is sent to the client; a token that cannot be decoded, or whose payload has expired (Expirer), gives 401 VTL-0004. Without WithTokenDecoder it replies "Ok" and stores nothing. The stored payload is available as ctx.TokenPayload() in later messages. See Security context and closing connections.
• WithWsAuthFunc is called for every message with the endpoint's Perms; WS endpoints with Perms require it. HTTP middleware does not run for WS messages.
• Invalid data gives a 400 VTL-0007 error message. If the Inputer input implements Validator, Validate() is called after decoding, before Handle; an error gives ErrValidationFailed (400, VTL-0006) as in HTTP. Errors are sent, logged and reported to metrics and the Alarmer like HTTP errors.
• A message that is not valid JSON or has no path gives 400 VTL-0007, an unknown path gives 404 VTL-0008 (ErrUnknownPath). These errors are sent and logged like other errors (on the WithLogger logger, or the BuildHandlers one, with "method":"WS"), but not reported to metrics: no endpoint is known.
• The metric size of a successful message is the size of the reply.
• WS handlers have no Go context: WithTimeout, WithDefaultTimeout and the Shutdown cancellation do not apply. LogReqBody/LogReqInput are ignored. WithRequestID logs connectionId instead of reqId.
• vatel.WithLogger(l) sets the logger of WS endpoints (lines get "layer":"ws"); without it they log to the logger passed to BuildHandlers.
• OnOpen and OnClose register connection callbacks. v.Shutdown closes all WebSocket connections with a "going away" status first and waits, within its ctx, until they have closed: their further messages are not served, the message being handled is finished, and a client that does not answer the close frame is disconnected after about one second (OnClose gets a nil error). A connection opened after that is closed at once, without the callbacks. wv.Shutdown() alone does not wait.
• A write to ctx.BodyWriter() after the connection is closed (by Shutdown or the client) returns websocket.ErrConnClosed instead of blocking. A write to a client that does not read blocks once the outbound queue (128 frames) is full; after the write timeout of a frame, vatel.WithWsWriteTimeout(d) (default vatel.DefaultWsWriteTimeout, 10 s; 0 means no limit), the write fails and the connection ends.
• A message larger than 1 MB (the MaxPayloadSize of github.com/regorov/websocket), also when assembled from fragments, closes the connection with status 1009 (message too big). OnClose gets the client's close status as a websocket.Error when the client closed the connection.
• A panic in a WS handler is recovered (see Panics): the client gets a 500 VTL-0005 error frame and the connection keeps serving messages. A panic in the OnOpen/OnClose callback is logged and alarmed; after an OnOpen panic the connection is closed with status 1011.
• UpgradeWithID(ctx, id): the ID must be unique among live connections. A connection with the ID of a live one is closed at once with status 1008 (policy violation), without the callbacks; its messages are not served and it does not share the token payload of the live connection.

Security context and closing connections

vatel does not know what an organization (tenant, workspace, ...) is: it gives the mechanism, the application compares the contexts. The recommended model is one connection = one security context (user + organization). A token of another context is not accepted on a live connection; the client opens a new connection with it.

wv.OnTokenUpdate(func(_ uint64, prev, next vatel.AuthPayload) error {
	if prev == nil {
		return nil // the first token of the connection sets its context
	}
	p, n := prev.(*Claims), next.(*Claims)
	switch {
	case p.UserID != n.UserID:
		return vatel.NewWsCloseError(vatel.WsStatusForbidden, "user changed", nil)
	case p.OrgID != n.OrgID:
		return vatel.NewWsCloseError(vatel.WsStatusContextChanged, "organization changed", nil)
	}
	return nil // a refresh of the same context
})

• OnTokenUpdate(f func(cid uint64, prev, next AuthPayload) error) runs without a lock. If another payload is stored for the connection while it runs (a concurrent UpdateAccessToken for the same cid), or the connection closes or starts closing, UpdateAccessToken returns ErrWsTokenConflict (409, VTL-0010) and stores nothing; it does not retry, as the callback need not be idempotent. For a connection that is already closing it returns ErrWsTokenConflict without calling the callback.
• WsCloseError (vatel.NewWsCloseError(code, reason, err), fields Code, Reason, Err). When the handler of any WS message — including updateAccessToken (through OnTokenUpdate) and the WithWsAuthFunc function — returns an error with a *WsCloseError in its chain (errors.As), the client first gets the usual error reply to that message, then the connection is closed with Code and Reason; its further messages are not served. The reply is built from Err when it has an *errors.Error with a status (an *errors.Error joined or wrapped next to the WsCloseError, outside Err, does not count); otherwise from the code: 4001 → 401 ErrUnauthorized, 4003 → 403 ErrForbidden, 4009 → 409 ErrWsContextChanged (VTL-0009), any other code → 400. It is logged and reported to metrics, never passed to the Alarmer. A rejected token is not stored. An application that calls wv.UpdateAccessToken itself gets the error and closes the connection with CloseConn.
• Reason is sent in the close frame, which holds at most 123 bytes of text: vatel cuts it on a UTF-8 character boundary (a longer text makes browsers drop the connection with 1006 and lose the code). It must not carry sensitive details: put them in Err (the log) or the error reply.
• wv.CloseConn(cid, code, reason) bool closes a live connection, e.g. when its user was removed from the organization, logged out, or the token was revoked; it returns false if there is no such connection (or it is already closing). Its further messages are not served; OnClose is called once it has closed.
• wv.VisitConns(func(cid uint64, tp vatel.AuthPayload) bool) walks the live connections with their payloads (nil before the first token), by ID, until the callback returns false. It runs on a snapshot without a lock, so the callback may call CloseConn, e.g. to close every connection of a user in an organization.
• Token expiry. A payload that implements vatel.Expirer (ExpiresAt() time.Time) with a non-zero time closes its connection with 4001 when it expires. Each accepted updateAccessToken restarts the timer, so the client sends a fresh token before the current one expires. A payload that has already expired is rejected with 401 and the connection keeps its previous payload. A payload stored with UpdateAccessToken for an ID before its connection opened (UpgradeWithID) that has expired by then is dropped: the connection opens without a payload (its next token is the first, prev == nil, and the authentication timeout applies). Once the payload of a connection has expired, the connection is over even if its timer has not fired yet: a message on it (including updateAccessToken) is not served and closes it with 4001 "token expired", a direct UpdateAccessToken for it returns ErrWsTokenConflict without calling OnTokenUpdate, and VisitConns leaves it out. A late token never extends an expired connection nor changes its security context: refresh the token before it expires.
• Authentication timeout. vatel.WithWsAuthTimeout(d) closes a connection with 4001 if no token was accepted within d after it opened (a rejected token does not count). Default 0: no limit. It has no effect without WithTokenDecoder.
• Timers stop when the connection closes and on Shutdown.

Close codes (vatel uses the first three; applications may add their own in 4000–4999):

Organizations. The organization of a message is taken only from the token payload of the connection (ctx.TokenPayload()), never from the message data. A subscription handler checks that the organization of the resource matches the organization of the token (the example reports a resource of another organization as not found, so its existence is not disclosed). The same holds for HTTP: the example's order endpoints take the organization from ctx.TokenPayload() only, filter lists by it, check it before reading, changing or deleting an order, and set it on created orders. The context belongs to the connection, not to the user: browser tabs working in different organizations use different connections.

Client contract. Send the token (updateAccessToken) right after connecting, and a fresh one before it expires. To switch the organization, close the WebSocket yourself (1000), open a new one with a token of the new organization and subscribe again. React to the close codes as in the table above. A complete server is in example/ws.go.

Other options

License

MIT, see LICENSE.