## Changes between Bunny 1.0.5 and 1.0.6

### Better Exception Handling in Consumers

Consumer work pools will now correctly catch all exceptions
when dispatching submitted operations, not just `Bunny::Exception`
subclasses.

### TLS Without Peer Verification

Bunny now successfully performs TLS upgrade when peer verification
is disabled.

Contribute by Jordan Curzon.

### Bunny::Session#with_channel Ensures the Channel is Closed

`Bunny::Session#with_channel` now makes sure the channel is closed
even if provided block raises an exception

Contributed by Carl Hoerberg.

### Channel Number = 0 is Rejected

`Bunny::Session#create_channel` will now reject channel number 0.

## Changes between Bunny 1.0.4 and 1.0.5

### Single Threaded Mode Fixes

Single threaded mode no longer fails with

```
undefined method `event_loop'
```

### connection.tune.channel_max No Longer Overflows

`connection.tune.channel_max` could previously be configured to values
greater than 2^16 - 1 (65535). This would result in a silent overflow
during serialization. The issue was harmless in practice but is still
a bug that can be quite confusing.

Bunny now caps max number of channels to 65535. This allows it to be
forward compatible with future RabbitMQ versions that may allow limiting
total # of open channels via server configuration.

### Thread Leaks Fixes

Bunny will now correctly release heartbeat sender when allocating
a new one (usually happens only when connection recovers from a network
failure).

### amq-protocol Update

Minimum `amq-protocol` version is now `1.9.0` which includes
bug fixes and performance improvements for channel ID allocator.

## Changes between Bunny 1.0.3 and 1.0.4

### Versioned Delivery Tag Fix

Versioned delivery tag now ensures all the arguments it operates
(original delivery tag, atomic fixnum instances, etc) are coerced to `Integer`
before comparison.

GitHub issues: #171.

## Changes between Bunny 1.0.2 and 1.0.3

### Eliminated Errouneous Debug Statement

`1.0.3` eliminates a debug log message that should have
never made it into a commit.

## Changes between Bunny 1.0.1 and 1.0.2

### Fixes CPU Burn on JRuby

A silly mistake in `1.0.1` testing process ended up reverting
the fix for #165 and #166. This release corrects it.

## Changes between Bunny 1.0.0 and 1.0.1

### Default CA's Paths Are Disabled on JRuby

Bunny uses OpenSSL provided CA certificate paths. This
caused problems on some platforms on JRuby (see [jruby/jruby#155](https://github.com/jruby/jruby/issues/1055)).

To avoid these issues, Bunny no longer uses default CA certificate paths on JRuby
(there are no changes for other Rubies), so it's necessary to provide
CA certificate explicitly.

### Fixes CPU Burn on JRuby

Bunny now uses slightly different ways of continuously reading from the socket
on CRuby and JRuby, to prevent abnormally high CPU usage on JRuby after a
certain period of time (the frequency of `EWOULDBLOCK` being raised spiked
sharply).

## Changes between Bunny 1.0.0.rc2 and 1.0.0.rc3

### [Authentication Failure Notification](http://www.rabbitmq.com/auth-notification.html) Support

`Bunny::AuthenticationFailureError` is a new auth failure exception
that subclasses `Bunny::PossibleAuthenticationFailureError` for
backwards compatibility.

As such, `Bunny::PossibleAuthenticationFailureError`'s error message
has changed.

This extension is available in RabbitMQ 3.2+.

### Bunny::Session#exchange_exists?

`Bunny::Session#exchange_exists?` is a new predicate that makes it
easier to check if a exchange exists.

It uses a one-off channel and `exchange.declare` with `passive` set to true
under the hood.

### Bunny::Session#queue_exists?

`Bunny::Session#queue_exists?` is a new predicate that makes it
easier to check if a queue exists.

It uses a one-off channel and `queue.declare` with `passive` set to true
under the hood.

