Make buffer max chunk delay reconfigurable on the fly (#313)

* Try making buffer max chunk delay reconfigurable on the fly

* Make buffer max_chunk_size configurable on the fly

* Make the MaxChunkDelay and MaxChunkSize available

Co-authored-by: Andy Keller <andykellr@users.noreply.github.com>

operator/buffer/buffer.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"time"
 
 	"github.com/observiq/stanza/entry"
 	"github.com/observiq/stanza/operator"
@@ -16,6 +17,10 @@ type Buffer interface {
 	ReadWait(context.Context, []*entry.Entry) (Clearer, int, error)
 	ReadChunk(context.Context) ([]*entry.Entry, Clearer, error)
 	Close() error
+	MaxChunkDelay() time.Duration
+	MaxChunkSize() uint
+	SetMaxChunkDelay(time.Duration)
+	SetMaxChunkSize(uint)
 }
 
 // Config is a struct that wraps a Builder

operator/buffer/disk.go

@@ -103,6 +103,8 @@ type DiskBuffer struct {
 
 	maxChunkDelay time.Duration
 	maxChunkSize  uint
+
+	reconfigMutex sync.RWMutex
 }
 
 // NewDiskBuffer creates a new DiskBuffer
@@ -242,15 +244,15 @@ LOOP:
 
 // ReadChunk is a thin wrapper around ReadWait that simplifies the call at the expense of an extra allocation
 func (d *DiskBuffer) ReadChunk(ctx context.Context) ([]*entry.Entry, Clearer, error) {
-	entries := make([]*entry.Entry, d.maxChunkSize)
+	entries := make([]*entry.Entry, d.MaxChunkSize())
 	for {
 		select {
 		case <-ctx.Done():
 			return nil, nil, ctx.Err()
 		default:
 		}
 
-		ctx, cancel := context.WithTimeout(ctx, d.maxChunkDelay)
+		ctx, cancel := context.WithTimeout(ctx, d.MaxChunkDelay())
 		defer cancel()
 		flushFunc, n, err := d.ReadWait(ctx, entries)
 		if n > 0 {
@@ -313,6 +315,30 @@ func (d *DiskBuffer) Read(dst []*entry.Entry) (f Clearer, i int, err error) {
 	return d.newClearer(newRead), readCount, nil
 }
 
+func (d *DiskBuffer) MaxChunkSize() uint {
+	d.reconfigMutex.RLock()
+	defer d.reconfigMutex.RUnlock()
+	return d.maxChunkSize
+}
+
+func (d *DiskBuffer) MaxChunkDelay() time.Duration {
+	d.reconfigMutex.RLock()
+	defer d.reconfigMutex.RUnlock()
+	return d.maxChunkDelay
+}
+
+func (d *DiskBuffer) SetMaxChunkSize(size uint) {
+	d.reconfigMutex.Lock()
+	d.maxChunkSize = size
+	d.reconfigMutex.Unlock()
+}
+
+func (d *DiskBuffer) SetMaxChunkDelay(delay time.Duration) {
+	d.reconfigMutex.Lock()
+	d.maxChunkDelay = delay
+	d.reconfigMutex.Unlock()
+}
+
 // newFlushFunc returns a function that marks read entries as flushed
 func (d *DiskBuffer) newClearer(newRead []*readEntry) Clearer {
 	return &diskClearer{

operator/buffer/memory.go

@@ -68,6 +68,7 @@ type MemoryBuffer struct {
 	sem           *semaphore.Weighted
 	maxChunkDelay time.Duration
 	maxChunkSize  uint
+	reconfigMutex sync.RWMutex
 }
 
 // Add inserts an entry into the memory database, blocking until there is space
@@ -105,15 +106,15 @@ func (m *MemoryBuffer) Read(dst []*entry.Entry) (Clearer, int, error) {
 
 // ReadChunk is a thin wrapper around ReadWait that simplifies the call at the expense of an extra allocation
 func (m *MemoryBuffer) ReadChunk(ctx context.Context) ([]*entry.Entry, Clearer, error) {
-	entries := make([]*entry.Entry, m.maxChunkSize)
+	entries := make([]*entry.Entry, m.MaxChunkSize())
 	for {
 		select {
 		case <-ctx.Done():
 			return nil, nil, ctx.Err()
 		default:
 		}
 
-		ctx, cancel := context.WithTimeout(ctx, m.maxChunkDelay)
+		ctx, cancel := context.WithTimeout(ctx, m.MaxChunkDelay())
 		defer cancel()
 		flushFunc, n, err := m.ReadWait(ctx, entries)
 		if n > 0 {
@@ -145,6 +146,30 @@ func (m *MemoryBuffer) ReadWait(ctx context.Context, dst []*entry.Entry) (Cleare
 	return m.newClearer(inFlightIDs[:i]), i, nil
 }
 
+func (m *MemoryBuffer) MaxChunkSize() uint {
+	m.reconfigMutex.RLock()
+	defer m.reconfigMutex.RUnlock()
+	return m.maxChunkSize
+}
+
+func (m *MemoryBuffer) MaxChunkDelay() time.Duration {
+	m.reconfigMutex.RLock()
+	defer m.reconfigMutex.RUnlock()
+	return m.maxChunkDelay
+}
+
+func (m *MemoryBuffer) SetMaxChunkSize(size uint) {
+	m.reconfigMutex.Lock()
+	m.maxChunkSize = size
+	m.reconfigMutex.Unlock()
+}
+
+func (m *MemoryBuffer) SetMaxChunkDelay(delay time.Duration) {
+	m.reconfigMutex.Lock()
+	m.maxChunkDelay = delay
+	m.reconfigMutex.Unlock()
+}
+
 type memoryClearer struct {
 	buffer *MemoryBuffer
 	ids    []uint64