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Merge 7665862 into 1f94462
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@maltoe
maltoe committed May 23, 2016
2 parents 1f94462 + 7665862 commit d94074b
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21 changes: 17 additions & 4 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -95,21 +95,34 @@ rescue Redlock::LockError
end
```

To extend the life of the lock, provided that you didn't let it expire:
To extend the life of the lock:

```ruby
begin
block_result = lock_manager.lock!("resource_key", 2000) do |lock_info|
# critical code
lock_manager.extend_life!(lock_info, 3000)
lock_manager.lock("resource key", 3000, extend: lock_info)
# more critical code
end
rescue Redlock::LockError
# error handling
end
```
There's also a non-bang version that returns true when the lock was
extended

The above code will also acquire the lock if the previous lock has expired and the lock is currently free. Keep in mind that this means the lock could have been acquired by someone else in the meantime. To only extend the life of the lock if currently locked by yourself, use `extend_life` parameter:

```ruby
begin
block_result = lock_manager.lock!("resource_key", 2000) do |lock_info|
# critical code
lock_manager.lock("resource key", 3000, extend: lock_info, extend_life: true)
# more critical code, only if lock was still hold
end
rescue Redlock::LockError
# error handling
end
```


## Run tests

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61 changes: 15 additions & 46 deletions lib/redlock/client.rb
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Expand Up @@ -37,9 +37,8 @@ def initialize(servers = DEFAULT_REDIS_URLS, options = {})
# +extend+: A lock ("lock_info") to extend.
# +block+:: an optional block to be executed; after its execution, the lock (if successfully
# acquired) is automatically unlocked.
def lock(resource, ttl, options={}, &block)
extend = options[:extend] || nil
lock_info = try_lock_instances(resource, ttl, extend)
def lock(resource, ttl, options = {}, &block)
lock_info = try_lock_instances(resource, ttl, options)

if block_given?
begin
Expand All @@ -53,38 +52,6 @@ def lock(resource, ttl, options={}, &block)
end
end

# Extends the given lock for a given time. Returns true on success.
# Params:
# +to_extend+:: A lock ("lock_info") to extend.
# +ttl+:: The time-to-live in ms for the lock.
def extend_life(to_extend, ttl)
value = to_extend.fetch(:value)
resource = to_extend.fetch(:resource)


extended, time_elapsed = timed do
@servers.all? { |s| s.extend_life(resource, value, ttl) }
end

validity = ttl - time_elapsed - drift(ttl)

if extended
{ validity: validity, resource: resource, value: value }
else
@servers.each { |s| s.unlock(resource, value) }
false
end
end

# Extends the given lock for a given time. Raises LockError on failure
# Params:
# +to_extend+:: A lock ("lock_info") to extend.
# +ttl+:: The time-to-live in ms for the lock.
def extend_life!(to_extend, ttl)
new_lock_info = self.extend_life(to_extend, ttl)
raise LockError, 'failed to extend lock' unless new_lock_info
end