### Inline TLS Certificates and Keys

It is now possible to provide inline client
certificate and private key (as strings) instead
of filesystem paths. The options are the same:

* `:tls` which, when set to `true`, will set SSL context up and switch to TLS port (5671)
* `:tls_cert` which now can be a client certificate (public key) in PEM format
* `:tls_key` which now can be a client key (private key) in PEM format
* `:tls_ca_certificates` which is an array of string paths to CA certificates in PEM format

For example:

``` ruby
conn = Bunny.new(:tls => true,
:tls_cert => ENV["TLS_CERTIFICATE"],
:tls_key => ENV["TLS_PRIVATE_KEY"],
:tls_ca_certificates => ["./examples/tls/cacert.pem"])
```

## Changes between Bunny 1.0.0.rc1 and 1.0.0.rc2

### Ruby 1.8.7 Compatibility Fixes

Ruby 1.8.7 compatibility fixes around timeouts.

## Changes between Bunny 1.0.0.pre6 and 1.0.0.rc1

### amq-protocol Update

Minimum `amq-protocol` version is now `1.8.0` which includes
a bug fix for messages exactly 128 Kb in size.

### Add timeout Bunny::ConsumerWorkPool#join

`Bunny::ConsumerWorkPool#join` now accepts an optional
timeout argument.

## Changes between Bunny 1.0.0.pre5 and 1.0.0.pre6

### Respect RABBITMQ_URL value

`RABBITMQ_URL` env variable will now have effect even if
Bunny.new is invoked without arguments.

## Changes between Bunny 1.0.0.pre4 and 1.0.0.pre5

### Ruby 1.8 Compatibility

Bunny is Ruby 1.8-compatible again and no longer references
`RUBY_ENGINE`.

### Bunny::Session.parse_uri

`Bunny::Session.parse_uri` is a new method that parses
connection URIs into hashes that `Bunny::Session#initialize`
accepts.

``` ruby
Bunny::Session.parse_uri("amqp://user:pwd@broker.eng.megacorp.local/myapp_qa")
```

### Default Paths for TLS/SSL CA's on All OS'es

Bunny now uses OpenSSL to detect default TLS/SSL CA's paths, extending
this feature to OS'es other than Linux.

Contributed by Jingwen Owen Ou.

## Changes between Bunny 1.0.0.pre3 and 1.0.0.pre4

### Default Paths for TLS/SSL CA's on Linux

Bunny now will use the following TLS/SSL CA's paths on Linux by default:

* `/etc/ssl/certs/ca-certificates.crt` on Ubuntu/Debian
* `/etc/ssl/certs/ca-bundle.crt` on Amazon Linux
* `/etc/ssl/ca-bundle.pem` on OpenSUSE
* `/etc/pki/tls/certs/ca-bundle.crt` on Fedora/RHEL

and will log a warning if no CA files are available via default paths
or `:tls_ca_certificates`.

Contributed by Carl Hörberg.

### Consumers Can Be Re-Registered From Bunny::Consumer#handle_cancellation

It is now possible to re-register a consumer (and use any other synchronous methods)
from `Bunny::Consumer#handle_cancellation`, which is now invoked in the channel's
thread pool.

### Bunny::Session#close Fixed for Single Threaded Connections

`Bunny::Session#close` with single threaded connections no longer fails
with a nil pointer exception.

## Changes between Bunny 1.0.0.pre2 and 1.0.0.pre3

This release has **breaking API changes**.

### Safe[r] basic.ack, basic.nack and basic.reject implementation

Previously if a channel was recovered (reopened) by automatic connection
recovery before a message was acknowledged or rejected, it would cause
any operation on the channel that uses delivery tags to fail and
cause the channel to be closed.

To avoid this issue, every channel keeps a counter of how many times
it has been reopened and marks delivery tags with them. Using a stale
tag to ack or reject a message will produce no method sent to RabbitMQ.
Note that unacknowledged messages will be requeued by RabbitMQ when connection
goes down anyway.

