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Async IO with CLibvenice #15

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c47bd9b
Make PostgreSQL use libmill for non-blocking goodness
robertjpayne Dec 1, 2016
0eb0a9b
Add safety around open/close
robertjpayne Dec 1, 2016
d053c79
Tidy up Postgres Connect to be async
robertjpayne Dec 1, 2016
eda562f
Remove unecessary print
robertjpayne Dec 1, 2016
912fe0d
Make it build with swift 3.0.2
Danappelxx Dec 22, 2016
7f6b3cf
Remove unused code
Danappelxx Dec 23, 2016
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2 changes: 1 addition & 1 deletion .swift-version
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Original file line number Diff line number Diff line change
@@ -1 +1 @@
3.0
3.0.2
3 changes: 2 additions & 1 deletion Package.swift
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Expand Up @@ -4,6 +4,7 @@ let package = Package(
name: "PostgreSQL",
dependencies: [
.Package(url: "https://github.com/Zewo/CLibpq.git", majorVersion: 0, minor: 13),
.Package(url: "https://github.com/Zewo/SQL.git", majorVersion: 0, minor: 14)
.Package(url: "https://github.com/Zewo/SQL.git", majorVersion: 0, minor: 14),
.Package(url: "https://github.com/Zewo/CLibvenice.git", majorVersion: 0, minor: 14),
]
)
211 changes: 151 additions & 60 deletions Sources/PostgreSQL/Connection.swift
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@@ -1,5 +1,7 @@
@_exported import SQL
import Foundation
import CLibpq
import CLibvenice
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@Danappelxx Danappelxx Dec 1, 2016

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CLibvenice -> Venice - I don't think we're using any api's that venice doesn't wrap (if we are, should use both?)

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@robertjpayne robertjpayne Dec 17, 2016

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Does Venice have an API to explicitly clean up a fdwait? We have to wait and then immediately clean it up otherwise when libpq goes to read it causes a crash.

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@Danappelxx Danappelxx Dec 17, 2016

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Hmm, doesn't look like it. Venice.poll just wraps fdwait - I guess we can use fdclean from CLibvenice.

import Axis

public struct ConnectionError: Error, CustomStringConvertible {
Expand All @@ -16,7 +18,6 @@ public final class Connection: ConnectionProtocol {
public var username: String?
public var password: String?
public var options: String?
public var tty: String?

public init?(uri: URL) {
do {
Expand All @@ -40,14 +41,13 @@ public final class Connection: ConnectionProtocol {
self.password = uri.password
}

public init(host: String, port: Int = 5432, databaseName: String, username: String? = nil, password: String? = nil, options: String? = nil, tty: String? = nil) {
public init(host: String, port: Int = 5432, databaseName: String, username: String? = nil, password: String? = nil, options: String? = nil) {
self.host = host
self.port = port
self.databaseName = databaseName
self.username = username
self.password = password
self.options = options
self.tty = tty
}
}

Expand Down Expand Up @@ -102,6 +102,7 @@ public final class Connection: ConnectionProtocol {
public var logger: Logger?

private var connection: OpaquePointer? = nil
private var fd: Int32 = -1

public let connectionInfo: ConnectionInfo

Expand All @@ -118,18 +119,63 @@ public final class Connection: ConnectionProtocol {
}

public func open() throws {
connection = PQsetdbLogin(
connectionInfo.host,
String(connectionInfo.port),
connectionInfo.options ?? "",
connectionInfo.tty ?? "",
connectionInfo.databaseName,
connectionInfo.username ?? "",
connectionInfo.password ?? ""
)

if let error = mostRecentError {
throw error
guard connection == nil else {
throw ConnectionError(description: "Connection already opened.")
}

var components = URLComponents()
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@Danappelxx Danappelxx Dec 17, 2016

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IMO, better style would be

let url: String = {
    var components = URLComponents()
    // ...
    return components.url!.absoluteString
}()

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@robertjpayne robertjpayne Dec 17, 2016

