compress: Add configurable compression levels

- Add support for configurable compression levels per host:
  * gzip-compression-level (1-9, default 6)
  * brotli-compression-level (0-11, default 6)
  * brotli-lgwin (10-24, default 16)
  * zstd-compression-level (1-22, default 12)

This enables fine-tuning compression performance vs. speed trade-offs
on a per-host basis

Author: JakeChampion

doc/admin-guide/plugins/compress.en.rst

@@ -192,6 +192,41 @@ be considered, if it is ``2``, only br or gzip will be considered, if it is ``4`
 only zstd, br, or gzip will be considered, and if it is ``5``, all combinations
 of zstd, br, and gzip will be considered.
 
+gzip-compression-level
+-----------------------
+
+Sets the compression level for gzip compression. Valid values are 1-9, where
+1 is fastest compression (lowest compression ratio) and 9 is slowest compression
+(highest compression ratio). The default is 6, which provides a good balance
+between compression speed and ratio.
+
+brotli-compression-level
+-------------------------
+
+Sets the compression level for Brotli compression. Valid values are 0-11, where
+0 is fastest compression (lowest compression ratio) and 11 is slowest compression
+(highest compression ratio). The default is 6, which provides a good balance
+between compression speed and ratio.
+
+brotli-lgwin
+------------
+
+Sets the window size for Brotli compression. Valid values are 10-24, where
+larger values provide better compression but use more memory. The default is 16.
+This parameter controls the sliding window size used during compression:
+
+- 10: 1KB window (fastest, least memory)
+- 16: 64KB window (default, good balance)
+- 24: 16MB window (slowest, most memory, best compression)
+
+zstd-compression-level
+----------------------
+
+Sets the compression level for Zstandard compression. Valid values are 1-22, where
+1 is fastest compression (lowest compression ratio) and 22 is slowest compression
+(highest compression ratio). The default is 12, which provides an excellent
+balance between compression speed and ratio for web content.
+
 Examples
 ========
 
@@ -207,6 +242,10 @@ might create a configuration with the following options::
    compressible-status-code 200, 206
    minimum-content-length 860
    flush false
+   gzip-compression-level 6
+   brotli-compression-level 6
+   brotli-lgwin 16
+   zstd-compression-level 12
 
    # Now set a configuration for www.example.com
    [www.example.com]
@@ -224,13 +263,15 @@ might create a configuration with the following options::
    flush true
    supported-algorithms gzip,deflate
 
-   # Supports brotli compression
+   # Supports brotli compression with custom settings
    [brotli.compress.com]
    enabled true
    compressible-content-type text/*
    compressible-content-type application/json
    flush true
    supported-algorithms br,gzip
+   brotli-compression-level 8
+   brotli-lgwin 20
 
    # Supports zstd compression for high efficiency
    [zstd.compress.com]
@@ -240,14 +281,19 @@ might create a configuration with the following options::
    compressible-content-type application/javascript
    flush true
    supported-algorithms zstd,gzip
+   zstd-compression-level 15
 
-   # Supports all compression algorithms
+   # Supports all compression algorithms with optimized settings
    [all.compress.com]
    enabled true
    compressible-content-type text/*
    compressible-content-type application/json
    flush true
    supported-algorithms zstd,br,gzip,deflate
+   gzip-compression-level 7
+   brotli-compression-level 9
+   brotli-lgwin 18
+   zstd-compression-level 10
 
    # This origin does it all
    [bar.example.com]

plugins/compress/README

@@ -24,4 +24,4 @@ compress.so <path-to-config>/sample.compress.config
 After modifying plugin.config, restart traffic server (sudo traffic_ctl server restart)
 the configuration is re-read when a management update is given (sudo traffic_ctl config reload)
 
-See sample.config.compress for an example configuration and the options that are available
+See sample.compress.config for an example configuration and the options that are available

plugins/compress/compress.cc

@@ -62,18 +62,7 @@ namespace compress_ns
 DbgCtl dbg_ctl{TAG};
 }
 
-const int   ZLIB_COMPRESSION_LEVEL = 6;
-const char *dictionary             = nullptr;
-
-// brotli compression quality 1-11. Testing proved level '6'
-#if HAVE_BROTLI_ENCODE_H
-const int BROTLI_COMPRESSION_LEVEL = 6;
-const int BROTLI_LGW               = 16;
-#endif
-
-#if HAVE_ZSTD_H
-const int ZSTD_COMPRESSION_LEVEL = 12;
-#endif
+const char *dictionary = nullptr;
 
 static const char *global_hidden_header_name = nullptr;
 
@@ -90,7 +79,7 @@ static void zstd_compress_finish(Data *data);
 static void zstd_compress_one(Data *data, const char *upstream_buffer, int64_t upstream_length);
 #endif
 static Data *
-data_alloc(int compression_type, int compression_algorithms)
+data_alloc(int compression_type, int compression_algorithms, HostConfiguration *hc)
 {
   Data *data;
   int   err;
@@ -103,6 +92,7 @@ data_alloc(int compression_type, int compression_algorithms)
   data->state                  = transform_state_initialized;
   data->compression_type       = compression_type;
   data->compression_algorithms = compression_algorithms;
+  data->hc                     = hc;
   data->zstrm.next_in          = Z_NULL;
   data->zstrm.avail_in         = 0;
   data->zstrm.total_in         = 0;
@@ -119,7 +109,7 @@ data_alloc(int compression_type, int compression_algorithms)
     window_bits = WINDOW_BITS_DEFLATE;
   }
 