This involves an API change: `Bunny::DeliveryMetadata#delivery_tag` is now
and instance of a class that responds to `#tag` and `#to_i` and is accepted
by `Bunny::Channel#ack` and related methods.

Integers are still accepted by the same methods.

## Changes between Bunny 1.0.0.pre1 and 1.0.0.pre2

### Exclusivity Violation for Consumers Now Raises a Reasonable Exception

When a second consumer is registered for the same queue on different channels,
a reasonable exception (`Bunny::AccessRefused`) will be raised.

### Reentrant Mutex Implementation

Bunny now allows mutex impl to be configurable, uses reentrant Monitor
by default.

Non-reentrant mutexes is a major PITA and may affect code that
uses Bunny.

Avg. publishing throughput with Monitor drops slightly from
5.73 Khz to 5.49 Khz (about 4% decrease), which is reasonable
for Bunny.

Apps that need these 4% can configure what mutex implementation
is used on per-connection basis.

### Eliminated Race Condition in Bunny::Session#close

`Bunny::Session#close` had a race condition that caused (non-deterministic)
exceptions when connection transport was closed before connection
reader loop was guaranteed to have stopped.

### connection.close Raises Exceptions on Connection Thread

Connection-level exceptions (including when a connection is closed via
management UI or `rabbitmqctl`) will now be raised on the connection
thread so they

* can be handled by applications
* do not start connection recovery, which may be uncalled for

### Client TLS Certificates are Optional

Bunny will no longer require client TLS certificates. Note that CA certificate
list is still necessary.

If RabbitMQ TLS configuration requires peer verification, client certificate
and private key are mandatory.

## Changes between Bunny 0.9.0 and 1.0.0.pre1

### Publishing Over Closed Connections

Publishing a message over a closed connection (during a network outage, before the connection
is open) will now correctly result in an exception.

Contributed by Matt Campbell.

### Reliability Improvement in Automatic Network Failure Recovery

Bunny now ensures a new connection transport (socket) is initialized
before any recovery is attempted.

### Reliability Improvement in Bunny::Session#create_channel

`Bunny::Session#create_channel` now uses two separate mutexes to avoid
a (very rare) issue when the previous implementation would try to
re-acquire the same mutex and fail (Ruby mutexes are non-reentrant).

## Changes between Bunny 0.9.0.rc1 and 0.9.0.rc2

### Channel Now Properly Restarts Consumer Pool

In a case when all consumers are cancelled, `Bunny::Channel`
will shut down its consumer delivery thread pool.

It will also now mark the pool as not running so that it can be
started again successfully if new consumers are registered later.

GH issue: #133.

### Bunny::Queue#pop_waiting is Removed

A little bit of background: on MRI, the method raised `ThreadErrors`
reliably. On JRuby, we used a different [internal] queue implementation
from JDK so it wasn't an issue.

`Timeout.timeout` uses `Thread#kill` and `Thread#join`, both of which
eventually attempt to acquire a mutex used by Queue#pop, which Bunny
currently uses for continuations. The mutex is already has an owner
and so a ThreadError is raised.

This is not a problem on JRuby because there we don't use Ruby's
Timeout and Queue and instead rely on a JDK concurrency primitive
which provides "poll with a timeout".

[The issue with `Thread#kill` and `Thread#raise`](http://blog.headius.com/2008/02/ruby-threadraise-threadkill-timeoutrb.html)
has been first investigated and blogged about by Ruby implementers
in 2008.

Finding a workaround will probably take a bit of time and may involve
reimplementing standard library and core classes.

We don't want this issue to block Bunny 0.9 release. Neither we want
to ship a broken feature. So as a result, we will drop
Bunny::Queue#pop_waiting since it cannot be reliably implemented in a
reasonable amount of time on MRI.

Per issue #131.

