fn: lb and pure-runner with non-blocking agent (#989)

* fn: lb and pure-runner with non-blocking agent *) Removed pure-runner capacity tracking code. This did not play well with internal agent resource tracker. *) In LB and runner gRPC comm, removed ACK. Now, upon TryCall, pure-runner quickly proceeds to call Submit. This is good since at this stage pure-runner already has all relevant data to initiate the call. *) Unless pure-runner emits a NACK, LB immediately streams http body to runners. *) For retriable requests added a CachedReader for http.Request Body. *) Idempotenty/retry is similar to previous code. After initial success in Engament, after attempting a TryCall, unless we receive NACK, we cannot retry that call. *) ch and naive places now wraps each TryExec with a cancellable context to clean up gRPC contexts quicker. * fn: err for simpler one-time read GetBody approach This allows for a more flexible approach since we let users to define GetBody() to allow repetitive http body read. In default LB case, LB executes a one-time io.ReadAll and sets of GetBody, which is detected by RunnerCall.RequestBody(). * fn: additional check for non-nil req.body * fn: attempt to override IO errors with ctx for TryExec * fn: system-tests log dest * fn: LB: EOF send handling * fn: logging for partial IO * fn: use buffer pool for IO storage in lb agent * fn: pure runner should use chunks for data msgs * fn: required config validations and pass APIErrors * fn: additional tests and gRPC proto simplification *) remove ACK/NACK messages as Finish message type works OK for this purpose. *) return resp in api tests for check for status code *) empty body json test in api tests for lb & pure-runner * fn: buffer adjustments *) setRequestBody result handling correction *) switch to bytes.Reader for read-only safety *) io.EOF can be returned for non-nil Body in request. * fn: clarify detection of 503 / Server Too Busy
2022-10-28 21:29:17 +03:00 · 2018-05-17 12:09:03 -07:00
parent 1083623045
commit 4ccde8897e
13 changed files with 541 additions and 336 deletions
--- a/api/agent/call.go
+++ b/api/agent/call.go
@@ -319,6 +319,12 @@ func (c *call) LbDeadline() time.Time {
 }

 func (c *call) RequestBody() io.ReadCloser {
+	if c.req.Body != nil && c.req.GetBody != nil {
+		rdr, err := c.req.GetBody()
+		if err == nil {
+			return rdr
+		}
+	}
 	return c.req.Body
 }

--- a/api/agent/config.go
+++ b/api/agent/config.go
@@ -55,6 +55,11 @@ const (
 	EnvEnableNBResourceTracker = "FN_ENABLE_NB_RESOURCE_TRACKER"

 	MaxDisabledMsecs = time.Duration(math.MaxInt64)
+
+	// defaults
+
+	DefaultHotPoll     = 200 * time.Millisecond
+	DefaultNBIOHotPoll = 20 * time.Millisecond
 )

 func NewAgentConfig() (*AgentConfig, error) {
@@ -71,7 +76,7 @@ func NewAgentConfig() (*AgentConfig, error) {

 	err = setEnvMsecs(err, EnvFreezeIdle, &cfg.FreezeIdle, 50*time.Millisecond)
 	err = setEnvMsecs(err, EnvEjectIdle, &cfg.EjectIdle, 1000*time.Millisecond)
-	err = setEnvMsecs(err, EnvHotPoll, &cfg.HotPoll, 200*time.Millisecond)
+	err = setEnvMsecs(err, EnvHotPoll, &cfg.HotPoll, DefaultHotPoll)
 	err = setEnvMsecs(err, EnvHotLauncherTimeout, &cfg.HotLauncherTimeout, time.Duration(60)*time.Minute)
 	err = setEnvMsecs(err, EnvAsyncChewPoll, &cfg.AsyncChewPoll, time.Duration(60)*time.Second)
 	err = setEnvMsecs(err, EnvCallEndTimeout, &cfg.CallEndTimeout, time.Duration(10)*time.Minute)
--- a/api/agent/lb_agent.go
+++ b/api/agent/lb_agent.go
@@ -1,8 +1,11 @@
 package agent

 import (
+	"bytes"
 	"context"
 	"errors"
+	"io"
+	"io/ioutil"
 	"sync/atomic"
 	"time"

@@ -36,12 +39,26 @@ type lbAgent struct {
 	callEndCount int64
 }

+func NewLBAgentConfig() (*AgentConfig, error) {
+	cfg, err := NewAgentConfig()
+	if err != nil {
+		return cfg, err
+	}
+	if cfg.MaxRequestSize == 0 {
+		return cfg, errors.New("lb-agent requires MaxRequestSize limit")
+	}
+	if cfg.MaxResponseSize == 0 {
+		return cfg, errors.New("lb-agent requires MaxResponseSize limit")
+	}
+	return cfg, nil
+}
+
 // NewLBAgent creates an Agent that knows how to load-balance function calls
 // across a group of runner nodes.
 func NewLBAgent(da DataAccess, rp pool.RunnerPool, p pool.Placer) (Agent, error) {

 	// TODO: Move the constants above to Agent Config or an LB specific LBAgentConfig
-	cfg, err := NewAgentConfig()
+	cfg, err := NewLBAgentConfig()
 	if err != nil {
 		logrus.WithError(err).Fatalf("error in lb-agent config cfg=%+v", cfg)
 	}
@@ -171,6 +188,17 @@ func (a *lbAgent) Submit(callI Call) error {

 	statsDequeueAndStart(ctx)

+	// pre-read and buffer request body if already not done based
+	// on GetBody presence.
+	buf, err := a.setRequestBody(ctx, call)
+	if buf != nil {
+		defer bufPool.Put(buf)
+	}
+	if err != nil {
+		logrus.WithError(err).Error("Failed to process call body")
+		return a.handleCallEnd(ctx, call, err, true)
+	}
+
 	// WARNING: isStarted (handleCallEnd) semantics
 	// need some consideration here. Similar to runner/agent
 	// we consider isCommitted true if call.Start() succeeds.
@@ -183,6 +211,48 @@ func (a *lbAgent) Submit(callI Call) error {
 	return a.handleCallEnd(ctx, call, err, true)
 }

+// setRequestGetBody sets GetBody function on the given http.Request if it is missing.  GetBody allows
+// reading from the request body without mutating the state of the request.
+func (a *lbAgent) setRequestBody(ctx context.Context, call *call) (*bytes.Buffer, error) {
+
+	r := call.req
+	if r.Body == nil || r.GetBody != nil {
+		return nil, nil
+	}
+
+	buf := bufPool.Get().(*bytes.Buffer)
+	buf.Reset()
+
+	// WARNING: we need to handle IO in a separate go-routine below
+	// to be able to detect a ctx timeout. When we timeout, we
+	// let gin/http-server to unblock the go-routine below.
+	errApp := make(chan error, 1)
+	go func() {
+
+		_, err := buf.ReadFrom(r.Body)
+		if err != nil && err != io.EOF {
+			errApp <- err
+			return
+		}
+
+		r.Body = ioutil.NopCloser(bytes.NewReader(buf.Bytes()))
+
+		// GetBody does not mutate the state of the request body
+		r.GetBody = func() (io.ReadCloser, error) {
+			return ioutil.NopCloser(bytes.NewReader(buf.Bytes())), nil
+		}
+
+		close(errApp)
+	}()
+
+	select {
+	case err := <-errApp:
+		return buf, err
+	case <-ctx.Done():
+		return buf, ctx.Err()
+	}
+}
+
 func (a *lbAgent) Enqueue(context.Context, *models.Call) error {
 	logrus.Error("Enqueue not implemented")
 	return errors.New("Enqueue not implemented")
--- a/api/agent/pure_runner.go
+++ b/api/agent/pure_runner.go
@@ -197,61 +197,39 @@ func (ch *callHandle) enqueueMsgStrict(msg *runner.RunnerMsg) error {
 	return err
 }

