RedisQueuedLocks ·

Distributed locks with "lock acquisition queue" capabilities based on the Redis Database.

Provides flexible invocation flow, parametrized limits (lock request ttl, lock ttls, queue ttls, fast failing, etc), logging and instrumentation.

Each lock request is put into the request queue (each lock is hosted by it's own queue separately from other queues) and processed in order of their priority (FIFO). Each lock request lives some period of time (RTTL) (with requeue capabilities) which guarantees the request queue will never be stacked.

Requirements
Experience
Algorithm
Installation
Setup
Configuration
Usage
- lock
- lock!
- lock_info
- queue_info
- locked?
- queued?
- unlock
- clear_locks
- extend_lock_ttl
- locks
- queues
- keys
- locks_info
- queues_info
- clear_dead_requests
Logging
Instrumentation
- Instrumentation Events
Roadmap
Contributing
License
Authors

Requirements

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Redis Version: ~> 7.x;
Redis Protocol: RESP3;
gem redis-client: ~> 0.20;
Ruby: >= 3.1;

Experience

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Battle-tested on huge ruby projects in production: ~1500 locks-per-second are obtained and released on an ongoing basis;
Works well with hiredis driver enabled (it is enabled by default on our projects where redis_queued_locks are used);

Algorithm

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Each lock request is put into the request queue (each lock is hosted by it's own queue separately from other queues) and processed in order of their priority (FIFO). Each lock request lives some period of time (RTTL) which guarantees that the request queue will never be stacked.

Soon: detailed explanation.

Installation

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gem 'redis_queued_locks'

bundle install
# --- or ---
gem install redis_queued_locks

require 'redis_queued_locks'

Setup

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require 'redis_queued_locks'

# Step 1: initialize RedisClient instance
redis_client = RedisClient.config.new_pool # NOTE: provide your own RedisClient instance

# Step 2: initialize RedisQueuedLock::Client instance
rq_lock_client = RedisQueuedLocks::Client.new(redis_client) do |config|
  # NOTE:
  #   - some your application-related configs;
  #   - for documentation see <Configuration> section in readme;
end

# Step 3: start to work with locks :)
rq_lock_client.lock("some-lock") { puts "Hello, lock!" }

Configuration

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redis_client = RedisClient.config.new_pool # NOTE: provide your own RedisClient instance

clinet = RedisQueuedLocks::Client.new(redis_client) do |config|
  # (default: 3) (supports nil)
  # - nil means "infinite retries" and you are only limited by the "try_to_lock_timeout" config;
  config.retry_count = 3

  # (milliseconds) (default: 200)
  config.retry_delay = 200

  # (milliseconds) (default: 25)
  config.retry_jitter = 25

  # (seconds) (supports nil)
  # - nil means "no timeout" and you are only limited by "retry_count" config;
  config.try_to_lock_timeout = 10

  # (milliseconds) (default: 5_000)
  # - lock's time to live
  config.default_lock_ttl = 5_000

  # (seconds) (default: 15)
  # - lock request timeout. after this timeout your lock request in queue will be requeued with new position (at the end of the queue);
  config.default_queue_ttl = 15

  # (boolean) (default: false)
  # - should be all blocks of code are timed by default;
  config.is_timed_by_default = false

  # (default: 100)
  # - how many items will be released at a time in #clear_locks and in #clear_dead_requests (uses SCAN);
  # - affects the performance of your Redis and Ruby Application (configure thoughtfully);
  config.lock_release_batch_size = 100

  # (default: 500)
  # - how many items should be extracted from redis during the #locks, #queues, #keys
  #   #locks_info, and #queues_info operations (uses SCAN);
  # - affects the performance of your Redis and Ruby Application (configure thoughtfully;)
  config.key_extraction_batch_size = 500

  # (default: 1 day)
  # - the default period of time (in milliseconds) after which a lock request is considered dead;
  # - used for `#clear_dead_requests` as default vaule of `:dead_ttl` option;
  config.dead_request_ttl = (1 * 24 * 60 * 60 * 1000) # one day in milliseconds

  # (default: RedisQueuedLocks::Instrument::VoidNotifier)
  # - instrumentation layer;
  # - you can provde your own instrumenter with `#notify(event, payload = {})`
  #   - event: <string> requried;
  #   - payload: <hash> requried;
  # - disabled by default via VoidNotifier;
  config.instrumenter = RedisQueuedLocks::Instrument::ActiveSupport

  # (default: -> { RedisQueuedLocks::Resource.calc_uniq_identity })
  # - uniqude idenfitier that is uniq per process/pod;
  # - prevents potential lock-acquirement collisions bettween different process/pods
  #   that have identical process_id/thread_id/fiber_id/ractor_id (identivcal acquier ids);
  # - it is calculated once per `RedisQueudLocks::Client` instance;
  # - expects the proc object;
  # - `SecureRandom.hex(8)` by default;
  config.uniq_identifier = -> { RedisQueuedLocks::Resource.calc_uniq_identity }

