I am using cloudfoundry with multiple instances. I am trying to generate heapdump using /actuator endpoint of spring.
My doubt is in case of cloudfoundry env where at a time 2 instances running , for which instance it will generate the heapdump. How to know the heapdump is for which instance and is there anyway we can hit a specific instance .
Note: I want to use spring boot actuator /heapdump url option only .
My doubt is in case of cloudfoundry env where at a time 2 instances running , for which instance it will generate the heapdump.
You can't really know where the request will land in advance. Requests to your app instances are load balanced by Gorouter (round-robin), so unless there is no traffic to your app, the request could hit either backend app instance.
You can, however, determine the app instance to which a request went, after the fact.
In a terminal, run cf logs for your app.
In another terminal, run curl -v .... The output will have a header called X-Vcap-Request-Id. Copy that guid.
< HTTP/1.1 200 OK
< Content-Type: text/html; charset=UTF-8
< Date: Thu, 20 May 2021 12:27:39 GMT
< Server: Apache
< Vary: Accept-Encoding
< X-Vcap-Request-Id: c254c0df-c03f-475f-6210-fe3eea7cf28a # <-- this line
< Content-Length: 399
Look in the output of cf logs for the guid you captured in the previous step. This will identify the access log entry for the request (see the vcap_request_id field). The app_index field on the same record will tell you which app received the request.
2021-05-20T08:27:39.85-0400 [RTR/0] OUT php-info.apps.pcfone.io - [2021-05-20T12:27:39.848995848Z] "GET / HTTP/1.1" 200 0 399 "-" "curl/7.64.1" "192.168.4.4:34744" "192.168.16.31:61075" x_forwarded_for:"23.115.134.147, 192.168.4.4" x_forwarded_proto:"https" vcap_request_id:"c254c0df-c03f-475f-6210-fe3eea7cf28a" response_time:0.008122 gorouter_time:0.000506 app_id:"c1985534-3ca3-4ada-8bd2-b9b7a57de440" app_index:"0" x_cf_routererror:"-" x_b3_traceid:"5bc96459099edbfd" x_b3_spanid:"5bc96459099edbfd" x_b3_parentspanid:"-" b3:"5bc96459099edbfd-5bc96459099edbfd"
How to know the heapdump is for which instance and is there anyway we can hit a specific instance .
This is what you want: https://docs.cloudfoundry.org/devguide/deploy-apps/routes-domains.html#surgical-routing
If you send the X-Cf-App-Instance you can pick a specific app instance. You can then target a specific app instance or ensure you get heap dumps from all of your app instances.
Ex: curl myapp.example.com -H "X-Cf-App-Instance: 5cdc7595-2e9b-4f62-8d5a-a86b92f2df0e:9"
The contents of X-Cf-App-Instance is X-Cf-App-Instance: APP_GUID:APP_INDEX. You can retrieve your app guid with cf app myapp --guid. The APP_INDEX is zero-based, so 0 is the first instance, 1 is the second instance, etc...