Add counts and add_new_item methods, without tests

go/WorkQueue.go

@@ -120,8 +120,76 @@ func (workQueue *WorkQueue) AddItem(ctx context.Context, db *redis.Client, item
 	return err
 }
 
+// AddNewItem adds an item to the work queue only if an item with the same ID doesn't already exist.
+//
+// This method uses WATCH to add the item atomically.
+//
+// Returns a boolean indicating if the item was added or not. The item is only not added if it
+// already exists or if an error (other than a transaction error, which triggers a retry) occurs.
+func (workQueue *WorkQueue) AddNewItem(
+	ctx context.Context,
+	db *redis.Client,
+	item Item,
+) (bool, error) {
+	txf := func(tx *redis.Tx) error {
+		processingItemsInQueueCmd := tx.LPos(ctx, workQueue.processingKey, item.ID, redis.LPosArgs{
+			Rank:   0,
+			MaxLen: 0,
+		})
+		workingItemsInQueueCmd := tx.LPos(ctx, workQueue.mainQueueKey, item.ID, redis.LPosArgs{
+			Rank:   0,
+			MaxLen: 0,
+		})
+
+		_, ProcessingQueueCheck := processingItemsInQueueCmd.Result()
+		_, WorkingQueueCheck := workingItemsInQueueCmd.Result()
+
+		if ProcessingQueueCheck == redis.Nil && WorkingQueueCheck == redis.Nil {
+			_, err := tx.TxPipelined(ctx, func(pipe redis.Pipeliner) error {
+				workQueue.AddItemToPipeline(ctx, pipe, item)
+				return nil
+			})
+			return err
+		} else {
+			return false
+		}
+	}
+
+	for {
+		err := db.Watch(ctx, txf, workQueue.processingKey, workQueue.mainQueueKey)
+		if err == nil {
+			return true, nil
+		}
+		if err == redis.TxFailedErr {
+			continue
+		}
+		return false, err
+	}
+}
+
+// Counts returns the queue length, and number of items currently being processed, atomically.
+func (workQueue *WorkQueue) Counts(
+    ctx context.Context,
+    db *redis.Client,
+) (queueLen, processingLen int64, err error) {
+	tx := db.TxPipeline()
+
+	queueLenPipe := tx.LLen(ctx, workQueue.mainQueueKey)
+	processingLenPipe := tx.LLen(ctx, workQueue.processingKey)
+
+	_, err = tx.Exec(ctx)
+	if err == nil {
+		queueLen, err = queueLenPipe.Result()
+	}
+	if err == nil {
+		processingLen, err = processingLenPipe.Result()
+	}
+
+	return
+}
+
 // Return the length of the work queue (not including items being processed, see
-// [WorkQueue.Processing]).
+// [WorkQueue.Processing] or [WorkQueue.Counts] to get both).
 func (workQueue *WorkQueue) QueueLen(ctx context.Context, db *redis.Client) (int64, error) {
 	return db.LLen(ctx, workQueue.mainQueueKey).Result()
 }

node/src/WorkQueue.ts

@@ -3,12 +3,12 @@
  * @description A work queue backed by a redis database.
  */
 
-import Redis, {ChainableCommander} from 'ioredis';
-import {v4 as uuidv4} from 'uuid';
-import {Item} from './Item';
-import {KeyPrefix} from './KeyPrefix';
+import Redis, { ChainableCommander } from 'ioredis';
+import { v4 as uuidv4 } from 'uuid';
+import { Item } from './Item';
+import { KeyPrefix } from './KeyPrefix';
 
-export {KeyPrefix, Item};
+export { KeyPrefix, Item };
 
 /**
  * A work queue backed by a redis database.
@@ -35,10 +35,11 @@ export class WorkQueue {
 
   /**
    * Add an item to the work queue. This adds the redis commands onto the pipeline passed.
+   *
    * Use `WorkQueue.addItem` if you don't want to pass a pipeline directly.
-   * Add the item data.
-   * @param {Pipeline} pipeline The pipeline that the data will be executed.
-   * @param {Item} item The Item which will be set in the Redis with the key of this.itemDataKey.of(item.id).
+   *
+   * @param {Pipeline} pipeline The pipeline that the commands to add the item will be pushed to.
+   * @param {Item} item The Item to be added.
    */
   addItemToPipeline(pipeline: ChainableCommander, item: Item) {
     // NOTE: it's important that the data is added first, otherwise someone before the data is ready.
@@ -48,11 +49,12 @@ export class WorkQueue {
   }
 
