option to drop post_action

[mikz]

#289 revealed limitations of post_action

this PR offers new experimental flag to turn off post_action
and use nginx timers instead

setting APICAST_REPORTING_THREADS to a value greater than 0 is going to enable asynchronous reporting to backend.

---

doing synchronous call in the post_action will
push the latency to the client on the same connection

using timers we can make that fully asynchronous
not being tied to the request phase at all

setting APICAST_REPORTING_THREADS environment variable
to a number greater than 0 will enable reporting in asynchronous
timers instead of synchronous call

the number defines a maximum number of parallel calls
to backend per worker

if there is new report coming but no connections is available
APIcast will wait for up to 10 seconds before falling back to the
synchronous call

please note this is experimental feature

TODO

• write a test case for Avoid throwing an error when there is no cached proxy object #302 (ca45731)

[octobot]

Spell Checker found issues

doc/management-api.md

Line	Typo
32	See [example-config.json](../examples/configurati
32	See [example-config.json](../examples/configuration/ex

doc/parameters.md

Line	Typo
3	APIcast v2 has a number of parameters co
3	ariables) that can modify the behavior of the gateway. The following
5	e that when deploying APIcast v2 with OpenShift, some of thee
15	Default: **stderr**
17	or more information. The file pathcan be either absolute, or relati
21	nfo
21	warn
46	Default: "apicast"
77	Values: a number > **60**
78	Default: 0
80	r. The value should be set to 0 or more than 60. For example,
80	ould be set to 0 or more than 60. For example, if `APICAST_CON
80	ONFIGURATION_CACHE` is set to 120, the gateway will reload the
80	eload the configuration every 2 minutes (120 seconds).
80	onfiguration every 2 minutes (120 seconds).
84	Default: "127.0.0.1"
86	ning Redis instance for OAuth 2.0 flow. REDIS_HOST parameter
90	Default: 6379
92	ning Redis instance for OAuth 2.0 flow. REDIS_PORT parameter
98	ning Redis instance for OAuth 2.0 flow. REDIS_URL parameter c
98	e used to set the full URI as DSN format like: `redis://PASSWOR
103	Default: 604800
105	uthenticate using OAuth, this param specifies the TTL (in seconds
109	pty, the DNS resolver will be autodiscovered.
161	Setting it to particual version will make it not auto
173	tificate bundle generated by [export-builtin-trusted-certs](https://github.com/openresty
177	Default: 0
178	Value:: integer >= 0
180	Value greater than 0 is going to enable out-of-ban
183	ronous reports can be running simultainesly

Spell Checker found issues

doc/management-api.md

Line	Typo
32	See [example-config.json](../examples/configurati
32	See [example-config.json](../examples/configuration/ex

doc/parameters.md

Line	Typo
3	APIcast v2 has a number of parameters co
3	ariables) that can modify the behavior of the gateway. The following
5	e that when deploying APIcast v2 with OpenShift, some of thee
15	Default: **stderr**
17	or more information. The file pathcan be either absolute, or relati
21	nfo
21	warn
46	Default: "apicast"
77	Values: a number > **60**
78	Default: 0
80	r. The value should be set to 0 or more than 60. For example,
80	ould be set to 0 or more than 60. For example, if `APICAST_CON
80	ONFIGURATION_CACHE` is set to 120, the gateway will reload the
80	eload the configuration every 2 minutes (120 seconds).
80	onfiguration every 2 minutes (120 seconds).
84	Default: "127.0.0.1"
86	ning Redis instance for OAuth 2.0 flow. REDIS_HOST parameter
90	Default: 6379
92	ning Redis instance for OAuth 2.0 flow. REDIS_PORT parameter
98	ning Redis instance for OAuth 2.0 flow. REDIS_URL parameter c
98	e used to set the full URI as DSN format like: `redis://PASSWOR
103	Default: 604800
105	uthenticate using OAuth, this param specifies the TTL (in seconds
109	pty, the DNS resolver will be autodiscovered.
161	Setting it to particual version will make it not auto
173	tificate bundle generated by [export-builtin-trusted-certs](https://github.com/openresty
177	Default: 0
178	Value:: integer >= 0
180	Value greater than 0 is going to enable out-of-ban
183	ronous reports can be running simultainesly

Generated by 🚫 Danger

[andrewdavidmackenzie]

This looks separate from no post_action changes, adding an /info endpoint, no?

[mikz]

Yes it is separate commit. Not really useful without the post_action changes because there where no timers before.

[davidor]

I ran some tests to make sure that setting APICAST_REPORTING_THREADS=0 does not introduce a performance regression in the normal Apicast flow.

I performed 2 tests, each of them comparing Apicast master branch with this PR:

1. Deployed an Apicast, an Apicast in echo mode (as api backend), and a 3scale backend. All of them in different machines. In this scenario Apicast is limited by the 3scale backend.
2. Deployed just an Apicast and another one in echo mode (as api backend) in separate machines.

The tests were performed using JMeter from an external machine. There are many factors that can affect the throughput, latencies, etc. So absolute numbers are not really meaningful. I just want to focus on the comparison between the master branch and this PR. I used c4.xlarge aws machines, configured Apicast with 4 workers, and run JMeter for 5 minutes.

Results for test 1:
Apicast master

PR

Results for test 2:
Apicast master

PR

The results are similar in both cases.

[andrewdavidmackenzie]

So, focussing on the second of the two comparisons:

In the Pr version:

Thruput is 97.7% of Master
95%ile latency is 107% of Master
99%ile latency is 92% of Master
Max latency is 177% of Master

If it solves a real problem for this and other customers with long latencies, then I guess 97.7% is acceptable....and maybe their are opportunities to optimize it further....