Support PPE profiling for HTTPCache / HTTPCachedFS

[KantaTamura]

This PR resolves the CachedHttpFs / HttpCache task in #258

Sample program to check tracing

import json
import tempfile
import pytorch_pfn_extras as ppe

from pfio.v2 import HTTPCachedFS, Local
from pfio.cache import HTTPCache
from pfio.testing import make_http_server


def cache_httpcache():
    filename = "cache_httpcache.json"
    tracer = ppe.profiler.get_tracer()

    with make_http_server() as (httpd, port):
        http_cache = f"http://localhost:{port}/"
        cache = HTTPCache(1, http_cache,
                          do_pickle=True, trace=True)

        cache.put(0, b"foo")
        assert b"foo" == cache.get(0)

    dict = tracer.state_dict()
    keys = [event["name"] for event in json.loads(dict['_event_list'])]
    print(keys)

    writer = ppe.writing.SimpleWriter(out_dir="")
    tracer.initialize_writer(filename, writer)
    tracer.flush(filename, writer)


def fs_httpcache():
    filename = "fs_httpcache.json"
    tracer = ppe.profiler.get_tracer()

    local_filename = "testfile"
    content = b"abcdabcd"

    with make_http_server() as (httpd, port), tempfile.TemporaryDirectory() as tmpdir:
        http_cache = f"http://localhost:{port}/"

        with Local(tmpdir, trace=True) as local_fs:
            fs = HTTPCachedFS(http_cache, local_fs)

            with fs.open(local_filename, mode="wb") as fp:
                fp.write(content)
            with fs.open(local_filename, mode="rb") as fp:
                assert fp.read(-1) == content
            with fs.open(local_filename, mode="rb") as fp:
                assert fp.read(-1) == content

    dict = tracer.state_dict()
    keys = [event["name"] for event in json.loads(dict['_event_list'])]
    print(keys)

    writer = ppe.writing.SimpleWriter(out_dir="")
    tracer.initialize_writer(filename, writer)
    tracer.flush(filename, writer)


cache_httpcache()
fs_httpcache()

• HTTPCache output

['pfio.cache.http.conn:put:request', 'pfio.cache.http.conn:put', 'pfio.cache.http:put', 'pfio.cache.http.conn:get:request', 'pfio.cache.http.conn:get', 'pfio.cache.http:get']

rendering of the output json (cache_httpcache.json) file with chrome://tracing is shown below

• HTTPCachedFS output

['pfio.v2.Local:open', 'pfio.v2.http_cache:open', 'pfio.v2.Local:write', 'pfio.v2.Local:exit-context', 'pfio.v2.http_cache:open', 'pfio.cache.http.conn:get:request', 'pfio.cache.http.conn:get', 'pfio.v2.Local:stat', 'pfio.v2.Local:open', 'pfio.v2.Local:read', 'pfio.v2.Local:exit-context', 'pfio.cache.http.conn:put:request', 'pfio.cache.http.conn:put', 'pfio.v2.http_cache:load_file', 'pfio.v2.http_cache:read', 'pfio.v2.http_cache:open', 'pfio.cache.http.conn:get:request', 'pfio.cache.http.conn:get', 'pfio.v2.http_cache:load_file', 'pfio.v2.http_cache:read']

rendering of the output json (fs_httpcache.json) file with chrome://tracing is shown below

[k5342]

one minor comment

[k5342]

Perhaps is_traced is better grammatically; what do you think?

[KantaTamura]

Yes, I think so