[SLING-5459] Recording of tracer logs

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Log Tracer 1.0.0
• Component/s: Extensions
• Assignee: Chetan Mehrotra
• Reporter: Chetan Mehrotra
• Created: 27/Jan/16 12:50
• Updated: 25/Apr/16 09:22
• Resolved: 19/Apr/16 10:00

Description

Sling Log Tracer currently provides support for fine grained control of enabling logs for specific request. To make this log more accessible it would be useful to have a feature where the client can also fetch the logs from specific request over HTTP.

This feature would work like below

1. Client sends an HTTP request with header Sling-Tracer-Record​ set to true

   curl -D - -u admin:admin \
     -H "Sling-Tracer-Record : true" \
    -d "./jcr:content/jcr:title=Summer Collection" \
    -d ":name=summer-collection" \
    -d "./jcr:primaryType=sling:Folder" \
    -d "./jcr:content/jcr:primaryType=nt:unstructured" \
    -d "tracers=oak-writes" \
    http://localhost:4802/content/dam/
   

2. Server includes a request id as part of Sling-Tracer-Request-Id response headers

   HTTP/1.1 201 Created
   Date: Wed, 27 Jan 2016 07:30:22 GMT
   Sling-Tracer-Request-Id: 9b5b01f6-f269-47c3-a889-2dc8d4d7938f
   X-Content-Type-Options: nosniff
   X-Frame-Options: SAMEORIGIN
   Location: /content/dam/summer-collection
   Content-Type: text/html; charset=UTF-8
   Transfer-Encoding: chunked
   

3. The logs in json format can then be fetched like http://localhost:4802/system/console/tracer/9b5b01f6-f269-47c3-a889-2dc8d4d7938f.json (see attached output. it includes following data for now. It can be extended as per need
   1. RequestProgressTracker logs
   2. JCR Queries made

Key points

1. Request id is randomly generated
2. The access to request log is via Web Console Plugin servlet hence its only accessible to admin user account
3. The request data would only be recorded for those request which have the ​Sling-Tracer-Record header set. The data would be kept in memory for some time with the assumption that client would fetch it soon. After some time the data would expire
4. This feature would need to explicitly enabled via config option
5. The feature is somewhat similar to 'Recent Request' support. However it exposes a JSON rendition and only keeps the data for request where client requested that.
6. For this feature dependency is added for Guava Cache to make use of space bound/expiring cache. We can to an extent use LinkedHashMap but given that Guava is now being used in Sling for Oak it makes sense to make use of its feature. If required can look into embedding minimum required set