journal

package
v0.1.0 Latest Latest
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 Go to latest Published: Jul 3, 2019 License: MIT Imports: 26 Imported by: 60

Documentation

Overview 

Package journal contains all runtime components for Gazette journals,
including Fragment & Spool for journal content, Head (serving
replications), Tail (reads), and Broker (for brokering new writes).

Code generated by mockery v1.0.0

Code generated by mockery v1.0.0

Code generated by mockery v1.0.0

Code generated by mockery v1.0.0

Code generated by mockery v1.0.0

Index

Constants

View Source 
const (
	AppendOpBufferSize = 100
)
View Source 
const ReplicateOpBufferSize = 10

Variables

View Source 
var (
	ErrExists            = errors.New("journal exists")
	ErrNotBroker         = errors.New("not journal broker")
	ErrNotFound          = errors.New("journal not found")
	ErrNotReplica        = errors.New("not journal replica")
	ErrNotYetAvailable   = errors.New("offset not yet available")
	ErrReplicationFailed = errors.New("replication failed")
	ErrWrongRouteToken   = errors.New("wrong route token")
	ErrWrongWriteHead    = errors.New("wrong write head")
)
View Source 
var ErrInvalidDelta = errors.New("invalid delta")

Functions

func ErrorFromResponse 

func ErrorFromResponse(response *http.Response) error

Maps a HTTP status code into a correponding Journal protocol error, or nil. Unknown status codes are converted into an error.

func NewWalkFuncAdapter 

func NewWalkFuncAdapter(callback func(Fragment) error, rewrites ...string) filepath.WalkFunc

NewWalkFuncAdapter returns a filepath.WalkFunc which parses encountered files as Fragments, and passes each to the provided |callback|. Prefix |rewrites| may be included, as pairs of "from", "to" prefixes which are applied in order. For example, NewWalkFuncAdapter(cb, "/from/", "/foo/to/", "/foo/", "/") would rewrite path "/from/bar" => "/to/bar".

func StatusCodeForError 

func StatusCodeForError(err error) int

Maps Journal protocol errors into a unique HTTP status code. Other errors are mapped into http.StatusInternalServerError.

Types

type AppendArgs 

type AppendArgs struct {
	Journal Name
	// Content to be appended to |Journal|. The append will consume |Content|
	// until io.EOF, and abort the append (without committing any content)
	// if any other error is returned by |Content.Read()|.
	Content io.Reader
	// Context which may trace, cancel or supply a deadline for the operation.
	Context context.Context
}

func (AppendArgs) String 

func (a AppendArgs) String() string

type AppendOp 

type AppendOp struct {
	AppendArgs

	// Channel by which broker returns operation status.
	Result chan AppendResult `json:"-"`
}

type AppendResult 

type AppendResult struct {
	// Any error that occurred during the append operation (PUT request.)
	Error error
	// Write head at the completion of the operation.
	WriteHead int64
	// RouteToken of the Journal. Set on ErrNotBroker.
	RouteToken
}

func (AppendResult) String 

func (a AppendResult) String() string

type AsyncAppend 

type AsyncAppend struct {
	// Read-only, and valid only after Ready is signaled.
	AppendResult
	// Signaled with the AppendOp has completed.
	Ready chan struct{}
}

Represents an AppendOp which is being asynchronously executed.

type Broker 

type Broker struct {
	// contains filtered or unexported fields
}

Broker is responsible for scattering journal writes to each replica, i.e., brokering transactions.

func NewBroker 

func NewBroker(journal Name) *Broker

func (*Broker) Append 

func (b *Broker) Append(op AppendOp)

func (*Broker) StartServingOps 

func (b *Broker) StartServingOps(writeHead int64) *Broker

StartServingOps starts a loop to consume config updates and serves appends. Updates are always handled before appends.

func (*Broker) Stop 

func (b *Broker) Stop()

Stop shuts down the broker. It blocks until all pending config updates and appends are handled.

func (*Broker) UpdateConfig 

func (b *Broker) UpdateConfig(config BrokerConfig)

type BrokerConfig 

type BrokerConfig struct {
	// Replica instances which should be involved in brokered transactions.
	Replicas []Replicator
	// Token representing the Broker's view of the current replication topology.
	// Sent with replication requests and verified for consensus by each remote
	// replica: for a transaction to succeed, all replicas must agree on the
	// current |RouteToken|.
	RouteToken
	// Next offset of the next brokered write transaction. Also sent with
	// replication requests and verifed for consensus by each remote replica:
	// for a transaction to succeed, all replicas must agree on the |WriteHead|.
	WriteHead int64
	// contains filtered or unexported fields
}

