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Vendor new queue-worker version
Introduces 0.4.6 of queue-worker - see upstream repo for changes. Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>
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Alex Ellis (VMware)
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gateway/vendor/github.com/nats-io/go-nats-streaming/README.md
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gateway/vendor/github.com/nats-io/go-nats-streaming/README.md
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@ -2,7 +2,7 @@
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NATS Streaming is an extremely performant, lightweight reliable streaming platform powered by [NATS](https://nats.io).
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[](http://opensource.org/licenses/MIT)
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[](https://www.apache.org/licenses/LICENSE-2.0)
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[](http://travis-ci.org/nats-io/go-nats-streaming)
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[](https://coveralls.io/r/nats-io/go-nats-streaming?branch=master)
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@ -17,9 +17,6 @@ NATS Streaming provides the following high-level feature set:
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- Please raise questions/issues via the [Issue Tracker](https://github.com/nats-io/go-nats-streaming/issues).
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## Known Issues
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- Time- and sequence-based subscriptions are exact. Requesting a time or seqno before the earliest stored message for a subject will result in an error (in SubscriptionRequest.Error)
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## Installation
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```bash
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@ -59,29 +56,29 @@ The options are described with examples below:
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// Subscribe starting with most recently published value
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sub, err := sc.Subscribe("foo", func(m *stan.Msg) {
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fmt.Printf("Received a message: %s\n", string(m.Data))
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}, StartWithLastReceived())
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}, stan.StartWithLastReceived())
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// Receive all stored values in order
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sub, err := sc.Subscribe("foo", func(m *stan.Msg) {
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fmt.Printf("Received a message: %s\n", string(m.Data))
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}, DeliverAllAvailable())
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}, stan.DeliverAllAvailable())
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// Receive messages starting at a specific sequence number
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sub, err := sc.Subscribe("foo", func(m *stan.Msg) {
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fmt.Printf("Received a message: %s\n", string(m.Data))
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}, StartAtSequence(22))
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}, stan.StartAtSequence(22))
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// Subscribe starting at a specific time
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var startTime time.Time
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...
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sub, err := sc.Subscribe("foo", func(m *stan.Msg) {
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fmt.Printf("Received a message: %s\n", string(m.Data))
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}, StartAtTime(startTime))
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}, stan.StartAtTime(startTime))
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// Subscribe starting a specific amount of time in the past (e.g. 30 seconds ago)
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sub, err := sc.Subscribe("foo", func(m *stan.Msg) {
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fmt.Printf("Received a message: %s\n", string(m.Data))
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}, StartAtTimeDelta(time.ParseDuration("30s")))
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}, stan.StartAtTimeDelta(time.ParseDuration("30s")))
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```
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### Durable Subscriptions
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@ -184,7 +181,7 @@ that is, the start position will take effect and delivery will start from there.
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### Durable Queue Groups
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As described above, for non durable queue subsribers, when the last member leaves the group,
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As described above, for non durable queue subscribers, when the last member leaves the group,
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that group is removed. A durable queue group allows you to have all members leave but still
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maintain state. When a member re-joins, it starts at the last position in that group.
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@ -220,7 +217,7 @@ The rules for non-durable queue subscribers apply to durable subscribers.
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As for non-durable queue subscribers, if a member's connection is closed, or if
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`Unsubscribe` its called, the member leaves the group. Any unacknowledged message
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is transfered to remaining members. See *Closing the Group* for important difference
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is transferred to remaining members. See *Closing the Group* for important difference
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with non-durable queue subscribers.
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#### Closing the Group
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@ -242,6 +239,58 @@ NATS Streaming subscriptions **do not** support wildcards.
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## Advanced Usage
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### Connection Status
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The fact that the NATS Streaming server and clients are not directly connected poses a challenge when it comes to know if a client is still valid.
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When a client disconnects, the streaming server is not notified, hence the importance of calling `Close()`. The server sends heartbeats
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to the client's private inbox and if it misses a certain number of responses, it will consider the client's connection lost and remove it
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from its state.