-  err = deflateInit2(&data->zstrm, ZLIB_COMPRESSION_LEVEL, Z_DEFLATED, window_bits, ZLIB_MEMLEVEL, Z_DEFAULT_STRATEGY);
+  err = deflateInit2(&data->zstrm, data->hc->zlib_compression_level(), Z_DEFLATED, window_bits, ZLIB_MEMLEVEL, Z_DEFAULT_STRATEGY);
 
   if (err != Z_OK) {
     fatal("gzip-transform: ERROR: deflateInit (%d)!", err);
@@ -139,8 +129,8 @@ data_alloc(int compression_type, int compression_algorithms)
     if (!data->bstrm.br) {
       fatal("Brotli Encoder Instance Failed");
     }
-    BrotliEncoderSetParameter(data->bstrm.br, BROTLI_PARAM_QUALITY, BROTLI_COMPRESSION_LEVEL);
-    BrotliEncoderSetParameter(data->bstrm.br, BROTLI_PARAM_LGWIN, BROTLI_LGW);
+    BrotliEncoderSetParameter(data->bstrm.br, BROTLI_PARAM_QUALITY, data->hc->brotli_compression_level());
+    BrotliEncoderSetParameter(data->bstrm.br, BROTLI_PARAM_LGWIN, data->hc->brotli_lgw_size());
     data->bstrm.next_in   = nullptr;
     data->bstrm.avail_in  = 0;
     data->bstrm.total_in  = 0;
@@ -462,7 +452,7 @@ zstd_compress_init(Data *data)
   }
 
   // Set compression level
-  size_t result = ZSTD_CCtx_setParameter(data->zstrm_zstd.cctx, ZSTD_c_compressionLevel, ZSTD_COMPRESSION_LEVEL);
+  size_t result = ZSTD_CCtx_setParameter(data->zstrm_zstd.cctx, ZSTD_c_compressionLevel, data->hc->zstd_compression_level());
   if (ZSTD_isError(result)) {
     error("Failed to set Zstd compression level: %s", ZSTD_getErrorName(result));
     return;
@@ -475,7 +465,7 @@ zstd_compress_init(Data *data)
     return;
   }
 
-  debug("zstd compression context initialized with level %d", ZSTD_COMPRESSION_LEVEL);
+  debug("zstd compression context initialized with level %d", data->hc->zstd_compression_level());
 }
 
 static void
@@ -981,9 +971,8 @@ compress_transform_add(TSHttpTxn txnp, HostConfiguration *hc, int compress_type,
   }
 
   connp     = TSTransformCreate(compress_transform, txnp);
-  data      = data_alloc(compress_type, algorithms);
+  data      = data_alloc(compress_type, algorithms, hc);
   data->txn = txnp;
-  data->hc  = hc;
 
   TSContDataSet(connp, data);
   TSHttpTxnHookAdd(txnp, TS_HTTP_RESPONSE_TRANSFORM_HOOK, connp);

plugins/compress/configuration.cc

@@ -108,7 +108,11 @@ enum ParserState {
   kParseRangeRequest,
   kParseFlush,
   kParseAllow,
-  kParseMinimumContentLength
+  kParseMinimumContentLength,
+  kParseGzipCompressionLevel,
+  kPaseBrotliCompressionLevel,
+  kParseBrotliLGWSize,
+  kParseZstdCompressionLevel,
 };
 
 void
@@ -368,6 +372,14 @@ Configuration::Parse(const char *path)
           state = kParseStart;
         } else if (token == "minimum-content-length") {
           state = kParseMinimumContentLength;
+        } else if (token == "gzip-compression-level") {
+          state = kParseGzipCompressionLevel;
+        } else if (token == "brotli-compression-level") {
+          state = kPaseBrotliCompressionLevel;
+        } else if (token == "brotli-lgwin") {
+          state = kParseBrotliLGWSize;
+        } else if (token == "zstd-compression-level") {
+          state = kParseZstdCompressionLevel;
         } else {
           warning("failed to interpret \"%s\" at line %zu", token.c_str(), lineno);
         }
@@ -404,6 +416,46 @@ Configuration::Parse(const char *path)
         current_host_configuration->set_minimum_content_length(strtoul(token.c_str(), nullptr, 10));
         state = kParseStart;
         break;
+      case kParseGzipCompressionLevel: {
+        int level = strtol(token.c_str(), nullptr, 10);
+        if (level < 1 || level > 9) {
+          error("gzip-compression-level must be between 1 and 9, got %d", level);
+        } else {
+          current_host_configuration->set_gzip_compression_level(level);
+        }
+        state = kParseStart;
+        break;
+      }
+      case kPaseBrotliCompressionLevel: {
+        int level = strtol(token.c_str(), nullptr, 10);
+        if (level < 0 || level > 11) {
+          error("brotli-compression-level must be between 0 and 11, got %d", level);
+        } else {
+          current_host_configuration->set_brotli_compression_level(level);
+        }
+        state = kParseStart;
+        break;
+      }
+      case kParseBrotliLGWSize: {
+        int lgw = strtol(token.c_str(), nullptr, 10);
+        if (lgw < 10 || lgw > 24) {
+          error("brotli-lgwin must be between 10 and 24, got %d", lgw);
+        } else {
+          current_host_configuration->set_brotli_lgw_size(lgw);
+        }
+        state = kParseStart;
+        break;
+      }
+      case kParseZstdCompressionLevel: {
+        int level = strtol(token.c_str(), nullptr, 10);
+        if (level < 1 || level > 22) {
+          error("zstd-compression-level must be between 1 and 22, got %d", level);
+        } else {
+          current_host_configuration->set_zstd_compression_level(level);
+        }
+        state = kParseStart;
+        break;
+      }
       }
     }
   }