  # (default: RedisQueuedLocks::Logging::VoidLogger)
  # - the logger object;
  # - should implement `debug(progname = nil, &block)` (minimal requirement) or be an instance of Ruby's `::Logger` class/subclass;
  # - at this moment the only debug logs are realised in following cases:
  #   - "[redis_queued_locks.start_lock_obtaining]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.start_try_to_lock_cycle]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.dead_score_reached__reset_acquier_position]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.lock_obtained]" (logs "lockkey", "queue_ttl", "acq_id", "acq_time");
  #   - "[redis_queued_locks.fail_fast_or_limits_reached__dequeue] (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.expire_lock]" # (logs "lock_key", "queue_ttl", "acq_id");
  # - by default uses VoidLogger that does nothing;
  config.logger = RedisQueuedLocks::Logging::VoidLogger

  # (default: false)
  # - adds additional debug logs;
  # - enables additional logs for each internal try-retry lock acquiring (a lot of logs can be generated depending on your retry configurations);
  # - it adds following logs in addition to the existing:
  #   - "[redis_queued_locks.try_lock.start]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.try_lock.rconn_fetched]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.try_lock.acq_added_to_queue]" (logs "lock_key", "queue_ttl", "acq_id)";
  #   - "[redis_queued_locks.try_lock.remove_expired_acqs]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.try_lock.get_first_from_queue]" (logs "lock_key", "queue_ttl", "acq_id", "first_acq_id_in_queue");
  #   - "[redis_queued_locks.try_lock.exit__queue_ttl_reached]" (logs "lock_key", "queue_ttl", "acq_id");
  #   - "[redis_queued_locks.try_lock.exit__no_first]" (logs "lock_key", "queue_ttl", "acq_id", "first_acq_id_in_queue", "<current_lock_data>");
  #   - "[redis_queued_locks.try_lock.exit__lock_still_obtained]" (logs "lock_key", "queue_ttl", "acq_id", "first_acq_id_in_queue", "locked_by_acq_id", "<current_lock_data>");
  #   - "[redis_queued_locks.try_lock.obtain__free_to_acquire]" (logs "lock_key", "queue_ttl", "acq_id");
  config.log_lock_try = false
end

Usage

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lock
lock!
lock_info
queue_info
locked?
queued?
unlock
clear_locks
extend_lock_ttl
locks
queues
keys
locks_info
queues_info
clear_dead_requests

#lock - obtain a lock

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If block is passed the obtained lock will be released after the block execution or the lock's ttl (what will happen first);
If block is not passed the obtained lock will be released after lock's ttl;
If block is passed the block's yield result will be returned;
If block is not passed the lock information will be returned;

def lock(
  lock_name,
  ttl: config[:default_lock_ttl],
  queue_ttl: config[:default_queue_ttl],
  timeout: config[:try_to_lock_timeout],
  timed: config[:is_timed_by_default],
  retry_count: config[:retry_count],
  retry_delay: config[:retry_delay],
  retry_jitter: config[:retry_jitter],
  raise_errors: false,
  fail_fast: false,
  identity: uniq_identity, # (attr_accessor) calculated during client instantiation via config[:uniq_identifier] proc;
  meta: nil,
  instrument: nil,
  logger: config[:logger],
  log_lock_try: config[:log_lock_try],
  &block
)

