Add more friendly error message for policy object

[lunixoid]

In our projects we use minio as the storage sever. Each bucket equals - git project. After building project CI uploads artefact into minio and sets mc policy download for subdirectory. Name of subdirectory in bucket depends on name of current brunch (develop, master).
So after some time of working our bucket policy file reach limit 20K and send us error:
Your proposed upload exceeds the maximum allowed object size.

We spent a lot of time to understand and resolve this issue, so I suggest to extend error message for this case.

[codecov]

Codecov Report

Merging #7412 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #7412      +/-   ##
==========================================
+ Coverage    47.4%   47.43%   +0.02%     
==========================================
  Files         294      294              
  Lines       46740    46740              
==========================================
+ Hits        22158    22172      +14     
+ Misses      22528    22517      -11     
+ Partials     2054     2051       -3

Impacted Files	Coverage Δ
cmd/api-errors.go	50.62% <ø> (ø)	⬆️
cmd/bucket-policy-handlers.go	88.99% <100%> (ø)	⬆️
cmd/posix.go	63.84% <0%> (+0.1%)	⬆️
cmd/fs-v1.go	62.18% <0%> (+0.37%)	⬆️
cmd/fs-v1-helpers.go	68.8% <0%> (+0.61%)	⬆️
cmd/bitrot-streaming.go	83.17% <0%> (+0.93%)	⬆️
cmd/posix-list-dir_unix.go	75% <0%> (+2.63%)	⬆️
cmd/retry.go	87.5% <0%> (+5.35%)	⬆️
cmd/disk-usage.go	78.94% <0%> (+10.52%)	⬆️

---

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[poornas]

@lunixoid, trying to understand why you need to give download access on each individual subdirectory prefix when you might want to just give download access on bucket/* which would in essence accomplish the same without policy bloat.

[harshavardhana]

Thanks for the PR, some review comments..

[lunixoid]

@lunixoid, trying to understand why you need to give download access on each individual subdirectory prefix when you might want to just give download access on bucket/* which would in essence accomplish the same without policy bloat.

It was my mistake, but in any case current error message don't help to understand the problem.
I did it because mc prints links to the each file in bucket only if I set policy download for each subdirectory. I use those links for auto downloading files while CI stages.

[harshavardhana]

Can you check why CI failed ?

[poornas]

LGTM

[minio-ops]

Mint Automation

Test	Result
mint-compression-xl.sh	✔️
mint-xl.sh	✔️
mint-compression-dist-xl.sh	✔️
mint-compression-fs.sh	✔️
mint-worm.sh	✔️
mint-dist-xl.sh	✔️
mint-gateway-nas.sh	✔️
mint-large-bucket.sh	❌ more...
mint-fs.sh	❌ more...

7412-b7e1f5e/mint-fs.sh.log:

Running with
SERVER_ENDPOINT:      72.28.97.60:31953
ACCESS_KEY:           minio
SECRET_KEY:           ***REDACTED***
ENABLE_HTTPS:         0
SERVER_REGION:        us-east-1
MINT_DATA_DIR:        /mint/data
MINT_MODE:            full
ENABLE_VIRTUAL_STYLE: 0

To get logs, run 'docker cp d222bbee8411:/mint/log /tmp/mint-logs'

(1/14) Running aws-sdk-go tests ... FAILED in 1 seconds
{
  "alert": "",
  "args": {
    "bucketName": "aws-sdk-go-test-oxvib3i3jp0e69",
    "expiry": 60000000000,
    "objectName": "presignedTest"
  },
  "duration": 214,
  "error": "RequestError: send request failed\ncaused by: Put http://72.28.97.60:31953/aws-sdk-go-test-oxvib3i3jp0e69: dial tcp 72.28.97.60:31953: connect: connection refused",
  "function": "PresignedPut",
  "message": "AWS SDK Go CreateBucket Failed",
  "name": "aws-sdk-go",
  "status": "FAIL"
}

Executed 0 out of 14 tests successfully.

7412-b7e1f5e/mint-large-bucket.sh.log:

Running with
SERVER_ENDPOINT:      72.28.97.55:32177
ACCESS_KEY:           minio
SECRET_KEY:           ***REDACTED***
ENABLE_HTTPS:         0
SERVER_REGION:        us-east-1
MINT_DATA_DIR:        /mint/data
MINT_MODE:            full
ENABLE_VIRTUAL_STYLE: 0

To get logs, run 'docker cp d80237274fd0:/mint/log /tmp/mint-logs'

(1/14) Running aws-sdk-go tests ... FAILED in 0 seconds
{
  "alert": "",
  "args": {
    "bucketName": "aws-sdk-go-test-t3wehwifls2f0w",
    "expiry": 60000000000,
    "objectName": "presignedTest"
  },
  "duration": 261,
  "error": "RequestError: send request failed\ncaused by: Put http://72.28.97.55:32177/aws-sdk-go-test-t3wehwifls2f0w: dial tcp 72.28.97.55:32177: connect: connection refused",
  "function": "PresignedPut",
  "message": "AWS SDK Go CreateBucket Failed",
  "name": "aws-sdk-go",
  "status": "FAIL"
}

Executed 0 out of 14 tests successfully.

[harshavardhana]

ping @poornas