Malformed XML using s3.upload

Today I ran into one of those problems that makes you question your sanity. A well used API to upload content to AWS S3 was returning an indecipherable error:

MalformedXML: The XML you provided was not well-formed or did not validate against our published schema

This was kind of funny, because I was writing the code in Typescript, and uploading JSON. XML was the furthest thing from my mind.

The code was running in an AWS Lambda, on NodeJS 14. The upload function I mentioned takes a NodeJS Stream as a parameter. I did a quick bit of internet research and found that the easiest way to turn the string that I had into a Stream was to use Readable.from like this:

const stream = Readable.from(payloadJson)

However, while this code _runs_, it does not work correctly! Don’t ask me why — or please do tell me why in the comments! What’s the fix?

  const stream = new Readable();
  stream._read = () => {}

That is some serious black magic. What an awful API! But it works.

APFS Snapshots and ARQ Backup

The other day I went to install Xcode and I was out of disk space. Deleting files helped but after a while, I noticed that no matter how many files I deleted, the disk free did not change.

I suspected that APFS Snapshots could be to blame. Because a snapshot keeps a reference to files at a point back in time. Potentially those big files I was throwing away in the Finder were still accessible.

I also uninstalled ARQ hoping this would help. it did not — somehow Arq backup had left two APFS snapshots behind, and those snapshots were causing many 10s of GB of data to be kept.

Listing Snapshots

Use this command to list the snapshots for your disk

?  ~ diskutil apfs listSnapshots /
Snapshot for disk1s6s1 (1 found)
+-- 70BB0FFB-....-....-....-..........
    Purgeable:   No
    NOTE:        This snapshot limits the minimum size of APFS Container disk1
?  ~ diskutil apfs listSnapshots /System/Volumes/Data
Snapshots for disk1s1 (2 found)
+-- 00XXX000-00XX-0X0X-X0X0-00XXX000XXX0
|   Name:        com_haystacksoftware_arqagent_0XXXX000-0XX0-00X0-X000-0X0X0XX00X00_0
|   XID:         00000000
|   Purgeable:   Yes
|   NOTE:        This snapshot limits the minimum size of APFS Container disk1
+-- 00000X00-0XXX-0000-00X0-00X0X00XX000
    Name:        com_haystacksoftware_arqagent_0XXXX000-0XX0-00X0-X000-0X0X0XX00X00_0
    XID:         00000000
    Purgeable:   Yes

Deleting Snapshots

Use this command to delete the found snapshots:

?  ~ diskutil apfs deleteSnapshot disk1s1 -uuid 00XXX000-00XX-0X0X-X0X0-00XXX000XXX0
Deleting APFS Snapshot 00XXX000-00XX-0X0X-X0X0-00XXX000XXX0 "com_haystacksoftware_arqagent_0XXXX000-0XX0-00X0-X000-0X0X0XX00X00_0" from APFS Volume disk1s1
Started APFS operation
Finished APFS operation

Voila. Instead of only 28GB free, I watched in Finder as the disk space available crept up … to over 100GB free!

How to Debug and see NSData / Data in Xcode debugger

Xcode’s debugger is bad about letting you see what the contents of a Data / NSData object are. Here’s my workaround:

  1. Use po to print out the base64 version of the object, e.g.

2. Copy that to the clipboard, then use the command line in Terminal to turn that into readable content

pbpaste | base64 -D | xxd

If you know it is plain text you can omit the xxd part.