lock_name - (required) [String]
- Lock name to be obtained.
ttl - (optional) - [Integer]
- Lock's time to live (in milliseconds);
- pre-configured in config[:default_lock_ttl];
queue_ttl - (optional) [Integer]
- Lifetime of the acuier's lock request. In seconds.
- pre-configured in config[:default_queue_ttl];
timeout - (optional) [Integer,NilClass]
- Time period a client should try to acquire the lock (in seconds). Nil means "without timeout".
- pre-configured in config[:try_to_lock_timeout];
timed - (optiona) [Boolean]
- Limit the invocation time period of the passed block of code by the lock's TTL.
- pre-configured in config[:is_timed_by_default];
- false by default;
retry_count - (optional) [Integer,NilClass]
- How many times we should try to acquire a lock. Nil means "infinite retries".
- pre-configured in config[:retry_count];
retry_delay - (optional) [Integer]
- A time-interval between the each retry (in milliseconds).
- pre-configured in config[:retry_delay];
retry_jitter - (optional) [Integer]
- Time-shift range for retry-delay (in milliseconds);
- pre-configured in config[:retry_jitter];
instrumenter - (optional) [#notify]
- See RedisQueuedLocks::Instrument::ActiveSupport for example;
- See Instrumentation section of docs;
- pre-configured in config[:isntrumenter] with void notifier (RedisQueuedLocks::Instrumenter::VoidNotifier);
raise_errors - (optional) [Boolean]
- Raise errors on library-related limits such as timeout or retry count limit;
- false by default;
fail_fast - (optional) [Boolean]
- Should the required lock to be checked before the try and exit immidietly if lock is already obtained;
- Should the logic exit immidietly after the first try if the lock was obtained by another process while the lock request queue was initially empty;
- false by default;
identity - (optional) [String]
- An unique string that is unique per RedisQueuedLock::Client instance. Resolves the collisions between the same process_id/thread_id/fiber_id/ractor_id identifiers on different pods or/and nodes of your application;
- It is calculated once during RedisQueuedLock::Client instantiation and stored in @uniq_identity ivar (accessed via uniq_dentity accessor method);
- Identity calculator is pre-configured in config[:uniq_identifier];
meta - (optional) [NilClass,Hash<String|Symbol,Any>]
- A custom metadata wich will be passed to the lock data in addition to the existing data;
- Custom metadata can not contain reserved lock data keys (such as lock_key, acq_id, ts, ini_ttl, rem_ttl);
- nil by default (means "no metadata");
instrument - (optional) [NilClass,Any]
- Custom instrumentation data wich will be passed to the instrumenter's payload with :instrument key;
- nil by default (means "no custom instrumentation data");
logger - (optional) [::Logger,#debug]
- Logger object used for loggin internal mutation oeprations and opertioan results / process progress;
- pre-configured in config[:logger] with void logger RedisQueuedLocks::Logging::VoidLogger;
log_lock_try - (optional) [Boolean]
- should be logged the each try of lock acquiring (a lot of logs can be generated depending on your retry configurations);
- pre-configured in config[:log_lock_try];
- false by default;
block - (optional) [Block]
- A block of code that should be executed after the successfully acquired lock.
- If block is passed the obtained lock will be released after the block execution or it's ttl (what will happen first);
- If block is not passed the obtained lock will be released after it's ttl;
- If you want the block to have a TTL too and this TTL to be the same as TTL of the lock use timed: true option (rql.lock("my_lock", timed: true, ttl: 5_000) { ... })

Return value:

If block is passed the block's yield result will be returned:

result = rql.lock("my_lock") { 1 + 1 }
result # => 2

If block is not passed the lock information will be returned:

result = rql.lock("my_lock")
result # =>
{
  ok: true,
  result: {
    lock_key: "rql:lock:my_lock",
    acq_id: "rql:acq:26672/2280/2300/2320/70ea5dbf10ea1056",
    ts: 1711909612.653696,
    ttl: 10000
  }
}

Lock information result:

Signature: [yield, Hash<Symbol,Boolean|Hash<Symbol,Numeric|String>>]
Format: { ok: true/false, result: <Symbol|Hash<Symbol,Hash>> };

for successful lock obtaining:

{
  ok: true,
  result: {
    lock_key: String, # acquierd lock key ("rql:lock:your_lock_name")
    acq_id: String, # acquier identifier ("process_id/thread_id/fiber_id/ractor_id/identity")
    ts: Float, # time (epoch) when lock was obtained (float, Time#to_f)
    ttl: Integer # lock's time to live in milliseconds (integer)
  }
}

# example:
{
  ok: true,
  result: {
    lock_key: "rql:lock:my_lock",
    acq_id: "rql:acq:26672/2280/2300/2320/70ea5dbf10ea1056",
    ts: 1711909612.653696,
    ttl: 10000
  }
}

for failed lock obtaining:

{ ok: false, result: :timeout_reached }
{ ok: false, result: :retry_count_reached }
{ ok: false, result: :fail_fast_no_try } # see <fail_fast> option
{ ok: false, result: :fail_fast_after_try } # see <fail_fast> option
{ ok: false, result: :unknown }

Examples:

obtain a lock:

rql.lock("my_lock") { print "Hello!" }

obtain a lock with custom lock TTL:

rql.lock("my_lock", ttl: 5_000) { print "Hello!" } # for 5 seconds

obtain a lock and limit the passed block of code TTL with lock's TTL:

rql.lock("my_lock", ttl: 5_000, timed: true) { sleep(4) }
# => OK

rql.lock("my_lock", ttl: 5_000, timed: true) { sleep(6) }
# => fails with RedisQueuedLocks::TimedLockTimeoutError

infinite lock obtaining (no retry limit, no timeout limit):

rql.lock("my_lock", retry_count: nil, timeout: nil)

try to obtain with a custom waiting timeout:

# First Ruby Process:
rql.lock("my_lock", ttl: 5_000) { sleep(4) } # acquire a long living lock

# Another Ruby Process:
rql.lock("my_lock", timeout: 2) # try to acquire but wait for a 2 seconds maximum
# =>
{ ok: false, result: :timeout_reached }

obtain a lock and immediatly continue working (the lock will live in the background in Redis with the passed ttl)

rql.lock("my_lock", ttl: 6_500) # blocks execution until the lock is obtained
puts "Let's go" # will be called immediately after the lock is obtained

add custom metadata to the lock (via :meta option):

rql.lock("my_lock", ttl: 123456, meta: { "some" => "data", key: 123.456 })

rql.lock_info("my_lock")
# =>
{
  "lock_key" => "rql:lock:my_lock",
  "acq_id" => "rql:acq:123/456/567/678/374dd74324",
  "ts" => 123456789,
  "ini_ttl" => 123456,
  "rem_ttl" => 123440,
  "some" => "data",
  "key" => "123.456" # NOTE: returned as a raw string directly from Redis
}

(:queue_ttl) setting a short limit of time to the lock request queue position (if a process fails to acquire the lock within this period of time (and before timeout/retry_count limits occurs of course) - it's lock request will be moved to the end of queue):

rql.lock("my_lock", queue_ttl: 5, timeout: 10_000, retry_count: nil)
# "queue_ttl: 5": 5 seconds time slot before the lock request moves to the end of queue;
# "timeout" and "retry_count" is used as "endless lock try attempts" example to show the lock queue behavior;

# lock queue: =>
[
 "rql:acq:123/456/567/676/374dd74324", 
 "rql:acq:123/456/567/677/374dd74322", # <- long living lock
 "rql:acq:123/456/567/679/374dd74321",
 "rql:acq:123/456/567/683/374dd74322", # <== we are here
 "rql:acq:123/456/567/685/374dd74329", # some other waiting process
]

# ... some period of time (2 seconds later)
# lock queue: =>
[
 "rql:acq:123/456/567/677/374dd74322", # <- long living lock
 "rql:acq:123/456/567/679/374dd74321",
 "rql:acq:123/456/567/683/374dd74322", # <== we are here
 "rql:acq:123/456/567/685/374dd74329", # some other waiting process
]

# ... some period of time (3 seconds later)
# ... queue_ttl time limit is reached
# lock queue: =>
[
 "rql:acq:123/456/567/685/374dd74329", # some other waiting process
 "rql:acq:123/456/567/683/374dd74322", # <== we are here (moved to the end of the queue)
]

#lock! - exceptional lock obtaining

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fails when (and with):
- (RedisQueuedLocks::LockAlreadyObtainedError) when fail_fast is true and lock is already obtained;
- (RedisQueuedLocks::LockAcquiermentTimeoutError) timeout limit reached before lock is obtained;
- (RedisQueuedLocks::LockAcquiermentRetryLimitError) retry_count limit reached before lock is obtained;

def lock!(
  lock_name,
  ttl: config[:default_lock_ttl],
  queue_ttl: config[:default_queue_ttl],
  timeout: config[:default_timeout],
  retry_count: config[:retry_count],
  retry_delay: config[:retry_delay],
  retry_jitter: config[:retry_jitter],
  identity: uniq_identity,
  fail_fast: false,
  meta: nil,
  instrument: nil,
  logger: config[:logger],
  log_lock_try: config[:log_lock_try],
  &block
)

See #lock method documentation.

#lock_info

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get the lock information;
returns nil if lock does not exist;
lock data (Hash<String,String|Integer>):
- "lock_key" - string - lock key in redis;
- "acq_id" - string - acquier identifier (process_id/thread_id/fiber_id/ractor_id/identity);
- "ts" - integer/epoch - the time lock was obtained;
- "init_ttl" - integer - (milliseconds) initial lock key ttl;
- "rem_ttl" - integer - (milliseconds) remaining lock key ttl;
- custom metadata- string/integer - custom metadata passed to the lock/lock! methods via meta: keyword argument (see lock method documentation);

# without custom metadata
rql.lock_info("your_lock_name")

# =>
{
  "lock_key" => "rql:lock:your_lock_name",
  "acq_id" => "rql:acq:123/456/567/678/374dd74324",
  "ts" => 123456789,
  "ini_ttl" => 123456789,
  "rem_ttl" => 123456789
}

# with custom metadata
rql.lock("your_lock_name", meta: { "kek" => "pek", "bum" => 123 })
rql.lock_info("your_lock_name")