# Unlocks a resource.
# Params:
# +lock_info+:: the lock that has been acquired when you locked the resource.
Expand Down Expand Up @@ -124,7 +91,7 @@ class RedisInstance
end
eos

EXTEND_LOCK_SCRIPT = <<-eos
EXTEND_LIFE_SCRIPT = <<-eos
if redis.call("get", KEYS[1]) == ARGV[1] then
redis.call("expire", KEYS[1], ARGV[2])
return 0
Expand All @@ -133,7 +100,6 @@ class RedisInstance
end
eos


def initialize(connection)
if connection.respond_to?(:client)
@redis = connection
Expand All @@ -150,9 +116,9 @@ def lock(resource, val, ttl)
end
end

def extend_life(resource, val, ttl)
def extend(resource, val, ttl)
recover_from_script_flush do
rc = @redis.evalsha @extend_lock_script_sha, keys: [resource], argv: [val, ttl]
rc = @redis.evalsha @extend_life_script_sha, keys: [resource], argv: [val, ttl]
rc == 0
end
end
Expand All @@ -170,7 +136,7 @@ def unlock(resource, val)
def load_scripts
@unlock_script_sha = @redis.script(:load, UNLOCK_SCRIPT)
@lock_script_sha = @redis.script(:load, LOCK_SCRIPT)
@extend_lock_script_sha = @redis.script(:load, EXTEND_LOCK_SCRIPT)
@extend_life_script_sha = @redis.script(:load, EXTEND_LIFE_SCRIPT)
end

def recover_from_script_flush
Expand All @@ -192,9 +158,11 @@ def recover_from_script_flush
end
end

def try_lock_instances(resource, ttl, extend)
@retry_count.times do
lock_info = lock_instances(resource, ttl, extend)
def try_lock_instances(resource, ttl, options)
tries = options[:extend] ? 1 : @retry_count

tries.times do
lock_info = lock_instances(resource, ttl, options)
return lock_info if lock_info

# Wait a random delay before retrying
Expand All @@ -204,11 +172,12 @@ def try_lock_instances(resource, ttl, extend)
false
end

def lock_instances(resource, ttl, extend)
value = extend ? extend.fetch(:value) : SecureRandom.uuid
def lock_instances(resource, ttl, options)
value = options[:extend] ? options[:extend].fetch(:value) : SecureRandom.uuid
method = options[:extend_life] ? :extend : :lock

locked, time_elapsed = timed do
@servers.select { |s| s.lock(resource, value, ttl) }.size
@servers.select { |s| s.send(method, resource, value, ttl) }.size
end

validity = ttl - time_elapsed - drift(ttl)
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6 changes: 3 additions & 3 deletions lib/redlock/testing.rb
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Expand Up @@ -4,17 +4,17 @@ class Client

alias_method :try_lock_instances_without_testing, :try_lock_instances

def try_lock_instances(resource, ttl, extend)
def try_lock_instances(resource, ttl, options)
if @testing_mode == :bypass
{
validity: ttl,
resource: resource,
value: extend ? extend.fetch(:value) : SecureRandom.uuid
value: options[:extend] ? options[:extend].fetch(:value) : SecureRandom.uuid
}
elsif @testing_mode == :fail
false
else
try_lock_instances_without_testing resource, ttl, extend
try_lock_instances_without_testing resource, ttl, options
end
end

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51 changes: 13 additions & 38 deletions spec/client_spec.rb
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Expand Up @@ -43,10 +43,19 @@
expect(@lock_info[:value]).to eq(my_lock_info[:value])
end

it "sets the given value when trying to extend a non-existent lock" do
@lock_info = lock_manager.lock(resource_key, ttl, extend: {value: 'hello world'})
expect(@lock_info).to be_lock_info_for(resource_key)
expect(@lock_info[:value]).to eq('hello world') # really we should test what's in redis
context 'when extend_life flag is given' do
it 'does not extend a non-existent lock' do
@lock_info = lock_manager.lock(resource_key, ttl, extend: {value: 'hello world'}, extend_life: true)
expect(@lock_info).to eq(false)
end
end

context 'when extend_life flag is not given' do
it "sets the given value when trying to extend a non-existent lock" do
@lock_info = lock_manager.lock(resource_key, ttl, extend: {value: 'hello world'}, extend_life: false)
expect(@lock_info).to be_lock_info_for(resource_key)
expect(@lock_info[:value]).to eq('hello world') # really we should test what's in redis
end
end

it "doesn't extend somebody else's lock" do
Expand Down Expand Up @@ -170,40 +179,6 @@
end
end

describe "extend" do
context 'when lock is available' do
before { @lock_info = lock_manager.lock(resource_key, ttl) }
after(:each) { lock_manager.unlock(@lock_info) if @lock_info }

it 'can extend its own lock' do
lock_info = lock_manager.extend_life(@lock_info, ttl)
expect(lock_info).to be_lock_info_for(resource_key)
end

it "can't extend a nonexistent lock" do
lock_manager.unlock(@lock_info)
lock_info = lock_manager.extend_life(@lock_info, ttl)
expect(lock_info).to eq(false)
end
end
end

describe "extend!" do
context 'when lock is available' do
before { @lock_info = lock_manager.lock(resource_key, ttl) }
after(:each) { lock_manager.unlock(@lock_info) if @lock_info }

it 'can extend its own lock' do
expect{ lock_manager.extend_life!(@lock_info, ttl) }.to_not raise_error
end

it "can't extend a nonexistent lock" do
lock_manager.unlock(@lock_info)
expect{ lock_manager.extend_life!(@lock_info, ttl) }.to raise_error(Redlock::LockError)
end
end
end

describe 'lock!' do
context 'when lock is available' do
it 'locks' do
Expand Down

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