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Better understanding of offset with appendV2 and finish
Attempting to upload large files. The regular upload method works without an issue. When I try to use appendV2 and Finish I get that the offset was incorrect and the correct offset. This post does di...
That makes sense. Thanks for clearing that up. I was thinking you provide the full file, then the offset was used to tell which part to upload. I also ran into an issue when the upload would not finish before attempting the next part so I made it recursive if the file part finished.
Anyone that find this. Here is my upload function for small and large files. It could be improved but it works.
func upload(file filePath: String, to dbxLocation: String) { if FileManager.default.fileExists(atPath: filePath) { print("File Exists") } else { return } let fileURL: URL = URL(filePath: filePath) var dbFilePath: String = "" if dbxLocation.last == "/" { dbFilePath = dbxLocation + fileURL.lastPathComponent } else { dbFilePath = dbxLocation + "/" + fileURL.lastPathComponent } print(dbFilePath) let fileSize = try? FileManager.default.attributesOfItem(atPath: filePath)[.size] as? UInt64 let chunkSize: UInt64 = 4 * 1024 * 1024 // Check to see if file is smaller than chunksize if fileSize! < chunkSize { dbxClient.files.upload(path: dbFilePath, input: fileURL).response(completionHandler: { response, error in if let response = response { print("File uploaded: \(response)") } else { print("Error upload session: \(error!)") } }) .progress { progressData in print(progressData) } print("small file") } else { let data: [Data] = try! self.split(file: fileURL, into: chunkSize) //start the upload session var offset: UInt64 = UInt64(data[0].count) dbxClient.files.uploadSessionStart(input: data[0]) .response(completionHandler: { [self] response, error in if let result = response { print(result) append(data: data, part: 1, sessionId: result.sessionId, offset: offset, chunkSize: chunkSize, fileSize: fileSize!, dbFilePath: dbFilePath) } else { // the call failed print(error!) } }) } } func append(data: [Data], part: Int, sessionId: String, offset: UInt64, chunkSize: UInt64, fileSize: UInt64, dbFilePath: String) { let chunk = data[part] if ((fileSize - offset) <= chunkSize) { dbxClient.files.uploadSessionFinish(cursor: Files.UploadSessionCursor(sessionId: sessionId, offset: offset), commit: Files.CommitInfo(path: dbFilePath), input: chunk) .response { response, error in if let result = response { print("File Uploaded: \(result)") } else { print(fileSize) print("Finish Error: \(error!)") } } } else { dbxClient.files.uploadSessionAppendV2(cursor: Files.UploadSessionCursor(sessionId: sessionId, offset: offset), input: chunk) .response {response , error in if let response = response { self.append(data: data, part: part + 1, sessionId: sessionId, offset: offset + UInt64(data[part].count), chunkSize: chunkSize, fileSize: fileSize, dbFilePath: dbFilePath) } else { print("Error appending data \(part) to file upload session: \(error!)") } } } } func split(file fileURL: URL, into chunkSize: UInt64) throws -> [Data] { let data = try Data(contentsOf: fileURL) let chunks = stride(from: 0, to: data.count, by: Int(chunkSize)).map { data.subdata(in: $0 ..< Swift.min($0 + Int(chunkSize), data.count)) } return chunks }
Greg-DB
Dropbox Staff
Dropbox StaffThe process you described isn't quite correct. Upload sessions work by having you upload just a portion of the file in each request (that is, per uploadSessionStart, uploadSessionAppendV2, or uploadSessionFinish call). You would not send the full file data in each request. For each request, you read off and upload just the next piece (the size being the "chunk size") of the file. You would use one upload session per file to upload, and the number of calls you make per upload session depends on the size of the file and the chunk size you use.
The chunk size is how much data to send per request, and the offset is how much data has been successfully sent to the server for that upload session so far. The chunk size doesn't need to be the same for each request, but for the sake of simplicity it is the same across requests in most implementations. The offset would increase over the life of the upload session as data is successfully uploaded.
In short, you would upload the first portion of the file's data with uploadSessionStart, the next portion(s) with uploadSessionAppendV2 if/as needed, and then the final portion with uploadSessionFinish.
