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fluent-bit: avoid re-reading kmsg lines on every reload

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This commit is contained in:
Mohd Husaam Mehdi 2025-12-05 15:50:31 +05:30
parent 27c1022601
commit 57c809a024
1 changed files with 103 additions and 0 deletions
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103
fluent-bit/patches/0030-kmsg_avoid_reread.patch Normal file
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@ -0,0 +1,103 @@
diff --git a/plugins/in_kmsg/in_kmsg.c b/plugins/in_kmsg/in_kmsg.c
index 15f10545..481d162b 100644
--- a/plugins/in_kmsg/in_kmsg.c
+++ b/plugins/in_kmsg/in_kmsg.c
@@ -104,6 +104,32 @@ static int boot_time(struct timeval *boot_time)
return 0;
}
+static void load_last_sequence(struct flb_in_kmsg_config *ctx)
+{
+ FILE *f = fopen(FLB_KMSG_SEQ_MARKER, "r");
+ if (!f) {
+ ctx->last_sequence = 0;
+ return;
+ }
+
+ if (fscanf(f, "%llu", &ctx->last_sequence) != 1) {
+ ctx->last_sequence = 0;
+ }
+
+ fclose(f);
+}
+
+static void save_last_sequence(struct flb_in_kmsg_config *ctx)
+{
+ FILE *f = fopen(FLB_KMSG_SEQ_MARKER, "w");
+ if (!f) {
+ return;
+ }
+
+ fprintf(f, "%llu\n", (unsigned long long)ctx->last_sequence);
+ fclose(f);
+}
+
static inline int process_line(const char *line,
struct flb_input_instance *i_ins,
struct flb_in_kmsg_config *ctx)
@@ -161,6 +187,11 @@ static inline int process_line(const char *line,
}
sequence = val;
+ /* skip lines we have already seen */
+ if (sequence <= ctx->last_sequence) {
+ return 0; /* skip old message */
+ }
+
p = ++end;
/* Timestamp */
@@ -225,6 +256,7 @@ static inline int process_line(const char *line,
ctx->log_encoder.output_buffer,
ctx->log_encoder.output_length);
+ ctx->last_sequence = sequence;
ret = 0;
}
else {
@@ -363,6 +395,10 @@ static int in_kmsg_init(struct flb_input_instance *ins,
return -1;
}
+ load_last_sequence(ctx);
+ flb_plg_debug(ctx->ins, "restored last_sequence=%llu",
+ (unsigned long long)ctx->last_sequence);
+
return 0;
}
@@ -373,6 +409,12 @@ static int in_kmsg_exit(void *data, struct flb_config *config)
flb_log_event_encoder_destroy(&ctx->log_encoder);
+ /*
+ * save the last read sequence number in a file,
+ * so that we know where to start next time
+ */
+ save_last_sequence(ctx);
+
if (ctx->fd >= 0) {
close(ctx->fd);
}
diff --git a/plugins/in_kmsg/in_kmsg.h b/plugins/in_kmsg/in_kmsg.h
index 0ea2e97a..4b9d98fd 100644
--- a/plugins/in_kmsg/in_kmsg.h
+++ b/plugins/in_kmsg/in_kmsg.h
@@ -27,6 +27,7 @@
#include <stdint.h>
#define FLB_KMSG_DEV "/dev/kmsg"
+#define FLB_KMSG_SEQ_MARKER "/tmp/fluent_bit_kmsg_last_seq"
#define FLB_KMSG_BUF_SIZE 4096
/* Alert levels, taken from util-linux sources */
@@ -60,6 +61,9 @@ struct flb_in_kmsg_config {
size_t buf_size;
struct flb_log_event_encoder log_encoder;
struct flb_input_instance *ins;
+
+ uint64_t last_sequence; /* last saved sequence */
+ const char *seq_file; /* path to seq file */
};