For example, here’s the output for a recent AlamoFire debugging session:

(lldb) po
some : "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"
? pbpaste | base64 -D | xxd
00000000: 7b22 7375 6363 6573 7322 3a74 7275 652c  {"success":true,
00000010: 2270 726f 6669 6c65 223a 7b22 7072 6f66  "profile":{"prof
00000020: 696c 6573 223a 5b7b 2266 696c 7465 7261  iles":[{"filtera
00000030: 626c 6522 3a66 616c 7365 2c22 6669 6c74  ble":false,"filt
00000040: 6572 5f70 7269 6f72 6974 7922 3a6e 756c  er_priority":nul
00000050: 6c2c 2266 696c 7465 725f 7465 7874 223a  l,"filter_text":
00000060: 6e75 6c6c 2c22 6669 6c74 6572 5f70 6172  null,"filter_par
00000070: 616d 6574 6572 7322 3a7b 7d2c 2271 7565  ameters":{},"que
00000080: 7374 696f 6e5f 6963 6f6e 223a 2242 6173  stion_icon":"Bas
00000090: 6963 735f 3030 3222 2c22 7175 6573 7469  ics_002","questi
000000a0: 6f6e 5f69 6422 3a32 2c22 7461 6773 223a  on_id":2,"tags":
000000b0: 5b22 6f70 696e 696f 6e73 225d 2c22 6465  ["opinions"],"de
000000c0: 636c 696e 6564 5f71 7565 7374 696f 6e22  clined_question"
000000d0: 3a66 616c 7365 2c22 636f 6d6d 656e 7422  :false,"comment"
000000e0: 3a22 222c 2263 7265 6174 6564 5f61 7422  :"","created_at"
000000f0: 3a22 3230 3230 2d31 322d 3038 5431 373a  :"2020-12-08T17:
00000100: 3335 3a31 322e 3937 355a 222c 2275 7064  35:12.975Z","upd
00000110: 6174 6564 5f61 7422 3a22 3230 3230 2d31  ated_at":"2020-1
00000120: 322d 3038 5431 373a 3335 3a31 322e 3937  2-08T17:35:12.97
00000130: 355a 222c 2263 686f 6963 6573 223a 5b7b  5Z","choices":[{
00000140: 226f 7264 6572 223a 302c 2261 6374 6976  "order":0,"activ
00000150: 6522 3a74 7275 652c 2269 6422 3a31 3131  e":true,"id":111
00000160: 3938 2c22 6368 6f69 6365 5f69 6422 3a32  98,"choice_id":2
00000170: 392c 2263 7573 746f 6d5f 656e 7472 6965  9,"custom_entrie
00000180: 7322 3a5b 5d2c 2263 7265 6174 6564 5f61  s":[],"created_a
00000190: 7422 3a22 3230 3230 2d31 322d 3130 5431  t":"2020-12-10T1
000001a0: 353a 3439 3a32 392e 3430 385a 227d 5d7d  5:49:29.408Z"}]}
000001b0: 5d7d 7d                                  ]}}

git tip: stage lines matching a regular expression

Have you ever wanted to make a big refactoring but realize now you’ve done too much for a single git commit?

What if there was a way to stage only the modifications that matched a regex (regular expression) somehow?

There is!

Use grepdiff. Install it from homebrew or macports. Use it to grep through the output of `git diff`.

First, preflight your regex to make sure it’s working:

git diff -U0 | grepdiff -E 'some[Pp]attern' --output-matching=hunk

Once it’s working well, pipe it to git to make it stage those lines:

git diff -U0 | grepdiff -E 'some[Pp]attern' --output-matching=hunk | git apply --cached --unidiff-zero

Then commit.

git commit -m "Rename the field somepattern to somePattern"<br>

Unknown field argument owner @ ‘onCreateXYZ’

if you run across an error like

{"errors":[{"message":"Validation error of type UnknownArgument: Unknown field argument owner @ 'onCreateXYZ'"}]}

While using AWS Amplify with DataStore, it’s probably due to your AppSync Schema being messed up. I’ve run into this when I had a model type two cognito @auth directives, e.g.

@auth(rules: [
{ allow: private, operations: [read] }
{ allow: private, provider: iam, operations: [create, read, update, delete] }
{allow:owner,ownerField: "owner" }

The code generator for AppSync gets confused in this case and creates incorrect Subscription definitions. They lack the `owner` parameter, as you can see if you sign into the AppSync dashboard for your environment, and tap on the Schema link.

