Add Blocking Sorted Set Pop Commands

Mordil · Mordil · commit 739223258c78 · 2019-05-27T12:56:55.000-07:00
Motivation:

To be a comprehensive library, all commands should be implemented, even if they are highly discouraged. Sorted Set's collection of commands were missing `bzpopmin` and `bzpopmax`.

Modifications:

`bzpopmin` and `bzpopmax` are supported with defaults and overloads for an easier API.
`RedisClient.channel` is now `internal` to have access during testing for bypassing normal guards for closing connections.

Result:

Users now have access to `bzpopmin` and `bzpopmax` commands.
diff --git a/Sources/NIORedis/Commands/SortedSetCommands.swift b/Sources/NIORedis/Commands/SortedSetCommands.swift
@@ -292,6 +292,149 @@ extension RedisClient {
     }
 }
 
+// MARK: Blocking Pop
+
+extension RedisClient {
+    /// Removes the element from a sorted set with the lowest score, blocking until an element is
+    /// available.
+    ///
+    /// - Important:
+    ///     This will block the connection from completing further commands until an element
+    ///     is available to pop from the set.
+    ///
+    ///     It is **highly** recommended to set a reasonable `timeout`
+    ///     or to use the non-blocking `zpopmin` method where possible.
+    ///
+    /// See [https://redis.io/commands/bzpopmin](https://redis.io/commands/bzpopmin)
+    /// - Parameters:
+    ///     - key: The key identifying the sorted set in Redis.
+    ///     - timeout: The time (in seconds) to wait. `0` means indefinitely.
+    /// - Returns:
+    ///     The element and its associated score that was popped from the sorted set,
+    ///     or `nil` if the timeout was reached.
+    @inlinable
+    public func bzpopmin(
+        from key: String,
+        timeout: Int = 0
+    ) -> EventLoopFuture<(Double, RESPValue)?> {
+        return bzpopmin(from: [key], timeout: timeout)
+            .map {
+                guard let response = $0 else { return nil }
+                return (response.1, response.2)
+            }
+    }
+
+    /// Removes the element from a sorted set with the lowest score, blocking until an element is
+    /// available.
+    ///
+    /// - Important:
+    ///     This will block the connection from completing further commands until an element
+    ///     is available to pop from the group of sets.
+    ///
+    ///     It is **highly** recommended to set a reasonable `timeout`
+    ///     or to use the non-blocking `zpopmin` method where possible.
+    ///
+    /// See [https://redis.io/commands/bzpopmin](https://redis.io/commands/bzpopmin)
+    /// - Parameters:
+    ///     - keys: A list of sorted set keys in Redis.
+    ///     - timeout: The time (in seconds) to wait. `0` means indefinitely.
+    /// - Returns:
+    ///     If timeout was reached, `nil`.
+    ///
+    ///     Otherwise, the key of the sorted set the element was removed from, the element itself,
+    ///     and its associated score is returned.
+    @inlinable
+    public func bzpopmin(
+        from keys: [String],
+        timeout: Int = 0
+    ) -> EventLoopFuture<(String, Double, RESPValue)?> {
+        return self._bzpop(command: "BZPOPMIN", keys, timeout)
+    }
+
+    /// Removes the element from a sorted set with the highest score, blocking until an element is
+    /// available.
+    ///
+    /// - Important:
+    ///     This will block the connection from completing further commands until an element
+    ///     is available to pop from the set.
+    ///
+    ///     It is **highly** recommended to set a reasonable `timeout`
+    ///     or to use the non-blocking `zpopmax` method where possible.
+    ///
+    /// See [https://redis.io/commands/bzpopmax](https://redis.io/commands/bzpopmax)
+    /// - Parameters:
+    ///     - key: The key identifying the sorted set in Redis.
+    ///     - timeout: The time (in seconds) to wait. `0` means indefinitely.
+    /// - Returns:
+    ///     The element and its associated score that was popped from the sorted set,
+    ///     or `nil` if the timeout was reached.
+    @inlinable
+    public func bzpopmax(
+        from key: String,
+        timeout: Int = 0
+    ) -> EventLoopFuture<(Double, RESPValue)?> {
+        return self.bzpopmax(from: [key], timeout: timeout)
+            .map {
+                guard let response = $0 else { return nil }
+                return (response.1, response.2)
+            }
+    }
+
+    /// Removes the element from a sorted set with the highest score, blocking until an element is
+    /// available.
+    ///
+    /// - Important:
+    ///     This will block the connection from completing further commands until an element
+    ///     is available to pop from the group of sets.
+    ///
+    ///     It is **highly** recommended to set a reasonable `timeout`
+    ///     or to use the non-blocking `zpopmax` method where possible.
+    ///
+    /// See [https://redis.io/commands/bzpopmax](https://redis.io/commands/bzpopmax)
+    /// - Parameters:
+    ///     - keys: A list of sorted set keys in Redis.
+    ///     - timeout: The time (in seconds) to wait. `0` means indefinitely.
+    /// - Returns:
+    ///     If timeout was reached, `nil`.
+    ///
+    ///     Otherwise, the key of the sorted set the element was removed from, the element itself,
+    ///     and its associated score is returned.
+    @inlinable
+    public func bzpopmax(
+        from keys: [String],
+        timeout: Int = 0
+    ) -> EventLoopFuture<(String, Double, RESPValue)?> {
+        return self._bzpop(command: "BZPOPMAX", keys, timeout)
+    }
+
+    @usableFromInline
+    func _bzpop(
+        command: String,
+        _ keys: [String],
+        _ timeout: Int
+    ) -> EventLoopFuture<(String, Double, RESPValue)?> {
+        let args = keys as [RESPValueConvertible] + [timeout]
+        return send(command: command, with: args)
+            // per the Redis docs,
+            // we will receive either a nil response,
+            // or an array with 3 elements in the form [Set Key, Element Score, Element Value]
+            .flatMapThrowing {
+                guard !$0.isNull else { return nil }
+                guard let response = [RESPValue]($0) else {
+                    throw NIORedisError.responseConversion(to: [RESPValue].self)
+                }
+                assert(response.count == 3, "Unexpected response size returned!")
+                guard
+                    let key = response[0].string,
+                    let score = Double(response[1])
+                else {
+                    throw NIORedisError.assertionFailure(message: "Unexpected structure in response: \(response)")
+                }
+                return (key, score, response[2])
+            }
+    }
+}
+
 // MARK: Increment
 
