Test scripts for postgres

[vidyalakshmir]

We need a test script to test Postgres

• Either repurpose the existing test suite (usually Makefile will have a target test or check) to run within lind-wasm or just write a test script that tests basic functionality of postgres
• Each app should have its own shell script test.sh (lind-wasm-apps/postgres/test.sh, which outputs exit 0 on success, anything else will count as a fail. For now, check for binaries being installed in the correct location, and determine success/failure for that.
• Binaries are usually placed in lindfs/bin directory (preferably without any extension)
• Make sure all paths that the test uses are relative to lindfs and the corresponding files are actually copied to lindfs. To refer a file /home/lind/lind-wasm/lindfs/tests/postgres/test.txt, please use tests/postgres/test.txt
• Test scripts that are copied to lindfs can be placed in lindfs/tests/postgres folder
  Command to run an app within lind:
  lind_run $app
  For example, to run /home/lind/lind-wasm/lindfs/bin/bash with an argument /home/lind/lind-wasm/lindfs/tests/bash/test1.sh, please run

lind_run bin/bash tests/bash/test1.sh

[rishabhBudhouliya]

@vidyalakshmir as first steps, I am checking out PR #107 and building postgres and confirm that the binaries are copied at the right place. After that sanity step, I will write a test script that starts with binary existence checks, then do basic functionality tests.

[vidyalakshmir]

Sounds good. You could check bash, sed or curl test scripts for reference.

[rishabhBudhouliya]

Current status

What works
I've created a test script that does:

• check if postgres binaries exist in lindfs/bin
• validate if postgres --version works or not
• validate if postgres --help runs or not

I've manually tested the script and it seems to be working as stated.

What doesn't work:

1. initdb -D /tmp/pgdata --no-locale

LIND DEBUG PANIC: Unsupported mmap flag detected! Only MAP_FIXED,   
  MAP_SHARED, MAP_PRIVATE, MAP_POPULATE AND MAP_ANONYMOUS allowed

2. postgres --single -D /tmp/pgdata

FATAL: signalfd() failed

[rishabhBudhouliya]

@vidyalakshmir @rennergade
I've been trying to make postgres run and have been running into different issues

1. Unsupported mmap flags
   The initdb -D /tmp/pgdata --no-locale command fails with a panic

LIND DEBUG PANIC: Unsupported mmap flag detected! Only MAP_FIXED, MAP_SHARED, MAP_PRIVATE, MAP_POPULATE AND MAP_ANONYMOUS allowed

2. postgres --single -D /tmp/pgdata

FATAL: signalfd() failed

3. After fixing the mmap flags issue, we run initdb -D /tmp/pgdata --no-locale again and fail due to

  popen("postgres --boot ...") ->  glibc's _IO_new_proc_open() -> __posix_spawn() -> __spawni() -> clone(CLONE_VM | CLONE_VFORK) -> segfault

It seems like we don't have clone syscall implemented in lind-wasm. Furthermore, file_tests/deterministic/popen.c test is in skiplist so I am assuming it fails right now.

I am unsure of the blast radius of the changes that I'd make here, so should I fix these to move forward? Apparently, spawni() is a glibc-internal optimization that avoids fork + exec() and calls CLONE instead which is not implemented in lind-wasm.

[rennergade]

We definitely have clone implemented.

Theres a long standing PR to fix spawni: Lind-Project/lind-wasm#360

@qianxichen233 just needs to update the comments to merge it, can you do that qianxi?

[vidyalakshmir]

@rishabhBudhouliya I just talked to Qianxi. He mentioned the following:

• For signalfd() failure, first pls test if signalfd() is actually supported within lind. You could write a simple test for that. If it is not supported, one way is to try 'disabling signalfd' when postgres is built. While running configure, you can disable certain functions/sycalls. (Check this in python build). ./configure --help should give all options to enable/disable different options.
• For spawni, it would be better to first test locally - the changes in this PR merged with current main - to see if this fix still applies. A simple test that uses popen() should work. Since it requires bash, compiling bash would be required. (change bash to sh, as open() expects sh).

[rishabhBudhouliya]

@vidyalakshmir @rennergade
I have used Qianxi's PR and I'm able to get past the popen() limitations.

After applying certain changes to make initdb work first, I am current facing two problems, one:

1. sudo ./lind-boot /bin/initdb.wasm -D /tmp/pgdata --no-locale

thread 'lind-fork-3' panicked at sysdefs/src/logging.rs:6:5:                                                                                                                                 
  LIND DEBUG PANIC: Unsupported mmap flag detected! Only MAP_FIXED, MAP_SHARED, MAP_PRIVATE, MAP_POPULATE AND MAP_ANONYMOUS allowed

On adding further logs, I saw:

mmap: flags=0x54040021, unknown=0x54040000

0x54040000 is being passed to mmap but I am unsure how is this garbage value being passed (not a valid mmap flag)

2. If I remove the debug panic for unsupported flags and still run initdb, I see

    $ sudo /home/lind/lind-wasm/build/lind-boot /bin/initdb.wasm -D           
  /tmp/pgdata --no-locale                                                     
    selecting default "max_connections" ...                                   
    shell-init: error retrieving current directory: getcwd: cannot access     
  parent directories: Invalid argument                                                                                         
                                                                              
    thread 'lind-fork-2' panicked at lind-multi-process/src/lib.rs:952:50:    
    exec-ed module error: failed to run main module                           
                                                                              
    Caused by:                                                                
        0: failed to invoke command default                                   
        1: wasm trap: indirect call type mismatch                             
                                                  

There were couple of roadblocks I had to solve to reach here, all of those are documented in branch: https://github.com/Lind-Project/lind-wasm/tree/test/mkfifo and and https://github.com/Lind-Project/lind-wasm-apps/tree/compile-postgres-bkp

[vidyalakshmir]

Thanks Rishabh. This is a good progress.
@qianxichen233 Do you have any pointers to fix above errors?

[rishabhBudhouliya]

Currently, the postgres effort is blocked on: Lind-Project/lind-wasm#923