# =>
{
  "lock_key" => "rql:lock:your_lock_name",
  "acq_id" => "rql:acq:123/456/567/678/374dd74324",
  "ts" => 123456789,
  "ini_ttl" => 123456789,
  "rem_ttl" => 123456789,
  "kek" => "pek",
  "bum" => "123" # NOTE: returned as a raw string directly from Redis
}

#queue_info

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Returns an information about the required lock queue by the lock name. The result represnts the ordered lock request queue that is ordered by score (Redis Sets) and shows lock acquirers and their position in queue. Async nature with redis communcation can lead the situation when the queue becomes empty during the queue data extraction. So sometimes you can receive the lock queue info with empty queue value (an empty array).

get the lock queue information;
queue represents the ordered set of lock key reqests:
- set is ordered by score in ASC manner (inside the Redis Set);
- score is represented as a timestamp when the lock request was made;
- represents the acquier identifier and their score as an array of hashes;
returns nil if lock queue does not exist;
lock queue data (Hash<String,String|Array<Hash<String|Numeric>>):
- "lock_queue" - string - lock queue key in redis;
- "queue" - array - an array of lock requests (array of hashes):
  - "acq_id" - string - acquier identifier (process_id/thread_id/fiber_id/ractor_id/identity by default);
  - "score" - float/epoch - time when the lock request was made (epoch);

rql.queue_info("your_lock_name")

# =>
{
  "lock_queue" => "rql:lock_queue:your_lock_name",
  "queue" => [
    { "acq_id" => "rql:acq:123/456/567/678/fa76df9cc2", "score" => 1711606640.540842},
    { "acq_id" => "rql:acq:123/567/456/679/c7bfcaf4f9", "score" => 1711606640.540906},
    { "acq_id" => "rql:acq:555/329/523/127/7329553b11", "score" => 1711606640.540963},
    # ...etc
  ]
}

#locked?

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is the lock obtaied or not?

rql.locked?("your_lock_name") # => true/false

#queued?

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is the lock queued for obtain / has requests for obtain?

rql.queued?("your_lock_name") # => true/false

#unlock - release a lock

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release the concrete lock with lock request queue;
queue will be relased first;
accepts:
- lock_name - (required) [String] - the lock name that should be released.
- :logger - (optional) [::Logger,#debug]
  - custom logger object;
  - pre-configured in config[:logger];
- :instrumenter - (optional) [#notify]
  - custom instrumenter object;
  - pre-configured in config[:instrumetner];
- :instrument - (optional) [NilClass,Any];
  - custom instrumentation data wich will be passed to the instrumenter's payload with :instrument key;
  - nil by default (no additional data);
if you try to unlock non-existent lock you will receive ok: true result with operation timings and :nothing_to_release result factor inside;

Return:

[Hash<Symbol,Boolean|Hash<Symbol,Numeric|String|Symbol>>] ({ ok: true/false, result: Hasn });
:result format;
- :rel_time - Float - time spent to process redis commands (in seconds);
- :rel_key - String - released lock key (RedisQueudLocks-internal lock key name from Redis);
- :rel_queue - String - released lock queue key (RedisQueuedLocks-internal queue key name from Redis);
- :queue_res - Symbol - :released (or :nothing_to_release if the required queue does not exist);
- :lock_res - Symbol - :released (or :nothing_to_release if the required lock does not exist);

Consider that lock_res and queue_res can have different value because of the async nature of invoked Redis'es commands.

rql.unlock("your_lock_name")

# =>
{
  ok: true,
  result: {
    rel_time: 0.02, # time spent to lock release (in seconds)
    rel_key: "rql:lock:your_lock_name", # released lock key
    rel_queue: "rql:lock_queue:your_lock_name", # released lock key queue
    queue_res: :released, # or :nothing_to_release
    lock_res: :released # or :nothing_to_release
  }
}

#clear_locks - release all locks and lock queues

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release all obtained locks and related lock request queues;
queues will be released first;
accepts:
- :batch_size - (optional) [Integer]
  - the size of batch of locks and lock queus that should be cleared under the one pipelined redis command at once;
  - pre-configured in config[:lock_release_batch_size];
- :logger - (optional) [::Logger,#debug]
  - custom logger object;
  - pre-configured value in config[:logger];
- :instrumenter - (optional) [#notify]
  - custom instrumenter object;
  - pre-configured value in config[:isntrumenter];
- :instrument - (optional) [NilClass,Any]
  - custom instrumentation data wich will be passed to the instrumenter's payload with :instrument key;
returns:
- [Hash<Symbol,Numeric>] - Format: { ok: true, result: Hash<Symbol,Numeric> };
- result data:
  - :rel_time - Numeric - time spent to release all locks and related queus;
  - :rel_key_cnt - Integer - the number of released Redis keys (queues+locks);