### More Flexible SSLContext Configuration

Bunny will now upgrade connection to SSL in `Bunny::Session#start`,
so it is possible to fine tune SSLContext and socket settings
before that:

``` ruby
require "bunny"

conn = Bunny.new(:tls => true,
:tls_cert => "examples/tls/client_cert.pem",
:tls_key => "examples/tls/client_key.pem",
:tls_ca_certificates => ["./examples/tls/cacert.pem"])

puts conn.transport.socket.inspect
puts conn.transport.tls_context.inspect
```

This also means that `Bunny.new` will now open the socket. Previously
it was only done when `Bunny::Session#start` was invoked.

## Changes between Bunny 0.9.0.pre13 and 0.9.0.rc1

### TLS Support

Bunny 0.9 finally supports TLS. There are 3 new options `Bunny.new` takes:

* `:tls` which, when set to `true`, will set SSL context up and switch to TLS port (5671)
* `:tls_cert` which is a string path to the client certificate (public key) in PEM format
* `:tls_key` which is a string path to the client key (private key) in PEM format
* `:tls_ca_certificates` which is an array of string paths to CA certificates in PEM format

An example:

``` ruby
conn = Bunny.new(:tls => true,
:tls_cert => "examples/tls/client_cert.pem",
:tls_key => "examples/tls/client_key.pem",
:tls_ca_certificates => ["./examples/tls/cacert.pem"])
```

### Bunny::Queue#pop_waiting

**This function was removed in v0.9.0.rc2**

`Bunny::Queue#pop_waiting` is a new function that mimics `Bunny::Queue#pop`
but will wait until a message is available. It uses a `:timeout` option and will
raise an exception if the timeout is hit:

``` ruby
# given 1 message in the queue,
# works exactly as Bunny::Queue#get
q.pop_waiting

# given no messages in the queue, will wait for up to 0.5 seconds
# for a message to become available. Raises an exception if the timeout
# is hit
q.pop_waiting(:timeout => 0.5)
```

This method only makes sense for collecting Request/Reply ("RPC") replies.

### Bunny::InvalidCommand is now Bunny::CommandInvalid

`Bunny::InvalidCommand` is now `Bunny::CommandInvalid` (follows
the exception class naming convention based on response status
name).

## Changes between Bunny 0.9.0.pre12 and 0.9.0.pre13

### Channels Without Consumers Now Tear Down Consumer Pools

Channels without consumers left (when all consumers were cancelled)
will now tear down their consumer work thread pools, thus making
`HotBunnies::Queue#subscribe(:block => true)` calls unblock.

This is typically the desired behavior.

### Consumer and Channel Available In Delivery Handlers

Delivery handlers registered via `Bunny::Queue#subscribe` now will have
access to the consumer and channel they are associated with via the
`delivery_info` argument:

``` ruby
q.subscribe do |delivery_info, properties, payload|
delivery_info.consumer # => the consumer this delivery is for
delivery_info.consumer # => the channel this delivery is on
end
```

This allows using `Bunny::Queue#subscribe` for one-off consumers
much easier, including when used with the `:block` option.

### Bunny::Exchange#wait_for_confirms

`Bunny::Exchange#wait_for_confirms` is a convenience method on `Bunny::Exchange` that
delegates to the method with the same name on exchange's channel.

## Changes between Bunny 0.9.0.pre11 and 0.9.0.pre12

### Ruby 1.8 Compatibility Regression Fix

`Bunny::Socket` no longer uses Ruby 1.9-specific constants.

### Bunny::Channel#wait_for_confirms Return Value Regression Fix

`Bunny::Channel#wait_for_confirms` returns `true` or `false` again.

## Changes between Bunny 0.9.0.pre10 and 0.9.0.pre11

### Bunny::Session#create_channel Now Accepts Consumer Work Pool Size

`Bunny::Session#create_channel` now accepts consumer work pool size as
the second argument:

``` ruby
# nil means channel id will be allocated by Bunny.
# 8 is the number of threads in the consumer work pool this channel will use.
ch = conn.create_channel(nil, 8)
```

### Heartbeat Fix For Long Running Consumers

Long running consumers that don't send any data will no longer
suffer from connections closed by RabbitMQ because of skipped
heartbeats.