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Personally just think that is a nit, it's a local scope var and mutated either way step by step…

components.scheme = "postgres"
components.host = connectionInfo.host
components.port = connectionInfo.port
components.user = connectionInfo.username
components.password = connectionInfo.password
components.path = "/\(connectionInfo.databaseName)"
if let options = connectionInfo.options {
components.queryItems = [URLQueryItem(name: "options", value: options)]
}
let url = components.url!.absoluteString

connection = PQconnectStart(url)

guard connection != nil else {
throw ConnectionError(description: "Could not allocate connection.")
}

guard PQstatus(connection) != CONNECTION_BAD else {
throw ConnectionError(description: "Could not start connection.")
}

fd = PQsocket(connection)
guard fd >= 0 else {
throw mostRecentError ?? ConnectionError(description: "Could not get file descriptor.")
}

loop: while true {
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@Danappelxx Danappelxx Dec 17, 2016

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Loop isn't nested, so I don't think a label is necessary

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@robertjpayne robertjpayne Dec 17, 2016

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Yeah I can get rid of that loop label

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@robertjpayne robertjpayne Dec 17, 2016

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Actually you can't break from a switch to break the loop, hence the label?

let status = PQconnectPoll(connection)
switch status {
case PGRES_POLLING_OK:
break loop
case PGRES_POLLING_READING:
mill_fdwait(fd, FDW_IN, 15.seconds.fromNow().int64milliseconds, nil)
fdclean(fd)
case PGRES_POLLING_WRITING:
mill_fdwait(fd, FDW_OUT, 15.seconds.fromNow().int64milliseconds, nil)
fdclean(fd)
case PGRES_POLLING_ACTIVE:
break
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@Danappelxx Danappelxx Dec 17, 2016

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continue instead of break to avoid the label. This might be "clever", though...

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@robertjpayne robertjpayne Dec 17, 2016

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Only if the loop label can be fixed

case PGRES_POLLING_FAILED:
throw mostRecentError ?? ConnectionError(description: "Could not connect to Postgres Server.")
default:
break
}
}

guard PQsetnonblocking(connection, 1) == 0 else {
throw mostRecentError ?? ConnectionError(description: "Could not set to non-blocking mode.")
}

guard PQstatus(connection) == CONNECTION_OK else {
throw mostRecentError ?? ConnectionError(description: "Could not connect to Postgres Server.")
}
}

Expand All @@ -142,87 +188,132 @@ public final class Connection: ConnectionProtocol {
}

public func close() {
PQfinish(connection)
connection = nil
if connection != nil {
PQfinish(connection!)
connection = nil
}
}

public func createSavePointNamed(_ name: String) throws {
try execute("SAVEPOINT \(name)", parameters: nil)
try execute("SAVEPOINT ?", parameters: [.string(name)])
}

public func rollbackToSavePointNamed(_ name: String) throws {
try execute("ROLLBACK TO SAVEPOINT \(name)", parameters: nil)
try execute("ROLLBACK TO SAVEPOINT ?", parameters: [.string(name)])
}

public func releaseSavePointNamed(_ name: String) throws {
try execute("RELEASE SAVEPOINT \(name)", parameters: nil)
try execute("RELEASE SAVEPOINT ?", parameters: [.string(name)])
}

@discardableResult
public func execute(_ statement: String, parameters: [Value?]?) throws -> Result {

var statement = statement.sqlStringWithEscapedPlaceholdersUsingPrefix("$") {
return String($0 + 1)
}

defer { logger?.debug(statement) }

guard let parameters = parameters else {
guard let resultPointer = PQexec(connection, statement) else {
throw mostRecentError ?? ConnectionError(description: "Empty result")
}

return try Result(resultPointer)
}

var parameterData = [UnsafePointer<Int8>?]()
var deallocators = [() -> ()]()
defer { deallocators.forEach { $0() } }

for parameter in parameters {
if let parameters = parameters {
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@Danappelxx Danappelxx Dec 17, 2016

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this function got really long - needs some cleaning

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@robertjpayne robertjpayne Dec 17, 2016