rql.clear_locks

# =>
{
  ok: true,
  result: {
    rel_time: 3.07,
    rel_key_cnt: 1234
  }
}

#extend_lock_ttl

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extends lock ttl by the required number of milliseconds;
expects the lock name and the number of milliseconds;
accepts:
- lock_name - (required) [String]
  - the lock name which ttl should be extended;
- milliseconds - (required) [Integer]
  - how many milliseconds should be added to the lock's TTL;
- :logger - (optional) [::Logger,#debug]
  - custom logger object;
  - pre-configured in config[:logger];
returns { ok: true, result: :ttl_extended } when ttl is extended;
returns { ok: false, result: :async_expire_or_no_lock } when a lock not found or a lock is already expired during some steps of invocation (see Important section below);
Important:
- the method is non-atomic cuz redis does not provide an atomic function for TTL/PTTL extension;
- the method consists of two commands:
  - (1) read current pttl;
  - (2) set new ttl that is calculated as "current pttl + additional milliseconds";
- the method uses Redis'es CAS (check-and-set) behavior;
- what can happen during these steps:
  - lock is expired between commands or before the first command;
  - lock is expired before the second command;
  - lock is expired AND newly acquired by another process (so you will extend the totally new lock with fresh PTTL);
- use it at your own risk and consider the async nature when calling this method;

rql.extend_lock_ttl("my_lock", 5_000) # NOTE: add 5_000 milliseconds

# => `ok` case
{ ok: true, result: :ttl_extended }

# => `failed` case
{ ok: false, result: :async_expire_or_no_lock }

#locks - get list of obtained locks

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uses redis SCAN under the hood;
accepts:
- :scan_size - Integer - (config[:key_extraction_batch_size] by default);
- :with_info - Boolean - false by default (for details see #locks_info);
returns:
- Set<String> (for with_info: false);
- Set<Hash<Symbol,Any>> (for with_info: true). See #locks_info for details;

rql.locks # or rql.locks(scan_size: 123)

=>
#<Set:
 {"rql:lock:locklock75",
  "rql:lock:locklock9",
  "rql:lock:locklock108",
  "rql:lock:locklock7",
  "rql:lock:locklock48",
  "rql:lock:locklock104",
  "rql:lock:locklock13",
  "rql:lock:locklock62",
  "rql:lock:locklock80",
  "rql:lock:locklock28",
  ...}>

#queues - get list of lock request queues

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uses redis SCAN under the hood;
accepts
- :scan_size - Integer - (config[:key_extraction_batch_size] by default);
- :with_info - Boolean - false by default (for details see #queues_info);
returns:
- Set<String> (for with_info: false);
- Set<Hash<Symbol,Any>> (for with_info: true). See #locks_info for details;

rql.queues # or rql.queues(scan_size: 123)

=>
#<Set:
 {"rql:lock_queue:locklock75",
  "rql:lock_queue:locklock9",
  "rql:lock_queue:locklock108",
  "rql:lock_queue:locklock7",
  "rql:lock_queue:locklock48",
  "rql:lock_queue:locklock104",
  "rql:lock_queue:locklock13",
  "rql:lock_queue:locklock62",
  "rql:lock_queue:locklock80",
  "rql:lock_queue:locklock28",
  ...}>

#keys - get list of taken locks and queues

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uses redis SCAN under the hood;
accepts: :scan_size - Integer - (config[:key_extraction_batch_size] by default);
returns: Set<String>

rql.keys # or rql.keys(scan_size: 123)

=>
#<Set:
 {"rql:lock_queue:locklock75",
  "rql:lock_queue:locklock9",
  "rql:lock:locklock9",
  "rql:lock_queue:locklock108",
  "rql:lock_queue:locklock7",
  "rql:lock:locklock7",
  "rql:lock_queue:locklock48",
  "rql:lock_queue:locklock104",
  "rql:lock:locklock104",
  "rql:lock_queue:locklock13",
  "rql:lock_queue:locklock62",
  "rql:lock_queue:locklock80",
  "rql:lock:locklock80",
  "rql:lock_queue:locklock28",
  ...}>

#locks_info - get list of locks with their info

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uses redis SCAN under the hod;
accepts scan_size:/Integer option (config[:key_extraction_batch_size] by default);
returns Set<Hash<Symbol,Any>> (see #lock_info and examples below for details).
- contained data: { lock: String, status: Symbol, info: Hash<String,Any> };
- :lock - String - lock key in Redis;
- :status - Symbol- :released or :alive
  - the lock may become relased durign the lock info extraction process;
  - :info for :released keys is empty ({});
- :info - Hash<String,Any> - lock data stored in the lock key in Redis. See #lock_info for details;

rql.locks_info # or rql.locks_info(scan_size: 123)