BrokerConfig is used to periodically update Broker with updated cluster topology and replication configuration.

type Client 

type Client interface {
	Creator
	Getter
	Header
	Writer
}

Composes Creator, Getter, Header, and Writer.

type Creator 

type Creator interface {
	Create(journal Name) error
}

Performs a Gazette POST operation.

type Doer 

type Doer interface {
	Do(*http.Request) (*http.Response, error)
}

Provides low-level routing and access to a Gazette service, suitable for proxying requests and modeled on http.Client. The client will perform journal-based routing to the appropriate Gazette instance. See gazette.Client.

type Fragment 

type Fragment struct {
	Journal    Name
	Begin, End int64
	Sum        [sha1.Size]byte

	// Backing file of the fragment, if present locally.
	File FragmentFile
	// If fragment is remote, the time of last modification.
	// NOTE(joshk): Does not get set in Client use.
	// TODO(johnny): Is this the appropriate factoring?
	RemoteModTime time.Time
}

func LocalFragments 

func LocalFragments(directory string, journal Name) []Fragment

LocalFragments returns fragments of |journal| under the local |directory|.

TODO(johnny): Collapse with NewWalkFuncAdapter above, or deprecate as part of a larger local-fragment change (Issues #30 & #31).

func ParseFragment 

func ParseFragment(journal Name, contentName string) (Fragment, error)

func (Fragment) AsDirectURL 

func (f Fragment) AsDirectURL(cfs cloudstore.FileSystem, duration time.Duration) (*url.URL, error)

func (Fragment) ContentName 

func (f Fragment) ContentName() string

func (*Fragment) ContentPath 

func (f *Fragment) ContentPath() string

func (Fragment) IsLocal 

func (f Fragment) IsLocal() bool

func (Fragment) ReaderFromOffset 

func (f Fragment) ReaderFromOffset(offset int64,
	cfs cloudstore.FileSystem) (io.ReadCloser, error)

func (Fragment) Size 

func (f Fragment) Size() int64

type FragmentFile 

type FragmentFile interface {
	Close() error
	Read(p []byte) (n int, err error)
	ReadAt(p []byte, off int64) (n int, err error)
	Seek(offset int64, whence int) (int64, error)
	Fd() uintptr
	Write(p []byte) (n int, err error)
}

Portions of os.File interface used by Fragment. An interface is used (rather than directly using *os.File) in support of test mocks.

type FragmentPersister 

type FragmentPersister interface {
	Persist(Fragment)
}

FragmentPersister accepts completed local fragment spools, which should be persisted to long-term storage. See |gazette.Persister|.

type FragmentSet 

type FragmentSet []Fragment

Maintains fragments ordered on |Begin| and |End|, with the invariant that no fragment is fully overlapped by another fragment in the set (though it may be overlapped by a combination of other fragments). Larger fragments are preferred (and will replace spans of overlapped smaller fragments). An implication of this invariant is that no two fragments have the same |Begin| or |End| (as that would imply an overlap). Both are monotonically increasing in the set: set[0].Begin represents the minimum offset, and set[len(set)-1].End represents the maximum offset.

func (*FragmentSet) Add 

func (s *FragmentSet) Add(fragment Fragment) bool

func (*FragmentSet) BeginOffset 

func (s *FragmentSet) BeginOffset() int64

func (*FragmentSet) EndOffset 

func (s *FragmentSet) EndOffset() int64

func (*FragmentSet) LongestOverlappingFragment 

func (s *FragmentSet) LongestOverlappingFragment(offset int64) int

Finds and returns the fragment covering |offset|, which has the most content after |offset|. If no fragment covers |offset|, the first fragment beginning after |offset| is returned.

type Getter 

type Getter interface {
	Get(args ReadArgs) (ReadResult, io.ReadCloser)
}

Performs a Gazette GET operation. 

type Head struct {
	// contains filtered or unexported fields
}

func NewHead 

func NewHead(journal Name, directory string, persister FragmentPersister,
	updates chan<- Fragment) *Head

func (*Head) Replicate 

func (h *Head) Replicate(op ReplicateOp)

func (*Head) StartServingOps 

func (h *Head) StartServingOps(writeHead int64) *Head

func (*Head) Stop 

func (h *Head) Stop()
type Header interface {
	Head(args ReadArgs) (result ReadResult, fragmentLocation *url.URL)
}

Performs a Gazette HEAD operation.

type IndexWatcher 

type IndexWatcher struct {
	// contains filtered or unexported fields
}

IndexWatcher monitors a journal's storage location in the cloud filesystem for new fragments, by performing periodic directory listings. When new fragment metadata arrives, it's published to the journal Tail via a shared channel, which indexes the fragment and makes it available for read requests.