   /**
-   * Add an item to the work queue.
+   * Add an item to the work queue. See `addNewItem` to avoid adding duplicate items.
+   *
    * This creates a pipeline and executes it on the database.
    *
    * @param {Redis} db The Redis Connection.
-   * @param item The item that will be executed using the method addItemToPipeline.
+   * @param item The item to be added.
    */
   async addItem(db: Redis, item: Item): Promise<void> {
     const pipeline = db.pipeline();
@@ -61,7 +63,47 @@ export class WorkQueue {
   }
 
   /**
-   * This is used to get the length of the Main Queue.
+   * Adds an item to the work queue only if an item with the same ID doesn't already exist.
+   *
+   * This method uses WATCH to add the item atomically. The db client passed must not be used by
+   * anything else while this method is running.
+   *
+   * Returns a boolean indicating if the item was added or not. The item is only not added if it
+   * already exists or if an error (other than a transaction error, which triggers a retry) occurs.
+   *
+   * @param {Redis} db The Redis Connection, this must not be used by anything else while this method is running.
+   * @param item The item that will be added, only if an item doesn't already exist with the same ID.
+   * @returns {boolean} returns true for success (item added to the queue), false if the item is in one of the queues.
+   */
+  async addNewItem(db: Redis, item: Item): Promise<boolean> {
+    for (;;) {
+      try {
+        await db.watch(this.mainQueueKey, this.processingKey);
+
+        const isItemInProcessingKey = await db.lpos(this.processingKey, item.id);
+        const isItemInMainQueueKey = await db.lpos(this.mainQueueKey, item.id);
+        if (isItemInProcessingKey !== null || isItemInMainQueueKey !== null) {
+          await db.unwatch();
+          return false;
+        }
+
+        const transaction = db.multi();
+        this.addItemToPipeline(transaction, item);
+        const results = await transaction.exec();
+        if (!results) {
+          continue;
+        }
+        return true;
+      } catch (err) {
+        await db.unwatch();
+        throw err;
+      }
+    }
+  }
+
+  /**
+   * Return the length of the work queue (not including items being processed, see
+   * `WorkQueue.processing` or `WorkQueue.counts` to get both).
    *
    * @param {Redis} db The Redis Connection.
    * @returns {Promise<number>} Return the length of the work queue (not including items being processed, see `WorkQueue.processing()`).
@@ -71,7 +113,7 @@ export class WorkQueue {
   }
 
   /**
-   * This is used to get the lenght of the Processing Queue.
+   * This is used to get the number of items currently being processed.
    *
    * @param {Redis} db The Redis Connection.
    * @returns {Promise<number>} The number of items being processed.
@@ -80,6 +122,22 @@ export class WorkQueue {
     return db.llen(this.processingKey);
   }
 
+  /**
+   * Returns the queue length, and number of items currently being processed, atomically.
+   * 
+   * @param {Redis} db The Redis Connection.
+   * @returns {Promise<[number, number]>} Return the length of main queue and processing queue, respectively.
+   */
+  async counts(db: Redis): Promise<[number, number]> {
+    const multi = db.multi();
+    multi.llen(this.mainQueueKey);
+    multi.llen(this.processingKey);
+    const result = (await multi.exec()) as Array<[Error | null, number]>;
+    const queueLength = result[0][1];
+    const processingLength = result[1][1];
+    return [queueLength, processingLength];
+  }
+
   /**
    * This method can be used to check if a Lease Exists or not for a itemId.
    *
@@ -116,8 +174,8 @@ export class WorkQueue {
   async lease(
     db: Redis,
     leaseSecs: number,
-    block = true,
-    timeout = 1
+    block: boolean = true,
+    timeout: number = 1
   ): Promise<Item | null> {
     let maybeItemId: string | null = null;
 

python/redis_work_queue/workqueue.py

@@ -1,9 +1,8 @@
 import uuid
-from redis import Redis
 from redis.client import Pipeline
-
 from redis_work_queue import Item
 from redis_work_queue import KeyPrefix
+from redis import Redis, WatchError
 
 
 class WorkQueue(object):
@@ -38,6 +37,33 @@ def add_item(self, db: Redis, item: Item) -> None:
         self.add_item_to_pipeline(pipeline, item)
         pipeline.execute()
 