+func convertError(err error) string {
+	code := models.GetAPIErrorCode(err)
+	return fmt.Sprintf("%d:%s", code, err.Error())
+}
+
 // enqueueCallResponse enqueues a Submit() response to the LB
 // and initiates a graceful shutdown of the session.
 func (ch *callHandle) enqueueCallResponse(err error) {
-	defer ch.finalize()
+	var details string

-	// Error response
 	if err != nil {
-		ch.enqueueMsgStrict(&runner.RunnerMsg{
+		details = convertError(err)
+	} else if ch.c != nil {
+		details = ch.c.Model().ID
+	}
+
+	logrus.Debugf("Sending Call Finish details=%v", details)
+
+	errTmp := ch.enqueueMsgStrict(&runner.RunnerMsg{
 		Body: &runner.RunnerMsg_Finished{Finished: &runner.CallFinished{
-				Success: false,
-				Details: fmt.Sprintf("%v", err),
+			Success: err == nil,
+			Details: details,
 		}}})
+
+	if errTmp != nil {
+		logrus.WithError(errTmp).Infof("enqueueCallResponse Send Error details=%v", details)
 		return
 	}

-	// EOF and Success response
-	ch.enqueueMsgStrict(&runner.RunnerMsg{
-		Body: &runner.RunnerMsg_Data{
-			Data: &runner.DataFrame{
-				Eof: true,
-			},
-		},
-	})
-
-	ch.enqueueMsgStrict(&runner.RunnerMsg{
-		Body: &runner.RunnerMsg_Finished{Finished: &runner.CallFinished{
-			Success: true,
-			Details: ch.c.Model().ID,
-		}}})
+	errTmp = ch.finalize()
+	if errTmp != nil {
+		logrus.WithError(errTmp).Infof("enqueueCallResponse Finalize Error details=%v", details)
 	}
-
-// enqueueAck enqueues a ACK or NACK response to the LB for ClientMsg_Try
-// request. If NACK, then it also initiates a graceful shutdown of the
-// session.
-func (ch *callHandle) enqueueAck(err error) error {
-	// NACK
-	if err != nil {
-		err = ch.enqueueMsgStrict(&runner.RunnerMsg{
-			Body: &runner.RunnerMsg_Acknowledged{Acknowledged: &runner.CallAcknowledged{
-				Committed: false,
-				Details:   fmt.Sprintf("%v", err),
-			}}})
-		if err != nil {
-			return err
-		}
-		return ch.finalize()
-	}
-
-	// ACK
-	return ch.enqueueMsgStrict(&runner.RunnerMsg{
-		Body: &runner.RunnerMsg_Acknowledged{Acknowledged: &runner.CallAcknowledged{
-			Committed:             true,
-			Details:               ch.c.Model().ID,
-			SlotAllocationLatency: time.Time(ch.allocatedTime).Sub(time.Time(ch.receivedTime)).String(),
-		}}})
 }

 // spawnPipeToFn pumps data to Function via callHandle io.PipeWriter (pipeToFnW)
@@ -400,9 +378,21 @@ func (ch *callHandle) Write(data []byte) (int, error) {
 		return 0, err
 	}

+	total := 0
+	// split up data into gRPC chunks
+	for {
+		chunkSize := len(data)
+		if chunkSize > MaxDataChunk {
+			chunkSize = MaxDataChunk
+		}
+		if chunkSize == 0 {
+			break
+		}
+
 		// we cannot retain 'data'
-	cpData := make([]byte, len(data))
-	copy(cpData, data)
+		cpData := make([]byte, chunkSize)
+		copy(cpData, data[0:chunkSize])
+		data = data[chunkSize:]

 		err = ch.enqueueMsg(&runner.RunnerMsg{
 			Body: &runner.RunnerMsg_Data{
@@ -414,9 +404,12 @@ func (ch *callHandle) Write(data []byte) (int, error) {
 		})

 		if err != nil {
-		return 0, err
+			return total, err
 		}
-	return len(data), nil
+		total += chunkSize
+	}
+
+	return total, nil
 }

 // getTryMsg fetches/waits for a TryCall message from
@@ -457,52 +450,12 @@ func (ch *callHandle) getDataMsg() *runner.DataFrame {
 	return msg
 }

+// TODO: decomission/remove this once dependencies are cleaned up
 type CapacityGate interface {
-	// CheckAndReserveCapacity must perform an atomic check plus reservation. If an error is returned, then it is
-	// guaranteed that no capacity has been committed. If nil is returned, then it is guaranteed that the provided units
-	// of capacity have been committed.
 	CheckAndReserveCapacity(units uint64) error
-
-	// ReleaseCapacity must perform an atomic release of capacity. The units provided must not bring the capacity under
-	// zero; implementations are free to panic in that case.
 	ReleaseCapacity(units uint64)
 }

-type pureRunnerCapacityManager struct {
-	totalCapacityUnits     uint64
-	committedCapacityUnits uint64
-	mtx                    sync.Mutex
-}
-
-type capacityDeallocator func()
-
-func newPureRunnerCapacityManager(units uint64) *pureRunnerCapacityManager {
-	return &pureRunnerCapacityManager{
-		totalCapacityUnits:     units,
-		committedCapacityUnits: 0,
-	}
-}
-
-func (prcm *pureRunnerCapacityManager) CheckAndReserveCapacity(units uint64) error {
-	prcm.mtx.Lock()
-	defer prcm.mtx.Unlock()
-	if prcm.totalCapacityUnits-prcm.committedCapacityUnits >= units {
-		prcm.committedCapacityUnits = prcm.committedCapacityUnits + units
-		return nil
-	}
-	return models.ErrCallTimeoutServerBusy
-}
-
-func (prcm *pureRunnerCapacityManager) ReleaseCapacity(units uint64) {
-	prcm.mtx.Lock()
-	defer prcm.mtx.Unlock()
-	if units <= prcm.committedCapacityUnits {
-		prcm.committedCapacityUnits = prcm.committedCapacityUnits - units
-		return
-	}
-	panic("Fatal error in pure runner capacity calculation, getting to sub-zero capacity")
-}
-
 // pureRunner implements Agent and delegates execution of functions to an internal Agent; basically it wraps around it
 // and provides the gRPC server that implements the LB <-> Runner protocol.
 type pureRunner struct {
@@ -510,7 +463,6 @@ type pureRunner struct {
 	listen     string
 	a          Agent
 	inflight   int32
-	capacity   CapacityGate
 }

 func (pr *pureRunner) GetAppID(ctx context.Context, appName string) (string, error) {
@@ -559,35 +511,27 @@ func (pr *pureRunner) spawnSubmit(state *callHandle) {
 	}()
 }