Activity tracking now takes sent frames into account.

### Time-bound continuations

If a network loop exception causes "main" session thread to never
receive a response, methods such as `Bunny::Channel#queue` will simply time out
and raise Timeout::Error now, which can be handled.

It will not start automatic recovery for two reasons:

* It will be started in the network activity loop anyway
* It may do more damage than good

Kicking off network recovery manually is a matter of calling
`Bunny::Session#handle_network_failure`.

The main benefit of this implementation is that it will never
block the main app/session thread forever, and it is really
efficient on JRuby thanks to a j.u.c. blocking queue.

Fixes #112.

### Logging Support

Every Bunny connection now has a logger. By default, Bunny will use STDOUT
as logging device. This is configurable using the `:log_file` option:

``` ruby
require "bunny"

conn = Bunny.new(:log_level => :warn)
```

or the `BUNNY_LOG_LEVEL` environment variable that can take one of the following
values:

* `debug` (very verbose)
* `info`
* `warn`
* `error`
* `fatal` (least verbose)

Severity is set to `warn` by default. To disable logging completely, set the level
to `fatal`.

To redirect logging to a file or any other object that can act as an I/O entity,
pass it to the `:log_file` option.

## Changes between Bunny 0.9.0.pre9 and 0.9.0.pre10

This release contains a **breaking API change**.

### Concurrency Improvements On JRuby

On JRuby, Bunny now will use `java.util.concurrent`-backed implementations
of some of the concurrency primitives. This both improves client stability
(JDK concurrency primitives has been around for 9 years and have
well-defined, documented semantics) and opens the door to solving
some tricky failure handling problems in the future.

### Explicitly Closed Sockets

Bunny now will correctly close the socket previous connection had
when recovering from network issues.

### Bunny::Exception Now Extends StandardError

`Bunny::Exception` now inherits from `StandardError` and not `Exception`.

Naked rescue like this

``` ruby
begin
# ...
rescue => e
# ...
end
```

catches only descendents of `StandardError`. Most people don't
know this and this is a very counter-intuitive practice, but
apparently there is code out there that can't be changed that
depends on this behavior.

This is a **breaking API change**.

## Changes between Bunny 0.9.0.pre8 and 0.9.0.pre9

### Bunny::Session#start Now Returns a Session

`Bunny::Session#start` now returns a session instead of the default channel
(which wasn't intentional, default channel is a backwards-compatibility implementation
detail).

`Bunny::Session#start` also no longer leaves dead threads behind if called multiple
times on the same connection.

### More Reliable Heartbeat Sender

Heartbeat sender no longer slips into an infinite loop if it encounters an exception.
Instead, it will just stop (and presumably re-started when the network error recovery
kicks in or the app reconnects manually).

### Network Recovery After Delay

Network reconnection now kicks in after a delay to avoid aggressive
reconnections in situations when we don't want to endlessly reconnect
(e.g. when the connection was closed via the Management UI).

The `:network_recovery_interval` option passed to `Bunny::Session#initialize` and `Bunny.new`
controls the interval. Default is 5 seconds.

### Default Heartbeat Value Is Now Server-Defined

Bunny will now use heartbeat value provided by RabbitMQ by default.

## Changes between Bunny 0.9.0.pre7 and 0.9.0.pre8

### Stability Improvements

Several stability improvements in the network
layer, connection error handling, and concurrency hazards.

### Automatic Connection Recovery Can Be Disabled

Automatic connection recovery now can be disabled by passing
the `:automatically_recover => false` option to `Bunny#initialize`).

When the recovery is disabled, network I/O-related exceptions will
cause an exception to be raised in thee thread the connection was
started on.

### No Timeout Control For Publishing

`Bunny::Exchange#publish` and `Bunny::Channel#basic_publish` no
longer perform timeout control (using the timeout module) which
roughly increases throughput for flood publishing by 350%.