+    def add_new_item(self, db: Redis, item: Item) -> bool:
+        """Adds an item to the work queue only if an item with the same ID doesn't already exist.
+
+        This method uses WATCH to add the item atomically. The db client passed must not be used by
+        anything else while this method is running.
+
+        Returns a boolean indicating if the item was added or not. The item is only not added if it
+        already exists or if an error (other than a transaction error, which triggers a retry) occurs."""
+        while True:
+            try:
+                pipeline = db.pipeline(transaction=True)
+                pipeline.watch(self._main_queue_key, self._processing_key)
+
+                if (
+                    pipeline.lpos(self._main_queue_key, item.id()) is not None
+                    or pipeline.lpos(self._processing_key, item.id()) is not None
+                ):
+                    pipeline.unwatch()
+                    return False
+
+                pipeline.multi()
+                self.add_item_to_pipeline(pipeline, item)
+                pipeline.execute()
+                return True
+            except WatchError:
+                continue
+
     def queue_len(self, db: Redis) -> int:
         """Return the length of the work queue (not including items being processed, see
         `WorkQueue.processing`)."""
@@ -47,6 +73,16 @@ def processing(self, db: Redis) -> int:
         """Return the number of items being processed."""
         return db.llen(self._processing_key)
 
+    def counts(self, db: Redis) -> tuple[int, int]:
+        """Returns the queue length, and number of items currently being processed, atomically.
+
+        The return value is `(qlen, processing)`."""
+        pipeline = db.pipeline(transaction=True)
+        pipeline.llen(self._main_queue_key)
+        pipeline.llen(self._processing_key)
+        results = pipeline.execute()
+        return results[0], results[1]
+
     def light_clean(self, db: Redis) -> None:
         processing: list[bytes | str] = db.lrange(
             self._processing_key, 0, -1)

rust/src/lib.rs

@@ -303,6 +303,23 @@ impl WorkQueue {
         db.llen(&self.processing_key)
     }
 
+    /// Returns the queue length, and number of items currently being processed, atomically.
+    ///
+    /// The output is `(queue_len, processing)`.
+    pub fn counts<'a, C: AsyncCommands>(
+        &'a self,
+        db: &'a mut C,
+    ) -> impl Future<Output = RedisResult<(usize, usize)>> + 'a {
+        async {
+            redis::pipe()
+                .atomic()
+                .llen(&self.main_queue_key)
+                .llen(&self.processing_key)
+                .query_async(db)
+                .await
+        }
+    }
+
     /// Request a work lease the work queue. This should be called by a worker to get work to
     /// complete. When completed, the `complete` method should be called.
     ///

tests/go/go.mod

@@ -6,10 +6,11 @@ go 1.20
 
 require (
 	github.com/mevitae/redis-work-queue/go v0.1.0
-	github.com/redis/go-redis/v9 v9.0.2
+	github.com/redis/go-redis/v9 v9.0.3
 )
 
 require (
+	github.com/bsm/redislock v0.9.3 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/google/uuid v1.3.0 // indirect

tests/go/go.sum

@@ -1,5 +1,9 @@
 github.com/bsm/ginkgo/v2 v2.5.0 h1:aOAnND1T40wEdAtkGSkvSICWeQ8L3UASX7YVCqQx+eQ=
+github.com/bsm/ginkgo/v2 v2.7.0 h1:ItPMPH90RbmZJt5GtkcNvIRuGEdwlBItdNVoyzaNQao=
 github.com/bsm/gomega v1.20.0 h1:JhAwLmtRzXFTx2AkALSLa8ijZafntmhSoU63Ok18Uq8=
+github.com/bsm/gomega v1.26.0 h1:LhQm+AFcgV2M0WyKroMASzAzCAJVpAxQXv4SaI9a69Y=
+github.com/bsm/redislock v0.9.3 h1:osmvugkXGiLDEhzUPdM0EUtKpTEgLLuli4Ky2Z4vx38=
+github.com/bsm/redislock v0.9.3/go.mod h1:Epf7AJLiSFwLCiZcfi6pWFO/8eAYrYpQXFxEDPoDeAk=
 github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
 github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
@@ -10,5 +14,7 @@ github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/redis/go-redis/v9 v9.0.2 h1:BA426Zqe/7r56kCcvxYLWe1mkaz71LKF77GwgFzSxfE=
 github.com/redis/go-redis/v9 v9.0.2/go.mod h1:/xDTe9EF1LM61hek62Poq2nzQSGj0xSrEtEHbBQevps=
+github.com/redis/go-redis/v9 v9.0.3 h1:+7mmR26M0IvyLxGZUHxu4GiBkJkVDid0Un+j4ScYu4k=
+github.com/redis/go-redis/v9 v9.0.3/go.mod h1:WqMKv5vnQbRuZstUwxQI195wHy+t4PuXDOjzMvcuQHk=
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=