-// handleTryCall based on the TryCall message, allocates a resource/capacity reservation
-// and creates callHandle.c with agent.call.
-func (pr *pureRunner) handleTryCall(tc *runner.TryCall, state *callHandle) (capacityDeallocator, error) {
+// handleTryCall based on the TryCall message, tries to place the call on NBIO Agent
+func (pr *pureRunner) handleTryCall(tc *runner.TryCall, state *callHandle) error {
 	state.receivedTime = strfmt.DateTime(time.Now())
 	var c models.Call
 	err := json.Unmarshal([]byte(tc.ModelsCallJson), &c)
 	if err != nil {
-		return func() {}, err
-	}
-
-	// Capacity check first
-	err = pr.capacity.CheckAndReserveCapacity(c.Memory)
-	if err != nil {
-		return func() {}, err
-	}
-
-	cleanup := func() {
-		pr.capacity.ReleaseCapacity(c.Memory)
+		state.enqueueCallResponse(err)
+		return err
 	}

 	agent_call, err := pr.a.GetCall(FromModelAndInput(&c, state.pipeToFnR), WithWriter(state))
 	if err != nil {
-		return cleanup, err
+		state.enqueueCallResponse(err)
+		return err
 	}

 	state.c = agent_call.(*call)
 	state.allocatedTime = strfmt.DateTime(time.Now())
+	pr.spawnSubmit(state)

-	return cleanup, nil
+	return nil
 }

 // Handles a client engagement
@@ -615,15 +559,13 @@ func (pr *pureRunner) Engage(engagement runner.RunnerProtocol_EngageServer) erro
 		return state.waitError()
 	}

-	dealloc, errTry := pr.handleTryCall(tryMsg, state)
-	defer dealloc()
-	// respond with handleTryCall response
-	err := state.enqueueAck(errTry)
-	if err != nil || errTry != nil {
+	errTry := pr.handleTryCall(tryMsg, state)
+	if errTry != nil {
 		return state.waitError()
 	}

-	var dataFeed chan *runner.DataFrame
+	dataFeed := state.spawnPipeToFn()
+
 DataLoop:
 	for {
 		dataMsg := state.getDataMsg()
@@ -631,11 +573,6 @@ DataLoop:
 			break
 		}

-		if dataFeed == nil {
-			pr.spawnSubmit(state)
-			dataFeed = state.spawnPipeToFn()
-		}
-
 		select {
 		case dataFeed <- dataMsg:
 			if dataMsg.Eof {
@@ -678,8 +615,29 @@ func DefaultPureRunner(cancel context.CancelFunc, addr string, da DataAccess, ce
 	return NewPureRunner(cancel, addr, da, cert, key, ca, nil)
 }

-func NewPureRunner(cancel context.CancelFunc, addr string, da DataAccess, cert string, key string, ca string, gate CapacityGate) (Agent, error) {
-	a := createAgent(da)
+func ValidatePureRunnerConfig() AgentOption {
+	return func(a *agent) error {
+
+		if a.cfg.MaxResponseSize == 0 {
+			return errors.New("pure runner requires MaxResponseSize limits")
+		}
+		if a.cfg.MaxRequestSize == 0 {
+			return errors.New("pure runner requires MaxRequestSize limits")
+		}
+
+		// pure runner requires a non-blocking resource tracker
+		if !a.cfg.EnableNBResourceTracker {
+			return errors.New("pure runner requires EnableNBResourceTracker true")
+		}
+
+		return nil
+	}
+}
+
+func NewPureRunner(cancel context.CancelFunc, addr string, da DataAccess, cert string, key string, ca string, unused CapacityGate) (Agent, error) {
+	// TODO: gate unused, decommission/remove it after cleaning up dependencies to it.
+
+	a := createAgent(da, ValidatePureRunnerConfig())
 	var pr *pureRunner
 	var err error
 	if cert != "" && key != "" && ca != "" {
@@ -688,13 +646,13 @@ func NewPureRunner(cancel context.CancelFunc, addr string, da DataAccess, cert s
 			logrus.WithField("runner_addr", addr).Warn("Failed to create credentials!")
 			return nil, err
 		}
-		pr, err = createPureRunner(addr, a, c, gate)
+		pr, err = createPureRunner(addr, a, c)
 		if err != nil {
 			return nil, err
 		}
 	} else {
 		logrus.Warn("Running pure runner in insecure mode!")
-		pr, err = createPureRunner(addr, a, nil, gate)
+		pr, err = createPureRunner(addr, a, nil)
 		if err != nil {
 			return nil, err
 		}
@@ -736,32 +694,20 @@ func creds(cert string, key string, ca string) (credentials.TransportCredentials
 	}), nil
 }

-func createPureRunner(addr string, a Agent, creds credentials.TransportCredentials, gate CapacityGate) (*pureRunner, error) {
+func createPureRunner(addr string, a Agent, creds credentials.TransportCredentials) (*pureRunner, error) {
 	var srv *grpc.Server
 	if creds != nil {
 		srv = grpc.NewServer(grpc.Creds(creds))
 	} else {
 		srv = grpc.NewServer()
 	}
-	if gate == nil {
-		memUnits := getAvailableMemoryUnits()
-		gate = newPureRunnerCapacityManager(memUnits)
-	}
+
 	pr := &pureRunner{
 		gRPCServer: srv,
 		listen:     addr,
 		a:          a,
-		capacity:   gate,
 	}

 	runner.RegisterRunnerProtocolServer(srv, pr)
 	return pr, nil
 }
-
-const megabyte uint64 = 1024 * 1024
-
-func getAvailableMemoryUnits() uint64 {
-	// To reuse code - but it's a bit of a hack. TODO: refactor the OS-specific get memory funcs out of that.
-	throwawayRT := NewResourceTracker(nil).(*resourceTracker)
-	return throwawayRT.ramAsyncTotal / megabyte
-}
--- a/api/agent/runner_client.go
+++ b/api/agent/runner_client.go
@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"errors"
 	"io"
+	"strconv"
+	"strings"
 	"time"

 	"google.golang.org/grpc"
@@ -12,6 +14,7 @@ import (

 	pb "github.com/fnproject/fn/api/agent/grpc"
 	"github.com/fnproject/fn/api/common"
+	"github.com/fnproject/fn/api/models"
 	pool "github.com/fnproject/fn/api/runnerpool"
 	"github.com/fnproject/fn/grpcutil"
 	"github.com/sirupsen/logrus"
@@ -19,6 +22,12 @@ import (

 var (
 	ErrorRunnerClosed    = errors.New("Runner is closed")
+	ErrorPureRunnerNoEOF = errors.New("Purerunner missing EOF response")
+)
+
+const (
+	// max buffer size for grpc data messages, 10K
+	MaxDataChunk = 10 * 1024
 )

 type gRPCRunner struct {
@@ -76,10 +85,15 @@ func (r *gRPCRunner) Address() string {
 	return r.address
 }