Apps that need delivery guarantees should use publisher confirms.

## Changes between Bunny 0.9.0.pre6 and 0.9.0.pre7

### Bunny::Channel#on_error

`Bunny::Channel#on_error` is a new method that lets you define
handlers for channel errors that are caused by methods that have no
responses in the protocol (`basic.ack`, `basic.reject`, and `basic.nack`).

This is rarely necessary but helps make sure no error goes unnoticed.

Example:

``` ruby
channel.on_error |ch, channel_close|
puts channel_close.inspect
end
```

### Fixed Framing of Larger Messages With Unicode Characters

Larger (over 128K) messages with non-ASCII characters are now always encoded
correctly with amq-protocol `1.2.0`.

### Efficiency Improvements

Publishing of large messages is now done more efficiently.

Contributed by Greg Brockman.

### API Reference

[Bunny API reference](http://reference.rubybunny.info) is now up online.

### Bunny::Channel#basic_publish Support For :persistent

`Bunny::Channel#basic_publish` now supports both
`:delivery_mode` and `:persistent` options.

### Bunny::Channel#nacked_set

`Bunny::Channel#nacked_set` is a counter-part to `Bunny::Channel#unacked_set`
that contains `basic.nack`-ed (rejected) delivery tags.

### Single-threaded Network Activity Mode

Passing `:threaded => false` to `Bunny.new` now will use the same
thread for publisher confirmations (may be useful for retry logic
implementation).

Contributed by Greg Brockman.

## Changes between Bunny 0.9.0.pre5 and 0.9.0.pre6

### Automatic Network Failure Recovery

Automatic Network Failure Recovery is a new Bunny feature that was earlier
impemented and vetted out in [amqp gem](http://rubyamqp.info). What it does
is, when a network activity loop detects an issue, it will try to
periodically recover [first TCP, then] AMQP 0.9.1 connection, reopen
all channels, recover all exchanges, queues, bindings and consumers
on those channels (to be clear: this only includes entities and consumers added via
Bunny).

Publishers and consumers will continue operating shortly after the network
connection recovers.

Learn more in the [Error Handling and Recovery](http://rubybunny.info/articles/error_handling.html)
documentation guide.

### Confirms Listeners

Bunny now supports listeners (callbacks) on

``` ruby
ch.confirm_select do |delivery_tag, multiple, nack|
# handle confirms (e.g. perform retries) here
end
```

Contributed by Greg Brockman.

### Publisher Confirms Improvements

Publisher confirms implementation now uses non-strict equality (`<=`) for
cases when multiple messages are confirmed by RabbitMQ at once.

`Bunny::Channel#unconfirmed_set` is now part of the public API that lets
developers access unconfirmed delivery tags to perform retries and such.

Contributed by Greg Brockman.

### Publisher Confirms Concurrency Fix

`Bunny::Channel#wait_for_confirms` will now correctly block the calling
thread until all pending confirms are received.

## Changes between Bunny 0.9.0.pre4 and 0.9.0.pre5

### Channel Errors Reset

Channel error information is now properly reset when a channel is (re)opened.

GH issue: #83.

### Bunny::Consumer#initial Default Change

the default value of `Bunny::Consumer` noack argument changed from false to true
for consistency.

### Bunny::Session#prefetch Removed

Global prefetch is not implemented in RabbitMQ, so `Bunny::Session#prefetch`
is gone from the API.

### Queue Redeclaration Bug Fix

Fixed a problem when a queue was not declared after being deleted and redeclared

GH issue: #80

### Channel Cache Invalidation

Channel queue and exchange caches are now properly invalidated when queues and
exchanges are deleted.

## Changes between Bunny 0.9.0.pre3 and 0.9.0.pre4

### Heartbeats Support Fixes

Heartbeats are now correctly sent at safe intervals (half of the configured
interval). In addition, setting `:heartbeat => 0` (or `nil`) will disable
heartbeats, just like in Bunny 0.8 and [amqp gem](http://rubyamqp.info).

