dcdbslurmjob: re-opening STDIN/STDOUT/STDERR if closed

- This prevents libuv from crashing dcdbslurmjob when the Cassandra
insertion mode is being used

tools/dcdbslurmjob/dcdbslurmjob.cpp

@@ -37,6 +37,8 @@
 #include <mosquitto.h>
 #include "dcdb/version.h"
 #include "version.h"
+#include "fcntl.h"
+#include "unistd.h"
 
 #define SLURM_JOBSTEP_SEP "."
 
@@ -54,6 +56,20 @@ void publishCallback(struct mosquitto *mosq, void *obj, int mid) {
 		done = true;
 }
 
+// Re-opens STDIN, STDOUT or STDERR to /dev/null if they are closed.
+// Prevents libuv from making dcdbslurmjob crash when using Cassandra.
+void fixFileDescriptors() {
+    std::string stdArr[3] = {"STDIN", "STDOUT", "STDERR"};
+    int fd = -1;
+    for(int idx=0; idx<=2; idx++) {
+        if(fcntl(idx, F_GETFD) < 0) {
+            std::cerr << "Warning: detected closed " << stdArr[idx] << " channel. Fixing..." << std::endl;
+            if((fd=open("/dev/null", O_RDWR)) < 0 || dup2(fd, idx) < 0) {
+                std::cerr << "Error: cannot re-open " << stdArr[idx] << " channel." << std::endl;
+            }
+        }
+    }
+}
 
 /*
  * Print usage information
@@ -347,6 +363,7 @@ int main(int argc, char** argv) {
 
     // Initialize transport
     if (cassandra) {
+        fixFileDescriptors();
 	    // Allocate and initialize connection to Cassandra.
 	    pickRandomHost(hostList, host, port);
 	    if (port == 0) {