+func isRetriable(err error) bool {
+	return models.GetAPIErrorCode(err) == models.GetAPIErrorCode(models.ErrCallTimeoutServerBusy)
+}
+
 func (r *gRPCRunner) TryExec(ctx context.Context, call pool.RunnerCall) (bool, error) {
 	logrus.WithField("runner_addr", r.address).Debug("Attempting to place call")
 	if !r.shutWg.AddSession(1) {
-		return true, ErrorRunnerClosed
+		// try another runner if this one is closed.
+		return false, ErrorRunnerClosed
 	}
 	defer r.shutWg.DoneSession()

@@ -90,6 +104,7 @@ func (r *gRPCRunner) TryExec(ctx context.Context, call pool.RunnerCall) (bool, e
 		// If we can't encode the model, no runner will ever be able to run this. Give up.
 		return true, err
 	}
+
 	runnerConnection, err := r.client.Engage(ctx)
 	if err != nil {
 		logrus.WithError(err).Error("Unable to create client to runner node")
@@ -97,113 +112,171 @@ func (r *gRPCRunner) TryExec(ctx context.Context, call pool.RunnerCall) (bool, e
 		return false, err
 	}

+	// After this point, we assume "COMMITTED" unless pure runner
+	// send explicit NACK
 	err = runnerConnection.Send(&pb.ClientMsg{Body: &pb.ClientMsg_Try{Try: &pb.TryCall{ModelsCallJson: string(modelJSON)}}})
 	if err != nil {
 		logrus.WithError(err).Error("Failed to send message to runner node")
-		return false, err
-	}
-	msg, err := runnerConnection.Recv()
-	if err != nil {
-		logrus.WithError(err).Error("Failed to receive first message from runner node")
-		return false, err
+		return true, err
 	}

-	switch body := msg.Body.(type) {
-	case *pb.RunnerMsg_Acknowledged:
-		if !body.Acknowledged.Committed {
-			logrus.Debugf("Runner didn't commit invocation request: %v", body.Acknowledged.Details)
-			return false, nil
-			// Try the next runner
-		}
-		logrus.Debug("Runner committed invocation request, sending data frames")
-		done := make(chan error)
-		go receiveFromRunner(runnerConnection, call, done)
-		sendToRunner(call, runnerConnection)
-		return true, <-done
+	recvDone := make(chan error, 1)

-	default:
-		logrus.Errorf("Unhandled message type received from runner: %v\n", msg)
-		return true, nil
+	go receiveFromRunner(runnerConnection, call, recvDone)
+	go sendToRunner(runnerConnection, call)
+
+	select {
+	case <-ctx.Done():
+		logrus.Infof("Engagement Context ended ctxErr=%v", ctx.Err())
+		return true, ctx.Err()
+	case recvErr := <-recvDone:
+		return !isRetriable(recvErr), recvErr
+	}
 }

-}
-
-func sendToRunner(call pool.RunnerCall, protocolClient pb.RunnerProtocol_EngageClient) error {
+func sendToRunner(protocolClient pb.RunnerProtocol_EngageClient, call pool.RunnerCall) {
 	bodyReader := call.RequestBody()
-	writeBufferSize := 10 * 1024 // 10KB
-	writeBuffer := make([]byte, writeBufferSize)
-	for {
-		n, err := bodyReader.Read(writeBuffer)
-		logrus.Debugf("Wrote %v bytes to the runner", n)
+	writeBuffer := make([]byte, MaxDataChunk)

-		if err == io.EOF {
-			err = protocolClient.Send(&pb.ClientMsg{
+	// IMPORTANT: IO Read below can fail in multiple go-routine cases (in retry
+	// case especially if receiveFromRunner go-routine receives a NACK while sendToRunner is
+	// already blocked on a read) or in the case of reading the http body multiple times (retries.)
+	// Normally http.Request.Body can be read once. However runner_client users should implement/add
+	// http.Request.GetBody() function and cache the body content in the request.
+	// See lb_agent setRequestGetBody() which handles this. With GetBody installed,
+	// the 'Read' below is an actually non-blocking operation since GetBody() should hand out
+	// a new instance of io.ReadCloser() that allows repetitive reads on the http body.
+	for {
+		// WARNING: blocking read.
+		n, err := bodyReader.Read(writeBuffer)
+		if err != nil && err != io.EOF {
+			logrus.WithError(err).Error("Failed to receive data from http client body")
+		}
+
+		// any IO error or n == 0 is an EOF for pure-runner
+		isEOF := err != nil || n == 0
+		data := writeBuffer[:n]
+
+		logrus.Debugf("Sending %d bytes of data isEOF=%v to runner", n, isEOF)
+		sendErr := protocolClient.Send(&pb.ClientMsg{
 			Body: &pb.ClientMsg_Data{
 				Data: &pb.DataFrame{
-						Data: writeBuffer,
-						Eof:  true,
+					Data: data,
+					Eof:  isEOF,
 				},
 			},
 		})
+		if sendErr != nil {
+			logrus.WithError(sendErr).Errorf("Failed to send data frame size=%d isEOF=%v", n, isEOF)
+			return
+		}
+		if isEOF {
+			return
+		}
+	}
+}
+
+func parseError(details string) error {
+	tokens := strings.SplitN(details, ":", 2)
+	if len(tokens) != 2 || tokens[0] == "" || tokens[1] == "" {
+		return errors.New(details)
+	}
+	code, err := strconv.ParseInt(tokens[0], 10, 64)
 	if err != nil {
-				logrus.WithError(err).Error("Failed to send data frame with EOF to runner")
+		return errors.New(details)
 	}
-			break
+	if code != 0 {
+		return models.NewAPIError(int(code), errors.New(tokens[1]))
 	}
-		err = protocolClient.Send(&pb.ClientMsg{
-			Body: &pb.ClientMsg_Data{
-				Data: &pb.DataFrame{
-					Data: writeBuffer,
-					Eof:  false,
-				},
-			},
-		})
-		if err != nil {
-			logrus.WithError(err).Error("Failed to send data frame")
-			return err
+	return errors.New(tokens[1])
 }
+
+func tryQueueError(err error, done chan error) {
+	select {
+	case done <- err:
+	default:
 	}
-	return nil
 }

 func receiveFromRunner(protocolClient pb.RunnerProtocol_EngageClient, c pool.RunnerCall, done chan error) {
 	w := c.ResponseWriter()
+	defer close(done)

