S3 Clients are leaving behind open PIPE file descriptors

[dyutishb]

Describe the bug

We are using the aws v2 sdk on of our processes which ran out of file descriptors which led us to investigate the open ones. We can see new FDs being added and not closed even if we do simple headBucket calls to s3.
Example of open FDs added:

java    6320 root  182u  a_inode               0,14         0      1057 [eventpoll:183]
java    6320 root  183r     FIFO               0,13       0t0    275505 pipe
java    6320 root  184w     FIFO               0,13       0t0    275505 pipe
java    6320 root  185u  a_inode               0,14         0      1057 [eventpoll:186]
java    6320 root  186r     FIFO               0,13       0t0    275506 pipe
java    6320 root  187w     FIFO               0,13       0t0    275506 pipe
java    6320 root  188u  a_inode               0,14         0      1057 [eventpoll:189]
java    6320 root  189r     FIFO               0,13       0t0    275507 pipe
java    6320 root  190w     FIFO               0,13       0t0    275507 pipe

Here's how we are building our client:

S3AsyncClient s3AsyncClient = S3AsyncClient.crtBuilder()
                                           .credentialsProvider(credentialsProvider)
                                           .region(Region.US_EAST_1)
                                           .build();
S3TransferManager s3TransferManager = S3TransferManager.builder()
                                                       .s3Client(s3AsyncClient)
                                                       .build();

We also have S3Client, StsClient and S3Presigner being setup similarly and we do an explicit .close() on each of them. Irrespective of the close() being called any file handles opened due to the clients should be garbage collected on destruction of the object which is not happening.
The same is not seen with the v1 SDK.

Expected Behavior

Any file descriptors opened due to operations by the sdk should be garbage collected when the clients are destroyed.

Current Behavior

Pipe and a_inode file descriptors being left behind even after closing on the clients.

Reproduction Steps

Create any process (imagine an api server which makes request to s3) which instantiates a s3 client and makes some basic requests like headBucket, keep the process up even after the request is completed. Compare the open file descriptors before and after the request using sudo lsof -p <pid> or sudo ls -l /proc/<pid>/fd.

Possible Solution

No response

Additional Information/Context

No response

AWS Java SDK version used

2.25.26

JDK version used

openjdk version "1.8.0_402"

Operating System and version

Rocky Linux release 9.4 (Blue Onyx)

[dyutishb]

We were able to narrow this down to the S3AsyncClient with CRT and S3TransferManager, here's an explanation of the scenario:

Step1. Check count of open file descriptors of java process using: sudo ls -l /proc/<pid>/fd | wc -l
Our output:

sudo ls -l /proc/733969/fd | wc -l
123

Step2. Execute this in the process:

S3AsyncClient s3AsyncClient = S3AsyncClient.crtBuilder()
                                           .credentialsProvider(credentialsProvider)
                                           .region(Region.US_EAST_1)
                                           .build();
S3TransferManager s3TransferManager = S3TransferManager.builder()
                                                       .s3Client(s3AsyncClient)
                                                       .build();

Step 3. Run same command as step1.
Our output:

sudo ls -l /proc/733969/fd | wc -l
205

Example of FDs opened by the processes: (run sudo ls -l /proc/<pid>/fd)

lrwx------ 1 dyutishb dyutishb 64 Jun 19 15:41 183 -> 'anon_inode:[eventpoll]'
lr-x------ 1 dyutishb dyutishb 64 Jun 19 15:41 184 -> 'pipe:[16427762]'
l-wx------ 1 dyutishb dyutishb 64 Jun 19 15:41 185 -> 'pipe:[16427762]'
lrwx------ 1 dyutishb dyutishb 64 Jun 19 15:41 186 -> 'anon_inode:[eventpoll]'
lr-x------ 1 dyutishb dyutishb 64 Jun 19 15:41 187 -> 'pipe:[16427763]'
l-wx------ 1 dyutishb dyutishb 64 Jun 19 15:41 188 -> 'pipe:[16427763]'

Step4. Close the clients using:

s3AsyncClient.close();
s3TransferManager.close();

Step 5. Repeat commands from step1 and 3:
Our output:

sudo ls -l /proc/733969/fd | wc -l
169

We still see similar open FDs:

lrwx------ 1 dyutishb dyutishb 64 Jun 19 15:41 161 -> 'anon_inode:[eventpoll]'
lr-x------ 1 dyutishb dyutishb 64 Jun 19 15:41 162 -> 'pipe:[16427755]'
l-wx------ 1 dyutishb dyutishb 64 Jun 19 15:41 163 -> 'pipe:[16427755]'
lrwx------ 1 dyutishb dyutishb 64 Jun 19 15:41 164 -> 'anon_inode:[eventpoll]'
lr-x------ 1 dyutishb dyutishb 64 Jun 19 15:41 165 -> 'pipe:[16427756]'
l-wx------ 1 dyutishb dyutishb 64 Jun 19 15:41 166 -> 'pipe:[16427756]'

The close() calls clears out some of the open pipe handles but not all are cleared and these are not released even on destruction of the object which is leading to our process having too many open handles.

[akshat62]

Similar to: #5271

[dreamerHarshit]

is there any for fix for this issue?

[n0ct1s-k8sh]

Greetings,

Are there any updates on this? Our production workloads in AWS are affected and some are in a permanent degradation status.

Thanks for your attention.