This is the way it should look:

onCreateUser(owner: String!): User @aws_subscribe(mutations: ["createUser"])

But this is what gets created

onCreateUser: User @aws_subscribe(mutations: ["createUser"]

Just change your schema.graphql back to having only one cognito auth type and push. AppSync schema should be back to normal and the error on launch will go away!

Xcode fails to export Ad hoc distribution

Has Xcode failed to export an Ad Hoc distribution file or upload to AppstoreConnect? Read on for a possible fix.

Xcode uses internal processes to do a lot of its work. Some of those tools can be influenced by environment variables that may be set up by your terminal shell.

Normally when Xcode is launched from the Finder, properties you set in your terminal shell don’t matter. But it’s different if you’ve learned to use the command line program open to launch Xcode. When you do that, the Xcode process inherits the terminal environment. Including virtual environment settings such as virtualenv, pyenv, or a version manager such as rvm. It’s that last one that can cause this inexplicable error:

Xcode mail fail exporting an .IPA file for Ad Hoc Provisioning with a message “An error was encountered:” and “The data couldn’t be read because it isn’t in the correct format.”

If you click Show Logs you might find:

2020-09-29 02:38:10 +0000 /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in require': incompatible library version - /Users/paddlefish/.rvm/gems/ruby-2.6.3/gems/date-3.0.0/lib/date_core.bundle (LoadError) from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:inrequire'
from /Users/paddlefish/.rvm/gems/ruby-2.6.3/gems/date-3.0.0/lib/date.rb:4:in <top (required)>' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:inrequire'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in require' from /Users/paddlefish/.rvm/gems/ruby-2.6.3/gems/CFPropertyList-3.0.2/lib/cfpropertylist/rbCFPropertyList.rb:4:in'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in require' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:inrequire'
from /Users/paddlefish/.rvm/gems/ruby-2.6.3/gems/CFPropertyList-3.0.2/lib/cfpropertylist.rb:3:in <top (required)>' from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:130:inrequire'
from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:130:in `rescue in require'

The fix suggested here is clever, but didn’t actually work for me. But it got me wondering — why would Xcode invoke my .bashrc or .zshrc file anyhow? It shouldn’t be creating a shell process at all to run its commands. That got me thinking maybe the Xcode process itself was tainted with a bad environment. Then I remembered, I often use open to start Xcode, e.g. from a source code directory with an ios directory containing an Xcode workspace:

$ open ./ios/myproject.xcworkspace

I open to be easier than clicking around in the Finder. Especially when my current working directory is already there.

But be forewarned — if you see Xcode starting to generate bizarre errors, it’s because of the Ruby Version Manager selecting a version of Ruby that doesn’t have the necessary Gems.

The fix couldn’t be easier. Quit Xcode. Then relaunch it — using the Dock, the Finder, or Apple Menu recent applications. Just not the shell command, open.

comm to compare files with the same name in the same directory (another bash command-line interface [cli] trick)

Suppose you have two related projects with a similar file/folder structure. You want to compare the files by the same name in the two projects. You can use some magic of pipes to build a list of filenames that are the same (and in the same relative directories) in the two projects like this:

(find src -name '*.ts'| sort) | comm -12 - <(cd ../other_project && find src -name '*.ts' | sort)

It’s simple to then feed that into vimdiff or whatever is your favorite command-line diff tool using a for expression

for x in `(find src -name '*.ts'| sort) | comm -12 - <(cd ../other_project && find src -name '*.ts' | sort)`; do vim -d $x ../other_project/$x; done

Replace ../other_project with the path to the other directory to compare.

GSI (Global Secondary Index) errors with Amplify push

Have you ever used AWS Amplify with AppSync and done the command amplify push only to have it work for about 5 minutes and then fail, with an annoying error, “Attempting to edit the global secondary index”?