+	isPartialWrite := false
+
+DataLoop:
 	for {
 		msg, err := protocolClient.Recv()
 		if err != nil {
-			logrus.WithError(err).Error("Failed to receive message from runner")
-			done <- err
+			logrus.WithError(err).Info("Receive error from runner")
+			tryQueueError(err, done)
 			return
 		}

 		switch body := msg.Body.(type) {
+
+		// Process HTTP header/status message. This may not arrive depending on
+		// pure runners behavior. (Eg. timeout & no IO received from function)
 		case *pb.RunnerMsg_ResultStart:
 			switch meta := body.ResultStart.Meta.(type) {
 			case *pb.CallResultStart_Http:
+				logrus.Debugf("Received meta http result from runner Status=%v", meta.Http.StatusCode)
 				for _, header := range meta.Http.Headers {
 					w.Header().Set(header.Key, header.Value)
 				}
+				if meta.Http.StatusCode > 0 {
+					w.WriteHeader(int(meta.Http.StatusCode))
+				}
 			default:
 				logrus.Errorf("Unhandled meta type in start message: %v", meta)
 			}
+
+		// May arrive if function has output. We ignore EOF.
 		case *pb.RunnerMsg_Data:
-			w.Write(body.Data.Data)
+			logrus.Debugf("Received data from runner len=%d isEOF=%v", len(body.Data.Data), body.Data.Eof)
+			if !isPartialWrite {
+				// WARNING: blocking write
+				n, err := w.Write(body.Data.Data)
+				if n != len(body.Data.Data) {
+					isPartialWrite = true
+					logrus.WithError(err).Infof("Failed to write full response (%d of %d) to client", n, len(body.Data.Data))
+					if err == nil {
+						err = io.ErrShortWrite
+					}
+					tryQueueError(err, done)
+				}
+			}
+
+		// Finish messages required for finish/finalize the processing.
 		case *pb.RunnerMsg_Finished:
-			if body.Finished.Success {
-				logrus.Infof("Call finished successfully: %v", body.Finished.Details)
-			} else {
-				logrus.Infof("Call finished unsuccessfully: %v", body.Finished.Details)
+			logrus.Infof("Call finished Success=%v %v", body.Finished.Success, body.Finished.Details)
+			if !body.Finished.Success {
+				err := parseError(body.Finished.GetDetails())
+				tryQueueError(err, done)
 			}
-			// There should be an EOF following the last packet
-			if _, err := protocolClient.Recv(); err != io.EOF {
-				logrus.WithError(err).Error("Did not receive expected EOF from runner stream")
-				done <- err
-			}
-			close(done)
-			return
+			break DataLoop
+
 		default:
-			logrus.Errorf("Unhandled message type from runner: %v", body)
+			logrus.Error("Ignoring unknown message type %T from runner, possible client/server mismatch", body)
 		}
 	}
+
+	// There should be an EOF following the last packet
+	for {
+		msg, err := protocolClient.Recv()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			logrus.WithError(err).Infof("Call Waiting EOF received error")
+			tryQueueError(err, done)
+			break
+		}
+
+		switch body := msg.Body.(type) {
+		default:
+			logrus.Infof("Call Waiting EOF ignoring message %T", body)
+		}
+		tryQueueError(ErrorPureRunnerNoEOF, done)
+	}
 }
--- a/api/runnerpool/ch_placer.go
+++ b/api/runnerpool/ch_placer.go
@@ -47,7 +47,10 @@ func (p *chPlacer) PlaceCall(rp RunnerPool, ctx context.Context, call RunnerCall

 				r := runners[i]

-				placed, err := r.TryExec(ctx, call)
+				tryCtx, tryCancel := context.WithCancel(ctx)
+				placed, err := r.TryExec(tryCtx, call)
+				tryCancel()
+
 				if err != nil {
 					logrus.WithError(err).Error("Failed during call placement")
 				}
--- a/api/runnerpool/naive_placer.go
+++ b/api/runnerpool/naive_placer.go
@@ -49,7 +49,10 @@ func (sp *naivePlacer) PlaceCall(rp RunnerPool, ctx context.Context, call Runner
 				i := atomic.AddUint64(&sp.rrIndex, uint64(1))
 				r := runners[int(i)%len(runners)]

-				placed, err := r.TryExec(ctx, call)
+				tryCtx, tryCancel := context.WithCancel(ctx)
+				placed, err := r.TryExec(tryCtx, call)
+				tryCancel()
+
 				if err != nil {
 					logrus.WithError(err).Error("Failed during call placement")
 				}
--- a/system_test.sh
+++ b/system_test.sh
@@ -39,6 +39,12 @@ esac
 # avoid port conflicts with api_test.sh which are run in parallel
 export FN_API_URL="http://localhost:8085"
 export FN_DS_DB_PING_MAX_RETRIES=60
+
+# pure runner and LB agent required settings below
+export FN_MAX_REQUEST_SIZE=6291456
+export FN_MAX_RESPONSE_SIZE=6291456
+export FN_ENABLE_NB_RESOURCE_TRACKER=1
+
 cd test/fn-system-tests && FN_DB_URL=${FN_DB_URL} FN_API_URL=${FN_API_URL} go test -v -parallel ${2:-1} ./...; cd ../../

 remove_system_containers
--- a/test/fn-api-tests/exec_test.go
+++ b/test/fn-api-tests/exec_test.go
@@ -43,14 +43,14 @@ func CallAsync(t *testing.T, u url.URL, content io.Reader) string {

 func CallSync(t *testing.T, u url.URL, content io.Reader) string {
 	output := &bytes.Buffer{}
-	hdrs, err := CallFN(u.String(), content, output, "POST", []string{})
+	resp, err := CallFN(u.String(), content, output, "POST", []string{})
 	if err != nil {
 		t.Errorf("Got unexpected error: %v", err)
 	}

-	callId := hdrs.Get("FN_CALL_ID")
+	callId := resp.Header.Get("FN_CALL_ID")
 	if callId == "" {
-		t.Errorf("Assertion error.\n\tExpected call id header in response, got: %v", hdrs)
+		t.Errorf("Assertion error.\n\tExpected call id header in response, got: %v", resp.Header)
 	}

 	t.Logf("Sync execution call ID: %v", callId)
@@ -221,13 +221,13 @@ func TestCanCauseTimeout(t *testing.T) {
 	}{Seconds: 11})
 	output := &bytes.Buffer{}

-	headers, _ := CallFN(u.String(), content, output, "POST", []string{})
+	resp, _ := CallFN(u.String(), content, output, "POST", []string{})

 	if !strings.Contains(output.String(), "Timed out") {
 		t.Errorf("Must fail because of timeout, but got error message: %v", output.String())
 	}
 	cfg := &call.GetAppsAppCallsCallParams{
-		Call:    headers.Get("FN_CALL_ID"),
+		Call:    resp.Header.Get("FN_CALL_ID"),
 		App:     s.AppName,
 		Context: s.Context,
 	}
--- a/test/fn-api-tests/formats_test.go
+++ b/test/fn-api-tests/formats_test.go
@@ -41,7 +41,7 @@ func TestFnJSONFormats(t *testing.T) {
 	})
 	content := bytes.NewBuffer(b)
 	output := &bytes.Buffer{}
-	headers, err := CallFN(u.String(), content, output, "POST", []string{})
+	resp, err := CallFN(u.String(), content, output, "POST", []string{})
 	if err != nil {
 		t.Errorf("Got unexpected error: %v", err)
 	}
@@ -56,7 +56,7 @@ func TestFnJSONFormats(t *testing.T) {
 	expectedHeaderNames := []string{"Content-Type", "Content-Length"}
 	expectedHeaderValues := []string{"application/json; charset=utf-8", strconv.Itoa(output.Len())}
 	for i, name := range expectedHeaderNames {
-		actual := headers.Get(name)
+		actual := resp.Header.Get(name)
 		expected := expectedHeaderValues[i]
 		if !strings.Contains(expected, actual) {
 			t.Errorf("HTTP header assertion error for %v."+
--- a/test/fn-api-tests/utils.go
+++ b/test/fn-api-tests/utils.go
@@ -212,7 +212,7 @@ func EnvAsHeader(req *http.Request, selectedEnv []string) {
 	}
 }