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Possibly, it works though? It's still pretty small

for parameter in parameters {

guard let value = parameter else {
parameterData.append(nil)
continue
}

guard let value = parameter else {
parameterData.append(nil)
let data: AnyCollection<Int8>
switch value {
case .buffer(let value):
data = AnyCollection(value.map { Int8($0) })

case .string(let string):
data = AnyCollection(string.utf8CString)
}

let pointer = UnsafeMutablePointer<Int8>.allocate(capacity: Int(data.count))
deallocators.append {
pointer.deallocate(capacity: Int(data.count))
}

for (index, byte) in data.enumerated() {
pointer[index] = byte
}

parameterData.append(pointer)
}
}

let sendResult: Int32 = parameterData.withUnsafeBufferPointer { buffer in
if buffer.isEmpty {
return PQsendQuery(self.connection, statement)
} else {
return PQsendQueryParams(self.connection,
statement,
Int32(parameterData.count),
nil,
buffer.baseAddress!,
nil,
nil,
0)
}
}

guard sendResult == 1 else {
throw mostRecentError ?? ConnectionError(description: "Could not send query.")
}

// write query
while true {
mill_fdwait(fd, FDW_OUT, -1, nil)
fdclean(fd)
let status = PQflush(connection)
guard status >= 0 else {
throw mostRecentError ?? ConnectionError(description: "Could not send query.")
}
guard status == 0 else {
continue
}
break
}

let data: AnyCollection<Int8>
switch value {
case .buffer(let value):
data = AnyCollection(value.map { Int8($0) })
// read response
var lastResult: OpaquePointer? = nil
while true {
guard PQconsumeInput(connection) == 1 else {
throw mostRecentError ?? ConnectionError(description: "Could not send query.")
}

case .string(let string):
data = AnyCollection(string.utf8CString)
guard PQisBusy(connection) == 0 else {
mill_fdwait(fd, FDW_IN, -1, nil)
fdclean(fd)
continue
}

let pointer = UnsafeMutablePointer<Int8>.allocate(capacity: Int(data.count))
deallocators.append {
pointer.deallocate(capacity: Int(data.count))
guard let result = PQgetResult(connection) else {
break
}

for (index, byte) in data.enumerated() {
pointer[index] = byte
if lastResult != nil {
PQclear(lastResult!)
lastResult = nil
}

parameterData.append(pointer)
}

let result: OpaquePointer = try parameterData.withUnsafeBufferPointer { buffer in
guard let result = PQexecParams(
self.connection,
statement,
Int32(parameters.count),
nil,
buffer.isEmpty ? nil : buffer.baseAddress,
nil,
nil,
0
) else {
throw mostRecentError ?? ConnectionError(description: "Empty result")
let status = PQresultStatus(result)
guard status == PGRES_COMMAND_OK || status == PGRES_TUPLES_OK else {
throw mostRecentError ?? ConnectionError(description: "Query failed.")
}
return result

lastResult = result
}

return try Result(result)
guard lastResult != nil else {
throw mostRecentError ?? ConnectionError(description: "Query failed.")
}
return try Result(lastResult!)
}
}
5 changes: 3 additions & 2 deletions Tests/PostgreSQLTests/PostgreSQLTests.swift
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Expand Up @@ -103,14 +103,15 @@ extension Album: ModelProtocol {
// MARK: - Tests

public class PostgreSQLTests: XCTestCase {
let connection = try! PostgreSQL.Connection(info: .init(URL(string: "postgres://localhost:5432/swift_test")!))
var connection: Connection!

let logger = Logger(name: "SQL Logger", appenders: [StandardOutputAppender()])

override public func setUp() {
super.setUp()

do {
connection = try! PostgreSQL.Connection(info: .init(URL(string: "postgres://localhost:5432/swift_test")!))
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@Danappelxx Danappelxx Dec 17, 2016

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Is there a reason the connection is being reconstructed each time? Is this the right way to use the api now?

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@robertjpayne robertjpayne Dec 17, 2016

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For tests each test should use it's own connection, we shouldn't share it due to busy states/dangling etc…

Connections are also unrecoverable ( you can't "reconnect" )

try connection.open()
try connection.execute("DROP TABLE IF EXISTS albums")
try connection.execute("DROP TABLE IF EXISTS artists")
Expand Down