[IMPALA-9112] Consider removing hdfsExists calls when writing files to S3

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Fix Version/s: Not Applicable
• Component/s: Backend
• Epic Color: ghx-label-13
• Assignee: Sahil Takiar
• Reporter: Sahil Takiar
• Created: 31/Oct/19 16:07
• Updated: 04/Dec/20 19:12
• Resolved: 04/Dec/20 19:12

Description

There are a few places in the backend where we call hdfsExists before writing out a file. This can cause issues when writing data to S3, because S3 can cache 404 Not Found errors. This issue manifests itself with errors such as:

ERROR: Error(s) moving partition files. First error (of 1) was: Hdfs op (RENAME s3a://[bucket-name]/[table-name]/_impala_insert_staging/3943ae7ccf00711e_59606d8800000000/.3943ae7ccf00711e-59606d880000000b_562151879_dir/year=2015/3943ae7ccf00711e-59606d880000000b_1994902389_data.0.parq TO s3a://[bucket-name]/[table-name]/3943ae7ccf00711e-59606d880000000b_1994902389_data.0.parq) failed, error was: s3a://[bucket-name]/[table-name]/_impala_insert_staging/3943ae7ccf00711e_59606d8800000000/.3943ae7ccf00711e-59606d880000000b_562151879_dir/year=2015/3943ae7ccf00711e-59606d880000000b_1994902389_data.0.parq
Error(5): Input/output error
Root cause: AmazonS3Exception: Not Found (Service: Amazon S3; Status Code: 404; Error Code: 404 Not Found; Request ID: []; S3 Extended Request ID: [])

HADOOP-13884, HADOOP-13950, HADOOP-16490 - the HDFS clients allow specifying an "overwrite" option when creating a file; this can avoid doing any HEAD requests when opening a file.