-func CallFN(u string, content io.Reader, output io.Writer, method string, env []string) (http.Header, error) {
+func CallFN(u string, content io.Reader, output io.Writer, method string, env []string) (*http.Response, error) {
 	if method == "" {
 		if content == nil {
 			method = "GET"
@@ -239,7 +239,7 @@ func CallFN(u string, content io.Reader, output io.Writer, method string, env []

 	io.Copy(output, resp.Body)

-	return resp.Header, nil
+	return resp, nil
 }

 func init() {
--- a/test/fn-system-tests/exec_test.go
+++ b/test/fn-system-tests/exec_test.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"net/http"
 	"net/url"
 	"path"
 	"strings"
@@ -55,6 +56,7 @@ func TestCanExecuteFunction(t *testing.T) {
 	rt := s.BasicRoute()
 	rt.Image = "fnproject/fn-test-utils"
 	rt.Format = "json"
+	rt.Memory = 64
 	rt.Type = "sync"

 	s.GivenRouteExists(t, s.AppName, rt)
@@ -73,7 +75,7 @@ func TestCanExecuteFunction(t *testing.T) {
 	content := bytes.NewBuffer([]byte(body))
 	output := &bytes.Buffer{}

-	_, err = apiutils.CallFN(u.String(), content, output, "POST", []string{})
+	resp, err := apiutils.CallFN(u.String(), content, output, "POST", []string{})
 	if err != nil {
 		t.Errorf("Got unexpected error: %v", err)
 	}
@@ -82,11 +84,147 @@ func TestCanExecuteFunction(t *testing.T) {
 	if err != nil || echo != "HelloWorld" {
 		t.Fatalf("getEchoContent/HelloWorld check failed on %v", output)
 	}
+
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("StatusCode check failed on %v", resp.StatusCode)
+	}
+}
+
+func TestCanExecuteBigOutput(t *testing.T) {
+	s := apiutils.SetupHarness()
+	s.GivenAppExists(t, &sdkmodels.App{Name: s.AppName})
+	defer s.Cleanup()
+
+	rt := s.BasicRoute()
+	rt.Image = "fnproject/fn-test-utils"
+	rt.Format = "json"
+	rt.Memory = 64
+	rt.Type = "sync"
+
+	s.GivenRouteExists(t, s.AppName, rt)
+
+	lb, err := LB()
+	if err != nil {
+		t.Fatalf("Got unexpected error: %v", err)
+	}
+	u := url.URL{
+		Scheme: "http",
+		Host:   lb,
+	}
+	u.Path = path.Join(u.Path, "r", s.AppName, s.RoutePath)
+
+	// Approx 5.3MB output
+	body := `{"echoContent": "HelloWorld", "sleepTime": 0, "isDebug": true, "trailerRepeat": 410000}`
+	content := bytes.NewBuffer([]byte(body))
+	output := &bytes.Buffer{}
+
+	resp, err := apiutils.CallFN(u.String(), content, output, "POST", []string{})
+	if err != nil {
+		t.Errorf("Got unexpected error: %v", err)
+	}
+
+	t.Logf("getEchoContent/HelloWorld size %d", len(output.Bytes()))
+
+	echo, err := getEchoContent(output.Bytes())
+	if err != nil || echo != "HelloWorld" {
+		t.Fatalf("getEchoContent/HelloWorld check failed on %v", output)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("StatusCode check failed on %v", resp.StatusCode)
+	}
+}
+
+func TestCanExecuteTooBigOutput(t *testing.T) {
+	s := apiutils.SetupHarness()
+	s.GivenAppExists(t, &sdkmodels.App{Name: s.AppName})
+	defer s.Cleanup()
+
+	rt := s.BasicRoute()
+	rt.Image = "fnproject/fn-test-utils"
+	rt.Format = "json"
+	rt.Memory = 64
+	rt.Type = "sync"
+
+	s.GivenRouteExists(t, s.AppName, rt)
+
+	lb, err := LB()
+	if err != nil {
+		t.Fatalf("Got unexpected error: %v", err)
+	}
+	u := url.URL{
+		Scheme: "http",
+		Host:   lb,
+	}
+	u.Path = path.Join(u.Path, "r", s.AppName, s.RoutePath)
+
+	// > 6MB output
+	body := `{"echoContent": "HelloWorld", "sleepTime": 0, "isDebug": true, "trailerRepeat": 600000}`
+	content := bytes.NewBuffer([]byte(body))
+	output := &bytes.Buffer{}
+
+	resp, err := apiutils.CallFN(u.String(), content, output, "POST", []string{})
+	if err != nil {
+		t.Errorf("Got unexpected error: %v", err)
+	}
+
+	exp := "{\"error\":{\"message\":\"function response too large\"}}\n"
+	actual := output.String()
+
+	if !strings.Contains(exp, actual) || len(exp) != len(actual) {
+		t.Errorf("Assertion error.\n\tExpected: %v\n\tActual: %v", exp, output.String())
+	}
+
+	if resp.StatusCode != http.StatusBadGateway {
+		t.Fatalf("StatusCode check failed on %v", resp.StatusCode)
+	}
+}
+
+func TestCanExecuteEmptyOutput(t *testing.T) {
+	s := apiutils.SetupHarness()
+	s.GivenAppExists(t, &sdkmodels.App{Name: s.AppName})
+	defer s.Cleanup()
+
+	rt := s.BasicRoute()
+	rt.Image = "fnproject/fn-test-utils"
+	rt.Format = "json"
+	rt.Memory = 64
+	rt.Type = "sync"
+
+	s.GivenRouteExists(t, s.AppName, rt)
+
+	lb, err := LB()
+	if err != nil {
+		t.Fatalf("Got unexpected error: %v", err)
+	}
+	u := url.URL{
+		Scheme: "http",
+		Host:   lb,
+	}
+	u.Path = path.Join(u.Path, "r", s.AppName, s.RoutePath)
+
+	// empty body output
+	body := `{"sleepTime": 0, "isDebug": true, "isEmptyBody": true}`
+	content := bytes.NewBuffer([]byte(body))
+	output := &bytes.Buffer{}
+
+	resp, err := apiutils.CallFN(u.String(), content, output, "POST", []string{})
+	if err != nil {
+		t.Errorf("Got unexpected error: %v", err)
+	}
+
+	actual := output.String()
+
+	if 0 != len(actual) {
+		t.Errorf("Assertion error.\n\tExpected empty\n\tActual: %v", output.String())
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("StatusCode check failed on %v", resp.StatusCode)
+	}
 }

 func TestBasicConcurrentExecution(t *testing.T) {
-	SystemTweaker().ChangeNodeCapacities(512)
-	defer SystemTweaker().RestoreInitialNodeCapacities()

 	s := apiutils.SetupHarness()

