From 71ac6596afae91aa9c27bb931b14e63a9384c52d Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Wed, 21 Dec 2016 10:10:22 -0800
Subject: [PATCH] Warn about broken pipes in filters instead of exiting
 abruptly

---
 main.cpp   |  3 +++
 plugin.cpp | 16 +++++++++++-----
 tile.cpp   | 12 ++++++++++--
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/main.cpp b/main.cpp
index 18f4602..866d895 100644
--- a/main.cpp
+++ b/main.cpp
@@ -24,6 +24,7 @@
 #include <sys/resource.h>
 #include <pthread.h>
 #include <getopt.h>
+#include <signal.h>
 #include <vector>
 #include <string>
 #include <set>
@@ -2207,6 +2208,8 @@ int main(int argc, char **argv) {
 		}
 	}
 
+	signal(SIGPIPE, SIG_IGN);
+
 	files_open_at_start = open("/dev/null", O_RDONLY | O_CLOEXEC);
 	if (files_open_at_start < 0) {
 		perror("open /dev/null");
diff --git a/plugin.cpp b/plugin.cpp
index db623a6..db06357 100644
--- a/plugin.cpp
+++ b/plugin.cpp
@@ -12,6 +12,7 @@
 #include <pthread.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <errno.h>
 #include <cmath>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -42,8 +43,6 @@ struct writer_arg {
 void *run_writer(void *a) {
 	writer_arg *wa = (writer_arg *) a;
 
-	// XXX worry about SIGPIPE?
-
 	FILE *fp = fdopen(wa->write_to, "w");
 	if (fp == NULL) {
 		perror("fdopen (pipe writer)");
@@ -53,8 +52,16 @@ void *run_writer(void *a) {
 	layer_to_geojson(fp, *(wa->layer), wa->z, wa->x, wa->y, false, false);
 
 	if (fclose(fp) != 0) {
-		perror("fclose output to filter");
-		exit(EXIT_FAILURE);
+		if (errno == EPIPE) {
+			static bool warned = false;
+			if (!warned) {
+				fprintf(stderr, "Warning: broken pipe in postfilter\n");
+				warned = true;
+			}
+		} else {
+			perror("fclose output to filter");
+			exit(EXIT_FAILURE);
+		}
 	}
 
 	return NULL;
@@ -382,7 +389,6 @@ serial_feature parse_feature(json_pull *jp, int z, unsigned x, unsigned y, std::
 			}
 
 			auto fk = layermap.find(layername);
-			fprintf(stderr, "assign layer %zu\n", fk->second.id);
 			sf.layer = fk->second.id;
 
 			if (z < fk->second.minzoom) {
diff --git a/tile.cpp b/tile.cpp
index abce83e..e92d23b 100644
--- a/tile.cpp
+++ b/tile.cpp
@@ -1378,8 +1378,16 @@ void *run_prefilter(void *v) {
 	}
 
 	if (fclose(rpa->prefilter_fp) != 0) {
-		perror("fclose output to prefilter");
-		exit(EXIT_FAILURE);
+		if (errno == EPIPE) {
+			static bool warned = false;
+			if (!warned) {
+				fprintf(stderr, "Warning: broken pipe in prefilter\n");
+				warned = true;
+			}
+		} else {
+			perror("fclose output to prefilter");
+			exit(EXIT_FAILURE);
+		}
 	}
 	return NULL;
 }