func NewIndexWatcher 

func NewIndexWatcher(journal Name, cfs cloudstore.FileSystem,
	updates chan<- Fragment) *IndexWatcher

func (*IndexWatcher) StartWatchingIndex 

func (w *IndexWatcher) StartWatchingIndex() *IndexWatcher

func (*IndexWatcher) Stop 

func (w *IndexWatcher) Stop()

func (*IndexWatcher) WaitForInitialLoad 

func (w *IndexWatcher) WaitForInitialLoad()

type Mark 

type Mark struct {
	Journal Name
	Offset  int64
}

A Mark references a specific |Offset| within a |Journal|.

func NewMark 

func NewMark(name Name, offset int64) Mark

type MarkedReader 

type MarkedReader struct {
	Mark Mark
	io.ReadCloser
}

A MarkedReader delegates reads to an underlying reader, and maintains |Mark| such that it always points to the next byte to be read.

func NewMarkedReader 

func NewMarkedReader(mark Mark, r io.ReadCloser) *MarkedReader

func (*MarkedReader) AdjustedMark 

func (r *MarkedReader) AdjustedMark(br *bufio.Reader) Mark

AdjustedMark returns the current Mark adjusted for content read by |br| (which must wrap this MarkedReader) but unconsumed from |br|'s buffer.

func (*MarkedReader) Close 

func (r *MarkedReader) Close() error

func (*MarkedReader) Read 

func (r *MarkedReader) Read(p []byte) (int, error)

type MemoryBroker 

type MemoryBroker struct {
	// DelayWrites indicates that writes should queue (and their promises not resolve) until:
	//   * The next explicit Flush, or
	//   * DelayWrites is set to false and another Write occurs.
	DelayWrites bool
	// Content written to each journal.
	Content map[Name]*bytes.Buffer
	// Pending content which will be written on the next Flush (or write, if !DelayWrites).
	Pending map[Name]*bytes.Buffer
	// contains filtered or unexported fields
}

MemoryBroker provides an in-memory implementation of the Client interface. The intended use is within unit tests which exercise components coordinating through the Client interface.

func NewMemoryBroker 

func NewMemoryBroker() *MemoryBroker

NewMemoryBroker returns an initialized, zero-value MemoryBroker.

func (*MemoryBroker) Create 

func (j *MemoryBroker) Create(journal Name) error

func (*MemoryBroker) Flush 

func (j *MemoryBroker) Flush()

Flush resolves all pending writes and wakes any blocked read operations.

func (*MemoryBroker) Get 

func (j *MemoryBroker) Get(args ReadArgs) (ReadResult, io.ReadCloser)

func (*MemoryBroker) Head 

func (j *MemoryBroker) Head(args ReadArgs) (ReadResult, *url.URL)

func (*MemoryBroker) ReadFrom 

func (j *MemoryBroker) ReadFrom(name Name, r io.Reader) (*AsyncAppend, error)

func (*MemoryBroker) Write 

func (j *MemoryBroker) Write(name Name, b []byte) (*AsyncAppend, error)

type MockDoer 

type MockDoer struct {
	mock.Mock
}

MockDoer is an autogenerated mock type for the Doer type

func (*MockDoer) Do 

func (_m *MockDoer) Do(_a0 *http.Request) (*http.Response, error)

Do provides a mock function with given fields: _a0

type MockFragmentFile 

type MockFragmentFile struct {
	mock.Mock
}

MockFragmentFile is an autogenerated mock type for the FragmentFile type

func (*MockFragmentFile) Close 

func (_m *MockFragmentFile) Close() error

Close provides a mock function with given fields:

func (*MockFragmentFile) Fd 

func (_m *MockFragmentFile) Fd() uintptr

Fd provides a mock function with given fields:

func (*MockFragmentFile) Read 

func (_m *MockFragmentFile) Read(p []byte) (int, error)

Read provides a mock function with given fields: p

func (*MockFragmentFile) ReadAt 

func (_m *MockFragmentFile) ReadAt(p []byte, off int64) (int, error)

ReadAt provides a mock function with given fields: p, off

func (*MockFragmentFile) Seek 

func (_m *MockFragmentFile) Seek(offset int64, whence int) (int64, error)

Seek provides a mock function with given fields: offset, whence

func (*MockFragmentFile) Write 

func (_m *MockFragmentFile) Write(p []byte) (int, error)

