Performance regression with graal-based image

[gmile]

Describe the bug
When using graal docker image introduced in #53, .docx templates are rendered slower.

To Reproduce

1. download & extract a .docx template file into a /tmp/templates directory: lipsum_sample.docx.zip

2. Run two different containers, side by side (in separate Terminal windows):

   docker run --rm --name stencil-0.3.10       --publish 5000:8080 --volume /tmp/templates:/templates ghcr.io/erdos/stencil:0.3.10
   docker run --rm --name stencil-0.3.10-graal --publish 5001:8080 --volume /tmp/templates:/templates ghcr.io/erdos/stencil:0.3.10-graal

3. Run the tests:

   • for regular container:

     $ bash -c "for test in 1 2 3 4 5; do time curl -s localhost:5000/lipsum_sample.docx --header 'content-type: application/json' --data '{}' > /tmp/lipsum_sample_regular.docx; done"
     real    0m10.385s
     user    0m0.006s
     sys     0m0.010s
     
     real    0m4.191s
     user    0m0.005s
     sys     0m0.008s
     
     real    0m4.245s
     user    0m0.005s
     sys     0m0.008s
     
     real    0m4.239s
     user    0m0.005s
     sys     0m0.008s
     
     real    0m4.263s
     user    0m0.004s
     sys     0m0.008s
     $

   • for graal container:

     $ bash -c "for test in 1 2 3 4 5; do time curl -s localhost:5001/lipsum_sample.docx --header 'content-type: application/json' --data '{}' > /tmp/lipsum_sample_graal.docx; done"
     
     real    0m19.201s
     user    0m0.005s
     sys     0m0.008s
     
     real    0m12.841s
     user    0m0.004s
     sys     0m0.010s
     
     real    0m13.111s
     user    0m0.004s
     sys     0m0.007s
     
     real    0m12.936s
     user    0m0.004s
     sys     0m0.008s
     
     real    0m13.117s
     user    0m0.004s
     sys     0m0.007s
     $

4. Notice how graal-based image is consistently slower.

5. Stop the containers:

   docker kill stencil-0.3.10
   docker kill stencil-0.3.10-graal

Expected behavior
Performance of application in a graal-based image is on par with that of a regular one, or faster.

However, I know very little about GraalVM, as well as the goals to build a graalvm-based image. Perhaps, performance was not among the goals for this image.

Screenshots
No screenshots.

Documents
I've attached a link to the document above. It is a 800+ pages .docx file with no template placeholders in it.

Office versions:
Not applicable as far as I can see.

Environment where template is rendered:

• Stencil version: 0.3.10
• Java version: I used regular and graal stencil images.
• Operating System version: 10.14.6 (18G103)
• Docker version: 19.03.13, build 4484c46d9d

Additional context
No additional context.