@@ -96,6 +234,7 @@ func TestBasicConcurrentExecution(t *testing.T) {
 	rt := s.BasicRoute()
 	rt.Image = "fnproject/fn-test-utils"
 	rt.Format = "json"
+	rt.Memory = 32
 	rt.Type = "sync"

 	s.GivenRouteExists(t, s.AppName, rt)
@@ -117,7 +256,7 @@ func TestBasicConcurrentExecution(t *testing.T) {
 			body := `{"echoContent": "HelloWorld", "sleepTime": 0, "isDebug": true}`
 			content := bytes.NewBuffer([]byte(body))
 			output := &bytes.Buffer{}
-			_, err = apiutils.CallFN(u.String(), content, output, "POST", []string{})
+			resp, err := apiutils.CallFN(u.String(), content, output, "POST", []string{})
 			if err != nil {
 				results <- fmt.Errorf("Got unexpected error: %v", err)
 				return
@@ -128,6 +267,10 @@ func TestBasicConcurrentExecution(t *testing.T) {
 				results <- fmt.Errorf("Assertion error.\n\tActual: %v", output.String())
 				return
 			}
+			if resp.StatusCode != http.StatusOK {
+				results <- fmt.Errorf("StatusCode check failed on %v", resp.StatusCode)
+				return
+			}

 			results <- nil
 		}()
@@ -142,18 +285,19 @@ func TestBasicConcurrentExecution(t *testing.T) {
 }

 func TestSaturatedSystem(t *testing.T) {
-	// Set the capacity to 0 so we always look out of capacity.
-	SystemTweaker().ChangeNodeCapacities(0)
-	defer SystemTweaker().RestoreInitialNodeCapacities()

 	s := apiutils.SetupHarness()

 	s.GivenAppExists(t, &sdkmodels.App{Name: s.AppName})
 	defer s.Cleanup()

+	timeout := int32(5)
+
 	rt := s.BasicRoute()
 	rt.Image = "fnproject/fn-test-utils"
 	rt.Format = "json"
+	rt.Timeout = &timeout
+	rt.Memory = 300
 	rt.Type = "sync"

 	s.GivenRouteExists(t, s.AppName, rt)
@@ -172,15 +316,28 @@ func TestSaturatedSystem(t *testing.T) {
 	content := bytes.NewBuffer([]byte(body))
 	output := &bytes.Buffer{}

-	_, err = apiutils.CallFN(u.String(), content, output, "POST", []string{})
+	resp, err := apiutils.CallFN(u.String(), content, output, "POST", []string{})
 	if err != nil {
 		if err != apimodels.ErrCallTimeoutServerBusy {
 			t.Errorf("Got unexpected error: %v", err)
 		}
 	}
-	expectedOutput := "{\"error\":{\"message\":\"Timed out - server too busy\"}}\n"
+
+	// LB may respond either with:
+	//  timeout: a timeout during a call to a runner
+	//  too busy: a timeout during LB retry loop
+	exp1 := "{\"error\":{\"message\":\"Timed out - server too busy\"}}\n"
+	exp2 := "{\"error\":{\"message\":\"Timed out\"}}\n"
+
 	actual := output.String()
-	if !strings.Contains(expectedOutput, actual) || len(expectedOutput) != len(actual) {
-		t.Errorf("Assertion error.\n\tExpected: %v\n\tActual: %v", expectedOutput, output.String())
+
+	if strings.Contains(exp1, actual) && len(exp1) == len(actual) {
+	} else if strings.Contains(exp2, actual) && len(exp2) == len(actual) {
+	} else {
+		t.Errorf("Assertion error.\n\tExpected: %v or %v\n\tActual: %v", exp1, exp2, output.String())
+	}
+
+	if resp.StatusCode != http.StatusServiceUnavailable && resp.StatusCode != http.StatusGatewayTimeout {
+		t.Fatalf("StatusCode check failed on %v", resp.StatusCode)
 	}
 }
--- a/test/fn-system-tests/system_test.go
+++ b/test/fn-system-tests/system_test.go
@@ -7,7 +7,6 @@ import (

 	"github.com/fnproject/fn/api/agent"
 	"github.com/fnproject/fn/api/agent/hybrid"
-	"github.com/fnproject/fn/api/models"
 	pool "github.com/fnproject/fn/api/runnerpool"
 	"github.com/fnproject/fn/api/server"

@@ -18,7 +17,6 @@ import (
 	"os"
 	"strconv"
 	"strings"
-	"sync"
 	"testing"
 	"time"
 )
@@ -37,35 +35,42 @@ func NewSystemTestNodePool() (pool.RunnerPool, error) {
 	return agent.DefaultStaticRunnerPool(runners), nil
 }

-func SetUpSystem() error {
+type state struct {
+	memory string
+}
+
+func SetUpSystem() (*state, error) {
 	ctx := context.Background()
+	state := &state{}

 	api, err := SetUpAPINode(ctx)
 	if err != nil {
-		return err
+		return state, err
 	}
 	logrus.Info("Created API node")

 	lb, err := SetUpLBNode(ctx)
 	if err != nil {
-		return err
+		return state, err
 	}
 	logrus.Info("Created LB node")

-	pr0, nc0, err := SetUpPureRunnerNode(ctx, 0)
+	state.memory = os.Getenv(agent.EnvMaxTotalMemory)
+	os.Setenv(agent.EnvMaxTotalMemory, strconv.FormatUint(256*1024*1024, 10))
+
+	pr0, err := SetUpPureRunnerNode(ctx, 0)
 	if err != nil {
-		return err
+		return state, err
 	}
-	pr1, nc1, err := SetUpPureRunnerNode(ctx, 1)
+	pr1, err := SetUpPureRunnerNode(ctx, 1)
 	if err != nil {
-		return err
+		return state, err
 	}
-	pr2, nc2, err := SetUpPureRunnerNode(ctx, 2)
+	pr2, err := SetUpPureRunnerNode(ctx, 2)
 	if err != nil {
-		return err
+		return state, err
 	}
 	logrus.Info("Created Pure Runner nodes")
-	internalSystemTweaker.nodeCaps = []*testCapacityGate{nc0, nc1, nc2}

 	go func() { api.Start(ctx) }()
 	logrus.Info("Started API node")
@@ -77,10 +82,10 @@ func SetUpSystem() error {
 	logrus.Info("Started Pure Runner nodes")
 	// Wait for init - not great
 	time.Sleep(5 * time.Second)
-	return nil
+	return state, nil
 }

-func CleanUpSystem() error {
+func CleanUpSystem(st *state) error {
 	_, err := http.Get("http://127.0.0.1:8081/shutdown")
 	if err != nil {
 		return err
@@ -103,6 +108,13 @@ func CleanUpSystem() error {
 	}
 	// Wait for shutdown - not great
 	time.Sleep(5 * time.Second)
+
+	if st.memory != "" {
+		os.Setenv(agent.EnvMaxTotalMemory, st.memory)
+	} else {
+		os.Unsetenv(agent.EnvMaxTotalMemory)
+	}
+
 	return nil
 }

