Defining how your data is spread among workers is one of the most important aspects of distributed computation.
Pachyderm uses glob patterns to provide flexibility to define data distribution.
Pachyderm's concept of glob patterns is similar to Unix glob patterns. For example, the
ls *.md command matches all files with the
.md file extension.
The glob pattern applies to all of the directories/files in the branch specified by the
pfs section of the pipeline specification (referred to as PFS inputs). The directories/files that match are the datums that will be processed by the worker(s) that run your pipeline code.
You must configure a glob pattern for each PFS input of a pipeline specification.
We have listed some commonly used glob patterns. We will later illustrate their use in an example:
|Glob Pattern||Datum created|
| ||Pachyderm denotes the whole repository as a single datum and sends all input data to a single worker node to be processed together.|
| ||Pachyderm defines each top-level files / directories in the input repo, as a separate datum. For example, if you have a repository with ten files and no directory structure, Pachyderm identifies each file as a single datum and processes them independently.|
| ||Pachyderm processes each file / directory in each subdirectories as a separate datum.|
| ||Pachyderm processes each file in all directories and subdirectories as a separate datum.|
Glob patterns also let you take only a particular subset of the files / directories, a specific branch... as an input instead of the whole repo. We will elaborate on this more in the following example.
If you have more than one input repo in your pipeline, or want to consider more than one branch in a repo, or any combination of the above, you can define a different glob pattern for each PFS input. You can additionally combine the resulting datums by using the
group operator to create the final datums that your code processes. For more information, see Cross and Union, Join, Group.
Example of Defining Datums¶
Let's consider an input repo with the following structure where each top-level directory represents a US state with a
json file for each city in that state:
/California /San-Francisco.json /Los-Angeles.json ... /Colorado /Denver.json /Boulder.json ... /Washington /Seattle.json /Vancouver.json
Now let's consider what the following glob patterns would match respectively:
|Glob Pattern||Corresponding match||Example|
| ||This pattern matches ||If you add a new file |
| ||This pattern matches everything under the root directory. It defines one datum per state, which means that all the cities for a given state are processed together by a single worker, but each state is processed independently.||If you add a new file |
| ||This pattern matches files only under the ||If you add a new file |
| ||This pattern matches all files under the root directory that start with the character ||In the example, the |
| ||This pattern matches everything that's two levels deep relative to the root.||If we add County sub-directories to our states, |
| ||The match is applied at all levels of your directory structure. This is a recursive glob pattern. Let's look at the additional example below for more detail.|
Example: The case of the
/** glob pattern
Say we have the following repo structure:
/nope1.txt /test1.txt /foo-1 /nope2.txt /test2.txt /foo-2 /foo-2_1 /nope3.txt /test3.txt /anothertest.txt
teststarting from our input repo's root directory. In this case, the resulting datums will be:
- /test1.txt - /foo-1/test2.txt - /foo-2/foo-2_1/test3.txt - /foo-2/foo-2_1/anothertest.txt
Test a Glob pattern¶
You can use the
pachctl glob file command to preview which filesystem objects a pipeline defines as datums. This command helps you to test various glob patterns before you use them in a pipeline.
- If you set the
/, Pachyderm detects all top-level filesystem objects in the
trainrepository as one datum:
pachctl glob file train@master:/
NAME TYPE SIZE / dir 15.11KiB
- If you set the
/*, Pachyderm detects each top-level filesystem object in the
trainrepository as a separate datum:
pachctl glob file train@master:/*
NAME TYPE SIZE /IssueSummarization.py file 1.224KiB /requirements.txt file 74B /seq2seq_utils.py file 13.81KiB
Test your Datums¶
The granularity of your datums defines how your data will be distributed across the available workers allocated to a job. Pachyderm allows you to check those datums:
- for a pipeline currently being developed
- for a past job
Testing your glob pattern before creating a pipeline¶
You can use the
pachctl list datum -f <my_pipeline_spec.json> command to preview the datums defined by a pipeline given its specification file.
The pipeline does not need to have been created for the command to return the list of datums. This "dry run" helps you adjust your glob pattern when creating your pipeline.
pachctl list datum -f edges.json
ID FILES STATUS TIME - images@b8687e9720f04b7ab53ae8c64541003b:/46Q8nDz.jpg - - - images@b8687e9720f04b7ab53ae8c64541003b:/8MN9Kg0.jpg - - - images@b8687e9720f04b7ab53ae8c64541003b:/Togu2RY.jpg - - - images@b8687e9720f04b7ab53ae8c64541003b:/g2QnNqa.jpg - - - images@b8687e9720f04b7ab53ae8c64541003b:/w7RVTsv.jpg - -
Running list datum on a past job¶
You can use the
pachctl list datum <pipeline>@<job_ID> command to check the datums processed by a given job.
$ pachctl list datum edges@b8687e9720f04b7ab53ae8c64541003b
ID FILES STATUS TIME a4149cd1907145f982e0eb49c50af3f1d4d8fecaa8647d62f2d9d93e30578df8 images@b8687e9720f04b7ab53ae8c64541003b:/w7RVTsv.jpg success Less than a second e2b4628dd88b179051ba0576e06fac12ae2e4d16165296212d0e98de501d17df images@b8687e9720f04b7ab53ae8c64541003b:/Togu2RY.jpg success Less than a second 353b6d2a5ac78f56facc7979e190affbb8f75c6f74da84b758216a8df77db473 images@7856142de8714c11b004610ea7af2378:/8MN9Kg0.jpg skipped Less than a second b751702850acad5502dc51c3e7e7a1ac10ba2199fdb839989cd0c5430ee10b84 images@fc9a12ee149a4499a1a7da0a31971b37:/46Q8nDz.jpg skipped Less than a second de9e3703322eff2ab90e89ff01a18c448af9870f17e78438c5b0f56588af9c44 images@7856142de8714c11b004610ea7af2378:/g2QnNqa.jpg skipped Less than a second
In this example, you can see that the job
b8687e9720f04b7ab53ae8c64541003b only processed 2 datums from the images input repo. The rest was skipped as it had been processed by previous jobs already. Notice that the ID of the datums is now showing.
Stats and Datum Metadata
list datumon a given job execution of a pipeline allows you to additionally display the STATUS (running, failed, success) and TIME of each datum.
You might want to follow up with inspect datum pipeline@job_number datum ID to detail the files that a specific datum includes.System Response:
$ pachctl inspect datum edges@b8687e9720f04b7ab53ae8c64541003b a4149cd1907145f982e0eb49c50af3f1d4d8fecaa8647d62f2d9d93e30578df8Add
ID a4149cd1907145f982e0eb49c50af3f1d4d8fecaa8647d62f2d9d93e30578df8 Job ID b8687e9720f04b7ab53ae8c64541003b State SUCCESS Data Downloaded 606.3KiB Data Uploaded 26.96KiB Total Time 582.000134ms Download Time 40.062075ms Process Time 535.387088ms Upload Time 6.550971ms PFS State: REPO COMMIT PATH edges.meta b8687e9720f04b7ab53ae8c64541003b /pfs/a4149cd1907145f982e0eb49c50af3f1d4d8fecaa8647d62f2d9d93e30578df8 Inputs: REPO COMMIT PATH images b8687e9720f04b7ab53ae8c64541003b /w7RVTsv.jpg
--rawfor a full JSON version of the datum's metadata.