# =>
=> #<Set:
 {{:lock=>"rql:lock:some-lock-123",
   :status=>:alive,
   :info=>{
    "acq_id"=>"rql:acq:41478/4320/4340/4360/848818f09d8c3420",
    "ts"=>1711607112.670343,
    "ini_ttl"=>15000,
    "rem_ttl"=>13998}},
  {:lock=>"rql:lock:some-lock-456",
   :status=>:released,
   :info=>{},
  ...}>

#queues_info - get list of queues with their info

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uses redis SCAN under the hod;
accepts scan_size:/Integer option (config[:key_extraction_batch_size] by default);
returns Set<Hash<Symbol,Any>> (see #queue_info and examples below for details).
- contained data: { queue: String, requests: Array<Hash<String,Any>> }
- :queue - String - lock key queue in Redis;
- :requests - Array<Hash<String,Any>> - lock requests in the que with their acquier id and score.

rql.queues_info # or rql.qeuues_info(scan_size: 123)

=> #<Set:
 {{:queue=>"rql:lock_queue:some-lock-123",
   :requests=>
    [{"acq_id"=>"rql:acq:38529/4500/4520/4360/66093702f24a3129", "score"=>1711606640.540842},
     {"acq_id"=>"rql:acq:38529/4580/4600/4360/66093702f24a3129", "score"=>1711606640.540906},
     {"acq_id"=>"rql:acq:38529/4620/4640/4360/66093702f24a3129", "score"=>1711606640.5409632}]},
  {:queue=>"rql:lock_queue:some-lock-456",
   :requests=>
    [{"acq_id"=>"rql:acq:38529/4380/4400/4360/66093702f24a3129", "score"=>1711606640.540722},
     {"acq_id"=>"rql:acq:38529/4420/4440/4360/66093702f24a3129", "score"=>1711606640.5407748},
     {"acq_id"=>"rql:acq:38529/4460/4480/4360/66093702f24a3129", "score"=>1711606640.540808}]},
  ...}>

#clear_dead_requests

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In some cases your lock requests may become "dead". It means that your lock request lives in lock queue in Redis without any processing. It can happen when your processs that are enqueeud to the lock queue is failed unexpectedly (for some reason) before the lock acquire moment occurs and when no any other process does not need this lock anymore. For this case your lock reuquest will be cleared only when any process will try to acquire this lock again (cuz lock acquirement triggers the removement of expired requests).

In order to help with these dead requests you may periodically call #clear_dead_requests with corresponding :dead_ttl option, that is pre-configured by default via config[:dead_request_ttl].

:dead_ttl option is required because of it is no any fast and resource-free way to understand which request is dead now and is it really dead cuz each request queue can host their requests with a custom queue ttl for each request differently.

Accepts:

:dead_ttl - (optional) [Integer]
- lock request ttl after which a lock request is considered dead;
- has a preconfigured value in config[:dead_request_ttl] (1 day by default);
:sacn_size - (optional) [Integer]
- the batch of scanned keys for Redis'es SCAN command;
- has a preconfigured valie in config[:lock_release_batch_size];
:logger - (optional) [::Logger,#debug]
- custom logger object;
- pre-configured in config[:logger];
:instrumenter - (optional) [#notify]
- custom instrumenter object;
- pre-configured in config[:isntrumenter];
:instrument - (optional) [NilClass,Any]
- custom instrumentation data wich will be passed to the instrumenter's payload with :instrument key;
- nil by default (no additional data);

Returns: { ok: true, processed_queues: Set<String> } returns the list of processed lock queues;

rql.clear_dead_requests(dead_ttl: 60 * 60 * 1000) # 1 hour in milliseconds

# =>
{
  ok: true,
  processed_queues: [
    "rql:lock_queue:some-lock-123",
    "rql:lock_queue:some-lock-456",
    "rql:lock_queue:your-other-lock",
    ...
  ]
}

Logging

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default logs (raised from #lock/#lock!):

"[redis_queued_locks.start_lock_obtaining]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.start_try_to_lock_cycle]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.dead_score_reached__reset_acquier_position]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.lock_obtained]" # (logs "lockkey", "queue_ttl", "acq_id", "acq_time");
"[redis_queued_locks.fail_fast_or_limits_reached__dequeue]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.expire_lock]" # (logs "lock_key", "queue_ttl", "acq_id");

additional logs (raised from #lock/#lock! with confg[:log_lock_try] == true):