@@ -116,7 +128,7 @@ func SetUpAPINode(ctx context.Context) (*server.Server, error) {
 	opts = append(opts, server.WithWebPort(8085))
 	opts = append(opts, server.WithType(nodeType))
 	opts = append(opts, server.WithLogLevel(getEnv(server.EnvLogLevel, server.DefaultLogLevel)))
-	opts = append(opts, server.WithLogDest(server.DefaultLogDest, "API"))
+	opts = append(opts, server.WithLogDest(getEnv(server.EnvLogDest, server.DefaultLogDest), "API"))
 	opts = append(opts, server.WithDBURL(getEnv(server.EnvDBURL, defaultDB)))
 	opts = append(opts, server.WithMQURL(getEnv(server.EnvMQURL, defaultMQ)))
 	opts = append(opts, server.WithLogURL(""))
@@ -131,7 +143,7 @@ func SetUpLBNode(ctx context.Context) (*server.Server, error) {
 	opts = append(opts, server.WithWebPort(8081))
 	opts = append(opts, server.WithType(nodeType))
 	opts = append(opts, server.WithLogLevel(getEnv(server.EnvLogLevel, server.DefaultLogLevel)))
-	opts = append(opts, server.WithLogDest(server.DefaultLogDest, "LB"))
+	opts = append(opts, server.WithLogDest(getEnv(server.EnvLogDest, server.DefaultLogDest), "LB"))
 	opts = append(opts, server.WithDBURL(""))
 	opts = append(opts, server.WithMQURL(""))
 	opts = append(opts, server.WithLogURL(""))
@@ -156,85 +168,14 @@ func SetUpLBNode(ctx context.Context) (*server.Server, error) {
 	return server.New(ctx, opts...), nil
 }

-type testCapacityGate struct {
-	runnerNumber           int
-	committedCapacityUnits uint64
-	maxCapacityUnits       uint64
-	mtx                    sync.Mutex
-}
-
-const (
-	InitialTestCapacityUnitsPerRunner = 1024
-)
-
-func NewTestCapacityGate(nodeNum int, capacity uint64) *testCapacityGate {
-	return &testCapacityGate{
-		runnerNumber:           nodeNum,
-		maxCapacityUnits:       capacity,
-		committedCapacityUnits: 0,
-	}
-}
-
-func (tcg *testCapacityGate) CheckAndReserveCapacity(units uint64) error {
-	tcg.mtx.Lock()
-	defer tcg.mtx.Unlock()
-	if tcg.committedCapacityUnits+units <= tcg.maxCapacityUnits {
-		logrus.WithField("nodeNumber", tcg.runnerNumber).WithField("units", units).WithField("currentlyCommitted", tcg.committedCapacityUnits).Info("Runner is committing capacity")
-		tcg.committedCapacityUnits = tcg.committedCapacityUnits + units
-		return nil
-	}
-	logrus.WithField("nodeNumber", tcg.runnerNumber).WithField("currentlyCommitted", tcg.committedCapacityUnits).Debug("Runner is out of capacity")
-	return models.ErrCallTimeoutServerBusy
-}
-
-func (tcg *testCapacityGate) ReleaseCapacity(units uint64) {
-	tcg.mtx.Lock()
-	defer tcg.mtx.Unlock()
-	if units <= tcg.committedCapacityUnits {
-		logrus.WithField("nodeNumber", tcg.runnerNumber).WithField("units", units).WithField("currentlyCommitted", tcg.committedCapacityUnits).Info("Runner is releasing capacity")
-		tcg.committedCapacityUnits = tcg.committedCapacityUnits - units
-		return
-	}
-	panic("Fatal error in test capacity calculation, getting to sub-zero capacity")
-}
-
-func (tcg *testCapacityGate) ChangeMaxCapacity(newCapacity uint64) {
-	tcg.mtx.Lock()
-	defer tcg.mtx.Unlock()
-	logrus.WithField("nodeNumber", tcg.runnerNumber).WithField("oldCapacity", tcg.maxCapacityUnits).WithField("newCapacity", newCapacity).Info("Runner is changing max capacity")
-	tcg.maxCapacityUnits = newCapacity
-}
-
-type systemTweaker struct {
-	nodeCaps []*testCapacityGate
-}
-
-var internalSystemTweaker systemTweaker
-
-func SystemTweaker() *systemTweaker {
-	return &internalSystemTweaker
-}
-
-func (twk *systemTweaker) ChangeNodeCapacities(newCapacity uint64) {
-	for _, nc := range twk.nodeCaps {
-		nc.ChangeMaxCapacity(newCapacity)
-	}
-}
-
-func (twk *systemTweaker) RestoreInitialNodeCapacities() {
-	for _, nc := range twk.nodeCaps {
-		nc.ChangeMaxCapacity(InitialTestCapacityUnitsPerRunner)
-	}
-}
-
-func SetUpPureRunnerNode(ctx context.Context, nodeNum int) (*server.Server, *testCapacityGate, error) {
+func SetUpPureRunnerNode(ctx context.Context, nodeNum int) (*server.Server, error) {
 	nodeType := server.ServerTypePureRunner
 	opts := make([]server.ServerOption, 0)
 	opts = append(opts, server.WithWebPort(8082+nodeNum))
 	opts = append(opts, server.WithGRPCPort(9190+nodeNum))
 	opts = append(opts, server.WithType(nodeType))
 	opts = append(opts, server.WithLogLevel(getEnv(server.EnvLogLevel, server.DefaultLogLevel)))
-	opts = append(opts, server.WithLogDest(server.DefaultLogDest, "PURE-RUNNER"))
+	opts = append(opts, server.WithLogDest(getEnv(server.EnvLogDest, server.DefaultLogDest), "PURE-RUNNER"))
 	opts = append(opts, server.WithDBURL(""))
 	opts = append(opts, server.WithMQURL(""))
 	opts = append(opts, server.WithLogURL(""))
@@ -242,18 +183,18 @@ func SetUpPureRunnerNode(ctx context.Context, nodeNum int) (*server.Server, *tes

 	ds, err := hybrid.NewNopDataStore()
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	grpcAddr := fmt.Sprintf(":%d", 9190+nodeNum)
 	cancelCtx, cancel := context.WithCancel(ctx)
-	capacityGate := NewTestCapacityGate(nodeNum, InitialTestCapacityUnitsPerRunner)
-	prAgent, err := agent.NewPureRunner(cancel, grpcAddr, ds, "", "", "", capacityGate)
+
+	prAgent, err := agent.NewPureRunner(cancel, grpcAddr, ds, "", "", "", nil)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	opts = append(opts, server.WithAgent(prAgent), server.WithExtraCtx(cancelCtx))

-	return server.New(ctx, opts...), capacityGate, nil
+	return server.New(ctx, opts...), nil
 }

 func pwd() string {
@@ -308,20 +249,15 @@ func whoAmI() net.IP {
 	return nil
 }

-func TestCanInstantiateSystem(t *testing.T) {
-	SystemTweaker().ChangeNodeCapacities(128)
-	defer SystemTweaker().RestoreInitialNodeCapacities()
-}
-
 func TestMain(m *testing.M) {
-	err := SetUpSystem()
+	state, err := SetUpSystem()
 	if err != nil {
 		logrus.WithError(err).Fatal("Could not initialize system")
 		os.Exit(1)
 	}
 	// call flag.Parse() here if TestMain uses flags
 	result := m.Run()
-	err = CleanUpSystem()
+	err = CleanUpSystem(state)
 	if err != nil {
 		logrus.WithError(err).Warn("Could not clean up system")
 	}