 extension RedisClient {
diff --git a/Sources/NIORedis/RedisClient.swift b/Sources/NIORedis/RedisClient.swift
@@ -76,7 +76,7 @@ public final class RedisConnection: RedisClient {
         }
     }
 
-    private let channel: Channel
+    let channel: Channel
     private var logger: Logger
 
     private let autoflush = Atomic<Bool>(value: true)
diff --git a/Tests/NIORedisTests/Commands/SortedSetCommandsTests.swift b/Tests/NIORedisTests/Commands/SortedSetCommandsTests.swift
@@ -155,6 +155,26 @@ final class SortedSetCommandsTests: XCTestCase {
         XCTAssertEqual(results[1].1, 10)
     }
 
+    func test_bzpopmin() throws {
+        let nilMin = try connection.bzpopmin(from: #function, timeout: 1).wait()
+        XCTAssertNil(nilMin)
+
+        let min1 = try connection.bzpopmin(from: key).wait()
+        XCTAssertEqual(min1?.0, 1)
+        let min2 = try connection.bzpopmin(from: [#function, key]).wait()
+        XCTAssertEqual(min2?.0, key)
+        XCTAssertEqual(min2?.1, 2)
+
+        let blockingConnection = try Redis.makeConnection().wait()
+        let expectation = XCTestExpectation(description: "bzpopmin should never return")
+        _ = blockingConnection.bzpopmin(from: #function)
+            .always { _ in expectation.fulfill() }
+
+        let result = XCTWaiter.wait(for: [expectation], timeout: 1)
+        XCTAssertEqual(result, .timedOut)
+        try blockingConnection.channel.close().wait()
+    }
+
     func test_zpopmax() throws {
         let min = try connection.zpopmax(from: key).wait()
         XCTAssertEqual(min?.1, 10)
@@ -167,6 +187,26 @@ final class SortedSetCommandsTests: XCTestCase {
         XCTAssertEqual(results[1].1, 1)
     }
 
+    func test_bzpopmax() throws {
+        let nilMax = try connection.bzpopmax(from: #function, timeout: 1).wait()
+        XCTAssertNil(nilMax)
+
+        let max1 = try connection.bzpopmax(from: key).wait()
+        XCTAssertEqual(max1?.0, 10)
+        let max2 = try connection.bzpopmax(from: [#function, key]).wait()
+        XCTAssertEqual(max2?.0, key)
+        XCTAssertEqual(max2?.1, 9)
+
+        let blockingConnection = try Redis.makeConnection().wait()
+        let expectation = XCTestExpectation(description: "bzpopmax should never return")
+        _ = blockingConnection.bzpopmax(from: #function)
+            .always { _ in expectation.fulfill() }
+
+        let result = XCTWaiter.wait(for: [expectation], timeout: 1)
+        XCTAssertEqual(result, .timedOut)
+        try blockingConnection.channel.close().wait()
+    }
+
     func test_zincrby() throws {
         var score = try connection.zincrby(3_00_1398.328923, element: 1, in: key).wait()
         XCTAssertEqual(score, 3_001_399.328923)
@@ -352,7 +392,9 @@ final class SortedSetCommandsTests: XCTestCase {
         ("test_zcount", test_zcount),
         ("test_zlexcount", test_zlexcount),
         ("test_zpopmin", test_zpopmin),
+        ("test_bzpopmin", test_bzpopmin),
         ("test_zpopmax", test_zpopmax),
+        ("test_bzpopmax", test_bzpopmax),
         ("test_zincrby", test_zincrby),
         ("test_zunionstore", test_zunionstore),
         ("test_zinterstore", test_zinterstore),

Original file line number	Diff line number	Diff line change
`@@ -76,7 +76,7 @@ public final class RedisConnection: RedisClient {`
`76`	`76`	`}`
`77`	`77`	`}`
`78`	`78`
`79`		`- private let channel: Channel`
	`79`	`+ let channel: Channel`
`80`	`80`	`private var logger: Logger`
`81`	`81`
`82`	`82`	`private let autoflush = Atomic<Bool>(value: true)`