Default `:heartbeat` value is now `600` (seconds), the same as RabbitMQ 3.0
default.

### Eliminate Race Conditions When Registering Consumers

Fixes a potential race condition between `basic.consume-ok` handler and
delivery handler when a consumer is registered for a queue that has
messages in it.

GH issue: #78.

### Support for Alternative Authentication Mechanisms

Bunny now supports two authentication mechanisms and can be extended
to support more. The supported methods are `"PLAIN"` (username
and password) and `"EXTERNAL"` (typically uses TLS, UNIX sockets or
another mechanism that does not rely on username/challenge pairs).

To use the `"EXTERNAL"` method, pass `:auth_mechanism => "EXTERNAL"` to
`Bunny.new`:

``` ruby
# uses the EXTERNAL authentication mechanism
conn = Bunny.new(:auth_method => "EXTERNAL")
conn.start
```

### Bunny::Consumer#cancel

A new high-level API method: `Bunny::Consumer#cancel`, can be used to
cancel a consumer. `Bunny::Queue#subscribe` will now return consumer
instances when the `:block` option is passed in as `false`.

### Bunny::Exchange#delete Behavior Change

`Bunny::Exchange#delete` will no longer delete pre-declared exchanges
that cannot be declared by Bunny (`amq.*` and the default exchange).

### Bunny::DeliveryInfo#redelivered?

`Bunny::DeliveryInfo#redelivered?` is a new method that is an alias
to `Bunny::DeliveryInfo#redelivered` but follows the Ruby community convention
about predicate method names.

### Corrected Bunny::DeliveryInfo#delivery_tag Name

`Bunny::DeliveryInfo#delivery_tag` had a typo which is now fixed.

## Changes between Bunny 0.9.0.pre2 and 0.9.0.pre3

### Client Capabilities

Bunny now correctly lists RabbitMQ extensions it currently supports in client capabilities:

* `basic.nack`
* exchange-to-exchange bindings
* consumer cancellation notifications
* publisher confirms

### Publisher Confirms Support

[Lightweight Publisher Confirms](http://www.rabbitmq.com/blog/2011/02/10/introducing-publisher-confirms/) is a
RabbitMQ feature that lets publishers keep track of message routing without adding
noticeable throughput degradation as it is the case with AMQP 0.9.1 transactions.

Bunny `0.9.0.pre3` supports publisher confirms. Publisher confirms are enabled per channel,
using the `Bunny::Channel#confirm_select` method. `Bunny::Channel#wait_for_confirms` is a method
that blocks current thread until the client gets confirmations for all unconfirmed published
messages:

``` ruby
ch = connection.create_channel
ch.confirm_select

ch.using_publisher_confirmations? # => true

q = ch.queue("", :exclusive => true)
x = ch.default_exchange

5000.times do
x.publish("xyzzy", :routing_key => q.name)
end

ch.next_publish_seq_no.should == 5001
ch.wait_for_confirms # waits until all 5000 published messages are acknowledged by RabbitMQ
```

### Consumers as Objects

It is now possible to register a consumer as an object instead
of a block. Consumers that are class instances support cancellation
notifications (e.g. when a queue they're registered with is deleted).

To support this, Bunny introduces two new methods: `Bunny::Channel#basic_consume_with`
and `Bunny::Queue#subscribe_with`, that operate on consumer objects. Objects are
supposed to respond to three selectors:

* `:handle_delivery` with 3 arguments
* `:handle_cancellation` with 1 argument
* `:consumer_tag=` with 1 argument

An example:

``` ruby
class ExampleConsumer < Bunny::Consumer
def cancelled?
@cancelled
end

def handle_cancellation(_)
@cancelled = true
end
end

# "high-level" API
ch1 = connection.create_channel
q1 = ch1.queue("", :auto_delete => true)

consumer = ExampleConsumer.new(ch1, q)
q1.subscribe_with(consumer)

# "low-level" API
ch2 = connection.create_channel
q1 = ch2.queue("", :auto_delete => true)

consumer = ExampleConsumer.new(ch2, q)
ch2.basic_consume_with.(consumer)
```

### RABBITMQ_URL ENV variable support

If `RABBITMQ_URL` environment variable is set, Bunny will assume
it contains a valid amqp URI string and will use it. This is convenient
with some PaaS technologies such as Heroku.

