Cache Preloading

Distributed load allows users to load data from UFS to Alluxio cluster efficiently. This can be used to initialize the Alluxio cluster to be able to immediately serve cached data when running workloads on top of Alluxio. For example, distributed load can be used to prefetch data for machine learning jobs, speeding up the training process. Distributed load can utilize file segmentation and multi-replication to enhance file distribution in scenarios with highly concurrent data access.

Usage

There are two recommended ways to trigger distributed load:

job load CLI

The job load command can be used to load data from UFS (Under File System) to the Alluxio cluster. The CLI sends a load request to the Alluxio coordinator, which subsequently distributes the load operation to all worker nodes.

bin/alluxio job load [flags] <path>

# Example output
Progress for loading path '/path':
        Settings:       bandwidth: unlimited    verify: false
        Job State: SUCCEEDED
        Files Processed: 1000
        Bytes Loaded: 125.00MB
        Throughput: 2509.80KB/s
        Block load failure rate: 0.00%
        Files Failed: 0

For detailed usage of CLI, please refer to the job load documentation.

REST API

Similar to the CLI, the REST API can also be used to load data. Requests can be sent to any worker node, which would forward it to the Alluxio coordinator to distribute to all other worker nodes.

Submit the job by sending a POST request with the path to the directory and submit as the optType query parameter.

curl --request POST 'http://{worker_host}:{http_port}/v1/load?path={path}&opType=submit'

Example request and response:

curl -v -X POST http://172.30.16.110:19999/v1/load?path=s3://test&opType=submit

# Example output
* About to connect() to 172.30.16.110 port 19999 (#0)
*   Trying 172.30.16.110...
* Connected to 172.30.16.110 (172.30.16.110) port 19999 (#0)
> POST /v1/load?path=s3://test&opType=submit HTTP/1.1
> User-Agent: curl/7.29.0
> Host: 172.30.16.110:19999
> Accept: */*
> Content-Length: 183
>
* upload completely sent off: 183 out of 183 bytes
< HTTP/1.1 200 OK
< Date: Wed, 10 Apr 2024 05:47:17 GMT
< Content-Length: 4
< Server: Jetty(9.4.53.v20231009)
<
* Connection #0 to host 172.30.16.110 left intact
true

Progress can be checked by sending a GET request with the same path and progress as the opType query parameter.

curl --request GET 'http://{worker_host}:{http_port}/v1/load?path={path}&opType=progress'

Example request and response:

curl -v -X GET http://host:19999/v1/load?path=s3://test&opType=progress
result:
* About to connect() to 172.30.16.110 port 19999 (#0)
*   Trying 172.30.16.110...
* Connected to 172.30.16.110 (172.30.16.110) port 19999 (#0)
> GET /v1/load?path=s3://test&opType=progress
> User-Agent: curl/7.29.0
> Host: 172.30.16.110:19999
> Accept: */*
> Content-Length: 81
>
* upload completely sent off: 81 out of 81 bytes
< HTTP/1.1 200 OK
< Date: Wed, 10 Apr 2024 05:48:49 GMT
< Content-Length: 572
< Server: Jetty(9.4.53.v20231009)
<
* Connection #0 to host 172.30.16.110 left intact
"{\"mVerbose\":true,\"mJobState\":\"RUNNING\",\"mVerificationEnabled\":false,\"mSkippedByteCount\":0,\"mLoadedByteCount\":0,\"mScannedInodesCount\":18450,\"mLoadedNonEmptyFileCopiesCount\":0,\"mThroughput\":0,\"mFailureFilesPercentage\":0.0,\"mFailureSubTasksPercentage\":0.0,\"mRetrySubTasksPercentage\":0.0,\"mFailedFileCount\":0,\"mRecentFailedSubtasksWithReasons\":[],\"mRecentRetryingSubtasksWithReasons\":[],\"mSkipIfExists\":true,\"mMetadataOnly\":true,\"mRunningStage\":\"LOADING\",\"mRetryDeadLetterQueueSize\":0,\"mTimeElapsed\":87237,\"mSegmentEnabled\":false}"

The load operation can be terminated by sending a POST request with the same path and stop as the opType query parameter.

curl --request POST 'http://{worker_host}:{http_port}/v1/load?path={path}&opType=stop'

Example request and response:

curl -v -X POST http://host:19999/v1/load?path=s3://test&opType=stop

* Example result:
* About to connect() to 172.30.16.110 port 19999 (#0)
*   Trying 172.30.16.110...
* Connected to 172.30.16.110 (172.30.16.110) port 19999 (#0)
> POST /v1/load?path=s3://test&opType=stop
> User-Agent: curl/7.29.0
> Host: 172.30.16.110:19999
> Accept: */*
> Content-Length: 42
>
* upload completely sent off: 42 out of 42 bytes
< HTTP/1.1 200 OK
< Date: Wed, 10 Apr 2024 05:51:56 GMT
< Content-Length: 5
< Server: Jetty(9.4.53.v20231009)
<
* Connection #0 to host 172.30.16.110 left intact
true