Here's a minimal example implementation in Python that may be illustrative and more easy to read:
import os
import dropbox
ACCESS_TOKEN = "ACCESS_TOKEN_HERE"
local_file_path = "LOCAL_PATH_TO_FILE_HERE"
dbx = dropbox.Dropbox(ACCESS_TOKEN)
f = open(local_file_path, "rb")
file_size = os.path.getsize(local_file_path)
dest_path = "REMOTE_PATH_IN_DROPBOX_FOR_UPLOADED_FILE"
CHUNK_SIZE = 4 * 1024 * 1024
upload_session_start_result = dbx.files_upload_session_start(f.read(CHUNK_SIZE))
cursor = dropbox.files.UploadSessionCursor(session_id=upload_session_start_result.session_id,
offset=f.tell())
commit = dropbox.files.CommitInfo(path=dest_path)
while f.tell() <= file_size:
if ((file_size - f.tell()) <= CHUNK_SIZE):
print(dbx.files_upload_session_finish(f.read(CHUNK_SIZE),
cursor,
commit))
break
else:
dbx.files_upload_session_append_v2(f.read(CHUNK_SIZE),
cursor)
cursor.offset = f.tell()
f.close()
That makes sense. Thanks for clearing that up. I was thinking you provide the full file, then the offset was used to tell which part to upload. I also ran into an issue when the upload would not finish before attempting the next part so I made it recursive if the file part finished.
Anyone that find this. Here is my upload function for small and large files. It could be improved but it works.
func upload(file filePath: String, to dbxLocation: String) {
if FileManager.default.fileExists(atPath: filePath) {
print("File Exists")
} else {
return
}
let fileURL: URL = URL(filePath: filePath)
var dbFilePath: String = ""
if dbxLocation.last == "/" {
dbFilePath = dbxLocation + fileURL.lastPathComponent
} else {
dbFilePath = dbxLocation + "/" + fileURL.lastPathComponent
}
print(dbFilePath)
let fileSize = try? FileManager.default.attributesOfItem(atPath: filePath)[.size] as? UInt64
let chunkSize: UInt64 = 4 * 1024 * 1024
// Check to see if file is smaller than chunksize
if fileSize! < chunkSize {
dbxClient.files.upload(path: dbFilePath, input: fileURL).response(completionHandler: { response, error in
if let response = response {
print("File uploaded: \(response)")
} else {
print("Error upload session: \(error!)")
}
})
.progress { progressData in print(progressData) }
print("small file")
} else {
let data: [Data] = try! self.split(file: fileURL, into: chunkSize)
//start the upload session
var offset: UInt64 = UInt64(data[0].count)
dbxClient.files.uploadSessionStart(input: data[0])
.response(completionHandler: { [self] response, error in
if let result = response {
print(result)
append(data: data, part: 1, sessionId: result.sessionId, offset: offset, chunkSize: chunkSize, fileSize: fileSize!, dbFilePath: dbFilePath)
} else {
// the call failed
print(error!)
}
})
}
}
func append(data: [Data], part: Int, sessionId: String, offset: UInt64, chunkSize: UInt64, fileSize: UInt64, dbFilePath: String) {
let chunk = data[part]
if ((fileSize - offset) <= chunkSize) {
dbxClient.files.uploadSessionFinish(cursor: Files.UploadSessionCursor(sessionId: sessionId, offset: offset), commit: Files.CommitInfo(path: dbFilePath), input: chunk)
.response { response, error in
if let result = response {
print("File Uploaded: \(result)")
} else {
print(fileSize)
print("Finish Error: \(error!)")
}
}
} else {
dbxClient.files.uploadSessionAppendV2(cursor: Files.UploadSessionCursor(sessionId: sessionId, offset: offset), input: chunk)
.response {response , error in
if let response = response {
self.append(data: data, part: part + 1, sessionId: sessionId, offset: offset + UInt64(data[part].count), chunkSize: chunkSize, fileSize: fileSize, dbFilePath: dbFilePath)
} else {
print("Error appending data \(part) to file upload session: \(error!)")
}
}
}
}
func split(file fileURL: URL, into chunkSize: UInt64) throws -> [Data] {
let data = try Data(contentsOf: fileURL)
let chunks = stride(from: 0, to: data.count, by: Int(chunkSize)).map {
data.subdata(in: $0 ..< Swift.min($0 + Int(chunkSize), data.count))
}
return chunks
}About Dropbox API Support & Feedback
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