Write provides a mock function with given fields: p

type MockGetter 

type MockGetter struct {
	mock.Mock
}

MockGetter is an autogenerated mock type for the Getter type

func (*MockGetter) Get 

func (_m *MockGetter) Get(args ReadArgs) (ReadResult, io.ReadCloser)

Get provides a mock function with given fields: args

type MockHeader 

type MockHeader struct {
	mock.Mock
}

MockHeader is an autogenerated mock type for the Header type

func (*MockHeader) Head 

func (_m *MockHeader) Head(args ReadArgs) (ReadResult, *url.URL)

Head provides a mock function with given fields: args

type MockWriter 

type MockWriter struct {
	mock.Mock
}

MockWriter is an autogenerated mock type for the Writer type

func (*MockWriter) ReadFrom 

func (_m *MockWriter) ReadFrom(journal Name, r io.Reader) (*AsyncAppend, error)

ReadFrom provides a mock function with given fields: journal, r

func (*MockWriter) Write 

func (_m *MockWriter) Write(journal Name, buffer []byte) (*AsyncAppend, error)

Write provides a mock function with given fields: journal, buffer

type Name 

type Name string

A typed journal name. By convention, journals are named using a forward- slash notation which captures their hierarchical relationships into organizations, topics and partitions. For example, a complete Name might be: "company-journals/interesting-topic/part-1234"

func (Name) String 

func (n Name) String() string

type ReadArgs 

type ReadArgs struct {
	Journal Name
	// Desired offset to begin reading from. Value -1 has special handling, where
	// the read is performed from the current write head. All other positive
	// values specify a desired exact byte offset to read from. If the offset is
	// not available (eg, because it represents a portion of Journal which has
	// been permantently deleted), the broker will return the next available
	// offset. Callers should therefore always inspect the ReadResult Offset.
	Offset int64
	// Whether the operation should block until content becomes available.
	// ErrNotYetAvailable is returned if a non-blocking read has no ready content.
	Blocking bool
	// Context which may trace, cancel or supply a deadline for the operation.
	Context context.Context

	// Deprecated: Server-side support for deadlines will be removed. Use
	// context.WithDeadline instead.
	// The time at which blocking will expire
	Deadline time.Time
}

func (ReadArgs) String 

func (a ReadArgs) String() string

type ReadOp 

type ReadOp struct {
	ReadArgs

	// Channel by which replica returns a ReadResult.
	Result chan ReadResult `json:"-"`
}

type ReadResult 

type ReadResult struct {
	Error error
	// The effective offset of the operation.
	Offset int64
	// Write head at the completion of the operation.
	WriteHead int64
	// RouteToken of the Journal. Set on ErrNotReplica.
	RouteToken
	// Result fragment, set iff |Error| is nil.
	Fragment Fragment
}

func (ReadResult) String 

func (a ReadResult) String() string

type Replica 

type Replica struct {
	// contains filtered or unexported fields
}

Replica manages journal components required to serve brokered writes, replications, and reads. A Replica instance is capable of switching roles at any time (and multiple times), from a pure replica which may serve replication requests only, to a broker of the journal.

func NewReplica 

func NewReplica(journal Name, localDir string, persister FragmentPersister,
	cfs cloudstore.FileSystem) *Replica

func (*Replica) Append 

func (r *Replica) Append(op AppendOp)

func (*Replica) Read 

func (r *Replica) Read(op ReadOp)

func (*Replica) Replicate 

func (r *Replica) Replicate(op ReplicateOp)

func (*Replica) Shutdown 

func (r *Replica) Shutdown()

func (*Replica) StartBrokeringWithPeers 

func (r *Replica) StartBrokeringWithPeers(routeToken RouteToken, peers []Replicator)

Switch the Replica into broker mode. Appends will be brokered to |peers| with the topology captured by |routeToken|.

func (*Replica) StartReplicating 

func (r *Replica) StartReplicating(routeToken RouteToken)

Switch the Replica into pure-replica mode.

type ReplicateArgs 

type ReplicateArgs struct {
	Journal Name
	// WriteHead (eg, first byte) of the replicated transaction.
	// Already known and verified by all journal replicas.
	WriteHead int64
	// RouteToken of the transaction, also known and verified by all replicas.
	RouteToken
	// Flags whether replicas should begin a new spool for this transaction.
	NewSpool bool
	// Context which may trace, cancel or supply a deadline for the operation.
	Context context.Context
}

func (ReplicateArgs) String 

func (a ReplicateArgs) String() string

type ReplicateOp 

type ReplicateOp struct {
	ReplicateArgs

	// Channel by which replica returns a ReplicateResult.
	Result chan ReplicateResult `json:"-"`
}

type ReplicateResult 

type ReplicateResult struct {
	Error error
	// Iff |Error| is ErrWrongWriteHead, then |ErrorWriteHead| is the replica's
	// own, strictly greater write head.
	ErrorWriteHead int64
	// Set iff |Error| is nil.
	Writer WriteCommitter
}

func (ReplicateResult) String 

func (a ReplicateResult) String() string

type Replicator 

type Replicator interface {
	Replicate(op ReplicateOp)
}

A Replicator is able to serve a ReplicateOp. It may be backed by a local Spool, or by a remote Gazette process.

