Enabling and Using Tracing Functionality
Introduction
On this page, we will enable and use the Opentelemetry Tracing functionality to get a visual representation of our Extension. Once again, we will use the UIP VSCode Plugin to test our changes, for now.
Step 1 - Enabling Tracing
Go ahead and open configurations.yml and add in the properties block:
properties:
agent:
log_level: Info
netname: UIP-DBG-01
otel:
enable_tracing: true
export_metrics: false
trace_endpoint: http://192.168.56.11:4318
metrics_endpoint: http://localhost:4318
service_name: vscode-uip-debugger
uip_service_name: uip/${extension_name}
api:
extension_start:
- name: es1
log_level: Inherited
runtime_dir: /home/shrey/dev/extensions/test/OtelDemoTest
fields:
src_folder: /tmp/test_src
dst_folder: /tmp/test_dst
file_type:
- txt
As part of UIP VSCode Plugin version 2.1.0, the properties -> agent object was enhanced with new netname and otel properties. To enable tracing, we have set enable_tracing to true and set trace_endpoint to the Opentelemetry Collector URL (this will need to be changed according to your setup).
Enabling in UA
Similar properties exist in uags.conf and omss.conf that can be used to enable tracing in the Agent. See OTEL_ENABLE_TRACING - UAG configuration option and OTEL_ENABLE_TRACING - OMS configuration option.
Step 2 – Visualizing Default Spans
Now that we have enabled tracing, we actually don't have to do anything else to get a basic trace. Go ahead and delete all the files inside /tmp/test_dst and debug the Extension again using F5. Once finished, head on over to Jaeger (or whatever trace visualization tool you have set up) and you should see:
Without modifying the Extension code at all, we have a meaningful way of looking at the Extension instance. Go ahead and inspect the spans (debug start, api: extension_start, etc.) by clicking on them; you will find useful information such as the fields passed into extension_start(), rc, unv_output etc. all consolidated in one place.
Step 3 – Adding Additional Spans
Even though the default spans above offer insight into our Extension, we are not able to clearly see when a file gets transferred or even how long it takes. Let's add some custom spans to capture this information. Go ahead and update extension.py as follows:
from __future__ import print_function
from universal_extension import UniversalExtension
from universal_extension import ExtensionResult
from universal_extension import ui
from universal_extension import logger
from universal_extension import utility
from universal_extension import otel
import time
import shutil
import os
import random
import json
if otel.is_compatible:
from opentelemetry import trace
class Extension(UniversalExtension):
def __init__(self):
"""Initializes an instance of the 'Extension' class"""
# Call the base class initializer
super(Extension, self).__init__()
self.stop = False
self.setup_tracer()
def setup_tracer(self):
if otel.is_compatible:
self.tracer = trace.get_tracer(__name__)
else:
self.tracer = utility.NoOp()
def transfer_file(self, src_path, dst_path, span):
span.set_attributes({"src_file": src_path, "dst_folder": dst_path})
# Ensure destination directory exits
if not os.path.exists(dst_path):
raise FileNotFoundError(
"Destination directory ({0}) does not exist".format(dst_path)
)
# Ensure the source file is not already present in the destination
# directory (unless overwrite is selected)
if os.path.exists(os.path.join(dst_path, os.path.basename(src_path))):
logger.info(
"'{0}' already exists in '{1}'".format(
os.path.basename(src_path), dst_path
)
)
if otel.is_compatible:
span.set_status(
trace.Status(
status_code=trace.StatusCode.ERROR,
description="'{0}' already exists in '{1}'".format(
os.path.basename(src_path), dst_path
),
)
)
return False
shutil.copy(src_path, dst_path)
time.sleep(random.uniform(0, 2))
return True
def extension_start(self, fields):
"""Required method that serves as the starting point for work performed
for a task instance.
Parameters
----------
fields : dict
populated with field values from the associated task instance
launched in the Controller
Returns
-------
ExtensionResult
once the work is done, an instance of ExtensionResult must be
returned. See the documentation for a full list of parameters that
can be passed to the ExtensionResult class constructor
"""
files_transferred = []
src = fields["src_folder"]
dst = fields["dst_folder"]
file_types = [
ft.lower() if ft.startswith(".") else "." + ft.lower()
for ft in fields["file_type"]
]
if not os.path.exists(src):
raise FileNotFoundError("'{0}' does not exist".format(src))
all_file_list = os.listdir(src)
# filter the files
file_list = []
for f in all_file_list:
file_path = os.path.join(src, f)
file_type = os.path.splitext(file_path)[1]
if os.path.isfile(file_path) and file_type in file_types:
file_list.append(file_path)
logger.info(
"Found {0} files that can be transferred".format(len(file_list))
)
for f in file_list:
if self.stop:
break
span_ctx = (
utility.noop_context()
if not otel.is_compatible
else self.tracer.start_as_current_span("transferring file")
)
with span_ctx as span:
if self.transfer_file(f, dst, span):
files_transferred.append(f)
ui.update_progress(
int(len(files_transferred) / len(file_list) * 100)
)
logger.info("Transferred '{0}' to '{1}'".format(f, dst))
return ExtensionResult(
rc=0 if len(file_list) - len(files_transferred) == 0 else 1,
unv_output="The following files were transferred: \n {0}".format(
json.dumps(files_transferred)
),
message="{0} files found and {1} files transferred".format(
len(file_list), len(files_transferred)
),
)
def extension_cancel(self):
self.stop = True
- Lines 7-8 import the new
utilityandotelmodules used to integrate Opentelemetry into the Extension. - Lines 16-17 conditionally import the
tracemodule fromopentelemetry. We are doing it conditionally because Opentelemetry is only supported on Python 3.7 and higher. If your Extension is not supported on <3.7, then you do not need to guard the import withotel.is_compatible - Lines 27-33:
- Lines 29-33 define a separate method to set up the Opentelemetry tracer used to create custom spans. Once again, it is guarded with
otel.is_compatible. If Opentelemetry is not compatible, then we assignutility.NoOp()toself.tracer, which will mimic the actual tracer object without affecting anything. - Line 27 calls the
self.setup_tracer()method
- Lines 29-33 define a separate method to set up the Opentelemetry tracer used to create custom spans. Once again, it is guarded with
- Lines 35-66:
- Line 35 modifies the
transfer_file()method to accept an additional parameter calledspan - Line 36 adds the source file and the destination folder as attributes on the
spanobject - Lines 52-60 explicitly set the status of the
spanas error when the source file exists in the destination folder.
- Line 35 modifies the
- Lines 116-129:
- Lines 116-120 create a
span_ctxvariable that will store the Span Context. This is needed to ensure the Extension does not break, if Opentelemetry is not compatible. - Lines 122-128 use
span_ctxto create a Span object calledspanwhich is then passed intoself.transfer_file.
- Lines 116-120 create a
Now, let's visualize our changes. From the last debugging session, the /tmp/test_dst folder should contain a.txt and b.txt. Keep these in there (if you have deleted them, just copy them manually). Go ahead and modify the configurations.yml to also transfer zip and json files:
fields:
src_folder: /tmp/test_src
dst_folder: /tmp/test_dst
file_type:
- txt
- zip
- json
Once modified, press F5 and head on over to Jaeger. You should see:
We can now clearly see how long each file takes to transfer. We can see that a.txt and b.txt failed to transfer because they were already in the destination folder. c.zip and d.json succeeded, and we can see their transfer times. Inspect the spans, and you will be able to see the custom src_file and dst_folder attributes that we added.