It happens sometimes, especially in development when iterating on the design of relationship in your schema. GraphQL is a powerful language for expressing relationships between objects in your data model. This limitation of DynamoDB makes this iteration painful. DynamoDB cannot update, modify, create, or delete more than on GSI (Global Secondary Index) at a time on a particular table.

How Did I Get Here

You probably made multiple changes to your schema. Every time you add a line like @key(name: "keyName", field: ["objectId"]) you’re ultimately causing Amplify to add a GSI to your DynamoDB Table. Add more than one between calls to amplify push and you’re going to encounter this error.

The Solution: Easy Part

The first thing to do is to log into the AWS Console, navigate to DynamoDB, and examine your table and it’s indexes. amplify push will complete BEFORE the indexes are finished being created in DynamoDB. If you try to push a second time before DynamoDB is finished, you’ll get an error.

Look for any line that says “Creating”. If it’s there, you just have to wait. Click the refresh button periodically to find out if it’s finished yet. Then try amplify push again.

The Harder, But Sure Fix

Some folks recommend amplify remove api and then amplify add api as a way to fix this problem. That is a BIG hammer. For one thing, it will DELETE ALL YOUR DATA. For another, it’s not needed. And also, if you have inter-dependencies, the remove call might fail, for example if you have an amplify function connected to Cognito as a post-user-sign-up hook.

Step 1: Find the CloudFormation Template for each Table

Use AWS Console to navigate to CloudFormation. Find the top level cloud formation stack for your environment. Click on that and look at its resources until you find api. Then click on that until you find the templates for each of the Object types in your schema. We’ll need to go through the following steps for *each* of those.

Step 2: Download the Current Template

I simply copied the current template onto my clipboard, and then saved it as a new file:

pbpaste > cur_$X.json

Use YOUR object name, not Segment. Forgive me, I am a Command Line geek. Use whatever tools you want, e.g. create a new file in a text editor, paste it, and then use your favorite file comparison tool for the next step.

Step 3: Compare AND EDIT the Template

I’m a vim user so this was all I had to do to compare them

vim -d cur_$X.json amplify/backend/api/appname/build/stacks/$X.json

Use YOUR appname, not appname.

Look at the section GlobalSecondaryIndexes. Are there more than 1 difference between the current template and the new one the Amplify want’s to create? Edit the downloaded JSON, bringing over only one of the changes, so that there’s only one difference. We’ll be adding those over one at a time, deploying the change after each edit. Yes, I know, this is tedious. But it’s better than destroying your entire environment and losing all the data.

Step 4: Update the Template in CloudFormation

Now go to the template for that Object. Click Update from the Template tab. It will say “It is recommended to update through the root stack“. Choose “Update nested stack”.

The screen that recommends you update the root stack.

Select “Replace current template” and “Upload a template file”

The Screen you see when going to update a CloudFormation Template

and upload your edited JSON file

Select your Edited CloudFormation JSON template

Then click Next a bunch

Updating a CloudFormation Template requires you answer a bunch of questions. Fortunately it has the right answers already selected.

You will have to give it permission to do something with IAM. Click the box.

A scary warning that CloudFormation is going to update IAM

With luck, it will succeed

When the CloudFormation template is properly updated, you’ll see the words “UPDATE_COMPLETE”. If it failed, you’ll see “UPDATE_ROLLBACK_COMPLETE” in red.

Step 5: Goto Step 3

If you had to remove more than one GSI change, add it back — again one-at-a-time and repeat starting at Step 3.

Step 6: Goto Step 2

Repeat this for all your Objects (which each has their own Table).

Step 7: Amplify Push Will Work!

Now that the GSIs have all been created, amplify push will be successful!

? Generated GraphQL operations successfully and saved at src/graphql
? Code generated successfully and saved in file src/API.ts
? All resources are updated in the cloud
GraphQL endpoint: https://<redacted>