javascript.lang.best-practice.zlib-async-loop.zlib-async-loop

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Creating and using a large number of zlib objects simultaneously can cause significant memory fragmentation. It is strongly recommended that the results of compression operations be cached or made synchronous to avoid duplication of effort.

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Defintion

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rules:
  - id: zlib-async-loop
    patterns:
      - pattern-either:
          - pattern-inside: |
              for (...) {
                  ...
              }
          - pattern-inside: |
              while (...) {
                  ...
              }
          - pattern-inside: |
              do {
                  ...
              } while (...)
          - pattern-inside: |
              $SMTH.forEach(...)
          - pattern-inside: |
              $SMTH.map(...)
          - pattern-inside: |
              $SMTH.reduce(...)
          - pattern-inside: |
              $SMTH.reduceRight(...)
      - pattern: zlib.$METHOD(...);
      - metavariable-regex:
          metavariable: $METHOD
          regex: ^.+$(?<!Sync)
    message: Creating and using a large number of zlib objects simultaneously can
      cause significant memory fragmentation. It is strongly recommended that
      the results of compression operations be cached or made synchronous to
      avoid duplication of effort.
    metadata:
      references:
        - https://nodejs.org/api/zlib.html#zlib_threadpool_usage_and_performance_considerations
      category: best-practice
      technology:
        - javascript
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
    severity: WARNING
    languages:
      - javascript
      - typescript

Examples

zlib-async-loop.js

const zlib = require('zlib');

const payload = Buffer.from('This is some data');

for (let i = 0; i < 30000; ++i) {
    // ruleid: zlib-async-loop
    zlib.deflate(payload, (err, buffer) => {});
}

[1,2,3].forEach((el) => {
    // ruleid: zlib-async-loop
    zlib.deflate(payload, (err, buffer) => {});
})

for (let i = 0; i < 30000; ++i) {
    // ok: zlib-async-loop
    zlib.deflateSync(payload);
}

// ok: zlib-async-loop
zlib.deflate(payload, (err, buffer) => {});