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Before version `0.4.0`, the client library was not sending PINGs to the streaming server to detect connection failure. This was problematic
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especially if an application was never sending data (had only subscriptions for instance). Picture the case where a client connects to a
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NATS Server which has a route to a NATS Streaming server (either connecting to a standalone NATS Server or the server it embeds). If the
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connection between the streaming server and the client's NATS Server is broken, the client's NATS connection would still be ok, yet, no
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communication with the streaming server is possible. This is why relying on `Conn.NatsConn()` to check the status is not helpful.
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Starting version `0.4.0` of this library and server `0.10.0`, the client library will now send PINGs at regular intervals (default is 5 seconds)
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and will close the streaming connection after a certain number of PINGs have been sent without any response (default is 3). When that
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happens, a callback - if one is registered - will be invoked to notify the user that the connection is permanently lost, and the reason
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for the failure.
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Here is how you would specify your own PING values and the callback:
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```go
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// Send PINGs every 10 seconds, and fail after 5 PINGs without any response.
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sc, err := stan.Connect(clusterName, clientName,
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stan.Pings(10, 5),
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stan.SetConnectionLostHandler(func(_ stan.Conn, reason error) {
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log.Fatalf("Connection lost, reason: %v", reason)
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}))
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```
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Note that the only way to be notified is to set the callback. If the callback is not set, PINGs are still sent and the connection
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will be closed if needed, but the application won't know if it has only subscriptions.
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When the connection is lost, your application would have to re-create it and all subscriptions if any.
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When no NATS connection is provided to the `Connect()` call, the library creates its own NATS connection and will now
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set the reconnect attempts to "infinite", which was not the case before. It should therefore be possible for the library to
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always reconnect, but this does not mean that the streaming connection will not be closed, even if you set a very high
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threshold for the PINGs max out value. Keep in mind that while the client is disconnected, the server is sending heartbeats to
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the clients too, and when not getting any response, it will remove that client from its state. When the communication is restored,
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the PINGs sent to the server will allow to detect this condition and report to the client that the connection is now closed.
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Also, while a client is "disconnected" from the server, another application with connectivity to the streaming server may
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connect and uses the same client ID. The server, when detecting the duplicate client ID, will try to contact the first client
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to know if it should reject the connect request of the second client. Since the communication between the server and the
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first client is broken, the server will not get a response and therefore will replace the first client with the second one.
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Prior to client `0.4.0` and server `0.10.0`, if the communication between the first client and server were to be restored,
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and the application would send messages, the server would accept those because the published messages client ID would be
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valid, although the client is not. With client at `0.4.0+` and server `0.10.0+`, additional information is sent with each
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message to allow the server to reject messages from a client that has been replaced by another client.
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### Asynchronous Publishing
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The basic publish API (`Publish(subject, payload)`) is synchronous; it does not return control to the caller until the NATS Streaming server has acknowledged receipt of the message. To accomplish this, a [NUID](https://github.com/nats-io/nuid) is generated for the message on creation, and the client library waits for a publish acknowledgement from the server with a matching NUID before it returns control to the caller, possibly with an error indicating that the operation was not successful due to some server problem or authorization error.
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@ -301,7 +350,7 @@ ah := func(nuid string, err error) {
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}
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for i := 1; i < 1000; i++ {
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// If the server is unable to keep up with the publisher, the number of oustanding acks will eventually
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// If the server is unable to keep up with the publisher, the number of outstanding acks will eventually
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// reach the max and this call will block
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guid, _ := sc.PublishAsync("foo", []byte("Hello World"), ah)
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}
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@ -327,24 +376,5 @@ sc.Subscribe("foo", func(m *stan.Msg) {
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## License
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(The MIT License)
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Copyright (c) 2012-2016 Apcera Inc.
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to
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deal in the Software without restriction, including without limitation the
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rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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sell copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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IN THE SOFTWARE.
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Unless otherwise noted, the NATS source files are distributed
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under the Apache Version 2.0 license found in the LICENSE file.
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