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Posted to notifications@couchdb.apache.org by GitBox <gi...@apache.org> on 2020/02/25 11:28:09 UTC
[GitHub] [couchdb] iilyak opened a new pull request #2597: Add support for
X-Couch-Trace header
iilyak opened a new pull request #2597: Add support for X-Couch-Trace header
URL: https://github.com/apache/couchdb/pull/2597
## Overview
Sometime it is useful to be able to trigger open tracing using single header in the request.
For such cases this PR introduces `X-Couch-Trace` header. This header combined with the following config in `default.ini` would cause tracing of the request.
```
[tracing.filters]
all = (#{external := External}) when External == true -> true
```
*Note*:
- We check for existence of the header and don't care about its value
- This feature could allow malicious user to launch resource exhaustion attack on tracing infrastructure (elastic search backend of jaeger). You are absolutely safe if you don't use `(#{external := External}) when External == true`.
## Testing recommendations
1. update rel/overlay/etc/default.ini as follows
```
diff --git a/rel/overlay/etc/default.ini b/rel/overlay/etc/default.ini
index 592445c28..69091eab3 100644
--- a/rel/overlay/etc/default.ini
+++ b/rel/overlay/etc/default.ini
@@ -572,15 +572,15 @@ min_priority = 2.0
; - jaeger.thrift over udp
; - jaeger.thrift over http
; ## Common settings
-; enabled = false ; true | false
-; app_name = couchdb ; value to use for the `location.application` tag
-; protocol = udp ; udp | http - which reporter to use
+enabled = true ; true | false
+app_name = couchdb ; value to use for the `location.application` tag
+protocol = http ; udp | http - which reporter to use
; ## jaeger.thrift over udp reporter
; thrift_format = compact ; compact | binary
; agent_host = 127.0.0.1
; agent_port = 6831
; ## jaeger.thrift over udp reporter
-; endpoint = http://127.0.0.1:14268
+endpoint = http://127.0.0.1:14268
[tracing.filters]
;
@@ -603,4 +603,4 @@ min_priority = 2.0
; corresponding operation name key configured. Thus, users can easily
; log every generated trace by including the following:
;
-; all = (#{}) -> true
+all = (#{external := External}) when External == true -> true
```
2. start jaeger in docker container
```
docker run -d -p 6831:6831/udp -p 16686:16686 -p 14268:14268 jaegertracing/all-in-one:1.14
```
3. Start couchdb dev/run --admin=adm:pass
4. Create database curl -X PUT -u adm:pass http://127.0.0.1:15984/test
5. Query database curl -X GET -u adm:pass http://127.0.0.1:15984/test/_all_docs -H 'X-Couch-Trace: true'
6. Open http://localhost:16686/ in the browser and search for spans (you should find some traces)
## Checklist
- [x] Code is written and works correctly
- [ ] Changes are covered by tests
- [ ] Any new configurable parameters are documented in `rel/overlay/etc/default.ini`
- [ ] A PR for documentation changes has been made in https://github.com/apache/couchdb-documentation
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[GitHub] [couchdb] iilyak merged pull request #2597: Add support for
X-Couch-Trace header
Posted by GitBox <gi...@apache.org>.
iilyak merged pull request #2597: Add support for X-Couch-Trace header
URL: https://github.com/apache/couchdb/pull/2597
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[GitHub] [couchdb] iilyak commented on issue #2597: Add support for
X-Couch-Trace header
Posted by GitBox <gi...@apache.org>.
iilyak commented on issue #2597: Add support for X-Couch-Trace header
URL: https://github.com/apache/couchdb/pull/2597#issuecomment-591981275
Currently open tracing implementation in CouchDB supports B3 headers (see https://github.com/apache/couchdb/tree/prototype/fdb-layer/src/ctrace#b3-propagation). The B3 headers were invented by zipkin and ended up in some opentracing solutions.
Unfortunately semantics of B3 headers doesn't allow expressing the following:
* I want to trace this request but I don't have RootSpan please create it for me
I was not aware that there is a concurrent W3C standard. It is probably quite new. Here is what I found on Jaeger page:
```
In the future Jaeger will support the upcoming W3C Trace-Context specification.....
```
I briefly looked into W3C standard this morning. It doesn't look like there is a specific header which can be used to enable tracing without specifying root span at the same time. Although I admit my 15 min reading of the spec could miss it.
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[GitHub] [couchdb] iilyak commented on issue #2597: Add support for
X-Couch-Trace header
Posted by GitBox <gi...@apache.org>.
iilyak commented on issue #2597: Add support for X-Couch-Trace header
URL: https://github.com/apache/couchdb/pull/2597#issuecomment-593338317
> But keep an eye on opentelemetry :), the spec and many of the clients (hopefully including the Erlang/Elixir library) will be going into beta in March.
Thank you this is definitely good to know.
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[GitHub] [couchdb] tsloughter commented on issue #2597: Add support for
X-Couch-Trace header
Posted by GitBox <gi...@apache.org>.
tsloughter commented on issue #2597: Add support for X-Couch-Trace header
URL: https://github.com/apache/couchdb/pull/2597#issuecomment-591718469
Why a custom header? W3C has a trace header https://www.w3.org/TR/trace-context/ and it is being supported by many languages and vendors in the OpenTracing/OpenCensus successor https://opentelemetry.io/, including Erlang/Elixir https://github.com/open-telemetry/opentelemetry-erlang-api/
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[GitHub] [couchdb] tsloughter commented on issue #2597: Add support for
X-Couch-Trace header
Posted by GitBox <gi...@apache.org>.
tsloughter commented on issue #2597: Add support for X-Couch-Trace header
URL: https://github.com/apache/couchdb/pull/2597#issuecomment-592020554
Ah ok, now I get what you are doing.
For B3 I think they actually have a "debug" header that you can send without id's that is meant to force a trace. But w3c traceheader I don't think has added such a feature yet.
Probably no reason to depend on it for this simple case of forcing a trace with no root from the client.
But keep an eye on opentelemetry :), the spec and many of the clients (hopefully including the Erlang/Elixir library) will be going into beta in March. Can't tell what you use currently for tracing and reporting traces -- something custom and built-in?
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