type RetryReader 

type RetryReader struct {
	// MarkedReader manages the current reader and offset tracking.
	MarkedReader
	// Whether read operations should block (the default). If Blocking is false,
	// than Read operations may return ErrNotYetAvailable.
	Blocking bool
	// LastResult retains the result of the last journal read operation.
	// Callers may access it to inspect metadata returned by the broker.
	// It may be invalidated on every Read call.
	LastResult ReadResult
	// Getter against which to perform read operations.
	Getter Getter
	// Context to use in read operations issued to Getter.
	Context context.Context
}

RetryReader wraps a Getter and MarkedReader to provide callers with a long-lived journal reader. RetryReader transparently handles and retries errors, and will block as needed to await new journal content.

func NewRetryReader deprecated 

func NewRetryReader(mark Mark, getter Getter) *RetryReader

Deprecated: Use NewRetryReaderContext instead. NewRetryReader returns a RetryReader at |mark|, using the provided |getter| for all operations.

func NewRetryReaderContext 

func NewRetryReaderContext(ctx context.Context, mark Mark, getter Getter) *RetryReader

NewRetryReaderContext returns a RetryReader at |mark|, using the provided |getter| and |ctx| for all operations.

func (*RetryReader) AdjustedSeek 

func (rr *RetryReader) AdjustedSeek(offset int64, whence int, br *bufio.Reader) (int64, error)

AdjustedSeek sets the offset for the next Read, accounting for buffered data and updating the buffer as needed.

func (*RetryReader) Read 

func (rr *RetryReader) Read(p []byte) (n int, err error)

Read returns the next available bytes of journal content, retrying as required retry errors or await content to be written. Read will return a non-nil error in the following cases:

  • If the RetryReader context is cancelled.
  • If Blocking is false, and ErrNotYetAvailable is returned by the broker.

All other errors are retried.

func (*RetryReader) Seek 

func (rr *RetryReader) Seek(offset int64, whence int) (int64, error)

Seek sets the offset for the next Read. It returns an error if (and only if) |whence| is io.SeekEnd, which is not supported.

type RouteToken 

type RouteToken string

Token which describes the ordered set of responsible servers for a Journal: the first acts as broker, and the rest serve replications and reads (only). Structured as '|'-separated URLs rooting the server's Journal hierarchy. Ex: "http://srv-2/a/root|https://srv-1|http://12.34.56.7:8080/other/root".

type Spool 

type Spool struct {
	Fragment
	// contains filtered or unexported fields
}

func NewSpool 

func NewSpool(directory string, at Mark) (*Spool, error)

func (*Spool) Commit 

func (s *Spool) Commit(delta int64) error

func (*Spool) LocalPath 

func (s *Spool) LocalPath() string

func (*Spool) Write 

func (s *Spool) Write(buf []byte) (n int, err error)

type Tail 

type Tail struct {
	// contains filtered or unexported fields
}

func NewTail 

func NewTail(journal Name, updates <-chan Fragment) *Tail

func (*Tail) EndOffset 

func (t *Tail) EndOffset() int64

func (*Tail) Read 

func (t *Tail) Read(op ReadOp)

func (*Tail) StartServingOps 

func (t *Tail) StartServingOps() *Tail

func (*Tail) Stop 

func (t *Tail) Stop()

type WriteCommitter 

type WriteCommitter interface {
	io.Writer
	// Commits the first |count| bytes of previous Write([]byte) content.
	Commit(count int64) error
}

A WriteCommitter extends Writer with a protocol for committing those writes.

type Writer 

type Writer interface {
	// Appends |buffer| to |journal|. Either all of |buffer| is written, or none
	// of it is. Returns a Promise which is resolved when the write has been
	// fully committed.
	Write(journal Name, buffer []byte) (*AsyncAppend, error)

	// Appends |r|'s content to |journal|, by reading until io.EOF. Either all of
	// |r| is written, or none of it is. Returns a Promise which is resolved when
	// the write has been fully committed.
	ReadFrom(journal Name, r io.Reader) (*AsyncAppend, error)
}

A Writer allows for append-only writes to a named journal.

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