## Changes between Bunny 0.9.0.pre1 and 0.9.0.pre2

### Change Bunny::Queue#pop default for :ack to false

It makes more sense for beginners that way.

### Bunny::Queue#subscribe now support the new :block option

`Bunny::Queue#subscribe` support the new `:block` option
(a boolean).

It controls whether the current thread will be blocked
by `Bunny::Queue#subscribe`.

### Bunny::Exchange#publish now supports :key again

`Bunny::Exchange#publish` now supports `:key` as an alias for
`:routing_key`.

### Bunny::Session#queue et al.

`Bunny::Session#queue`, `Bunny::Session#direct`, `Bunny::Session#fanout`, `Bunny::Session#topic`,
and `Bunny::Session#headers` were added to simplify migration. They all delegate to their respective
`Bunny::Channel` methods on the default channel every connection has.

### Bunny::Channel#exchange, Bunny::Session#exchange

`Bunny::Channel#exchange` and `Bunny::Session#exchange` were added to simplify
migration:

``` ruby
b = Bunny.new
b.start

# uses default connection channel
x = b.exchange("logs.events", :topic)
```

### Bunny::Queue#subscribe now properly takes 3 arguments

``` ruby
q.subscribe(:exclusive => false, :ack => false) do |delivery_info, properties, payload|
# ...
end
```

## Changes between Bunny 0.8.x and 0.9.0.pre1

### New convenience functions: Bunny::Channel#fanout, Bunny::Channel#topic

`Bunny::Channel#fanout`, `Bunny::Channel#topic`, `Bunny::Channel#direct`, `Bunny::Channel#headers`,
and`Bunny::Channel#default_exchange` are new convenience methods to instantiate exchanges:

``` ruby
conn = Bunny.new
conn.start

ch = conn.create_channel
x = ch.fanout("logging.events", :durable => true)
```

### Bunny::Queue#pop and consumer handlers (Bunny::Queue#subscribe) signatures have changed

Bunny `< 0.9.x` example:

``` ruby
h = queue.pop

puts h[:delivery_info], h[:header], h[:payload]
```

Bunny `>= 0.9.x` example:

``` ruby
delivery_info, properties, payload = queue.pop
```

The improve is both in that Ruby has positional destructuring, e.g.

``` ruby
delivery_info, _, content = q.pop
```

but not hash destructuring, like, say, Clojure does.

In addition we return nil for content when it should be nil
(basic.get-empty) and unify these arguments betwee

* Bunny::Queue#pop

* Consumer (Bunny::Queue#subscribe, etc) handlers

* Returned message handlers

The unification moment was the driving factor.

### Bunny::Client#write now raises Bunny::ConnectionError

Bunny::Client#write now raises `Bunny::ConnectionError` instead of `Bunny::ServerDownError` when network
I/O operations fail.

### Bunny::Client.create_channel now uses a bitset-based allocator

Instead of reusing channel instances, `Bunny::Client.create_channel` now opens new channels and
uses bitset-based allocator to keep track of used channel ids. This avoids situations when
channels are reused or shared without developer's explicit intent but also work well for
long running applications that aggressively open and release channels.

This is also how amqp gem and RabbitMQ Java client manage channel ids.

### Bunny::ServerDownError is now Bunny::TCPConnectionFailed

`Bunny::ServerDownError` is now an alias for `Bunny::TCPConnectionFailed`