What causes "getClassPath: failed calloc: %s " in apache/hadoop?

Pre-expand and shorten the CLASSPATH so the calloc is small or unnecessary

getClassPath: failed calloc: %s

Error message

getClassPath: failed calloc: %s

What it means

After a sizing pass computes the expanded classpath length, getClassPath allocates the result buffer with calloc(length, 1). On failure it prints 'failed calloc: ...' with strerror(errno) and returns NULL, so the expanded classpath is never built and the JVM is not created.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/jni_helper.c:616

        if ((length == 0) && (strlen(classpath) != 0)) {
            fprintf(stderr, "Something went wrong with getting the wildcard \
              expansion length\n" );
        }
#endif

        expandedClasspath = strdup(classpath);

#ifdef _LIBHDFS_JNI_HELPER_DEBUGGING_ON_
        printf("Expanded classpath=%s\n", expandedClasspath);
#endif

        return expandedClasspath;
    }

    // Allocte memory for expanded classpath string
    expandedClasspath = calloc(length, sizeof(char));
    if (expandedClasspath == NULL) {
        fprintf(stderr, "getClassPath: failed calloc: %s\n", strerror(errno));
        return NULL;
    }

    // Actual expansion
    retval = getClassPath_helper(classpath, expandedClasspath);
    if (retval < 0) {
        free(expandedClasspath);
        return NULL;
    }

    // This should not happen, but dotting i's and crossing t's
    if (retval != length) {
        fprintf(stderr,
          "Expected classpath expansion length to be %zu but instead got %zu\n",
          length, retval);
        free(expandedClasspath);
        return NULL;
    }

View on GitHub (pinned to 2add963021)

Solutions

Pre-expand and shorten the CLASSPATH so the calloc is small or unnecessary
Raise memory limits before the first libhdfs call
Replace wildcard entries with explicit jar lists

Defensive patterns

Strategy: fallback

Try / catch

if (hdfsConnect(uri, user) == NULL && errno == EINTERNAL) {
    /* check stderr for 'failed calloc': shrink/expand wildcard entries or raise limits */
}

Prevention

Pre-expand wildcards so the expansion buffer stays small
Set memory limits with JVM bootstrap headroom in mind

When it happens

Trigger: Very large wildcard-expanded classpaths (the buffer can be megabytes) with insufficient free memory; ulimit -v or cgroup caps hit during allocation.

Common situations: Big Hadoop installations expanded via wildcards; constrained containers; the same conditions that cause the earlier strdup failure.

Related errors

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/57c97e8857660969. Report an issue: GitHub.