plugins/compress/configuration.h

@@ -53,7 +53,11 @@ class HostConfiguration : private atscppapi::noncopyable
       remove_accept_encoding_(false),
       flush_(false),
       compression_algorithms_(ALGORITHM_GZIP),
-      minimum_content_length_(1024)
+      minimum_content_length_(1024),
+      zlib_compression_level_(6),
+      brotli_compression_level_(6),
+      brotli_lgw_size_(16),
+      zstd_compression_level_(12)
   {
   }
 
@@ -129,6 +133,51 @@ class HostConfiguration : private atscppapi::noncopyable
     minimum_content_length_ = x;
   }
 
+  unsigned int
+  zlib_compression_level() const
+  {
+    return zlib_compression_level_;
+  }
+
+  void
+  set_gzip_compression_level(int level)
+  {
+    zlib_compression_level_ = level;
+  }
+
+  unsigned int
+  brotli_compression_level() const
+  {
+    return brotli_compression_level_;
+  }
+  void
+  set_brotli_compression_level(int level)
+  {
+    brotli_compression_level_ = level;
+  }
+
+  unsigned int
+  brotli_lgw_size() const
+  {
+    return brotli_lgw_size_;
+  }
+  void
+  set_brotli_lgw_size(unsigned int lgw)
+  {
+    brotli_lgw_size_ = lgw;
+  }
+
+  int
+  zstd_compression_level() const
+  {
+    return zstd_compression_level_;
+  }
+  void
+  set_zstd_compression_level(int level)
+  {
+    zstd_compression_level_ = level;
+  }
+
   void update_defaults();
   void add_allow(const std::string &allow);
   void add_compressible_content_type(const std::string &content_type);
@@ -148,6 +197,10 @@ class HostConfiguration : private atscppapi::noncopyable
   bool         flush_;
   int          compression_algorithms_;
   unsigned int minimum_content_length_;
+  unsigned int zlib_compression_level_;
+  unsigned int brotli_compression_level_;
+  unsigned int brotli_lgw_size_;
+  int          zstd_compression_level_;
 
   StringContainer compressible_content_types_;
   StringContainer allows_;

plugins/compress/sample.compress.config

@@ -37,6 +37,22 @@
 # minimum-content-length: minimum content length for compression to be enabled (in bytes)
 # - this setting only applies if the origin response has a Content-Length header
 #
+# gzip-compression-level: compression level for gzip (1-9, default 6)
+# - 1 is fastest compression (lowest compression ratio)
+# - 9 is slowest compression (highest compression ratio)
+#
+# brotli-compression-level: compression level for brotli (0-11, default 6)
+# - 0 is fastest compression (lowest compression ratio)
+# - 11 is slowest compression (highest compression ratio)
+#
+# brotli-lgwin: window size for brotli compression (10-24, default 16)
+# - larger values provide better compression but use more memory
+# - 10: 1KB window, 16: 64KB window, 24: 16MB window
+#
+# zstd-compression-level: compression level for zstandard (1-22, default 12)
+# - 1 is fastest compression (lowest compression ratio)
+# - 22 is slowest compression (highest compression ratio)
+#
 ######################################################################
 
 #first, we configure the default/global plugin behaviour
@@ -58,6 +74,12 @@ minimum-content-length 1024
 #supported algorithms
 supported-algorithms br,gzip,zstd
 
+# Compression level settings (optional)
+gzip-compression-level 6
+brotli-compression-level 6
+brotli-lgwin 16
+zstd-compression-level 12
+
 #override the global configuration for a host.
 #www.foo.nl does NOT inherit anything
 [www.foo.nl]
@@ -68,6 +90,12 @@ compressible-content-type text/*
 compressible-status-code 200,206,409
 minimum-content-length 1024
 
+# Custom compression settings for this host
+gzip-compression-level 8
+brotli-compression-level 9
+brotli-lgwin 20
+zstd-compression-level 15
+
 allow /this/*.js
 allow !/notthis/*.js
 allow !/notthat*