In a typical Symfony project there are multiple caches built when running the cache:warmup command. By pre-building those caches and putting them into the container, the startup time can be reduced.

Doctrine

1. Metadata Cache: Stores class metadata. ✅ Already in container
2. Query Cache: Stores DQL queries converted to SQL. This is generated at runtime.
   💡Can be collected on CI -> Turned out to be too complex, instead I recommend to use a cache with 2 adapters: a local file cache backed by a shared external cache like Redis.
3. Result Cache: Stores results of queries. ❌Only at runtime
4. Proxy directory: Generated proxy objects which make lazy loading of entities possible. /var/www/app/var/cache/[env]/doctrine/orm/Proxies ✅ Already in container

Symfony

1. Route annotations: Parsed controller route annotations.
2. Container: Service configuration and initialization. ⚠️ contains credentials when using parameters. Switch to environment variables instead.
3. Translations: /var/www/app/var/cache/[env]/translations/catalogue.gl.whsXFTx.php
4. Annotations: A huge file of all annotations /var/www/app/var/cache/[env]/annotations.php
5. Routes: ⚠️ contains domain names /var/www/app/var/cache/[env]/url_generating_routes.php

Twig

1. Template cache: Twig templates compiled to PHP files.

Use env variables instead of parameters

1. Make a script that checks that all parameters are accessed with %env(parameter_name)% to not leak any parameters
2. Replace parameters with environment variables in Website project
3. Make a script that checks that no parameter values are included in the generated container

How to test:

• Build a new image that includes cache warm-up while building (and removes it from the entrypoint.sh)
• Start the image with CACHE_WARMUP=0 and run a request or bin/console. Run docker diff [image-hash] to list the changed files since the start.
• The output should show show no files in var/cache/[env]/ContainerXYZ and way less files compared to running the image with CACHE_WARMUP=1

Measurements

Measurements of a web-server pod using PHP-FPM and a separate nginx container:

• ~1m 44 seconds to boot new node (EC2 instance)
• ~15 seconds image pull
• ~20 seconds cache building and warmup
• ~5 seconds nginx retry interval
• 70 seconds initial readiness probe delay

Times before optimizations
Best time: 1 + 70s = 71 s
Worst time: 60 + 44 + 1 + 15 + 70 = 190 = 3m 10s

Reducing the initial readiness probe delay (best case):
1 + 25s = 26s reduction of 63,4% vs current best case

Pre-building cache (best case):
1 + 1s = 2s reduction of 97,1% vs current best case

Pre-building cache (worst case):
1m 44s + 15 + 1 + 1 = 2m 1s ~33% faster than current worst case

Preload

⚠️ Something is wrong with preload, unclear what.

Without preload:

hyperfine -r 1000 --warmup 10 "bash test.sh"
  Time (mean ± σ):      68.9 ms ±  12.6 ms    [User: 3.7 ms, System: 5.9 ms]
  Range (min … max):    42.3 ms … 179.9 ms    1000 runs

With preload:

hyperfine -r 1000 --warmup 10 "bash test.sh"
  Time (mean ± σ):      67.2 ms ±  32.9 ms    [User: 3.5 ms, System: 5.5 ms]
  Range (min … max):    57.5 ms … 1074.3 ms    1000 runs

#published