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server.go
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server.go
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// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package server
import (
"context"
"errors"
"fmt"
"io"
"net"
"net/http"
"net/url"
"sync"
"time"
"github.com/gorilla/handlers"
"github.com/rs/cors"
"github.com/ava-labs/avalanchego/snow"
"github.com/ava-labs/avalanchego/snow/engine/common"
"github.com/ava-labs/avalanchego/utils/logging"
)
const (
baseURL = "/ext"
serverShutdownTimeout = 10 * time.Second
)
var (
errUnknownLockOption = errors.New("invalid lock options")
)
type RouteAdder interface {
AddRoute(handler *common.HTTPHandler, lock *sync.RWMutex, base, endpoint string, loggingWriter io.Writer) error
}
// Server maintains the HTTP router
type Server struct {
// log this server writes to
log logging.Logger
// generates new logs for chains to write to
factory logging.Factory
// Maps endpoints to handlers
router *router
// points the the router handlers
handler http.Handler
// Listens for HTTP traffic on this address
listenAddress string
// http server
srv *http.Server
}
// Initialize creates the API server at the provided host and port
func (s *Server) Initialize(
log logging.Logger,
factory logging.Factory,
host string,
port uint16,
allowedOrigins []string,
wrappers ...Wrapper,
) {
s.log = log
s.factory = factory
s.listenAddress = fmt.Sprintf("%s:%d", host, port)
s.router = newRouter()
s.log.Info("API created with allowed origins: %v", allowedOrigins)
corsWrapper := cors.New(cors.Options{
AllowedOrigins: allowedOrigins,
AllowCredentials: true,
})
s.handler = corsWrapper.Handler(s.router)
for _, wrapper := range wrappers {
s.handler = wrapper.WrapHandler(s.handler)
}
}
// Dispatch starts the API server
func (s *Server) Dispatch() error {
listener, err := net.Listen("tcp", s.listenAddress)
if err != nil {
return err
}
s.log.Info("HTTP API server listening on %q", s.listenAddress)
s.srv = &http.Server{Handler: s.handler}
return s.srv.Serve(listener)
}
// DispatchTLS starts the API server with the provided TLS certificate
func (s *Server) DispatchTLS(certFile, keyFile string) error {
listener, err := net.Listen("tcp", s.listenAddress)
if err != nil {
return err
}
s.log.Info("HTTPS API server listening on %q", s.listenAddress)
return http.ServeTLS(listener, s.handler, certFile, keyFile)
}
// RegisterChain registers the API endpoints associated with this chain. That is,
// add <route, handler> pairs to server so that API calls can be made to the VM.
// This method runs in a goroutine to avoid a deadlock in the event that the caller
// holds the engine's context lock. Namely, this could happen when the P-Chain is
// creating a new chain and holds the P-Chain's lock when this function is held,
// and at the same time the server's lock is held due to an API call and is trying
// to grab the P-Chain's lock.
func (s *Server) RegisterChain(chainName string, ctx *snow.Context, engine common.Engine) {
go s.registerChain(chainName, ctx, engine)
}
func (s *Server) registerChain(chainName string, ctx *snow.Context, engine common.Engine) {
var (
handlers map[string]*common.HTTPHandler
err error
)
ctx.Lock.Lock()
handlers, err = engine.GetVM().CreateHandlers()
ctx.Lock.Unlock()
if err != nil {
s.log.Error("failed to create %s handlers: %s", chainName, err)
return
}
httpLogger, err := s.factory.MakeChain(chainName, "http")
if err != nil {
s.log.Error("failed to create new http logger: %s", err)
return
}
s.log.Verbo("About to add API endpoints for chain with ID %s", ctx.ChainID)
// all subroutes to a chain begin with "bc/<the chain's ID>"
defaultEndpoint := "bc/" + ctx.ChainID.String()
// Register each endpoint
for extension, handler := range handlers {
// Validate that the route being added is valid
// e.g. "/foo" and "" are ok but "\n" is not
_, err := url.ParseRequestURI(extension)
if extension != "" && err != nil {
s.log.Error("could not add route to chain's API handler because route is malformed: %s", err)
continue
}
if err := s.AddChainRoute(handler, ctx, defaultEndpoint, extension, httpLogger); err != nil {
s.log.Error("error adding route: %s", err)
}
}
}
// AddChainRoute registers a route to a chain's handler
func (s *Server) AddChainRoute(handler *common.HTTPHandler, ctx *snow.Context, base, endpoint string, loggingWriter io.Writer) error {
url := fmt.Sprintf("%s/%s", baseURL, base)
s.log.Info("adding route %s%s", url, endpoint)
// Apply logging middleware
h := handlers.CombinedLoggingHandler(loggingWriter, handler.Handler)
// Apply middleware to grab/release chain's lock before/after calling API method
h, err := lockMiddleware(h, handler.LockOptions, &ctx.Lock)
if err != nil {
return err
}
// Apply middleware to reject calls to the handler before the chain finishes bootstrapping
h = rejectMiddleware(h, ctx)
return s.router.AddRouter(url, endpoint, h)
}
// AddRoute registers a route to a handler.
