How do I use http keep-alive in OTLP/HTTP ?

[chinawilon]

I use the OpenTelemetry-Collector as agent co-located with my application, and I found something not meeting expectations!

config yaml

exporters:
  otlp:
    endpoint: pl.ap-guangzhou.apm.tencentcs.com:4317
    tls:
      insecure: true
processors:
  batch:
    send_batch_size: 10000
    timeout: 10s
receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 127.0.0.1:4317
      http:
        endpoint: 127.0.0.1:4318
service:
  telemetry:
    logs:
      level: debug
    metrics:
      level: detailed
      address: 0.0.0.0:18888
  pipelines:
    traces:
      processors:
        - batch
      exporters:
        - otlp
      receivers:
        - otlp

• Use short connections, and How do I use http keep-alive?

11:55:17.660931 lo    In  IP localhost.51988 > localhost.4318: Flags [S], seq 3007409422, win 65495, options [mss 65495,sackOK,TS val 2231205146 ecr 0,nop,wscale 7], length 0
11:55:17.660941 lo    In  IP localhost.4318 > localhost.51988: Flags [S.], seq 3691109094, ack 3007409423, win 65483, options [mss 65495,sackOK,TS val 2231205146 ecr 2231205146,nop,wscale 7], length 0
11:55:17.660950 lo    In  IP localhost.51988 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2231205146 ecr 2231205146], length 0
11:55:17.660998 lo    In  IP localhost.51988 > localhost.4318: Flags [P.], seq 1:4410, ack 1, win 512, options [nop,nop,TS val 2231205146 ecr 2231205146], length 4409
11:55:17.661002 lo    In  IP localhost.4318 > localhost.51988: Flags [.], ack 4410, win 490, options [nop,nop,TS val 2231205146 ecr 2231205146], length 0
11:55:17.661276 lo    In  IP localhost.4318 > localhost.51988: Flags [P.], seq 1:116, ack 4410, win 512, options [nop,nop,TS val 2231205146 ecr 2231205146], length 115
11:55:17.661292 lo    In  IP localhost.51988 > localhost.4318: Flags [.], ack 116, win 512, options [nop,nop,TS val 2231205146 ecr 2231205146], length 0
11:55:17.662797 lo    In  IP localhost.51988 > localhost.4318: Flags [F.], seq 4410, ack 116, win 512, options [nop,nop,TS val 2231205148 ecr 2231205146], length 0
11:55:17.662853 lo    In  IP localhost.4318 > localhost.51988: Flags [F.], seq 116, ack 4411, win 512, options [nop,nop,TS val 2231205148 ecr 2231205148], length 0

• Many ACK from Collector to Application, and What's it used for?

root@VM-80-2-ubuntu:/data/web# tcpdump -i any port 4318
tcpdump: data link type LINUX_SLL2
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
11:47:12.461706 lo    In  IP localhost.4318 > localhost.36454: Flags [.], ack 3353824839, win 512, options [nop,nop,TS val 2230719946 ecr 2230704842], length 0
11:47:12.461718 lo    In  IP localhost.36454 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2230719946 ecr 2202369654], length 0
11:47:12.717707 lo    In  IP localhost.4318 > localhost.43862: Flags [.], ack 1629484599, win 512, options [nop,nop,TS val 2230720202 ecr 2230705098], length 0
11:47:12.717714 lo    In  IP localhost.43862 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2230720202 ecr 2214981986], length 0
11:47:12.973740 lo    In  IP localhost.4318 > localhost.54468: Flags [.], ack 298931131, win 512, options [nop,nop,TS val 2230720458 ecr 2230705355], length 0
11:47:12.973752 lo    In  IP localhost.54468 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2230720459 ecr 2217383604], length 0
11:47:13.741729 lo    In  IP localhost.4318 > localhost.37488: Flags [.], ack 1290580590, win 512, options [nop,nop,TS val 2230721226 ecr 2230706122], length 0
11:47:13.741736 lo    In  IP localhost.37488 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2230721227 ecr 2167737606], length 0
11:47:13.745693 lo    In  IP localhost.4318 > localhost.35244: Flags [.], ack 1765188201, win 512, options [nop,nop,TS val 2230721230 ecr 2230706123], length 0
11:47:13.745702 lo    In  IP localhost.35244 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2230721230 ecr 2204772629], length 0
11:47:14.765712 lo    In  IP localhost.4318 > localhost.59602: Flags [.], ack 3169972842, win 512, options [nop,nop,TS val 2230722250 ecr 2230707146], length 0
11:47:14.765722 lo    In  IP localhost.59602 > localhost.4318: Flags [.], ack 1, win 512, options [nop,nop,TS val 2230722250 ecr 2224589987], length 0