MINOR: compression: CPU usage limit

New option 'maxcompcpuusage' in global section.
Sets the maximum CPU usage HAProxy can reach before stopping the
compression for new requests or decreasing the compression level of
current requests.  It works like 'maxcomprate' but with the Idle.

doc/configuration.txt

@@ -456,6 +456,7 @@ The following keywords are supported in the "global" section :
    - maxconn
    - maxconnrate
    - maxcomprate
+   - maxcompcpuusage
    - maxpipes
    - maxsslconn
    - noepoll
@@ -697,6 +698,16 @@ maxcomprate <number>
   tune.comp.maxlevel.  A value of zero means there is no limit, this is the
   default value.
 
+maxcompcpuusage <number>
+  Sets the maximum CPU usage HAProxy can reach before stopping the compression
+  for new requests or decreasing the compression level of current requests.
+  It works like 'maxcomprate' but measures CPU usage instead of incoming data
+  bandwidth. The value is expressed in percent of the CPU used by haproxy. In
+  case of multiple processes (nbproc > 1), each process manages its individual
+  usage. A value of 100 disable the limit. The default value is 100. Setting
+  a lower value will prevent the compression work from slowing the whole
+  process down and from introducing high latencies.
+
 maxpipes <number>
   Sets the maximum per-process number of pipes to <number>. Currently, pipes
   are only used by kernel-based tcp splicing. Since a pipe contains two file
@@ -722,7 +733,6 @@ maxzlibmem <number>
   with "show info" on the line "MaxZlibMemUsage", the memory used by zlib is
   "ZlibMemUsage" in bytes.
 
-
 noepoll
   Disables the use of the "epoll" event polling system on Linux. It is
   equivalent to the command-line argument "-de". The next polling system

include/proto/compression.h

@@ -25,6 +25,8 @@
 
 #include <types/compression.h>
 
+extern unsigned int compress_min_idle;
+
 int comp_append_type(struct comp *comp, const char *type);
 int comp_append_algo(struct comp *comp, const char *algo);
 
@@ -40,6 +42,7 @@ int identity_reset(struct comp_ctx *comp_ctx);
 int identity_end(struct comp_ctx **comp_ctx);
 
 
+
 #ifdef USE_ZLIB
 extern long zlib_used_memory;
 

src/cfgparse.c

@@ -887,6 +887,20 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 		}
 		global.maxzlibmem = atol(args[1]) * 1024L * 1024L;
 	}
+	else if (!strcmp(args[0], "maxcompcpuusage")) {
+		if (*(args[1]) == 0) {
+			Alert("parsing [%s:%d] : '%s' expects an integer argument between 0 and 100.\n", file, linenum, args[0]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+		compress_min_idle = 100 - atoi(args[1]);
+		if (compress_min_idle < 0 || compress_min_idle > 100) {
+			Alert("parsing [%s:%d] : '%s' expects an integer argument between 0 and 100.\n", file, linenum, args[0]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+}
+
 	else if (!strcmp(args[0], "ulimit-n")) {
 		if (global.rlimit_nofile != 0) {
 			Alert("parsing [%s:%d] : '%s' already specified. Continuing.\n", file, linenum, args[0]);

src/compression.c

@@ -51,6 +51,7 @@ long zlib_used_memory = 0;
 
 #endif
 
+unsigned int compress_min_idle = 0;
 static struct pool_head *pool_comp_ctx = NULL;
 
 
@@ -560,21 +561,19 @@ int deflate_flush(struct comp_ctx *comp_ctx, struct buffer *out, int flag)
 	out_len = (out->size - buffer_len(out)) - strm->avail_out;
 	out->i += out_len;
 
-	/* compression rate limit */
-	if (global.comp_rate_lim > 0) {
-
-		if (read_freq_ctr(&global.comp_bps_out) > global.comp_rate_lim) {
-			/* decrease level */
-			if (comp_ctx->cur_lvl > 0) {
-				comp_ctx->cur_lvl--;
-				deflateParams(&comp_ctx->strm, comp_ctx->cur_lvl, Z_DEFAULT_STRATEGY);
-			}
-
-		} else if (comp_ctx->cur_lvl < global.tune.comp_maxlevel) {
-			/* increase level */
-			comp_ctx->cur_lvl++ ;
+	/* compression limit */
+	if ((global.comp_rate_lim > 0 && (read_freq_ctr(&global.comp_bps_out) > global.comp_rate_lim)) ||    /* rate */
+	   (idle_pct < compress_min_idle)) {                                                                     /* idle */
+		/* decrease level */
+		if (comp_ctx->cur_lvl > 0) {
+			comp_ctx->cur_lvl--;
 			deflateParams(&comp_ctx->strm, comp_ctx->cur_lvl, Z_DEFAULT_STRATEGY);
 		}
+
+	} else if (comp_ctx->cur_lvl < global.tune.comp_maxlevel) {
+		/* increase level */
+		comp_ctx->cur_lvl++ ;
+		deflateParams(&comp_ctx->strm, comp_ctx->cur_lvl, Z_DEFAULT_STRATEGY);
 	}
 
 	return out_len;

src/proto_http.c

@@ -2099,6 +2099,10 @@ int select_compression_response_header(struct session *s, struct buffer *res)
 		if (read_freq_ctr(&global.comp_bps_in) > global.comp_rate_lim)
 			goto fail;
 
+	/* limit cpu usage */
+	if (idle_pct < compress_min_idle)
+		goto fail;
+
 	/* initialize compression */
 	if (s->comp_algo->init(&s->comp_ctx, global.tune.comp_maxlevel) < 0)
 		goto fail;