func (s *Server) AddRoute(handler *common.HTTPHandler, lock *sync.RWMutex, base, endpoint string, loggingWriter io.Writer) error {
url := fmt.Sprintf("%s/%s", baseURL, base)
s.log.Info("adding route %s%s", url, endpoint)
// Apply logging middleware
h := handlers.CombinedLoggingHandler(loggingWriter, handler.Handler)
// Apply middleware to grab/release chain's lock before/after calling API method
h, err := lockMiddleware(h, handler.LockOptions, lock)
if err != nil {
return err
}
return s.router.AddRouter(url, endpoint, h)
}
// Wraps a handler by grabbing and releasing a lock before calling the handler.
func lockMiddleware(handler http.Handler, lockOption common.LockOption, lock *sync.RWMutex) (http.Handler, error) {
switch lockOption {
case common.WriteLock:
return middlewareHandler{
before: lock.Lock,
after: lock.Unlock,
handler: handler,
}, nil
case common.ReadLock:
return middlewareHandler{
before: lock.RLock,
after: lock.RUnlock,
handler: handler,
}, nil
case common.NoLock:
return handler, nil
default:
return nil, errUnknownLockOption
}
}
// Reject middleware wraps a handler. If the chain that the context describes is
// not done bootstrapping, writes back an error.
func rejectMiddleware(handler http.Handler, ctx *snow.Context) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { // If chain isn't done bootstrapping, ignore API calls
if !ctx.IsBootstrapped() {
w.WriteHeader(http.StatusServiceUnavailable)
// Doesn't matter if there's an error while writing. They'll get the StatusServiceUnavailable code.
_, _ = w.Write([]byte("API call rejected because chain is not done bootstrapping"))
} else {
handler.ServeHTTP(w, r)
}
})
}
// AddAliases registers aliases to the server
func (s *Server) AddAliases(endpoint string, aliases ...string) error {
url := fmt.Sprintf("%s/%s", baseURL, endpoint)
endpoints := make([]string, len(aliases))
for i, alias := range aliases {
endpoints[i] = fmt.Sprintf("%s/%s", baseURL, alias)
}
return s.router.AddAlias(url, endpoints...)
}
// AddAliasesWithReadLock registers aliases to the server assuming the http read
// lock is currently held.
func (s *Server) AddAliasesWithReadLock(endpoint string, aliases ...string) error {
// This is safe, as the read lock doesn't actually need to be held once the
// http handler is called. However, it is unlocked later, so this function
// must end with the lock held.
s.router.lock.RUnlock()
defer s.router.lock.RLock()
return s.AddAliases(endpoint, aliases...)
}
// Call ...
func (s *Server) Call(
writer http.ResponseWriter,
method,
base,
endpoint string,
body io.Reader,
headers map[string]string,
) error {
url := fmt.Sprintf("%s/vm/%s", baseURL, base)
handler, err := s.router.GetHandler(url, endpoint)
if err != nil {
return err
}
req, err := http.NewRequest("POST", "*", body)
if err != nil {
return err
}
for key, value := range headers {
req.Header.Set(key, value)
}
handler.ServeHTTP(writer, req)
return nil
}
// Shutdown this server
func (s *Server) Shutdown() error {
if s.srv == nil {
return nil
}
ctx, cancel := context.WithTimeout(context.Background(), serverShutdownTimeout)
defer cancel()
return s.srv.Shutdown(ctx)
}