Is it reproduced with a recent Jenkins version?

No response from the reporter, so resolving as incomplete.

Reopening as per JENKINS-29121.

I'm not seeing this behaviour with large file parameters, whether the build is executed on master or a slave.

But I'm not using buildWithParameters, but rather the build format documented here:
https://wiki.jenkins-ci.org/display/JENKINS/Remote+access+API#RemoteaccessAPI-Submittingjobs

i.e.

curl -v -X POST http://jenkins.local:8080/job/upload-test/build \
  --form f0=@/data/fw123.bin \
  --form json='{"parameter": [{"name":"firmware.bin", "file":"f0"}]}'

When the job is running, I see "Copying file to firmware.bin" in the console output.
But checking /tmp and the java.io.tmpdir directory on the slave while this is happening shows no temporary files being created.

toshee2000: Can you provide more detail on exactly how you're starting a job?

Basically, I execute a job by POSTing to Jenkins using python's requests module via a remote PC.
i.e.

import requests
with open("file.zip", "rb") as z:
    file_to_send = {"jenkins_file.zip": z}
    requests.post("http://jenkins.local:8080/job/my_job/buildWithParameters", files=file_to_send)

An upload_*.tmp file is created in /tmp directory of the master after executing the script. The master then builds the job on one of its nodes but the tmp file is not deleted even after the build is completed.

I observed that jenkins_file.zip is created in the node's workspace once the job starts building (as expected) but no file is copied/created in the node's java.io.tmpdir directory.

The guide I used for configuring my job's parameters can be found here:
https://wiki.jenkins-ci.org/display/JENKINS/Parameterized+Build

orrc:
I tried using your curl command with my job but it doesn't seem to set the parameters correctly. The parameters do not reflect on the http://jenkins.local:8080/job/my_job/build_number/parameters page. Although, I noticed this time, it automatically deleted the upload_*.tmp that was generated.

orrc Jenkins itself (on job/foo/api) documents that parameterized builds should be started via /buildWithParameters. The POST to /build with JSON is just replicating what the browser does when you submit the form and IMO therefore more fragile/subject to change.

Update:
I encountered another problem with the upload_*.tmp files.

I executed the job many times such that several builds will be queued on one node (and several upload_*.tmp files created in /tmp directory of the master), and then I restarted Jenkins in the middle. Those builds before restart were built successfully (upload_*.tmp files still not deleted). The remaining builds after restart, surprisingly, failed with the following error in the console:

FATAL: null
java.lang.NullPointerException
	at hudson.model.FileParameterValue$2.setUp(FileParameterValue.java:143)
	at hudson.model.Build$BuildExecution.doRun(Build.java:156)
	at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:537)
	at hudson.model.Run.execute(Run.java:1744)
	at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
	at hudson.model.ResourceController.execute(ResourceController.java:98)
	at hudson.model.Executor.run(Executor.java:374)

From previous successful builds, the console showed:

Copying file to jenkins_file.zip

All upload_*.tmp files were still in /tmp directory after the error occurred.

Added:
Maybe this is an entirely different bug. Based on my tests, only file parameters greater than 10kB generate upload_*.tmp files in /tmp directory. The error described above also occurred even for file parameters smaller than 10kB, which didn't create an upload_*.tmp in the first place.

This is still an issue in 2.121.3, and there is no viable workaround that I can find.