"[redis_queued_locks.try_lock.start]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.try_lock.rconn_fetched]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.try_lock.acq_added_to_queue]" # (logs "lock_key", "queue_ttl", "acq_id)";
"[redis_queued_locks.try_lock.remove_expired_acqs]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.try_lock.get_first_from_queue]" # (logs "lock_key", "queue_ttl", "acq_id", "first_acq_id_in_queue");
"[redis_queued_locks.try_lock.exit__queue_ttl_reached]" # (logs "lock_key", "queue_ttl", "acq_id");
"[redis_queued_locks.try_lock.exit__no_first]" # (logs "lock_key", "queue_ttl", "acq_id", "first_acq_id_in_queue", "<current_lock_data>");
"[redis_queued_locks.try_lock.exit__lock_still_obtained]" # (logs "lock_key", "queue_ttl", "acq_id", "first_acq_id_in_queue", "locked_by_acq_id", "<current_lock_data>");
"[redis_queued_locks.try_lock.obtain__free_to_acquire]" # (logs "lock_key", "queue_ttl", "acq_id");

Instrumentation

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Instrumentation Events

An instrumentation layer is incapsulated in instrumenter object stored in config (RedisQueuedLocks::Client#config[:instrumenter]).

Instrumenter object should provide notify(event, payload) method with the following signarue:

event - string;
payload - hash<Symbol,Any>;

redis_queued_locks provides two instrumenters:

RedisQueuedLocks::Instrument::ActiveSupport - ActiveSupport::Notifications instrumenter that instrument events via ActiveSupport::Notifications API;
RedisQueuedLocks::Instrument::VoidNotifier - instrumenter that does nothing;

By default RedisQueuedLocks::Client is configured with the void notifier (which means "instrumentation is disabled").

Instrumentation Events

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List of instrumentation events

redis_queued_locks.lock_obtained;
redis_queued_locks.lock_hold_and_release;
redis_queued_locks.explicit_lock_release;
redis_queued_locks.explicit_all_locks_release;

Detalized event semantics and payload structure:

"redis_queued_locks.lock_obtained"
- a moment when the lock was obtained;
- raised from #lock/#lock!;
- payload:
  - :ttl - integer/milliseconds - lock ttl;
  - :acq_id - string - lock acquier identifier;
  - :lock_key - string - lock name;
  - :ts - integer/epoch - the time when the lock was obtaiend;
  - :acq_time - float/milliseconds - time spent on lock acquiring;
  - :instrument - nil/Any - custom data passed to the lock/lock! method as :instrument attribute;
"redis_queued_locks.lock_hold_and_release"
- an event signalizes about the "hold+and+release" process is finished;
- raised from #lock/#lock! when invoked with a block of code;
- payload:
  - :hold_time - float/milliseconds - lock hold time;
  - :ttl - integer/milliseconds - lock ttl;
  - :acq_id - string - lock acquier identifier;
  - :lock_key - string - lock name;
  - :ts - integer/epoch - the time when lock was obtained;
  - :acq_time - float/milliseconds - time spent on lock acquiring;
  - :instrument - nil/Any - custom data passed to the lock/lock! method as :instrument attribute;
"redis_queued_locks.explicit_lock_release"
- an event signalizes about the explicit lock release (invoked via RedisQueuedLock#unlock);
- raised from #unlock;
- payload:
  - :at - float/epoch - the time when the lock was released;
  - :rel_time - float/milliseconds - time spent on lock releasing;
  - :lock_key - string - released lock (lock name);
  - :lock_key_queue - string - released lock queue (lock queue name);
"redis_queued_locks.explicit_all_locks_release"
- an event signalizes about the explicit all locks release (invoked via RedisQueuedLock#clear_locks);
- raised from #clear_locks;
- payload:
  - :rel_time - float/milliseconds - time spent on "realese all locks" operation;
  - :at - float/epoch - the time when the operation has ended;
  - :rel_keys - integer - released redis keys count (released queue keys + released lock keys);

Roadmap

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strict redlock algorithm support (support for many RedisClient instances);
deadlock detection (with some options for auto-resolving);
Semantic Error objects for unexpected Redis errors;
better specs with 100% test coverage (total rework);
(non-timed locks): per-ruby-block-holding-the-lock sidecar Ractor and in progress queue in RedisDB that will extend the acquired lock for long-running blocks of code (that invoked "under" the lock whose ttl may expire before the block execution completes). It makes sense for non-timed locks only;
lock request prioritization;
support for LIFO strategy;
support for Random Access strategy;
more structured logging (separated docs);
RedisQueuedLocks::Acquier::Try.try_to_lock - detailed successful result analization;
better code stylization (+ some refactorings);
statistics with UI;

Contributing

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Fork it ( https://github.com/0exp/redis_queued_locks )
Create your feature branch (git checkout -b feature/my-new-feature)
Commit your changes (git commit -am '[feature_context] Add some feature')
Push to the branch (git push origin feature/my-new-feature)
Create new Pull Request

License

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Released under MIT License.

Authors

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Rustam Ibragimov