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envelope_stream_connector.go
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envelope_stream_connector.go
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package loggregator
import (
"context"
"crypto/tls"
"io/ioutil"
"log"
"time"
gendiodes "code.cloudfoundry.org/go-diodes"
"code.cloudfoundry.org/go-loggregator/rpc/loggregator_v2"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials"
)
// EnvelopeStreamConnector provides a way to connect to loggregator and
// consume a stream of envelopes. It handles reconnecting and provides
// a stream for the lifecycle of the given context. It should be created with
// the NewEnvelopeStreamConnector constructor.
type EnvelopeStreamConnector struct {
addr string
tlsConf *tls.Config
// Buffering
bufferSize int
alerter func(int)
log Logger
}
// NewEnvelopeStream creates a new EnvelopeStreamConnector. Its TLS
// configuration must share a CA with the loggregator server.
func NewEnvelopeStreamConnector(
addr string,
t *tls.Config,
opts ...EnvelopeStreamOption,
) *EnvelopeStreamConnector {
c := &EnvelopeStreamConnector{
addr: addr,
tlsConf: t,
log: log.New(ioutil.Discard, "", 0),
}
for _, o := range opts {
o(c)
}
return c
}
// EnvelopeStreamOption configures a EnvelopeStreamConnector.
type EnvelopeStreamOption func(*EnvelopeStreamConnector)
// WithEnvelopeStreamLogger allows for the configuration of a logger.
// By default, the logger is disabled.
func WithEnvelopeStreamLogger(l Logger) EnvelopeStreamOption {
return func(c *EnvelopeStreamConnector) {
c.log = l
}
}
// WithEnvelopeStreamBuffer enables the EnvelopeStream to read more quickly
// from the stream. It puts each envelope in a buffer that overwrites data if
// it is not being drained quick enough. If the buffer drops data, the
// 'alerter' function will be invoked with the number of envelopes dropped.
func WithEnvelopeStreamBuffer(size int, alerter func(missed int)) EnvelopeStreamOption {
return func(c *EnvelopeStreamConnector) {
c.bufferSize = size
c.alerter = alerter
}
}
// EnvelopeStream returns batches of envelopes. It blocks until its context
// is done or a batch of envelopes is available.
type EnvelopeStream func() []*loggregator_v2.Envelope
// Stream returns a new EnvelopeStream for the given context and request. The
// lifecycle of the EnvelopeStream is managed by the given context. If the
// underlying gRPC stream dies, it attempts to reconnect until the context
// is done.
func (c *EnvelopeStreamConnector) Stream(ctx context.Context, req *loggregator_v2.EgressBatchRequest) EnvelopeStream {
s := newStream(ctx, c.addr, req, c.tlsConf, c.log)
if c.alerter != nil || c.bufferSize > 0 {
d := NewOneToOneEnvelopeBatch(
c.bufferSize,
gendiodes.AlertFunc(c.alerter),
gendiodes.WithPollingContext(ctx),
)
go func() {
for {
select {
case <-ctx.Done():
return
default:
}
d.Set(s.recv())
}
}()
return d.Next
}
return s.recv
}
type stream struct {
log Logger
ctx context.Context
req *loggregator_v2.EgressBatchRequest
client loggregator_v2.EgressClient
rx loggregator_v2.Egress_BatchedReceiverClient
}
func newStream(
ctx context.Context,
addr string,
req *loggregator_v2.EgressBatchRequest,
c *tls.Config,
log Logger,
) *stream {
conn, err := grpc.Dial(
addr,
grpc.WithTransportCredentials(credentials.NewTLS(c)),
)
if err != nil {
// This error occurs on invalid configuration. And more notably,
// it does NOT occur if the server is not up.
panic("Invalid gRPC dial configuration: " + err.Error())
}
client := loggregator_v2.NewEgressClient(conn)
return &stream{
ctx: ctx,
req: req,
client: client,
log: log,
}
}
func (s *stream) recv() []*loggregator_v2.Envelope {
for {
ok := s.connect(s.ctx)
if !ok {
return nil
}
batch, err := s.rx.Recv()
if err != nil {
s.rx = nil
continue
}
return batch.Batch
}
}
func (s *stream) connect(ctx context.Context) bool {
for {
select {
case <-ctx.Done():
return false
default:
if s.rx != nil {
return true
}
var err error
s.rx, err = s.client.BatchedReceiver(
ctx,
s.req,
)
if err != nil {
s.log.Printf("Error connecting to Logs Provider: %s", err)
time.Sleep(50 * time.Millisecond)
continue
}
return true
}
}
}